ENGINEERING MUSIC SOUND REPRODUCTION AMPLIFIERS

ENGINEERING MUSIC SOUND REPRODUCTION AMPLIFIERS
JANUARY, 1955
50c
1
ENGINEERING
MUSIC
SOUND
U
REPRODUCTION
This circuit represents the output stage of one of the modern
power amplifiers described-along with "front ends "
the 40 -page Amplifier and Preamplifier section. See page 21.
-in
One of, the originating stations, of the wired -audio network
throughout .1/lT's, do?rnitorieà which permits students to
exchange music from the'ir record collections. See page 16.
-
AMPLIFIERS AND PREAMPLIFIERS
a 40-page section
THREE- CHANNEL PREAMPLIFIER -MIXER,.
THE M. I. T. AUDIO NETWORK
SUCCESS FOUND IN "SOUND" PRINCIPLE'
f`r
www.americanradiohistory.com
AmericanRadioHistory.Com
ut RnxtJcart111g ( òmp.am-
"OUR BEST PORTABLE RECORDER YET"
says Richard Parks, Asst. Chief Engineer, ABC, San Francisco
"This new Ampex 600 really fills a need. We like it. It's light. It's compact. And its fidelity and timing accuracy leave nothing to be desired.
Now no matter how important the program material, we can send the
600 out after it. The results that come back are as good as we could
have recorded inside our studio on Ampex 350s. For program protection the 600's third head is an excellent feature. The engineer monitors
as he records. There's no guesswork. The recording is always right."
"The photo shows Bill Adams, our farm reporter. He has made extensive
use of the 600 for farm interviews."
Model 600
NOW THERE'S AN AMPEX FOR EVERY BROADCAST NEED
The new 600 completes the Ampex line. In any station it's an ideal
portable, and for many it's an all purpose machine. The Ampex 600
fits limited space and limited budgets, but does an unlimited job. Base
price is $498. In portable case it's $545. The Ampex 620, a portable
amplifier- speaker unit in matching case is a superb quality monitoring
unit, usable inside or out; price is $149.50.
The Ampex 350 is the versatile broadcast studio machine. It has a remote
control plug -in, two speeds, 10 Y2 -inch reels, easy editing and quick
accessibility for service. Its durability defies time and hard usage.
Bulletins on the low cost Ampex 600, the versatile 350, the 450 eight -hour reproducer
and the Ampex Tope Duplicator are available on request. Write today to Dept. B -1881
Model 350
I(,11(1i111
CORPORATION
<+
934 CHARTER
Distributors in principal U.
I)/
-
STREET
S.
lc',-('('r1(,l
;11- /1(.111111
REDWOOD CITY, CALIFORNIA
cities; Canadian distribution by the Canadian General Electric Company.
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AmericanRadioHistory.Com
VOL. 39, No.
JANUARY, 1955
Successor to RADIO, Eat. 1917.
1
AU D Io
ENGINEFRI NG
MUSIC
SOUND REPRODUCTION
C. G.
McProud, Editor and Publisher
Henry A. Schober, Business Manager
Harrie K. Richardson, Associate Editor
Florence Rowland, Production Manager
Edgar E. Newman, Circulation Director
S. L. Cahn, Advertising Director
Representatives
H. Thorpe Covington and Dick Knott
Special Representatives
7530 North Sheridan Road, Chicago 26, III.
Sanford R. Cowan, Mid-West Representative
67 W. 44th St., New York 36, N. Y.
West Coast
lames
C. Calloway
I. W. Harbison
816 W. 5th St., Los Angeles 17, Calif.
CONTENTS
Audio Patents Richard H. Dorf
2
Coming Events
4
New Literature
6
Letters
8
-
-
About Music Harold Lawrence
Editor's Report
10
12
-
Three-Channel Preamplifier- Mixer Harold Reed
The MIT Audio Network -David Klepper
15
16
Success Found in "Sound" Principles-Bert Ennis
18
Amplifiers and Preamplifiers
A complete 40 -page section
21
-
Equipment Report -Harman -Kardon Festival
Record Revue-Edward Tatnall Canby
61
New Products
68
Audio Fair -Los Angeles
70
Audio ETC
71
-
62
Edward Tatnall Canby
Industry Notes
79
Advertising Index
80
LAVALIER
Model 646 Dynamic
-
Remarkably small, versatile microphone
for chest, desk or hand use. Frees hands
of announcer or performer for demonstration or dramatic effects. Recessed
screw in grille for adjustment of high
frequency response to suit the application. No additional closely associated
auxiliary equipment required.
Peak -free response
h 15,000 cgs.
Output -57 db.
Omnidirectional.
Acoustically treated
grille minimizes wind
and breath blasts. E -V
Acoustalloy diaphragm.
Available in 50, 150
or 250 ohms.
Non -reflecting gray
finish. Size: 14e" diam.
644" long. Net wt:
642 oz. 30 ft. cable.
Supplied with neck
cord and support Clips.
Model 646. list, $140.
40
Model 416 Desk Stand.
1.1.1 $5.
Normal Trade
Discount Applies
Available from E -V Authorized Distributors
Ititle registered U. S. Pat. OR.) la published monthly by Radio Blagaelnes, Inc., Henry A. Schober, President;
McProud, Secretary, Executive and Editorial Offices, 204 Front St., Mineola, N. Y. Subscription rates -U. S.,
Possessions, Canada and Mexico, $4.00 for one year, 87.00 for two years, all other countries, $5.00 per year. Single
copies 50e. Printed In U. S. A. at Business Press, Inc., 10 McGovern Ave.. Lancaster, Pa. All rights reserved. Entire
contents copyright 1955 by Radio Magazines, Inc. Entered as Second Class Matter February 9, 1950 at the Post Office,
Lancaster, Pe. under the Act or March 3, 1879.
AUDIS
C. G.
RADIO MAGAZINES, INC., P. 0. Box 629, MINEOLA, N. Y.
AUDIO
JANUARY, 1955
Write for Bulletin No.
RECTO VOICE,
201
INC.
BUCHANAN, MICH.
1
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TRANSISTOR &
DIGITAL COMPUTER
AUDIO PATENTS
TECHNIQUES
applied to the design, development
and application of
AUTOMATIC RADAR DATA
PROCESSING, TRANSMISSION
AND CORRELATION IN
LARGE GROUND NETWORKS
ENGINEERS
&
PHYSICISTS
Digital computers similar to the successful
Hughes airborne fire control computers
are being applied by the Ground Systems
Department to the information processing
and computing functions of large ground
radar weapons control systems.
The application of digital and transistor
techniques to the problems of large ground
radar networks has created new positions
at all levels in the Ground Systems Department. Engineers and physicists with experience in the fields listed, or with exceptional
ability, are invited to consider joining us.
RICHARD H. DORF"
IT IS UNFORTUNATE that broadcast stations,
both FM and AM, are forced to have
limiting amplifiers somewhere in the
system, usually at the transmitter. The reason, of course, is that oves-modulation must
be prevented despite vagaries of performers
and incidental noises which, but for the
limiter, would drive the modulator into distortion and FCC unhappiness. The reason
for the adjective "unfortunate" is that in
some cases limiting tends to reduce the
sound quality of the result, particularly on
FM. We have in the past in this space decried the tendency of some operators to
crank studio gain up with the idea of keeping a high modulation level and letting the
limiter skim off the top, and we will again
offer to shoot on sound the boys at the
knobs who make a pp indistinguishable
from a if.
Aside from music, however, some dramatic sound effects, such as pistol shots, are
reduced in effectiveness by normal limiter
action. A pistol shot is a high- intensity but
very short-duration sound. If the height of
the pulse it creates is levelled off by a fast acting limiter to the normal peak of most
program material, the shot sound loses its
effect, since the sound power created by a
narrow pulse is small and it must have abnormally high peak amplitude to sound
loud.
To cure this defect in usual limiters, Jarrett L. Hathaway and Raymond E. Lafferty have invented and assigned to RCA
s Audio Consultant, 255 W. 84th St.,
New York 24, N. Y.
an improvement which acts as a limiter
should except when a high -intensity, shortduration pulse hits it. Such pulses are allowed to go through. The patent is numbered 2,692,306, and the schematic diagram
the patent gives (with a few additional
notations) is shown in the Fig 1.
The audio signal goes first through a
standard voltage -amplifier stage, which is
shown as a box since it is conventional.
From there it goes to a 6J5 V, connected as
what the inventors call a phase inverter and
this column vowed long ago to call a phase
splitter. R, and R, are the equal -value plate
and cathode resistors.
The two phase-opposed signals go next
through blocking capacitors C, and Ca to
the control grids of two 6SA7's, the plates
of which are connected to the ends of the
output transformer in the standard push pull arrangement. This is not a power
stage; the transformer secondary normally
drives a push-pull power- output stage.
The control grids of the 6SA7's are
biased by a negative voltage source, G-,
through grid leaks R. and R,. The screens
are supplied with positive voltage through
potentiometer R,, the arm of which can be
adjusted for tube balancing. The cathodes
and suppressor grids are grounded.
The 6SA7 is a pentagrid tube normally
used as a converter or first detector in radio
receivers but also often used as a gain-control stage in compressors and expanders. It
is so convenient for this purpose because the
third grid, which is used for level control,
is effectively shielded by grids 2 and 4 from
the control grid and from the plate. By ap-
fields include
6SA7
V2
B+
TRANSISTOR CIRCUITS
DIGITAL COMPUTING NETS
MAGNETIC DRUM AND CORE MEMORY
LOGICAL DESIGN
PROGRAMMING
VERY HIGH POWER MODULATORS
AND TRANSMITTERS
R2
C2
AMP
STAGE
AF IN
OU T
R1
Et
6SA7
V3
Bt
!IN
NE--48
Scientific and Engineering Staff
45V
CATHODE
RESEARCH AND
DEVELOPMENT LABORATORIES
Culver City, Los Angeles County, California
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IN54
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HUGHES
OUTPUó
Ci
V1
INPUT AND OUTPUT DEVICES
SPECIAL DISPLAYS
MICROWAVE CIRCUITS
Bto-álI
RS
C
óJ5
C3
R6
-
OUT
-
r
6J5
v4
CONTROL
AMP RECT
(6SR7)
FILTER
R7
-
C4
6.SV=E2
Relocation of applicant must not cause
disruption of an urgent military project.
Fig.
1.
AUDIO
2
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AmericanRadioHistory.Com
JANUARY, 1955
plying a d.c. signal to grid 3, the electron
flow from cathode to plate can be varied,
resulting in a control over the gain of the
stage.
The d.c. for this purpose is derived from
a control amplifier and rectifier which is
conventional and is shown in block form.
This stage may use a 6SR7, which is a
duo-diode- triode, the triode amplifying and
the diodes rectifying the amplified signal.
This control stage derives signal from the
plate of V, er V, (V, in the drawing), so
that the d.c. emerging from the stage is
proportional to the r.m.s. level of the audio
signal developed at the output of the push pull V.-V, stage. The control rectifier is
wired so that the d.c. provided is negative.
This is applied to the third grids of both
6SA7's. As a result, an increase of signal
level out of the 6SA7's causes an increase
in negative d.c. out of the 6SR7. Applied to
the third 6SA7 grids, the d.c. causes a reduction in 6SA7 gain, reducing the output
level. The control can never, of course,
reduce 6SA7 output to zero, since then
there would be no voltage to excite the
6SR7 control stage.
In practice this is a special kind of feedback loop which tends to keep the output of
the amplifier from varying too greatly. If
some sort of a delay is incorporated in the
6SR7 stage to prevent it from working
until the output level exceeds a certain
threshold, the circuit may be designed with
a high control -stage gain for use as a limiter. If there is no delay and control -stage
gain is moderate, it is simply a volume
compressor.
The filter across the control -stage output
tends to remove a.c. ripple from the rectified signal so that it does not act as simple
audio feedback, as well as to give a short
delay so that the gain of the amplifier is
not cut instantly giving an unpleasant sound.
In this invention the delay is very short,
about 1 millisecond.
As described up to this point, the circuit
may be that of a standard limiter, and it
will, of course, limit the amplitude of such
sounds as a pistol shot, with the loss in
dramatic effect which we mentioned earlier.
However, additional circuitry is provided.
Signal is obtained from the cathode of
V, and fed through a crystal diode and
capacitor C, to the grid of V,. The diode is
present to act as a delay. Its anode is biased
6.5 volts negative by voltage source E,. Because of the combined action of the V, bias
source E, and the tube cathode current, the
cathode of V,-and the cathode of the
1N54 -is 4.5 volts positive. Thus there is
normally no conduction through the diode.
However, when an audio peak comes along
which in 24 db or more above an established
"threshold" value, the cathode of the 1N54
goes sufficiently negative to allow the peak
to pass through it and develop a pulse
across diode load resistor R.. R. is bypassed to ground through C, and R, is a
bias isolation resistor.
The pulse across R, is coupled through
C, to the V, grid. Only rather narrow
pulses can pass through C, since it has a
small value and will not pass slower voltage changes; the grid of V, is therefore not
responsive to large peaks unless they contain a high-frequency component as a pulse
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eliminates turntable rumble, amplifier overload, low frequency hum.
Plus 2 - position bass boost
turnover: 250 cycle for voiced
selection programs; 350 cycle
for concerts or where bass
reinforcement is desired.
...
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Compare the audibly better performance
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The SARGENT-RAYMENT Co.
Oakland 20, California
electronics since 1926
1401 Middle Harbor Road
Artisans
in
does.
AUDIO
-
Dual concentric treble
JANUARY, 1955
3
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E
The negative grid pulse on
V+
produces
a positive pulse at the plate. This is rather
large, since the plate resistor has a high
value and the plate voltage is normally low.
The positive pulse is large enough to ignite
the NE -48 neon lamp, transforming it from
an open circuit to a rather low resistance,
and passes to the No. 3 grids of the 6SA7's,
right along with the large negative pulse
from the 6SR7 stage which has also resulted from the high -amplitude sound. The
another first from
SONOTONE
positive and negative pulses tend to cancel.
Therefore, the 6SA7 gain is not reduced,
and the pistol shot or other high-amplitude
pulsed sound goes through without reduction in level.
What the inventors have done, therefore,
is to use a standard method of limiting,
but to incorporate an auxiliary circuit to
cancel the limiting action when a short,
high pulse comes through. The additional
circuitry required for this special purpose is
minimal and would not be important in a
broadcast limiting amplifier, but it appears
to do the job. Of course there are occasions
when other sounds of a pulse nature might
come through unwanted, and a switch can
easily be installed to cut off the auxiliary
circuit at will, perhaps by simply removing
plate voltage from V4.
There isn't much more detail in the
patent, but you may examine it yourself
by sending 25 cents, along with the patent
number, to The Commissioner of Patents,
Washington 25, D.C.
wide -range
high -compliance
single -needle ceramic cartridge
Here at last is a high fidelity cartridge at a moderate price,
available in either of two needle sizes
one for 45 and 33% rpm, the other for 78 rpm.
-
Performance is at the same high level as the world- famous
Sonotone "Turnover."
Send coupon for free bulletin showing the exceptional specifications
of this new cartridge.
ELECTRONIC APPLICATIONS DIVISION
SONOTONE CORPORATION
Jan. 20-21- Symposium on Printed Circuits, sponsored by R.E.T.M.A. Univ.
of Penn. Auditorium, Philadelphia, Pa.
Feb. 10-12- Southwestern region of the
I.R.E. seventh annual conference and
electronics show, Baker Hotel, Dallas.
Feb. 10-13 -Audio Fair -Los Angeles,
Alexandria Hotel, Los Angeles, Calif.
Feb. 17- 18-National Conference on Transistor circuits, Irvine Auditorium, Univ.
of Pennsylvania, Philadelphia, Pa. Registration, W. J. Popowski, MinneapolisHoneywell Regulator Co., 176 W. Loudon
St., Philadelphia 20, Pa.
Elmsford, New York
Mar. 21-24--Radio Engineering Show
and I.R.E. National Convention, Kings bridge Armory, N.Y.C.
SONOTONE CORI'ORATION, DEPT. A
ELMSFORD, N. Y.
Please send me free bulletin describing your new 1P Cartridge.
May 26-27- Electronic Components Conference, Los Angeles, Calif.
NAMF
ADDRESS
APT
CITY
STATF
L
May 16-19- Electronic Parts Distributors
Show, Conrad Hilton Hotel, Chicago.
Sept. 30 -Oct. 1 -2-The 1955 High Fidelity
Show, Palmer House, Chicago.
AUDIO
4
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JANUARY, 1955
At
the Chicago, New York
and Boston High Fidelity Shows
More People Asked This Question Than Any Other:
"Which Rek-O-Kut Turntable Shall
Buy...
I
the RONDINE, the RONDINE Deluxe or the RONDINE Jr.?"
In previous years, the question was: "Shall I buy a turntable
or a record changer ?" And about eight months ago we released
an advertised statement in answer to this question. Thus far,
more than 40,000 people have requested reprint copies of
this statement.*
This year, we presented the Rondine
line in Chicago. At the very first showing we knew that we had passed the
severest test. The acclaim was over-
whelming. It exceeded our wildest
hopes and expectations. And the pat tern has since been the same ... New
Boston
everywhere. Now
York
the one question that stands out is:
"Which shall I choose: the Rondine
at $69.95, the Rondine Deluxe at
$119.95 or the Rondine Jr. at $49.95 ?"
...
...
The RONDINE Deluxe (3- speed)
priced at $119.95 is powered by a hysteresis motor. The speed of a hysteresis
motor is synchronous with the frequency of the line current. Like the
motor of an electric clock (which it resembles in principle only) the speed is
constant and accurate to the split
second. It has the least vibration of any
motor, and therefore, the least rumble.
The Rondine Deluxe represents the very
finest equipment available. It is the indicated choice where the system and
speaker with which it is to be used are
capable of reproducing low frequencies
to below 40 cycles.
*You may obtain a reprint of: "Shall
I Buy a Turntable or Record
Changer?', plus complete Rondine
specifications, by writing Dept. VA -1.
AUDIO
The RONDINE (3- speed) priced at
$69.95 is driven by a specially built
4 -pole induction motor. Vibration and
noise have been effectively reduced
through the use of selected motor bear-
Select the Rek -O -Kut turntable suitable
for your particular needs. For, whether
you choose the Rondine, the Rondine
Deluxe or Rondine Jr., you can expect
rugged, reliable construction and precision performance. You can expect con-
-
stant, steady motion freedom from
wow. and flutter and you can be sure
of smooth, quiet operation.
So certain are we that the speeds, once
set, are critically accurate that we make
no provision for external adjustments
by you
except for occasional maintenance. And we include a built -in strobe
disc capable of revealing as little as
Moth of 1% speed discrepancy. We
know of no manufacturer who places
greater reliance upon the dependability
of his product.
-
-
ings, dynamically balanced rotors and
perfectly concentric drive pulleys. Each
motor is individually tested for speed
under load conditions, and permanent
compensations are introduced for accurate timing. Rumble content is so low
that in a system capable of reproducing
Basically, this is all the result of special40 cycles, it can be detected only with
ized experience gained over many years
appreciable bass boost. The Rondine in the service of recording and broadmeets the requirements of most high cast studios. It is this store of engineerquality home systems.
ing 'know-how' which has enabled us
The RONDINE Jr. (2- speed) priced at
$49.95 is driven by the same type of
motor as the Rondine, and what has
been said for the Rondine is equally
applicable here. Where the user can dispense with the 78 rpm record speed, the
Rondine Jr. represents true economy
without the slightest sacrifice in quality
-
over the Rondine. It is the ideal home
system turntable where there is no accumulated 78 rpm library, and where
future record purchases will be limited
to the modem 333/4 and 45 rpm types.
to develop a completely simplified
mechanics in turntable design; to
streamline every operation with no more
parts than are absolutely essential for
efficient, functional performance. These
efforts have been repaid in enabling us
to achieve greater noise reduction, easier
maintenance and added years of useful
service.
No matter what turntable or record
changer you now use, a Rek -O -Kut
Rondine any one of the three will
make a marked improvement in the performance of your high fidelity system.
-
-
REK O KUT COMPANY
Makers of Fine Recording and Playback Equipment
Engineered for the Studio
Designed for the Home
3e -01 Ctuoens boulevard, Long Island City 1, N. Y.
JANUARY, 1955
5
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in
THOR5
exclusive
direct -drive
the difference
to the ear
NEW LITERATURE
Allied Radio Corporation, 100 N. Western
Ave., Chicago 80, Ill., recently announced
publication of a completely revised edition
of "A Dictionary of Electronic Terms"
which contains more than 3500 terms used
in television, radio and industrial electronics. Edited by Gordon R. Partridge,
Ph.d., associate professor of electrical
engineering, University of Purdue, the
publication answers the need for an accurate, up -to -date reference source of words
used in all branches of electronics. Definitions range from many words no longer
in use, retained for historic reasons, to
the new language of color television and
the electronics of nuclear physics. Containing more than 160 illustrations and many
diagrams, this book will be helpful to
everyone interested in electronics. Requests for copy should specify stock
number 37 -K -766 and must include s
remittance of twenty-five cents.
á
...`
is
here...
Bound EQnipment Division, StrombergCarlson Company, Rochester 21, N. Y.,
recently issued two publications of specific
interest to users and distributors of audio
equipment. One is a colorful pocket -sire
folder which illustrates and describes the
complete line of the company's Custom 400
hi -fi components and cabinets. The other
is a 6 -page catalog -type folder featuring
the division's full line of amplifiers, microphones, speakers, housings, re- entrant
horns, drivers, and accessories for public -
E 53 PA
Transcription
Turntable
address use.
Karvey Radio Company, Inc., 103 W.
43rd St., New York 36, N. Y., devotes five
pages of its new audio equipment catalog
to an explanation of high fidelity which
is intended to assist the reader in selecting
Rubber belts, pulleys, idler wheels and other wearable elements of friction -drive turn- components for his home hi -fl system.
The catalog consists of 34 pages highly tables contribute to unwanted noise and pitch variation. There are none of these in a Thorens illustrated and filled with descriptive material and price information on equipment
. instead the ideals of silence and speed regularity are realized by a direct -drive motor of most leading manufacturers. Copy will
be mailed free on request.
whose speed is perfectly controlled by a governor. You can manually adjust the speed for
Amperex Electronic Corporation, 230
"exact pitch" on 78, 45 and 33 -1/3 rpm records. Furthermore,
is not affected by heat Duffy Ave., Hicksville, N. Y., in a colorful
spy
6 -page folder, announces a special group
of premium- quality tubes with a guaranteed minimum life of 10,000 hours. Designed for use in equipment where unsupervised, uninterrupted operation is
Acting through an electronically balanced rotor shaft further silenced by a mechanical essential, the new tubes have
been fieldin such applications as telephone
filter, the turntable is kept free of wow or waver. Only direct -drive permits better positioning tested
equipment, coaxial cable telephony, beam
and machining of fast- rotating parts, as well as better vibration dampening thus primary transmitters, and radar.
Altus Lansing Corporation, 161 Sixth
sources of rumble are eliminated. In test, a Thorens turntable maintains a noise level of
Ave., New York 13, N. Y., provides detailed
information on high -fidelity equip-48db
truly unparalleled performance indeed.
ment it manufactures in a new catalog
which will be mailed on request. The booklet covers AM -FM tuners, preamplifiers,
amplifiers,
speakers, enclosures, and variFor first installation or replacement, it is certainly worth your while to hear the quality ous accessories.
Also the catalog contains
of Thorens turntables, players and changers before you make your choice. You will agree, a great deal of information which will
prove helpful in selecting the various
we know, that at last
components for a complete high -fidelity
the difference to the ear is here!
music system.
or load conditions!
-
...
...
At leading
CD-43
high fidelity
departments
Write
for latest
literature:
THORENS COMPANY, DEPT. A, NEW HYDE PARK, N. Y.
6
The Turner Company, 929 17th St., N. E..,
Cedar Rapids, Iowa, covers microphones.
pickup cartridges, microphone interiors,
and microphone accessories in a new
general catalog which is now ready for
distribution. In a unique departure from
usual catalog make -up, names and addresses of all Turner representatives are
listed on the front cover. Illustrated and
described are 40 microphone models of
various types and impedances, with stock
numbers assigned for ease of ordering.
Requests for copy should specify Catalog
\.
961 -A.
AUDIO
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AmericanRadioHistory.Com
JANUARY, 1955
I
IN TV
1
FM
AM
BROADCASTING
I
IN PUBLIC ADDRESS SYSTEMS
Hotel Ballrooms
Auditoriums
Stadiums
Industrial Paging
School Installations
Wired Music Applications
IN RECORDING STUDIO
APPLICATIONS
Tape Recording
Disc Recording
Sound -on -Film Recording
I
I
I
I
I
q==
I
I
1
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L_
----J--- =--_------
UNI-LEVEL AMPLIFIER
you have the answer to any audio engineer's prayers. The G -E
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Its expansion- compression characterisHERE
you can count on the BA -9 -A to eliminate
"blasts ". You'll get higher average output. You'll save time and effort while performance is greatly improved.
Mail this coupon and complete specifications will be sent to you immediately.
tics smooth out and increase average
levels for all types of program material.
Yes, in any sound system that's troubled by variations in voice intensity,
73ogress Is Our Most important Pioduct
GENERAL
AUDIO
I( ELECTRIC
General Electric Co., Broadcast Equipment,
Sec. X4415, Electronics Park, Syracuse, N.Y.
Please send me information and detailed specs
on the new G -E Uni -Level Amplifier.
NAME
ADDRESS
CITY
JANUARY, 1955
STATE
7
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AmericanRadioHistory.Com
FOR LOWEST MICROPHONICS AND
LETTERS
HUM IN HIGH -GAIN CIRCUITRY
Balancing Tubes
Suc:
I should like to call attention to a method of balancing the
sections of dual triodes as reported by R. E. Aitchison (Nature,
174, 704. 1954). He claimed that 50 per cent of the dual triodes
(12AU7, 12AX7, etc, with center -tapped heaters) could be
balanced by a heater -voltage adjustment of 5 per cent. The
method consists of changing cathode emission in the tubes by
connecting a potentiometer of a few ohms resistance across
the heaters and adjusting the slider to obtain balance. One leg
of the supply voltage is connected to the slider and the other to
the heater tap.
A similar expedient could be used to balance separate tubes
in an output stage, for example:
FREDERICK KAVANAGH,
1826 N. Pennsylvania St.,
Indianapolis 2, Ind.
Improving (?) Loudspeaker Performance
12AX7 TWIN TRIODE VOLTAGE AMPLIFIER. Picks up low level
signals without introducing objectionable hum.
5881 BEAM POWER AMPLIFIER. Provides the ultimate in re-
liability where the 6L6
is
normally called for.
Premium performance to satisfy the most critical hi -fi enthusiast is engineered
into these two popular Tung -Sol Tubes. Ratings, uniformity and dependability
of the I2AX7 and 5881 demonstrate that Tung -Sol quality control methods can
achieve in regular production the performance levels required for highest
quality equipment.
TUNG -SOL ELECTRIC INC., Newark 4,
N.J.
SALES OFFICES:
Atlanta, Chicago, Culver City (Los Angeles), Dallas, Denver, Detroit, Newark, Seattle.
Tung-Sol
ture Tubes.
makes All -Glass Sealed Beam Lamps, Miniature Lamps, Signal Flashers, PicR. dio. TV and Special Purpose Electron Tubes and Semiconductor Products.
SIR:
The notion put forward by Weems in the September, 1954
issue under the above title (less the "2 ") is as old as the history
of dynamic speakers, and it doesn't work. At least, while it may
reduce the bass resonance of the speaker, it introduces other
forms of distortion that make the speaker so treated not in any
way high - fidelity.
The completely flexible outer surround was a British idea;
the first flexible surround on an American speaker was on the
1926 Rice -Kellogg, but it wasn't all that flexible. Among early
British dynamics with cloth surrounds were the 1927 G.E.C.
(which had wire spoke rear suspension!) a 1927 Baker, and the
1927 Hartley- Turner. At a later date other speakers appeared
and many articles appeared in the British technical press of those
days, for making dynamic speakers at home was a well- established hobby, it being generally considered that the professional
designers didn't know how to do it. The flexible cloth surround
was "It," but the home designers didn't know how to test the
"It" speaker. There is a fatal snag in unlimbering the cone
in a conventional magnet design.
If the cone is free to move, the voice coil will pass into a
weaker magnetic field on the first half -cycle of a sinusoidal signal ; it will not return to the norm on the second half -cycle
because it is in a weaker field. What happens is called electromechanical rectification. If the rear suspension is stiff enough to
pull the coil back into the gap, the application of a two -component signal will cause modulation of the higher frequency by
the lower- simple intermodulation distortion. If, now, the
suspension is stiff enough to haul the coil back to the norm,
but free enough to give a low bass resonance, application of a
sinusoidal signal will still cause electro- mechanical rectification
because the magnetic field in the usual design of magnet is much
more intense behind the front magnet plate than before it. The
total result of loosening the suspension is, therefore, to introduce
two forms of distortion -electro- mechanical rectification, which
desensitises the speaker on every loud signal, and intermodulation distortion whenever a low- frequency signal accompanies
a high- frequency signal.
This can be proved by actual test and demonstration, but it
is a simple matter to check up at home. Subject a speaker, treated
in the way described by Weems (and others) to a nice big output from an organ record which gives highs while it is also
giving well -recorded pedal organ, and the result is audibly
distressing-best described as "burbling." The only way of
avoiding this is to design the magnet so that some loss of sensitivity must be put up with, since only so much flux can be
gotten out of a limited diameter of center pole.
H. A. HARTLEY,
62, Latymer Court,
London W.6, England.
Literary Trash!
Sir:
Clownish articles such as "Hi -Fi- Manship at the Fair" by
Charles Sinclair are literary trash, should occupy no space in
AUDIO, and are not worth reading.
William Paul Thompson,
RADIO, TV AND SPECIAL PURPOSE TUBES
(Opinion or fact? En.)
Audio Technician,
Union Theological Seminary,
New York 27, N. Y.
AUDIO
8
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
INGS CAN'T BE RUSHED
SOM
IT TAKES TIME
TO GO
FROM RED TO GREEN
and it takes time to make a good recording disc...
Know -when is as vital as know -how in making a fine recording disc. This most
sensitive "instrument" must be handled with special care at every point -from
original preparation of materials down to the method of wrapping.
Slam -bang mass production could never achieve anything like the flawless
recording discs produced by Presto. For Presto takes all the time in the world
make Presto discs the best -performing and permanent in the world.
-to
PRESTO GREEN ORANGE BROWN
AND WHITE LABEL DISCS ARE
USED THROUGHOUT THE
WORLD -WHEREVER
FINE RECORDING IS DONE
RECORDING
TIME -CONSUMING
STEP
IN MAKING A PRESTO
RECORDING DISC
1
recording di<ci. start ssith an
aluminum base. The slightest flaw in the
aluminum shows up in the finished disc.
That's why Presto takes the time to specify
and inspect every aluminum blank. It must
be milled precisely. Thickness must be
100% uniform. Circles must be die-cut
100% perfect. The approved aluminum
discs go into production. Edges are
burred. Platters are cleaned. And every disc)
is polished to shimmering smoothness
the slow-but-sure way by hand. Presto
Recording Discs take time to make. That's
why they are well worth your time
and money!
CORPORATION
PARAMUS, NEW JERSEY
Export Division:
Canadian Division:
WORLD'S
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AND
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25 Warren Street, New York 7, N. Y.
Instantaneous Recording Service, 42 Lombard St., Toronto
-
DISCS
HAROLD LAWRENCE
Living with Bach
LIKE SHAKESPEARE and Einstein, Johann
Sebastian Bach is universally recognized as a "great." Then he is put on a
The Completely New
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shelf -or, rather, a pedestal-and promptly
forgotten for all practical purposes. In the
mind of the layman, Bach is conjured up in
an unfortunate set of impressions: here was
an austere and unapproachable master who
wrote ponderous fugues, involved counterpoint, and pietic cantatas. With few exceptions, the name commands respect but not
reverence. In a sullen hush, the average
music lover will sit through performances
of a keyboard suite, cello sonata, or some
other less familiar composition. When
asked during intermission what he thought
of this or that piece, he may lack the courage to admit that he found it a crashing
bore. Although a number of soloists and
groups make Bach come alive in interpretations that reveal a love and comprehension
of the composer and his period, too many
performers (and, as a result, the bulk of
the listening public) are still in the Romantic age in their attitude toward the Eisenach
master.
The inventory of Bachian misinterpretations, ranging from pecadillos to lollapaluzas, is almost long enough to fill the pages
of The Red Book. Here are a few examples.
The British tradition of choral singing is a
fine thing except when it gets out of hand
numerically, in which case it can transform
a work like the Saint Matthew Passion into
something more suitable for a sports arena
than for a church or concert hall. Pitted
against a vocal army, the instrumental
forces are virtually drowned out except in
solo movements. In the opening of the B
Minor Mass, the flutes and oboes carrying
the flowing contrapuntal line would, similarly, be reduced to an ineffectual murmur.
And, to compound the felony, a nineteenthcentury organ will muddy up the continuo
part; the concertmaster (probably of the
Auer school) will stake of the violin part
in the Gloria a miniature Wieniawski concerto, tremolo and capricious phrasing included; and last but not least, let's not forget the "massacre of the ornaments" -that
abysmal ignorance of the expressive meaning of Baroque embellishments such as the
turn, trill, mordent, etc.
Then there's the pianist to whom nothing
counts but the "theme." This he will bang
out for all it's worth in such works as the
Liszt transcription of the Organ Prelude
and Fugue in A Minor. Many other musical events may be taking place throughout:
x`
26 West 9th St., New York 11, -N.Y.
counter themes, fascinating modulations,
dynamic ebb and flow. But all these are
just flotsam and jetsam when the "subject"
comes along. The effect is as subtle as inserting a trumpet part (without mute) into
the third movement of the Debussy String
Quartet. An audible "twist of the dial" and
the volume drops; the stage is set, and
we're in for yet another repetition of the
theme.
Prominent among the Bach killers are
the "hyphenaters"-those composers and
conductors who want to help the cause
along by popularizing certain keyboard
works and chorale preludes. To them, the
Baroque organ is a "bubble- and-squeak type
of instrument" ; the harpsichord sounds like
the "ticking of a sewing machine"; and the
trio sonata is a form of eighteenth- century
potted palm music. Calling upon a battery
of percussion instruments, enough brass to
scare up a rousing performance of John
Philip Sousa's Semper Fidclis, and a full
complement of strings that would have
satisfied the orchestral palette of Gustav
Mahler, the transcribing maestro brings his
audience a version of a Fantasia and Fugue
that should send Bach spinning in his grave.
On the other extreme is the devoted
Baroque performer with a built -in metronome and a flair for turning the most inspired composition into the dullest finger
etude straight out of Czerny. He is generally far more scrupulous than the hyphen ater about obeying the composer's instructions (whenever they are plainly indicated)
and he will take pains in tracking down the
Urtext, or original manuscript. But the result is a dryasdust rendition that thoroughly
alienates the music lover who has not yet
gotten into early eighteenth-century music.
Even when Bach's cantatas are performed with a healthy respect for proper
balance, size of choral and instrumental
forces, we have to contend with the "glee
club" flavor which is so deeply ingrained in
American culture. The precision and discipline that are its main characteristics are
fine, but one is too conscious of the football
field, college reunion, and campus songfest.
Confronted with these musical crimes in
the name of Bach, it is no small wonder
that the discophile often loses interest in all
but a handful of Bach's works-and these
usually in "free" arrangements. All of
which makes his initial plunge into the
vast ocean that is Bach's list of works more
and more a dubious venture. Where to
start ? Tackling the Schwann catalogue's
Bach section in alphabetical order is defi(Continued on page 67)
AUDIO
10
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
CABLE: "AUDIOGERSH" NEW YORK
AUDIOGERSH
CORPORATION
23
N
P
A
R
K
P
L
A C
E
WORTH
4
E
W
Y O
R
K
7.
N.Y.
-8585
January
AN OPEN
LETTER TO ALL
1,
1955
MIRACORD XA100 USERS
We are pleased to report that the nation -wide acceptance given
our MIRACORD XA100 has been unprecedented and, naturally, most
gratifying.
This is our sincere "thank you" to each of you who has purchased
a MIRACORD XA100 and written us compliments and constructive
criticism.
We have heard from some of you that certain records do not always
drop on the "Magic Wand" spindle furnished with the first units
we delivered. The difficulty was caused, in the main, by imperfectly centered record labels projecting over the center hole
and interfering with the precision action of the "Magic Wand ".
This problem has been solved. We have made a slight but significant change in the "Magic Wand" dimensions - yet have maintained
the critical tolerances and unique principle which prevents any
of your records from developing enlarged or out -of -round center
holes. As a matter of fact, you will soon see photographs of records that have been dropped 100,000 and 500,000 times on the
MIRACORD XA100 with absolutely no damage to the record.
We want you to benefit from the new "Magic Wand" without delay!
If you have a MIRACORD XA100 automatic record changer that does
not drop records to your complete satisfaction, we will send you
the newly dimensioned "Magic Wand" at no charge whatsoever in
exchange for your present spindle.
We are happy to offer you this tangible evidence of our policy
of "satisfaction guaranteed ". Your enjoyment of the MIRACORD
XA100 is truly music to our ears - and we know it is to yours.
Cordially,
Milton
D.
Thalberg, President
AUDIOGERSH CORPORATION
EXCLUSIVE DISTRIBUTORS IN THE UNITED STATES FOR
AUDIO
JANUARY, 1955
RECORD PLAYERS
11
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AmericanRadioHistory.Com
EDITOR'S REPORT
DEFINITION OF "HIGH FIDELITY "
-II
-a
ARE INDEBTED to Charles V. Kettering
former New Yorker who has deserted the
metropolis for a life as manufacturers' representative in the Rocky Mountain area-specifically in
Aspen, Colorado -for a little envelop stuffer to, in his
words, "try to offset the misconceptions and downright
ignorance on the subject, and restore some of the lost
confidence of the buying public in purveyors of hi -fi
merchandise -the real thing." His leaflet says:
"What is this thing called High Fidelity (hi -fi for
short) of which we hear so much ? What does it mean
in simple language ?
"Take one word at a time
"'High'-define it as 'a high degree of.'
"'Fidelity'-use one word, 'faithfulness.'
"But 'faithfulness' to what ? There is only one answer
-'faithfulness to the original sound.'
"So the phrase 'High Fidelity' becomes 'a high degree
of faithfulness to the original sound.' Simple, isn't it?
It can be made even simpler by using only one word,
'Naturalness.'
"The term 'High Fidelity' is applied, of course, to
reproduced sound such as from a phonograph record,
tape recording, radio, TV, or a public address system.
Make your own test-it's easy.
"Does the symphony orchestra, dance band, chorus,
single instrument, or voice coming from a recording,
radio, or TV sound 'natural,' much as it does when
you hear it 'live' in the concert hall or studio? Can you
pick out the various instruments of the orchestra or
band as you hear them playing together in the record
and trace any given instrument (violin, flute, oboe,
clarinet, trumpet, string bass, brass bass, etc.) throughout the composition, by its distinctive quality? If you
can do that, your reproducing system must be a pretty
good one.
"If on the other hand you hear only a 'mass' of high
sounds, some more in the middle range without definite
character, and a lot of low 'boom boom' in the bass
range, and if, as is usually the case, the tone control is
turned down to make the music sound more pleasant,
the reproducing set or system can stand considerable
improvement.
'There are many degrees or levels of performance
in seeking perfection. Absolute perfection has never
been attained and likely never will be. However, fairly
close approaches have been made in laboratories at
tremendous cost in effort and equipment. Fortunately
for the average person, this research and development
of various components has resulted in quantity manufacture at modest prices. By choosing wisely, with the
help of an expert, very fine sound reproducing systems
can now be assembled from the best products of the
various manufacturers for only a few hundred dollars.
One of the many important reasons for the assembling
of fine 'components' into a sound reproducing 'system,'
aside from the finer quality, is the ease with which
improved components (preamplifier-equalizer, power
amplifier, turntable, pickup, speaker) can be substiWE
-
tuted as they become available, and thus keep up to
date at a minimum cost. This is next to impossible with
manufactured 'sets' commonly available, bearing a hi -fi
label.
"The manufacture of fine quality high-fidelity equipment has become highly specialized in a very short time.
Some specialize in the design and building of receivers
for radio and TV ; others in preamplifier -equalizers and
power amplifiers ; others in turntables, tape recorders,
loudspeakers, pickup arms and cartridges, as dictated
by the technical background and experience of the particular manufacturer.
"From the products of these manufacturers, the buyer
is offered the finest selection of components in a fairly
wide price range. Many individuals buy and assemble
their own home systems to suit their particular needs
or preferences -usually with more or less advice and
assistance from technically trained radio and service
men.
"A sound reproducing system can be only as good as
the weakest unit or 'link' in the chain of components.
For example, if the pickup does not correctly trace the
minute undulations of the record groove, the result is
distorted unnatural sound ; and the other units of the
system, no matter how fine, are powerless to improve
what the pickup feeds to them and make it sound 'natural.' Likewise, a poor preamplifier- equalizer, power
amplifier, turntable, or speaker will limit the finest
pickup in the world and reduce its output to the quality
level of the weakest unit.
"Pickups and loudspeakers, the beginning and the
end of the reproducing cycle (for records) are most
often at fault, even in very expensive systems, and great
care must be used in selecting them. The other components present special problems, and each could be discussed at length. The purpose here is to point the way
to better evaluation of the claims for 'hi-fi'--namely,
to judge by the sound that comes from any given reproducing system (or combination of components) the
degree to which it 'faithfully reproduces the original
sound.' And
is important to listen as often as possible to 'live' music in order to provide a correct basis
for judging...."
Thank you, Mr. Kettering. Please join our growing
circle of AUDIO Lifers, with our compliments.
-it
AUDIO FAIR MANAGER LEAVES AUDIO
Harry N. Reizes, manager ut The Audio Fair and
formerly advertising manager for AUDIO, has resigned
from AUDIO in order to devote more of his time to the
years' biggest audio show. He is also associated with
the Audio Fair-Los Angeles, and last year served as
consultant to the first New England High -Fidelity
Music Show. Mr. Reizes has been advertising manager
since the first issue of AUDIO ENGINEERING 'way back
in 1947.
Management of as large an enterprise as The Audio
Fair is an arduous task, and really demands full -time
attention. Our best wishes go with Harry-and we'll
expect still bigger and better Fairs in the future.
AUDIO
12
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
PICKERING
/ccirtriciges
models
gi.e.JZse./fea.,0
ed ginwe
gUe
240
bbd
L
`.l/1CeelL ...
they are sold separately for all standard arms or
mounted back -to -back
to make up the
famous
PICKERING 260 TURNOVER PICKUP.
The 220 and 240 are engineered to
maximize performance. By comparison they
are without equal ...
MODEL 220 -for 78 rpm records
diamond or sapphire stylus
The
Lighter- 5 1/2 grams
MODEL 240 -for 33' á
and 45 rpm records
diamond stylus only
Smaller -% by
The
MODEL
220 and 240 are
3/4
by
3748
inches
220 and 240
have
Highest Output -30 millivolts /1Ocm /sec.
More Compliance with Less Tracking Force
Lower Overall Distortion
Less Moving Mass
Wider Frequency Response
Mu -Metal Shielding for Less Hum
260- turnover
cartridge for 78 or 33,/3
and 45 rpm records
(the 220 and 240
bock -to -back)
These characteristics have real meaning to those who understand that
maximum performance depends upon components which meet professional
standards. If you wool the best that high fidelity can offer, ask your dealer
to demonstrate the 220, 240 and 260 Pickering cartridges .. .
.%die
/Ila1f /Ia
Y
PICKERING and eompany incorporated
ce
enc As4iGd
vr- Oraftcrei
Oeeanuide. L.L. Meer )brk
PICKERING COMPONENTS ARE PROFESSIONAL QUALITY
dr-g«
O'l
.
.
AUDIO
.
/J
r
aeJe '1,Uh0
Cll>?i
Demonstrated and sold by Leading Radio Parts Distributors everywhere. For the one nearest you and for deta:ied literature; write Dept. A -7.
JANUARY, 1955
13
www.americanradiohistory.com
AmericanRadioHistory.Com
FOR TV
.
.
.
IT DODGES
TROUBLE
Radio Relay station on route between Chicago, Ill.,
and De& Moines, Iowa. Every fifth or sixth rélaying tower is a control station, where high -spéed
There's no way to stop atmospheric changes that
threaten television with "fade." But, for TV that
travels over Bell's Radio Relay System, Bell Laboratories engineers have devised a way to sidestep Nature's interference.
When a fade threatens usually before the
viewer is aware -an electronic watchman sends
a warning signal back by wire to a control station
perhaps 200 miles away. An automatic switching
mechanism promptly transfers the picture to a
-
YOU
CAN'T STOP
switching equipment enables a TV picture to skip
out of a troubled channel and into a stand-by
protection channel faster than the eye can wink.
clear channel. The entire operation takes 1/500
of a second. When the fade ends, the picture is
switched back to the original channel.
This is an important addition to the automatic
alarm and maintenance system that guards Bell's
Long Distance network for television and telephone calls. It marks a new advance in Bell
Laboratories' microwave art, developed to make
your Long Distance telephone service, and your
TV pictures, better each year.
BELL TELEPHONE LABORATORIES
Improving telephone service for America provides careers for creative men in scientific and technical fields.
www.americanradiohistory.com
AmericanRadioHistory.Com
Three -Channel
Preamplifier -Mixer
HAROLD REED
When the equipment required to do a certain job does not exist, or where the requirements are
sufficiently unusual that no standard manufactured equipment could be purchased as a ready made item, there is only one solution-design and build it yourself. The versatility of this small
unit makes it adaptable for testing, experimenting, recording, and many other applications.
THERE ARE OCCASIONS When
It is desir-
able in sound reproducing systems,
not only to employ several microphones of similar type, but to use several
microphones of different types simultaneously. For example, carbon- buttontype microphones may be wanted for
certain applications while other requirements may call for the use of crystal
microphones. Still other sound reproducing activities may dictate the use of
low- impedance moving coil microphones.
The three -channel preamplifier -mixer
described in this article provides for
the use of three of any one of these different types, or any combination of the
three, thus satisfying most any need in
pick -up requirements.
This equipment consists of a three line,
Fig. 2. Rear view of
the preamplifier mixer chassis.
three -channel mixer -preamplifier
with 500 -ohm output suitable for feeding
a low- impedance line or low- impedance
tape recorder input. The 500 -ohm line
output may also be terminated with a
500-ohm resistor and bridged with a
high -impedance input monitor amplifier
and loudspeaker. Also, the terminated
500-ohm output may be used to feed the
high -impedance bridging input of a
recorder. Of course, if the line is already
terminated by equipment of 500 -ohm
input, the 500-ohm terminating resistor
is not required when bridging with a
high -impedance.
A description of the circuit configuration follows, referring to the schematic
1W
47,000
zo
UTC A-I
s
SW
1
AUDIO
v,e
1/2
.ozt^
6SL7
t
02
1
6SL7
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soon
022
MEG
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nSO _
O1
50V
N
o
OUT
ó
.01
f
`
a
50
T50V
A
1w
47,000
20
in Fig. 1.
There are three line inputs wired to
the dual selector switches Sw', Sw. and
Sw,. When a selector switch of any particular channel is set to position 1, the
line input of that switch goes directly
to the grid of the first stage of the preamplifier through the two sections of
the switch. The line input is, therefore,
suitable for use with high -impedance
microphones, such as the crystal type.
In position 2 of a selector switch of any
channel, the line is terminated in the
low -impedance input winding of the
A -11 input transformer, with the high impedance secondary winding going
to the grid of the first stage through
the second half of the selector switch.
This is the setting for use with low impedance microphones. Number 3
position of any input selector switch
is for use with carbon microphones. For
(Continued on page 66)
* 3917 Madison St, Hyattsville, Md.
JT
It
o
VIA
1/2
I
zo
LINE
2SOV
I
UTD
A-11
3
la
1
SW 2
V2A
V2
6SL7
=25oV
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p
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NOTE
LINE 2
0.22
MEG
s
UNLESS OTHERWISE INDICATED,
ALL
RESISTORS ARE 1/2 WATT
01
IW
47,000
1A
Fig. 1. Schematic of the three -channel preamplifier- mixer. Unique feature of this device is
its adaptability to practically any common type of microphone.
JANUARY, 1955
15
www.americanradiohistory.com
AmericanRadioHistory.Com
The MIT Audio Network
DAVID L. KLEPPER
Wired -audio system permits everyone to enjoy a wider variety of records than each
could possibly have in his own collection -and provides operating experience.
IT HAS OFTEN BEEN NOTED by visitors
that MIT is, for a school that is not
a conservatory, a most musical place.
The concert band, choral society, glee
club, and symphony orchestra are very
active, and their concerts are well attended. Couple this interest with one for
the technical aspects of sound reproduction and you have a very high enthusiasm
for high fidelity, an enthusiasm that has
led to the development of the audio line
network.
It was four years ago that two undergraduates, Dave Kessle and Philip
Benkard, decided to share their record
collections by running wires between
their rooms. Soon other students in their
dormitory wanted to be able to listen to
the music played in either room ; and
wires mixed with the ivy throughout the
East Campus Dormitories. The lines
were operated on a single wire, ground
return basis, and all sending and receiving amplifiers had to be securely
grounded to the plumbing system to
avoid hum. The line was usually connected to the speaker output of the sender's amplifier, although some people
went to the trouble of building line
amplifiers, and sent into a high -impedance, high-level input of the listener's
amplifier. A number of a.c.-d.c. radios
were also converted to allow them to receive the audio line signal.
As the number of listeners grew so
did the service given them. After the
two originators of the line left, with
their large record collections, the programming of Boston's FM stations was
regularly scheduled on the line
WXHR, Boston's all-classical-music
station, for almost all their air time;
WGBH, the Lowell Institute educational
station for all broadcasts of the Boston
Symphony and certain chamber -music
concerts; the Metropolitan Opera (when
it was available on FM) and the New
York Philharmonic on weekends.
WBUR, the Boston University station,
provided some classical music programming during afternoons. East Campus
became blanketed with the main audio
line. know as the Runkle line from the
-
Box 523B, MIT Graduate House, Cambridge 39, Mass.
Fig.
The elaborate
system owned
by
Robert
Schwartz, '57, of Burton House, includes a
Fisher FM tuner, Master Audio Control, and
50 -watt amplifier, and a Heathkit preamp and
a 6 -watt Williamson amplifier- the latter
being used only for cueing. Bob's interest is
mainly in popular music but when he feeds the
lines, the quality is professional.
f. A single -line transmission system using ground
as
the return.
dormitory of its two originators, as well
as other audio lines connecting people
not always happy with the Runkle-line
programming. One of these, the "Pops
line" earned quite a few listeners, and
one East Campus dormitory now boasts
a 12 -wire cable, each wire having a
different signal. The low- impedance output of the sending audio amplifiers keeps
down crosstalk.
The technical knowledge necessary to
operate an audio line connecting rooms
located nearby each other with a single
wire is not very great. It has already
been mentioned that a good ground for
all equipment is essential ; also necessary are switching systems to allow an
individual to either listen to or feed a
signal on the line, with precautions
against feedback ; L -pads to control the
speaker volume, allowing the sender to
keep the line volume constant ; and
reasonably high -quality equipment. The
amplifier of the sender can be a normal
feedback audio amplifier. The effective
(not the nominal 4 -, 8 -, or 16 -ohm) output impedance should be low enough to
prevent signal distortion because of
changes in the speaker impedance, a
condition met by all quality home amplitiers today. To prevent shorts and transient switching noises from appearing
on the line a high (10,000- to 100,000 Am) resistor should be in series with
the line to each listener's input; to protect the sender's equipment the line from
his output should be fused (a ifi -amp
fuse will do the job). A typical single wire audio line can be seen in Fig. 1.
Although the low- impedance output
of the audio amplifiers used kept down
hum for a considerable distance along
the Runkle line, in crossing the street
from the Runkle unit to the other East
Campus dormitories a considerable
quantity of power -line buzz and r.f. was
picked up, affecting the transmission
fidelity. Placing the main Runkle line in
a conduit under the street helped this
Fig. 3. Block diagram shows installation in one
AUDIO
16
www.americanradiohistory.com
AmericanRadioHistory.Com
living unit.
JANUARY, 1955
osc
MA=EItilaII
TOTAL
°
DISTANCE ABOUT
I
MUSIC
ViVM
LIBRARY
1
UNDER
CONSTRUCTION
WMIT
(WARE)
Fig. 2. This circuit, with a balanced transmission
line, was used between East Campus and
Graduate House for frequency- response testing.
problem considerably, but even then it
was recognized that eventually balanced
two-wire -line operation would provide
the solution for distant transmission of
music, and the underground line was
laid as a pair.'
Extending The System
Other living groups around campus
began operating their own much smaller
audio systems, and the question of tying
them all together often arose, but the
first attempt to extend the audio lines
outside of East Campus came last summer, when another student and the
writer moved across the Charles River
to Boston. Several listeners on the
Runkle line had thought of the possibility of renting a telephone pair to our
apartment, an idea we welcomed. MIT's
student engineering magazine, Tech Engineering News, now became interested in the project; it had for some
time used a high -fidelity system in its
East Campus office, and the staff members had always appreciated the music
coming to them over the magazine's
connection with the Runkle line.
Now they rented the Bell System pair
and collected each person's share from
us and the East Campus residents on
the audio line. Two 1:1 line -matching
transformers were built for this line
by Mystic Transformers, Winchester,
Mass. ; these not only had to have a flat
frequency response with negligible distortion at normal peak signal levels, but
also had to be unaffected by shorts and
handling by inexperienced personnel.
The line was operated somewhat differently from a normal program line,
a point to be discussed later.
The fall brought efforts toward an
expansion of the audio system throughout the MIT campus. The Institute was
installing additional phone service using
29 -pair cables; student labor removed
installation expenses, and the magazine
received the use of one pair linking the
East Campus dormitories with the
Graduate House. Further expansion
West to Burton and Baker houses, the
' A balanced line consists of two wires
terminated with a transformer at each end.
The only voltage appearing across the
transformer at the receiving end is the
signal voltage; the line is isolated from
differences in ground potential. Because the
only connections to ground are from a centertap on the line side of either or both
transformers, the signals on each wire are
opposite in phase, but equal in magnitude;
therefore, the line is known as a "balanced"
line.
AUDIO
MILE.
WMIT
TEN
TEN
GRAD
HOUSE
OFFICE
BAKER
BELL SYSTEM
RUNKLE
EAST
.MUNROE
COSMIC
RAY LAB
TEN BURTON
HOUSE
HOUSE
PAIR
ACOUST
LAB
CAMPUS
Fig. 4. The complete
MIT network using balanced transmission lines.
newer undergraduate living units, has
taken place through the use of a rented
Bell System pair ; this is to be replaced
with Institute -owned cable in the near
future. The interest of a number of
fraternities has been aroused, and several
are considering renting pairs to the
magazine office at East Campus. All
these lines are operated as balanced lines
and are terminated with transformers.
The first question often asked us by
electrical engineers who learn of the
operation of the audio line is "but what
about the impedance ?" By this they imply that something must be radically
wrong if the impedances are not
matched; the source and load impedances should be matched to the characteristic impedance of the line. This is
sometimes false. Efficiency considerations are entirely unimportant to us because a sending amplifier that is feeding
watt average power into its 4 -, 8-, or
16 -ohm speaker and L-pad load is already available. Bell System lines usually require the signal not to exceed
Author's rack contains a Browning RV -10B
tuner, modified McIntosh C-104 preamp, Williamson amplifier, Sessions timer, VU meter,
patch panel, and controls for noise suppressor.
Line jacks are closed circuit, with contacts
normalled to feed regular "network."
JANUARY, 1955
+4 db or 2.5 milliwatts into a 600 -ohm
line, a voltage level approximately equal
to that from a normal home amplifier
feeding a conventional speaker during
an average passage-about 1.23 volts
r.m.s.
It is, therefore, perfectly simple to
feed a balanced line bridge across the
output of such an amplifier through a
1:1 transformer ; the power fed to the
line will be negligible as far as the conventional hi -fi amplifier is concerned.
Loading the line at the receiving end
with its characteristic impedance may or
may not improve the line's frequency
response, depending on the length of
line involved. The line across the river
was loaded with 600 ohms at whichever
end was receiving; no accurate measurements were made, but the line
sounded best operated this way. The
present MIT pair between East Campus
and the Graduate House sounds best
with the receiving end unloaded. The
method of testing is shown in Fig. 2
and the response in Fig. 3. It is obviously easy to equalize this characteristic,
even with conventional tone controls.
Programming on the audio network
has been improved by lines from the
Charles Hayden Memorial Library
where music is played in the main room
from 9 a.m. to 9 p.m., and taps from
WMIT's transmitter lines in each of
the four living units. (WMIT is our
AM student -operated radio station with
transmitters in each living unit.) It is
after 1 a.m., when classical music from
FM and WMIT has ceased, that the ties
between the different living units really
prove their value; one student studying
late will share his collection with any
of the other approximately 400 owners
of amplifiers tied to the audio line -24hour service is not unusual.
The informal, comprehensive service
offered by the audio lines has resulted
in numerous purchases of amplifiers and
amplifier kits and speakers by students
unable to afford a complete high -fidelity
installation. The freshman can enjoy
the music coming from his 6 -watt
Heathkit and inexpensive speaker now,
and plan on purchasing or building a
record player and tuner in the future.
His musical horizons will be broadened
because he has the opportunity to listen
to almost every composer included in
the LP catalogue. Perhaps our example
may suggest similar systems for other
groups of music lovers living in close
proximity.
17
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Success Found in "Sound"
Principles
BERT ENNIS
Proving that sound business practices work in the sound business as well as
elsewhere, Nate Reiss has achieved a sucess measured not only in terms of financial reward but more importantly in the satisfaction of a well done job.
a young man in the
American municipality famed as
the automotive capital of the
world awoke to a momentous, long
pondered decision. It was a decision that
had been made many times before by
millions of young men like him-eager,
enthusiastic, energetic young Americans
seeking a particular place of their own
in the sun. He decided to go into business for himself. Long on ambition,
short on capital, a native Detroiter,
oddly enough the thriving automotive
industry was not the object of his business aspirations. He chose instead a
business, young and undeveloped as it
was, for which he had demonstrated a
natural affinity and talent, a business
which he was convinced possessed tremendous potentialities and untapped
avenues of exploitation. With a certain
amount of experience in this particular
field as his principal asset, he elected to
enter that area of commercial sound
then more or less loosely described as
"public address." 28 years ago not too
many had the vision to apprehend the
tremendously vital and profitable role
the use of public address equipment was
to play in practically every known facet
of industry, commerce, and entertainment.
Copy -book mottoes today are as trite
and as true as they were when the
"work- and -win" axioms appearing in
McGuffey's First Reader stirred the
initiative and fired the ambitions of
those whose learning flowed from the
pioneering scholastic trail blazed by the
zealous
circuit- rider -preacher -turnedschool -master. We don't know whether
our particular young man ever heard of
McGuffey. But we do know that before
he embarked upon the most important
step in his life he laid down certain rules
of conduct for himself, based on fundamentals as sound and as true as any of
those which enriched the pages of McGuffey's Reader. Necessary as they are
to the lasting success of most undertakings, the rules with which he charted his
course are sometimes more honored in
the breach than in the observance.
Before he sought his first contract,
this young Detroiter mentally framed
28
for his remarkable achievements in his
own particular field of endeavor.
YEARS AGO,
Altec Lansing Corp., 161 Sixth Ave.,
New York 13, N.Y.
The First lob
It was back in 1926 that Nate Reiss
undertook his first job, a job to which
he applied his cardinal rule of using only
the finest sound equipment available. In
the opinion of Reiss, Altec Lansing pub-,
lic- address components meet the quality
standards he established. Thus, since
1946 he has employed that company's
equipment on many projects large and
small; only recently he completed his
712th installation. During these 28 years
of service and success, Reiss Public
Address Systems has supplied the equipment and technical installation services
which have marked many of the largest
and most complex communications systems in auditoriums, stadiums, arenas,
factories, places of worship, schools, and
colleges all over the United States.
Throughout these 28 exciting and
achievement -filled years Reiss has hanNathan Reiss, founder and head of Reiss Public
dled the products of but two outstanding
Address Systems, Detroit.
manufacturers. His 712th installation,
the following resolutions: He would with Altec Lansing equipment, perhandle only the finest equipment avail- formed at a contract price of $12,500 was
able from the standpoint of quality ; lie in behalf of General Motors Prevue of
would accord every job, large or small, Progress.
But what about the very first job that
his most diligent efforts; he would seek
out and perform successfully "headache" came the way of the young, ambitious
assignments others had failed to achieve, Detroit installation engineer ? It was an
assignments competitors in his field had order for an installation in a church.
turned down as too tough to handle ; he The year was 1926. The place was Dewould keep faith with himself and his troit, and the church was St. Paul's
Cathedral. The equipment involved was
customers.
Who was this young man who 28 the old Western Electric 373W double years ago set these precepts of character button carbon microphone, 549 "loud and conduct for himself as he embarked speaking telephone" receivers on 6-A
upon his own business enterprise? He trumpet horns, and a 13C amplifier
answers now, as then, to the name of which drew its filament supply from a
Nathan D. Reiss, one of the outstanding 12 -volt battery, its plate supply from
figures in the field of commercial sound eight 485 EverReady batteries. The
not only in his native city of Detroit. check called for the payment of $1,325.
but wherever communications are used The intervening years brought payment
in industry and commerce, sport and en- for jobs in many structures throughout
tertainment throughout the United the country. The 700th installation he
States. The story of "Nate" Reiss is made was also in a church, this time St.
truly a copy -book epic, the story of a Boniface, also in Detroit, a public adsuccess founded on sound principles of dress system which included 633A miintegrity, ability, and character. It is crophones, 1510 and 1520A combination
the story that in the opinion of many amplifier, H803 multicell horn and 290B
will sooner or later merit consideration unit. The price? $1,384, almost identical
of a special award by one of the groups with the revenue from his first job.
which annually single out an individual
The young man who set forth 28
AUDIO
18
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JANUARY, 1955
years ago to prove that nothing succeeds
like success still possesses the same unlimited enthusiasm, energy and vision
which were his principal assets then.
These, and little more, were the mainstays that saw Reiss through his first
job. His place of business was a modest
store at an inconspicuous location in
Detroit. His staff? He smiles when you
ask him about that. With the aid of a
few engineers at odd intervals, from
radio station WJR, in Detroit, he handled his first assignment himself. Grown
to full stature now in a highly competitive field, his establishment today, while
well- ordered, highly organized, and adequate to handle the impressive contracts
which regularly come his way, is neither
ornate nor imposing in size.
His engineering staff is noted in
sound circles more for ability than size,
selected by the Reiss yardstick of experience, initiative, and integrity. Thus, the
surface manifestations of his success lie,
not in an impressive business facade,
overdone decor, and a huge staff. He is
content to let success express itself in
results, in the belief that results speak a
language understood by all who seek
performance and quality.
Sound Serves at Hydramatic Fire
These years have naturally embraced
a great variety of tasks, some of which
have taxed his ingenuity, experience,
and determination to the utmost. But
each one has been a challenge to the
man who deliberately set himself years
ago to the accomplishment of assignments when others had faltered and
failed. His recounting of the gigantic
task which fell to him and his organization late last year when the hydramatic
manufacturing plant of General Motors
was destroyed by fire is typical of his
"lets- get -it-done" attitude. Before the
embers had cooled, he was called upon
to install, with the least possible delay,
a super dispatching system at GM's
emergency headquarters set up at Livonia, Michigan. Time was important
he and his crew worked four times
-
around the clock. Herein lies a measure
of the man, a perfect exposition of the
principles in which his business was
founded. Following 96 sleepless hours,
the dispatching system was completed,
and in operation. During this period
there had been installed a single 632A
microphone at a central control board,
which, through two 1410A and fifteen
1430A amplifiers, drove twenty -six 730A
units on re- entrant horns, and five 730A
drivers on 31A horns, thus delivering
blanket sound over an area of many
acres. An assist was given in this monumental task by Altec Lansing, who
rushed much of the vitally needed equipment to Livonia by air express from
the company's plants in California.
Despite an instinctive reticence, Reiss
recently was induced to talk about this
round-the -clock installation. He said:
"On the Saturday morning after the fire
we were asked to install a rush PA system in the garage proper, which would
be used as an operating point for all
personnel involved in the salvage operation. It was vitally necessary that this
phase of Cadillac manufacture be restored to operation as quickly as possible. The principal purpose of our work
was to enable the numerous salvage
crews working over this great area to
direct efficiently the movement of the
various vehicles used for pickup and
delivery. There were two telephones on
a desk at the main entrance to the
garage that was to be used for the "focal
point." All transmission of orders and
requirements of personnel would be
called to or directed from that point.
The following day, Sunday, we were
called upon to install additional speakers
and amplifiers on the roof of the main
building, to cover the truck entrance and
the areas where a great amount of traffic
was involved. Thus those in charge of
salvage operations could page vehicle
drivers and personnel and facilitate their
movements to necessary locations. By
means of this system a fleet of almost
200 trucks, bull-dozers, tractors, cranes,
fire fighting equipment and first -aid
mobile units was kept constantly moving
over the huge area, thereby hastening in
no small degree the time necessary in
salvaging operations. On Monday, the
third day, we were asked to install additional speakers along the portion of the
roof remaining intact on the west side
of the plant, to cover additional traffic
in that area. So it went, meeting requests for additional speakers and amplifiers as the scope of the salvage opera-
tions grew. Operations at the central
"focal point" I spoke of were conducted
like those of a railroad dispatcher. Two
score boards were erected on which
were indicated in precise detail the
movement in and out of men, trucks, and
machines, enabling an accurate check to
be kept on progress being made, and
showing what tasks of salvage still had
to be performed. Eventually we were
compelled to lease telephone lines and
install telephones, coils, and bridging
amplifiers at remote locations to cover
the vast area devastated by the fire."
Thus, in matter -of-fact language,
Reiss describes what proved to be a remarkable job of "disaster" installation
equipment for the nation's greatest
manufacturer of automobiles. The equipment which he installed served General
Motors so well during the emergency
that it was kept in operation for a period
of six weeks, when the tremendous job
of salvage had been completed.
From Cadillac to Soap Box Derby
In contrast to the overtones of disaster
which marked his efforts at Livonia,
Reiss can look back on certain engineering accomplishments concerned with happier occasions. One of these is the famed
Soap Box Derby, the annual event held
at Derby Downs, Akron, and which attracts an audience from all over the
country estimated at 65,000 excited humans. For several years now he has been
called upon to provide the equipment and
installation which carries, via sound
waves, the announcements, shouts and
general happy commotion which marks
the careening vehicles piloted by young
Almost obscure on the main beam across the arch of the Blessed Sacrament Church, Detroit, (left), is an Altec multicell speaker. A total of 13
amplifiers are used in this installation. An equally unique placement of speakers serves Hill Auditorium of the University of Michigan, (right).
AUDIO
JANUARY, 1955
19
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AmericanRadioHistory.Com
Soap Box Derby entrants. Also in this
same exciting realm there falls to him
and his organization the job of seeing to
it that the sounds which mark the course
of the annual Detroit River Boat Races
are heard by the spectators who witness
this event.
It was said at the beginning that Nate
Reiss thrives on accomplishing the impossible in the field of communications,
on solving those problems which arise
from climatic vagaries, acoustical difficulties, architectural hazards. Thus, the
problems posed in providing efficient
equipment and operation for the Detroit
Boat Race are welcomed by him. With
all the aplomb that would normally accompany the stringing of a hundred feet
of cable, this specialist in "difficult" jobs
installed a staggering total of 26 miles
of wire along the Detroit River bank,
together with the exact type of equipment necessary to broadcast this exciting event properly.
The paths of Reiss and General Motors have crossed more than once-and
will continue to cross again, if all outward indications serve-to their mutual
satisfaction. In past years, Reiss has
been called upon to handle the intricate
engineering detail involved in the General Motors broadcast "Conference," in
which a speech of about ten minutes
duration has been carried to thousands
of the company's executives and employees throughout the United States.
As the prime contractor for this gigantic
communications task, Reiss and his organization handled the establishment and
installation of the equipment necessary
to carry the GM message, via telephone
lines, to 80 cities in the United States.
The variety of endeavors which have
marked these exciting, challenging years
have been truly remarkable. Over the
712 Altec installations he has made have
come the voices of famed sports announcers and the roar of the crowd in
arena and stadium, the word of God by
priest, rabbi, and minister from numerous church pulpits, the call for workers
in times of disaster, the speeches of industry tycoons, the history- making
statements of governmental representatives in connection with the harnessing
of the atom for industry and peace -time
use.
One of the high -water marks in his
eventful and successful career was his
efforts in connection with the gigantic
"Phoenix Project," wherein the United
The name Reiss has become almost
synonomous in connection with the public address requirements and facilities of
the University of Michigan. At various
times he has installed in this famous institution of learning sound systems totaling almost $100,000. Whether it be the
football stadium, field house, Hill Auditorium, Natural Science Building, Rackham Memorial Building, West Engineering Building, Angel Building, there
you will see equipment indicative of the
engineering magic of this unusual man. Manifestations of success are sometimes seen in imposing business facades
States government released information and large establishments, but "Nate"
concerning certain atomic developments Reiss has been content to let his achievefor industrial use. In this instance, and ments spell out the externals of success.
under the auspices of the University of His efforts and reputation have brought
Michigan, Reiss handled the sound the material things of life most men seek.
pickup from a central point in Ann
But over and above his two Cadillacs,
Arbor for transmission by telephone line his home in a Detroit suburb, or the
to hotel auditoriums and meeting rooms profits which all of us welcome, one
in 87 cities throughout the nation. In- senses a more significant symbol of his
cluded in this tremendous task was the success. It is a comprehension of the
pickup of individual programs from five continuing faith he has in the "sound"
cities throughout the country, their relay principles he laid down when he started
back into the Ann Arbor central control in business 28 years ago, and his satispoint, and then out again to the 87 city faction in knowing that he has not devinetworks. Because of the usual careful ated from them. There are the things he
preparation and precise engineering treasures, the things reflected by the
planning Reiss accorded this gigantic esteem of those who know him.
task, the entire program was conducted
We cannot forego a concluding word
without delay or breakdown. Six weeks of our own. The story of Nate Reiss
of study and survey made possible a offers
conclusive proof
the area of
country -wide audio network possibly sound communication inthat
its application
without parallel in his particular field of to public address .has indeed
come of
engineering. The complete coverage ac- age in industry
corded this project included all engineer- rapid development and commerce. The
of this efficient means
ing details, together with supplying, of
communication should convince those
setting up and operating the central
control of this network, and the arrang- engaged in this field, as well as those
ing for the terminal equipment in each who contemplate entry into it, that it is
of the 87 cities involved. Six weeks of an accepted, successful specialized induswork to assure the success of a project dustry offering reward and security.
with an actual life of 49 minutes.
(Continued on page 78)
Our Lady Queen of Apostles church, (left), at Hamtramck, Michigan,
features a speaker installation in the dome over the altar, shown
above, providing unusually good sound distribution throughout.
20
AUDIO
www.americanradiohistory.com
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JANUARY, 1955
AMPLIFIERS
and
PREAMPLIFIERS
AU D lo
JANUARY. 195s
"Look, old man, you really should do something about
those switching transients!"
With five tubes or fifteen, one chassis or four, your
amplifier is the heart of )our home music system
here
you control turnover, rolloff, tone, cutoff, and volume
and
turn it off. A thorough discussion of how and why they work,
and a description of commercially available products.
-for
-
www.americanradiohistory.com
AmericanRadioHistory.Com
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Amplifiers and Preamplifiers
C. G. McPROUD
A practical discussion covering the operation, design, construction, and
testing of all types of amplifiers used in home music systems, and a presentation of the interesting features of commercially available products.
TO SAY that a fully comprehensive
study of vacuum -tube amplifiers could
be incorporated in some twenty pages
of printed matter would be utter folly.
In fact, about six hundred pages of Radio
Designer's Handbook' are devoted to
vacuum tubes, audio amplifiers, and
power supplies, and much of that material consists of references. For a
further study of the subject, the reader
is respectfully referred to that volume,
since it is very complete and as up to
date as practicable for a book. It is
hoped, however, that the reader may be
able to gain a general understanding of
modern amplifiers from this short treatise, for like yesterday's news, last year's
amplifier is almost obsolete. Not quite,
of course, for some very fine home music
system amplifiers have been working
steadily for five to ten years -they lack
only some of the more recent features
which make for convenient operation.
They are still serviceable, giving pleasure to their owners and-best of all
minimum of trouble. One of the advantages of a typical high-quality amplifier
is that it rarely suffers a breakdown,
largely because the hi -fi amplifier is
usually built along professional lines,
with better components and larger factors of safety.
-a
Available in North and South America
from Tube Department, Radio Corporation
of America, Harrison, N. J., or from most
radio distributors; in U. K. and Europe
from Iliffe & Sons, Ltd., Dorset House,
Stamford Street, London, S.E.1, England;
in Australia and vicinity, from Amalgamated Wireless Valve Company Pty., Ltd.,
47 York Street, Sydney, Australia.
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Simplified schematic of
lower.
AUDIO
a
cathode fol-
1. The only commercially available output transformerless amplifier -the Stephens "Cita
del."
Fig.
Types of Amplifiers
There are two basic types of amplifiers
-voltage and power. Both increase the
signal voltage, but the voltage amplifier
is usually considered to work into a high
impedance, while the power amplifier
usually works into a low impedance.
Thus the selection of load impedance and
and operating conditions determines
whether an amplifier provides only an
increase in voltage or an increase in
voltage and power. In home- music-system amplifiers there are usually four or
more voltage- amplifier stages, and only
one power stage, which is the last stage
and the one which drives the loudspeaker.
The most common output stage consists of two tubes in push pull, although
for higher power outputs four, six, eight,
or more tubes may be used in push -pull
parallel. While the push -pull amplifier
stage does provide nearly complete cancellation of even harmonics, it has certain other faults which become apparent
at high power outputs, and designers
have resorted to variations of the push pull amplifier to correct these conditions.
Some designers have worked on the
idea of eliminating the output transformer from the circuit altogether, and a
few have succeeded. The output transformer is a very important element of the
typical amplifier, and its characteristics
affect frequency response, power output,
and distortion to a large extent The
transformer is usually the most costly
single item in an amplifier, for if it is to
be good, it requires a large core of expensive material, and it requires a complicated coil construction that is expensive to build. Thus if the output
transformer could be eliminated entirely,
JANUARY, 1955
the over -all cost would be reduced appreciably. Several experimental circuits
have been described in the technical press
-one as recently as last June-but the
only commercial model on the market for
home use is the Stephens Citadel, which
is designed for speakers with 500 -ohm
voice coils. This unit is shown in Fig. 1.
Another type of amplifier is the cathode follower, which is a circuit arrangement designed to convert a signal at a
high impedance to a signal at a low impedance. The output votlage from a cathode follower is usually between 0.5 and
0.9 times the signal applied to the grid,
but the lower impedance allows the stage
to feed a signal through a relatively long
shielded cable from the preamplifier control unit to the power amplifier without attenuation of the high frequencies.
The circuit configuration of the cathode
follower is shown in Fig. 2 -the signal
being fed in at the grid and the output
signal appearing at the cathode. The output impedance of this circuit configuration for usual values is approximately
Rk /(1 +gmRk). Thus with a typical triode having á gm of 2200, and using a
value of 10,000 ohms for Rk, the output
impedance would be 435 ohms. A wide
' D. P. Dickie, Jr. and A. Macovski, "A
transformerless 25 -watt amplifier for conventional loudspeakers," AUDIO, June 1954.
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circuit for the amplifier called
" cascode." This differs from the original conFig. 3. Simplified
cept of the cascode, but is used in this form
as a low -noise input stage in some preamplifiers.
23
www.americanradiohistory.com
AmericanRadioHistory.Com
variety of circuit arrangements is used
to provide for different bias voltages,
higher input impedances, and greater
power' output, but the operation of the
cathode follower is similar in each case.
Another amplifier circuit which has
made its appearance is called the cascode,
although it should more properly be described as a grounded- cathode stage
feeding a grounded-grid stage. This
circuit has the advantage of an extremely high input impedance and a
minimum of input capacitance, and is
advantageous in the first stage of preamplifiers operating from low-impedance, low-output pickups where a transformer might otherwise be required to
provide a signal voltage sufficiently high
to override the residual noise of the
standard type of amplifier circuit. A
typical arrangement of the cascode is
shown in Fig. 3, which is that of the
Fairchild 240 Preamplifier-Equalizer.
The typical music system amplifier
consists of two sections, electrically,
although they may be combined into one
physical entity to save space, or to keep
costs to a minimum. The performance of
the separate unit type of amplifier is
not necessarily any better than when the
entire amplifier is constructed on one
chassis -that is all a matter of design.
But for many installations it is more
convenient to locate the control unit
separate from the power amplifier, with
connections between the two for signal
and power, with possible connections for
additional power outlets for operation of
tuner, tape recorder, phonograph turntable, or other auxiliary equipment.
Regardless of the physical arrangement of the amplifier, the same functions
are requited. To begin with, the average
magnetic pickup provides an output signal well under 1/10 of a volt whereas a
one -watt signal across a 16-ohm loudspeaker represents 4 volts. This does
not appear to be a great difference in
signal voltage, but there is a great difference in power, since the output of the
pickup is considerably less than 1 millionth of a watt, whereas the power in
the loudspeaker is one watt.
Typical Amplifier Arrangement
-
The first section of the usual homemusic-system amplifier provides sufficient voltage gain to boost the output of
the pickup so that it approximates the
output of a tuner or other signal sources.
This section, known as the preamplifier.
provides the equalization necessary to
match the recording characteristics in
addition to sufficient gain so the phono
signal may be fed to the remainder of the
amplifier at approximately the same level
as that from other sources.
The preamplifier is usually followed by
the selector switch, and two or three
stages of amplification with tone and
volume controls, and, in some instances,
low -pass filters to reduce needle scratch
or unwanted high frequencies, and high pass filters to reduce rumble. One or
more voltage -amplifier stages follow,
raising the signal strength still further.
Some form of phase splitter provides two
equal and opposite signals to the grids of
the driver stage or of the output stage,
depending on the design, and the output
stage is transformer coupled to the loudspeaker.
The user is not generally concerned
with the actual circuitry, but is primarily
interested in what facilities are provided
in the way of equalization, tone control,
output impedances, and power output.
Power Output
For home use, an output of at least 10
watts should be available in order to
provide sufficient power to handle the
peaks of music reproduction. Some engineers are of the opinion that considerably more power is required than this
minimum, but it is felt that a reasonably
good system can be provided with a
maximum of 10 watts provided one does
not expect to drive several speakers
throughout the house with the one amplifier. Actually, the power required for
so-called "average" or "program" level
is nearer 1 /10 of a watt, but engineers
are agreed that a safety factor of 16 to
20 db is required above the average level
to take care of peaks. Thus with an
average of 1 /10 watt and a 20 -db factor
of safety, it is seen that 10 watts is the
minimum if peaks are to be reproduced
without distortion. The "hi -fi nut" type
of listener who uses his system to show
how it will play, and who likes his music
reproduction several db above concerthall volume would do well to provide a
minimum of 25 watts, and would be still
safer with 50 or more. However, the
great majority of music lovers have a
more practical outlook on music reproduction in the home, and would be well
served with a maximum of 10 watts.
The output stage of most modern
amplifiers consists of two tubes in push
pull, although some use four tubes in
push-pull -parallel arrangement. The argument has waxed long without resolving the facts as to whether pentodes. triodes, or tetrodes are better. Let it be
stated categorically that it is possible to
make excellent amplifiers with any of
these types of tubes, assuming that equivalent engineering skill is applied to the
design problem. It is perhaps easier to
build a triode output stage than one
using tetrodes or pentodes. since the circuit requirements are somewhat more
simple for the triodes. Undoubtedly one
of the reasons for the success of kit amplifiers using the Williamson circuit with
807's, KT -66's, or 6L6's as triodes was
that the builder without access to test
equipment could usually follow the instructions and end up with a good amplifier. With the evolution of this type of
amplifier into the Ultra -Linear circuit,
Some builders have encountered trouble
unless they could observe the results of
their work with a scope, and had an
audio oscillator capable of reaching 100
kc, together with a.f. voltmeters which
could measure up in this range. With
factory produced amplifiers, however,
there is little to choose between triode
and beam -tube operation, since it is assumed that each manufacturer will build
the best equipment he is able to within
the limitations of cost to the user.
The Output Stage
The power output stage is the controlling factor in the power vs. distortion
characteristics of the amplifier. Some
form of feedback is almost universally
used, but the matter in which it is
applied differs in various amplifiers.
Within the last year, several manufacturers have adopted a form of feedback
originally described in these pages3
which permits the user to adjust the
damping of the amplifier to suit the
characteristics of the loudspeaker. Thus
where the speaker impedance rises
both at the low-frequency end where the
resonant peaks of the speaker end of
most enclosures occur, and at the high frequency end where the inductive reactance of the voice coil rises -the output impedance of the amplifier can he
adjusted to match more nearly the impedance of the speaker. Some engineers
maintain that a loudspeaker should be
driven by a constant voltage source,
which provides high damping and which
means that the source impedance is very
low, whereas others believe that the
source impedance of the amplifier should
be more closely matched to the speaker.
There is no doubt that some types of
speaker enclosures will work better with
a matched impedance, whereas other
types seem to sound better with a low impedance source. Since this is largely a
matter of "cut and try" with a particular
speaker -amplifier combination, it is impossible to state a fixed rule that would
apply to every case. It is true that some
difference in listening quality is ohserved, and the choice should be made
by the individual listener. However,
since the output impedance in this type
of amplifier is under the control of the
user, he can adjust it so as to give him
the type of quality he wishes, and since
tastes differ this would be a satisfactory
solution. All of the amplifiers on the
market so far with some damping factor
control-regardless of what the individual manufacturer may choose to call the
circuit arrangement -are adjustable, and
the user may find that the ability to vary
this control is of some importance. It is
not believed by this observer, however,
that such a control should be used as an
operating tone control, but that it should
he set for any given installation and then
left in the position which the listener
believes sounds best.
-
Preamplifier Controls
The practice in modern amplifier is
to provide considerable flexibility in
equalization so that the user can match
any possible recording characteristic.
With the fairly complete standardization
finally arrived at by record industry. it
seems probable that most music lovers
who are just beginning a record collection would he satisfactorily served with
only one characteristic-the RIAAand further corrections in quality can be
made with the tone controls, assuming
Werner Clements, "New approach to
loudspeaker damping," AUDIO ENGINEERING,
August. 1951.
AUDIO
24
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JANUARY, 1955
New Integrated
Audio Amplifier
craftsmen
Unquestionably, Craftsmen's new SOLITAIRE is today's perfect answer to integrated audio
amplifier design. It combines an equalizer -preamplifier, a dual noise filter, and a 20 -watt
amplifier, with power sufficient to drive any speaker system perfectly. Its controls permit
unequalled flexibility, yet retain operating ease. Its chassis is housed in handsome, leather etched steel, a styling innovation.
-
Above all, the SOLITAIRE provides you with superior sound and more usable features per
dollar
another engineering achievement from Craftsmen, at only $113.50 net!
Specifications
Power Output: 20 watts - Reserve for 40 watt peaks.
Freq. Response: a I db 10 cycles to 30 KC at 20 watts.
Hum and Noise:
60 db on phono.
dh on high channels.
Equalization: 6 useable positions -AES, LONDON,
Less than 0.1% IM at normal listening levels,
measured through the total audio system--not the power
amplifier alone.
Treble Tone Control: 15 db boost and 13 db attenuation 10 KC.
with
Loudness Control: Full Fletcher- Munson compensation
-70
Distortion:
Damping Factor: 12:1.
Size: 4 s 141 s 111/2'. Might: 22 lbs.
Inputs: (4) Phono, TV, Tuner, Tape.
Output: Cathode follower for tape recorder.
RIAA, LP,
EUROPEAN, NAB.
Bass Tone Control: 15 db boost and
l3 db attenuation
at 50 cycles.
front panel level -set. loudness contour continuously variable from full to none.
Dual Filter System: Low cut filter, 3 positions: Flat. 40 cycles,
150 cycles, at 12 db per octave slope. High cut filter, 3 positions: flat, 6,500 cycles, 3,000 cycles, 12 db per octave slope.
For complete information send
for bulletin
13.
World's Largest Exclusive Makers of High Fidelity Equipment
The Radio Craftsmen Incorporated, Dept. U -1
4403 N. Ravenswood Ave., Chicago 40, Illinois
AUDIO
JANUARY, 1955
25
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AmericanRadioHistory.Com
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Fig. 4. Typical phono equalization curves.
that they have suitable curves. However,
many listeners have a large collections of
records dating back to the pre -LP days,
and even many of the earlier LP's and
especially the foreign recordings are not
within the limits specified by the AES,
NARTB, or the RIAA. For these, different equalization curves will be found
necessary, and it is not uncommon to
find six or eight curves being available.
The greatest flexibility is obtained when
the low-frequency characteristic is selected by one control and the rolloff by
another, so that the user can have any
turnover combined with any rolloff. This
is not considered as simple for the user,
and one of the criticisms of hi-fi amplifiers has been that the members of the
family other than the enthusiast himself
find it difficult to achieve satisfactory
record reproduction because of the complication of controls. However, since
tastes and demands differ, and since
both types of amplifiers are available,
everyone should find it possible to select
equipment that suits his particular desires. We have always felt that while
it is admittedly desirable to be able to
match a recording curve accurately, a
greater difference in the actual recording characteristic can result from moving a microphone a foot or so than the
relatively small difference resulting from
changing the rolloff from 16 db to 12 db
at 10,000 cps, for example. Thus it has
been recommended often in these pages
that the user should select an amplifier
that has sufficient flexibility of control
to cover practically any situation, and
then adjust the controls for best sound
quality, regardless of what the label on
the panel indicated. The sanie method
would suffice for the amplifier with only
one knob -provided the original selection of curves was satisfactory -since
the user could adjust the control for
optimum quality, regardless of what the
record indicated to be the curve with
which it was recorded. The extremely
critical listener will undoubtedly be
happier with an amplifier which provides
him with a wider variety of controls
than might suffice for the less critical.
Figure 4 shows a group of curves typical
of modern amplifiers.
Tone Controls
Practically all modern amplifiers employ separate treble and bass controls,
since this is the only way to give the
user adequate flexibility. Most of these
work on the principle of a "tosser"
that is, if a boost is required at the
.
-
treble end of the spectrum, the entire
band is amplified by the same amount
and the low end is attenuated by suitable
resistance -capacitance networks. Controls working on this principle have the
characteristic of raising and lowering
both lows and highs around a mid -frequency "hinge" which usually occurs between 700 and 1000 cps as shown in Fig.
5. Proper selection of circuit parameters
controls the shaping of the curves and
gives good listening quality. Note that
when we refer to "boosting" the highs,
for example, we are not actually increasing the amplification of the high frequencies, but we are attenuating the
lows, and leaving the highs =attenuated.
This gives the same result, of course,
and is somewhat easier to do without
resorting to resonant circuits which have
not been used in tone controls in high quality equipment for several years.
Another type of control that is encountered in a number of amplifiers is
known as the "Baxendall," after its
original designer. This control uses a
feedback network to boost or cut both
Fig. 5. Tone control curves using the conventional circuits. Regardless of the settings of
the controls, the response curves "hinge" about
a
midpoint.
ends of the spectrum, and instead of resulting in curves which hinge around
some center frequency, the maximum
boost or cut curves move horizontally
along the spectrum, so to speak, with a
typical series of curves being similar to
those of Fig. 6. Thus this circuit results
in changing the inflection point continually as the control is turned. This type of
control is preferred by some because it
provides compensation at the extremes
of frequency without affecting the midrange frequencies until the amount of
correction comes close to the maximum.
Still another type of control provides
for feeding separately equalized circuits
to the ends of the control and to a tap
at the center. This arrangement, while
somewhat more expensive to build, permits the designer to incorporate entirely
different characteristics to the boost and
cut positions of the control, and the effect
can be tailored to a closer degree than
the two other types.
Regardless of the type of controls used,
they are necessary to compensate for
different recording studio characteristics, for different acoustic conditions in
the listening room, and for the individual
preferences of the listener. Controls may
be used to make up for deficiencies in
loudspeaker or enclosure, with a fixed
amount of bass or treble boost being in-
troduced when the speaker is not adequate in those ranges, or for reducing
shrillness from an improperly balanced
tweeter.
Volume vs. Loudness Controls
Some means of controlling the volume
level of the reproduction is an absolute
necessity in any sound reproducing systern.,Different sound levels occur from
record to record, or between recordings
and broadcast programs; the time of
day and the current activity of the listener call for different sound levels;
some people want their music reproduced
softly while others prefer it at full concert volume. Therfore, some method of
controlling the volume is required.
The human ear has different characteristics of hearing at different levels of
sound, and when the reproduction takes
place at a level which is different than
that of the original sound, the balance
between highs and lows is different to
the ear. This has been investigated by
scientists, and is called the Fletcher Munson effect, after those who did the
original work on the subject. The ear is
most sensitive at the midfrequencies,
with sensitivity falling off rapidly as the
frequency lowers. Therefore, if we reproduce music at the same volume at
which it was performed, it will apparently have the same balance between lows
and highs. As we lower the volume,
there is an apparent loss of low frequencies. Some writers maintain that
this effect also occurs at the high -frequency end of the spectrum, but an inspection of the Fletcher -Munson curves
or sensitivity of the ear will show that
there is very little difference between the
sensitivity at 1000 cps and 10,000 cps at
any volume below 90 db. There is an
upward twist to the curve, as shown in
Fig. 7, but the curves are almost identical above 1000 cps.
At the low end, however, there is a
considerable difference in the shape of
the curves. If the level of a 1000 -cps
signal is reduced from 100 db to 60 db,
for example, equal loudness at 30 cps
requires a level of 85 db -which means
that a boost of 25 db (85 60) is required to make the reproduced signal
sound like the original. The average
sound level in an auditorium with a
symphony orchestra will usually he
somewhat in the vicinity of 85 db,
whereas that in the home is more likely
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Fig. 6. Response curves for the Baxendall type
of tone control. At intermediate settings, the
controls affect progressively smaller and smaller
sections of the frequency extremes.
AUDIO
26
1111 11
JANUARY, 1955
to be around 65 db. Environment often
requires that the music lover reproduce
his programs at still lower levels than
65 db, which increases the apparent lack
of bass. The loudness control, first described in these pages", is a device which
compensates for this variation in sensitivity of the ear as volume is lowered.
In its original form it provided steps of
about 5 db each which permitted the user
to correct the frequency characteristic to
match the ear more closely as he reduced the volume. However, the 5 -db
steps were too great to permit this control to serve as the volume control of the
- .system, and other controls made their
appearance with steps of around 2 db,
which is about the minimum change in
level the average ear can perceive on
program material. The control was
somewhat expensive to build, and other
types were engineered which could be
made more cheaply. The basic principle
has been retained, however, and the combination of volume and equalization controls is still used in many amplifiers. Not
everyone likes this type of control, so
various methods have been employed to
give the user greater flexibility. In some
there is a switch that changes the control
from a volume control to an equalized
loudness control simply by cutting the
reactive elements out of the circuit.
Others provide one control that is set
for the average level at which the sound
is to be reproduced, with the usual uncompensated volume control being used
to adjust the level. Whatever the method,
however, it is felt that the loudness control has made it possible for the listener
to have high -quality sound reproduction
without the need for ear -splitting volume
-which was the principal reason for
considerable criticism of early hi -fi installations.
Most loudness controls now incorporated in current amplifiers correct both
low and high ends of the spectrum, although the sensitivity of the ear, as mentioned previously, does not change appreciably above 1000 cps. Thus from a
purely scientific standpoint, no compensation should be required in the treble
range, but this is not borne out psychoacoustically. Most designers are of the
opinion that the best listening quality
is obtained with some compensation
added for the treble range in addition
to that for the bass range, and this type
of control is the one usually employed.
There is still some controversy about
whether this type of compensation is desirable or not. In any case, most modern
amplifiers have a loudness control, together with some means for cutting it
out at will.
Filters
Some amplifiers are equipped with
low -pass filters which serve to limit the
frequency range of the reproduction to
some predetermined cutoff point -usually selectable at will from a number of
- ° David C. Bomberger, "Loudness control
for reproducing systems." AUDIO ENGINEERING. May 1948.
AUDIO
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frequencies; such as 10,000, 7000, and
5000 cps. The need for low -pass filters
has abated somewhat since shellac records have faded from popularity, but
there is some justification in their use in
broadcast t eception, particularly in those
areas where the only program service is
AM radio. Wide-range receivers capable
of passing frequencies above 10,000 cps
are often troublesome because of the reproduction of "monkey chatter," the
name given to interference between the
carriers of two adjacent -channel stations.
The low -pass filter will effectively remove this type of disturbance, although
most high -quality AM radio receivers
have some provision for reducing the
pass band so as to limit the high-frequency response. Another use for the
low -pass filter is to reduce the apparent
distortion in a poor signal source by
eliminating frequencies in the higher
ranges.
Similar filter arrangements are often
provided with high -pass configurations
to cut off the transmission band just
above the rumble frequency from turntables which are not sufficiently rumble free for true wide -range reproduction.
The cure in this case lies in replacing a
poor turntable with one which is suitable for a hi -fi system, but the filter is
sometimes desirable even with high quality equipment in cases where the
source material is not perfect. Many
records will be found with rumble content.
Low -pass filters -to have a sufficiently
sharp cutoff -are usually constructed
with inductances and capacitances, and
unless carefully designed may be susceptible to hum pickup from adjacent
equipment. Most commercially available
amplifiers using L -C filters are arranged
so that the external pickup from the inductors is reduced to a minimum or
eliminated altogether, but the trouble
is often encountered in home -built equipment. Some amplifiers have filters with
controllable slope beyond cutoff, which
permits using the filter only to the extent necessary, thus producing a minimum of deleterious effect on the musical
reproduction. High -pass filters are almost universally of the R -C type. since
a sharp cutoff of low frequencies usually
JANUARY, 1955
500
,000
IN CYCLES
2000
5000
.0
000
20,000
PER SECOND
generates some undesirable effects above
the cutoff frequency and thus in the
transmitted band. Such undesirable products resulting from low -pass filters
would be outside the pass band, and
thus not be heard, so a sharper low -pass
filter can be used.
A low -pass filter effect can be obtained with any magnetic pickup by
shunting it with a capacitor and resistor.
The inductance of the pickup resonates
with the capacitor and causes a 12 -dbper- octave rolloff above the resonant
point. The resistor serves to eliminate
the peak just before rolloff, and provides
a smoother over -all response. The peak
ahead of rolloff is unpleasant to the ear,
and should be eliminated by proper
choice of the shunting resistor.
Auxiliary Services
To provide sufficient flexibility for the
average user, the amplifier must be able
to accomodate several inputs-phono,
radio tuner, TV, tape, and possibly crystal or ceramic pickup and microphone.
With the exception of the microphone,
these other sources have an output in
the vicinity of 1 volt, which makes it
possible to switch between them at the
input of the control section, with the
preamplifier output being of approximately the same level. When provision
is made to feed a signal source to a tape
recorder, it is preferably from a point
in the circuit ahead of the volume and
tone controls so that the quality of re-
production during the recording process
can be controlled to suit the listener
without affecting the signal fed to the
recorder. With such an arrangement it
is possible to adjust the tape recorder
volume control to a suitable level and
make the recording without necessarily
reproducing the incoming signal at the
same time. Some units have provision
for monitoring from the tape recorder
while the recording is being made, but
this requires that the recorder be
equipped with three heads -erase, record, and playback,- rather than only
two, which is most common practice
with medium and low- priced recorders.
However, when used with a three -head
machine, this arrangement is desirable
27
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FIRST
EVER DESIGNED
TYPICAL PERFORMANCE DATA
PRC.I and A -30 TONE CONTROL CURVES
WITH NEW CIRCLOTRON CIRCUIT*
WITH NEW CRITICAL DAMPING CONTROL
BASS'
required for ideal operation
20
FREER(
100
1000
FREOUENCY
into high - fidelity speaker systems
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IN
CYCLES
10000 20E00
PER SECOND
MAXIMUM POWER VS. FREQUENCY
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AVERAGE DE
2
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10
In a new historic development by A. M. Wiggins, ELECTRO -VOICE now
brings you closer than ever to the goal of perfection in high fidelity
reproduction! The E -V Circlotron Amplifier provides exclusive E -V Critical
Damping Control to insure proper match to a high quality loudspeaker
system- restores bass to proper balance -assures utmost pleasure from home
music systems -provides new efficiency for professional operation.
You need only compare to recognize the difference.
gectyvic
E
-V CIRCLOTRON CIRCUIT*
E -V
Advanced design removes all DC from
the output transformer. Allows cool,
optimum, efficient utilization of output
tubes. Provides unity coupling between
tubes. Completely eliminates all switching transients -greatly reduces distortion. Has less than one -quarter the
plate circuit impedance found in con-
ventional amplifier output circuits,
assures vastly extended, distortion -free
range response at full rated power.
Provides trouble -free operation and
long tube life.
EN Patents
Pend.
FREQUENCY IN CYCLES
and JAM INTERMOOULATION
DISTORTION VS. POWER OUTPUT
E d
!
3
RAIES
2
1
3
6
9
R
IS
ID
POWER OUTPUT
21
IN
Your
Electro -Voice
Distributor
invites you
distortion -subdues hangover due to
underdamping. Assures most efficient
sound reproduction.
to see and
BUCHANAN, MICHIGAN
13
I09190000
5
damping-minimizes low- frequency
Export:
5
PER SECOND
PRCI
g
CRITICAL DAMPING CONTROL
Exclusive E -V damping factor control
permits perfect match of amplifier output to the critical damping resistance
of the loudspeaker, as well as to type of
enclosure. Operates optimumly into
the variable impedance of a speaker
load rather than a purely resistive load
as in previous amplifiers. Control eliminates speaker bass losses from over -
Write for complete data and information
INC.
E
R00
5
24 27 30 33
36
RIMS
CLeteatuyn.
NEW E -V PREAMPLIFIER AND REMOTE CONTROL SETS (shown at bottom right)
Here is a further result of E -V planning, research and engineering...to help you
obtain the fullest efficiency, operating convenience and enjoyment from your high
fidelity equipment. The new Preamplifier and Remote Control Set (in two models)
is designed for use with the E -V Model A -30 Circlotron Line Amplifier. The
Preamplifier, with its Off -On and Function Selector Switches is used near the
equipment location for easy hookup. The Remote Control is separated for convenience
and flexibility to allow single cable connection to any remote position up to 75 feet,
or may be used at preamplifier location. Each is housed in a beautifully styled
hand -rubbed Mahogany or Korina Blonde cabinet.
ELECTRO-VOICE,
100
5
East 40th St., New York 16, U.S.A. Cables: Arlab
NIGH FIDELITY AMPLIFIERS, SPEAKER SYSTEMS, MICROPHONES, PHONO -CARTRIDGES, AND OTHER ELECTRO- ACOUSTIC PRODUCTS
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AmericanRadioHistory.Com
hear the
difference.
EXCLUSIVE NEW
E -V
Model A -20C
20
Watt Circlotron Amplifier
Compact, high quality, conservatively rated amplifier with all necessary controls for handling a complete high fidelity system.
Power Output: 20 watts rated, 40 watts on peaks. Frequency Response: ± .1 db 20- 20,000 cps at full 20 watts. Inputs: Ultra.
Linear phono, magnetic phono, tape or tv, tuner or tv, Hi -Z micro-
phone. Controls: Function selector, record compensation, level,
loudness, bass, treble, damping factor, and two hum adjustments
on chassis. High level output connector also available to feed tape
machine. Size: 103/4" wide x 111/2" deep x 73/a" high.
Model A20C.
List Price $183.33.
Audiophile Net $110.00
E -V
AMPLIFIERS
E -V
Model A -30
30 -Watt
Circlotron Line Amplifier
This professional -type amplifier sets a new standard for efficiency
in high fidelity reproduction. Power Output: 30 watts rated, 60
watts on peaks. Frequency Response: ± .5 db 20- 50,000 cps. Controls: Gain, damping factor, hum adjustment, power switch. Easy
mounting on baseboard, side, or rack. Volume control adaptable
for front panel accessibility. Size: 133/4" wide x 84" deep x 7"
high. Makes perfect combination with Preamplifier and Remote
Control Set shown below.
Model A30.
List Price $241.67.
Audiophile Net $145.00
Preamplifier and Remote Control Set -with Exclusive Vital Presence Control
with E -V Model A -30 Circlotron Amplifier. Model PRC -1 allows
both Ultra- Linear ceramic and magnetic phono- cartridge inputs. Model
PRC.2 is identical except without magnetic phono preamplifier. Frequency Response: ± .5 db 20- 20,000 cps. PRC -1 Inputs: Ultra- Linear
phono, high -level magnetic phono, low -level magnetic phono, tuner,
tape, tv, and auxiliary. Preamplifier Controls: On -Off switch, function
selector, 5 individual Input level controls. Remote Controls: Record
compensation switch, level control, volume -loudness switch, rumble
filter switch, presence switch, bass control, treble control. Size each
of the Preamplifier and the Remote Control is 103/4" wide x 71/2" deep
x 43/4" high. Supplied with 5 ft. cable on each. Extensions available
for Remote Control unit.
For use
,,,
-V Model PRC -1. Preamplifier and Remote
Includes Model M -1 Magnetic Phono Preamp
Complete with Mahogany or Norma Blonde
List Price $200.00. Audiophile
E
EV Model
E -V
Same, but
without the
plug -in unit.
cabinets.
Net $120.00
M -1
Magnetic
Audiophile Net $105.00
Model M -1. Magnetic Phono Preamplifier plug -In unit.
List Price $25.00. Audiophile Net $15.00
(Preamplifier and Remote Control units are also available without cabinets. Simply deduct $8.33 from list
price or $5.00 from audiophile net for each cabinet.)
Eor.kligh- fidelity at its Best, Make Your Choice
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AmericanRadioHistory.Com
PRC -2.
Phono Preamp unit.
List Price $175.00.
Control Set.
.
t
and permits the user to check the record- the reputable components manufacturers
ing gtiality as it is being made. Some on the basis of what sounds best to him.
It is desirable that he make his selection
talle recorders are equipped to permit
this type of monitoring within their own 4if an amplifier, for example, using the
amplifier equipment, but if not, Vie fa- same type'of phono pickup and Ole same
cility for doing so is useful in many in- type of loudspeaker -as well as the sanie
type of loudspeaker enclosure-as that
stances.
The tape input on the average am- with which he will use the amplifier.
plifier is designed to take a high- impedGiven a choice as to what single eleance output from the playback amplifier ment of a music system should be of the
and reproduce it through the complete highest possible quality if it should be
system, with usually heifer quality than necessary for budget reasons to econofrom the speaker and amplifier in the mize somewhere, it has always'lc?en the
writer's belief that the amplifiei is the
recorder itself.
The TV input is designed to take a most important. An excellent lou=dspeaker
signal from a TV set -usually from a will show up the deffeencies of a poor
cathode -follower circuit -and reproduce amplifier: gdícker thah;,,,k poor speaker
it through the amplifier and speaker of will ; if there is very little or no distorthe better- quality system. This requires tion in the `amplifier, it will not be rethat the TV receiver be equipped for this produced in whatever speaker is being
type of output, as the TV tuners are. It used, and even a mediocre speaker will
sound fairly well with a high -quality
is a fairly simple modification to a Conventional TV set to provide .this output, '"amplifier drigging it:
This. shoula'not be construed to indibut with the widespread use of trans formertess TV circuits, it is usually a cate that it is possible to have the finest
in
sound reproduction áith 46ty- quality
practice which will give plenty of trouble
components anywhere in 'the system. The
fo avoid hum, and the possibility of
grounding the a.c. line in the TV set old adage abdbt the chain being no
stronger t n its we'akest'link alaplies to
through the amplifier.
Microphone inputs require consider- audio equiment as well as its original
ably more gain thah'is usuallyy available subject. By all means, buy the hest equip in the average amplifier following flat- '-ment your budget will peniajtts onnect it
point of ci ?uit selection.,.I öw ér, sui,, ÿ'Itogether properly, and then relax and
the gain: f the ph9f6'''preáni ifier'it i'njoy the music.
adequate 5r any type of 'niicrophdöèAmplifier Performance
provided the low-frequency equalisation
is made inoperative-some amplifiers
The performance of an audio amplifier
have this provision. It is a desirables can not "lie measured readily by the inadjunct when the main amplifier system diividual'whó goes into his dealer's to
is used to feed a `tape recorder. for it make a purchase, but the information is
permits the use of high-quality'. inw- generally made available in the speciletel microphones, with resultant im- fication sheets on the equipment. It is
provement in the recordings. 11,n% ever, important to the user to know just what
most users would not find titi; feature to look for when he goes to make a
of sufficient value to warratl`ßginsisting purchase, and to have a general idea of
upon it.
how to interpret the specifications. In
practicallywevery instance, the manufacturer of high -fidelity audio components
Selecting an Amplifier
may be considered to be thoroughly
The choice of a good amplifier is one honest in stating his specifications, for
which is difficult to make, for from the he knows full well that occasionally a
specifications published by the manufacpotential buyer may insist that the perturers it is obvious that any of the am- formance data be checked to his own
plifiers made by the reputable manufac- satisfaction. Various'types of equipment
turers in the -high-fidelity field will give reports-in this magazine and others
satisfactory results. Furthermore, the as well as by the two consumer organability of the amplifier to continue to izations-serve to stamp a mark of apgive good sérvie. is usually dependent proval on the published specifications of
the inte`rtty of the manufacturer, a piece of equipment, and may be relied
YRgl if the user selects any of the ampliupon as unbiased and correctly measured
*fers froth'"the- well known components data.
I'manufaçtiirers, he is sure to get good
In discussing the performance of an
his money, and he may expect amplifier, for example, the points that
valtìe
long 'and'reliable service. Since: there is are most important are:
Intermodulation distortion
some difference in the soppd frontthe
Harmonic distortion
various'àthelifiers, it wotild be desirable
Power output (at rated distortion)
¿f the prospective purchaser could arFrequency response
ránge with his supplier to permit a
Hum and noise level
sort period of hópte trial before making
Tone -control range
final selection. To the inexperienced
Phono equalization
ear,' any good`hi. fi system sounds pleasant *for 'a short period-witness the Each of these will be discussed separately
sounds at an Audio Fair-but 'soine in the succeeding paragraphs. along
with accepted standards of measurement
components may not be as "easy to live
with" as others, and this can be deter- and the methods of making the measuremined only by living with them for a ments.
Intermodulation distortion. In this
time. In any case, our recommendation
writer's opinion, this is the most imis that the prospective purchaser make
his selection from any of the products of portant of the performance data of an
.
f.
un
r
áf
.di
'
amplifier, since' it is believed to come
closer to the effect upon the human ear
than harmonic distortion. The reason for
this is that all music, for example, is
composed of fundamental tones and overtones, and all of the overtones of any
musical note are harmonically related
to the fundamental. While not all harmonics are not pleasantly related to the
fundamental -the fifth and seventh often
being considered objectionable -most of
them are. and serve only to change the
timbre of the note somewhat. However,
the products of intermodulation distortion are not harmonically related to the
original tone, and are in most instances
unpleasant to the ear. AUDIO stands on
the belief that amplifiers should be rated
at the power output for which the inter modulation distortion measures 2 per
cent, using a -low frequency such as
60 cps and a high frequency or approximately 7000 cps, and a ratio of 4 :1.
There is no accepted standard for the
measurement of IM distortion, but most
Manufacturers use test frequencies of
approximately tltt:se values, and AUDIO
considers this as its own standard
with EQUIPMENT REPORT measurements
made on this basis.
The IM distortion measurement is
made by introducing into the input of
an amplifier a composite signal which is
composed of two frequencies. The output is connected to an IM analyzer which
eliminates the low frequency and measures the modulation of the high frequency by the low frequency as a percentage of the high-frequency signal.
This modulation is caused by non linearity in the amplifier. Any good amplifier will measure well under 1 per
cent IM distortion at outputs less than
watt, where the ¿average program
1
levet4vill usually beet for home listening. It is only on peaks that the
tortion reaches the higher values. Most
listeners are familiar 'with the roughness that often accompanies the loudest
passages in a musical selection, and
many say they instinctively cringe as
the volume rises to a'peak,.knowing
that it will be harsh and :unpielsarit.i,
This will not he the case 'where i1tl
distortion remains low even on peak
outputs, and cleanness of reproduction
can be had with the best amplifiers.
Some manufacturers use an IM signal
in which the two frequencies are at the
same level -with a ratio of i 1. This
gives a lower numerical value 'to the
distortion, but should not be compared
directly with a figpre' obtained with the
4 : 1 input signal. the power output at
which the distortion is measured should
be measured. in AUDIO'S opinion, as the
Equivalent Sine Wave Power, rather
than as the output which is shown by the
usual instruments. Equivalent Sine Wave
Power represents the power in a signal
which would be present if the peak value
of a sine wave equalled the peak value
of the composite IM signal. which is 25
per cent higher than the average power
in the signal. Thus, when an amplifier
is rated at Measured Power Output and
compared directly with an amplifier
rated at Equivalent Sine Wave Power
Output, it suffers numerically, although
-
Irdis-
AUDIO
30
JANUARY, 1955
a
www.americanradiohistory.com
AmericanRadioHistory.Com
x
the meaning is clear enough if one knows
the difference. The Equivalent Sine
Wave Power figure may be obtained by
multiplying the Measured Power Output
by 1.48, approximately.
No standards have yet been set for the
measurement of an equalized amplifier
such as a phono preamp. It is believed.
however, that a fair comparison would
be to introduce a composite signal into
the amplifier with the ratio adjusted so
that the ratio at the output of the
amplifier is 4 : 1. It ..makes little difference what method is used so long as
all measurements are made by the same
method and that figures have the..same
basis on which to compare them.
Harmonic Distortion. This form of
distortion is measured by introducing a
pure sine -wave signal to the input of an
amplifier and analyzing the output signal,
using either a wave analyzer or the
simpler harmonic distortion meter. All
amplifiers have some distortion, but the
figure for harmonic distortion should be
less than 1 per cent at rated output for
best quality of reproduction, and this
should be made up principally of second,
third, and fourth. Much fifth-harmonic
distortion is particularly objectionable,
and some authorities recommend the
rating of an amplifier at a. certain
(small) percentage of fifth. harmonic.
This requires the use of a.wave analyzer,
and natal! laboratories are so equipped.
The more common distortion measuring
equipment consists of eliminating the
fundamental from the output signal and
measuring the total remaining signal,
which is composed of all the distortion
products. This gives a slightly lower
numerical value than the sum of the
distortion figures for each of the orders
-second, third, fourth, and so on -but
so long as everyone uses the same method
the results can be compared.
Power Output. The power output of
an amplifier can be measured by several
different means, and all should be employed for a thorough analysis. One of
the easiest is by the use of an oscilloscope; observing the point at which the
sing wave signal begins to change its
shape -this point being known as the
"clipping" point. Every amplifier should
be tested by this method so as to make
sure that the clipping point is symmetrical on both halves of the sine wave, for
if there is a tendency for one side to clip
before the other, the result is unpleasant
to the ear. The power output at the
clipping point is likely to correspond to
that at a measured harmonic distortion
of 5 per cent, since the change in shape
of a sine-wave signal on the 'scope
screen is barely detectable until the distortion is around this value.
Amplifiers are most commonly rated
at a given percentage of IM or harmonic
distortion. The test signal
sine wave
for harmonic measurement and the composite signal for IM testing -is fed to the
input and the output measured by suitable equipment. At the distortion figure
for which the amplifier is to be rated, the
actual output power is measured, and
this is given as the rated power output
for the amplifier. In most instances the
amplifier i, terminated with a resistance
-
-a
AUDIO
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Greatest amplifier buy today and here's
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FOOLPROOF DAMPING CONTROL
con-
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200,000 cycle response. DISTORTION FREE
-less than 0.05 °° at 30 watt level, ex
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'
0.1 DB from 16 to 30,000 cycles. HUM
AND NOISE LEVEL -virtually non-me
table. DESIGNED FOR THE FUTURE
finest
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BUILT -IN PREAMPLIFIER POWER SUPPLY.
BUILT-IN POWER FOR NEWEST E.ECTROSTATIC TWEETERS. Other firsts.
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all controls on full. DISTORTION FREE
virtually non-measureable, exceeds FCC
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no transformers required with all present
phono cartridges. LOUDNESS CONTROL
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over 20 DB distortion -free boost and attenuation. FIVE
INPUT SELECTIONS. 16 PRECISION PLAYBACK CURVES
lifetime
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Built -in power for Weathers cartridge,
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icrophones. Distinguished satin -gold LJCITE
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AmericanRadioHistory.Com
different interpretation was intended. 1 watt is not too objectionable.
Tone Control Range. Modern ampliSuppose, for example, that a certain
piece of equipment were rated as having fiers are all equipped with separate bass
a frequency range from 50 to 9000 cps, and treble tone controls, and they are
t 5 db. If two lines are placed on the usually arranged to provide both boost
graph sheet, one 5 db above the reference and cut so the user can adjust the sound
and one 5 db below, the curve can then output to compensate for recording
be placed on the sheet so that the highest studio characteristics, loudspeaker depoint touches the top line and the fre- ficiencies, and acoustics in the listening
quency range is noted where the curve room. For specification purposes it is
crosses the lower line at both ends of usual to measure frequency response
the spectrum. Since the middle range of with both tone controls in the maximum
frequencies is usually relatively flat, this boost position and again with both in
means that the lowest and highest fre- the maximum cut position. This method
quencies, according to that rating, are gives the limits that can be obtained by
10 db down from the midrange frequen- manipulation of the controls, but is not
cies. The rating is strictly true, but it is absolutely accurate, since some types of
certainly misleading. It would be far controls affect the response at the 1000 better if audio equipment were rated as cps reference point. However, for most
having a frequency range of "30 to purposes this method is adequate, since
15,000 cps, with not more than ± 2 db it does show the character of the tone variation from the 1000 -cps level," or control curves, and will show up any
some substantially similar form.
resonances in the frequency- shaping
Hum and Noise Level. With high - circuits.
quality equipment, the hum and noise
For average use, it is sufficient that
present in an amplifier -or any other the tone controls provide a boost of 12
audio equipment-becomes important to 15 db at 50 cps and 10,000 cps, and a
because any good loudspeaker system cut of about the same magnitude at the
should be capable of reproducing the 60- low frequency and of 20 to 25 db at the
and 120 -cps hum frequencies, as well as high end. However, if the phono circuits
the noise frequencies which are likely are properly equalized, somewhat less
to he well above 5000 cps. Amplifiers are than these figures can be considered
generally rated as having a hum level n sufficient, particularly if a loudness condb below rated output, but AUDIO does
trol is provided.
not consider this a valid indication, for
Phono Equalization. Equalization for
with a 50 -watt amplifier, for example, magnetic pickups is measured in the same
this will result in a rating 7 db better way as frequency response, using each
than with a 10 -watt amplifier having of the separate positions individually. If
exactly the same hum and noise output. independent controls are provided for
This is a trifle misleading, for the turnover and rolloff, it is sufficient to
average listener will not necessarily use measure each end separately, using a
a 7 -db higher program level with a 50- fixed position for the other. Naturally.
watt amplifier than he will with a 10- the tone controls should be in the "flat"
watt amplifier. It is considered more position.
accurate to indicate hum and noise as n
While a large variety of equalization
db below 1 -watt. for example. or to sonic curves is provided, not all of them seem
other reference level. In the case of pre- to be necessary. particularly for the newamplifiers, the rating should be stated as comer to record collecting, since he is
n db below 1 -volt output, for example.
likely to restrict his buying to LP's and
This would permit a direct comparison 45's. all of which have a recording charbetween amplifiers, without any possi- acteristic which is, within limits, acceptbility of misinterpretation.
ably played on an RIAA curve. This is
With a high- quality speaker system, largely a matter of taste, and the most
a satisfactory hum level is obtained when critical listeners may want more flexithe hum is lower than 70 db below 1 bility than the basic three or four curves
watt, although a figure of 60 db below that are most necessary.
Measurement of phonograph equalization is usually made by simply connecting the audio signal generator ' to the
phono input jack and noting the output
as the frequency is varied. This does not
take into account the impedance of the
pickup cartridge, and some input circuits
depend upon this impedance to achieve
the desired rolloff or cutoff characteristics. The proper method of making
measurements on preamplifiers is to
place a pickup in series with a low
resistance -say, one to five ohms-and
connect this combination to the input.
The output from the generator is then
fed across the low resistance, suitably
matched for impedance. This serves two
gives a low
purposes simultaneously
voltage without unduly large attenuation
in the generator, and presents the proper
impedance to the input circuit of the preamplifier, thus giving true response
"Oo
curves.
Sorry!"
load equivalent to the nominal output
impedance. However, further tests
should be made with loudspeaker loads,
using a 'scope to observe the output
signal, and as a further check on stability
the amplifier should be tested with no
load and with a short-circuit across the
output-in the latter instance the 'scope
input should be connected to one of the
output tube grids. As a further check for
stability, amplifiers should be tested with
capacitance loads up to about 1 µf, and
with inductive loads up to about 100
mh. In no instance should any spurious
frequencies be geneiated as the input
signal is swept through theNntire audio
frequency range and over a *ide range
of power output.
Frequency Response. In this day of
high -quality output transformers and
the almost universal use of feedback,
there is no problem in obtaining a flat
frequency response over the entire audio frequency range. However, that is not
enough for good transient response,
which is the ability of an amplifier to
reproduce faithfully the starting and
stopping of a tone-such as that of a
piano or other percussion instrument.
In order to reproduce the start of a 1000 cps tone accurately, it is necessary that
the amplifier pass a frequency range
at least ten times the fundamental, or
10,000 cps. With music ranging in fundamental frequencies up to, say, 4000 cps,
it is obvious that the frequency response
of a satisfactory amplifier must extend
to 40,000 cps, even though the human ear
does not hear up in that range. This can
be proved, however, by reproducing a
selection through a high -quality amplifier with a pass band extending to
100,000, for example, and then listening
to the same selection with a 10,000 -cps
low -pass filter in the circuit. It will be
seen that there is a noticeable difference.
The frequency response of an amplifier
should be stated as "flat within ± 2 db
from 10 to 65,000 cps," using the applicable figures. The "±2 db" should be
interpreted to mean that the amplifier
response does not deviate more than ± 2
db from its output at 1000 cps (or some
other mean frequency), although in an
endeavor to show a better figure, some
literature has been observed in which a
-it
AUDIO
32
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
Nation
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Make sure you get your money's worth! Before you invest another
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FM
FM Mutamotic
5
PLUG -IN PREAMPLIFIER CONTROL
Plugs into either Horizon 20 amplifier or "Criterion" tuner. 10 position selector
switch for 3 high level inputs and phono input with 7 equalization positions.
Bass boost: +25 db and bass cut --15 db at 30 cps. Treble boost +12 db
db
kc,
and cut
db at 10 kc. Frequency response 20 cps
less than .2% at 1.5 Volts out;
loudness control switch. Distortion: Harmonic
Intermodulation
less than .3% at 1.5 Volts out. Hum & Noise: 70 db below
1.5 volts on high level inputs.
-20
-25
FM SECTION
.omaiWILW
Sensitivity:
.5 uy for 20 db quieting. Capture ratio:
rejects interfering signal up to 80% as strong as
desired signal. No distortion from reflective ghosts.
(At 20 watts rated output
Harmonic distortion: less than .3%1.6% at 25 watts(. Inter modulation distortion: less than 1%. Sensitivity: 1.6 volts.
Hum & Noise: 80 db below 20 watts. Frequency response:
20 cps -20 kc,±.1 db; 10 cps -100 kc, ±1 db. Power response:
20 cps -20 kc, ±.15 db; 10 cps -60 kc,
!
1
db.
UNITY -COUPLING
tuner.
complete
alIZSZt
...
Output: Cathode follower output. Hum & Noise level
60 db below audio signal. Full A.G.C. maintains I.F.
band pass regardless of input signal level. Instantaneous limiters provide lowest impulse noise of any
provides
r.25
"HORIZON 20"
20 Watt amplifier $84.95
Image rejection: better than 60 db I.F. pass bond
is flat within -f,1 db over band of 200 kc. Audio distortion: less than 0.5% from all levels of modulation.
Selectivity
rejection.
"Mutamotic" TUNING
Exclusive circuit eliminates hiss and
noise when tuning between stations
found in other FM tuners. Fine tun.
ing is unnecessary. Whenever there
is sound
station is tuned perfectly.
AM
NATIONAL HORIZON
COMPARE THESE
OUTSTANDING
"CRITERION"
SPECIFICATIONS
FM
Binaural
Exclusive circuit eliminates impulse distortion characteristic in
adjacent channel
conventional amplifiers. Transformer supplies only matching
impedance to speaker.
AM SECTION
Sensitivity: 10 uy at antenna terminals for signal -tonoise ratio of 10 db.
Image ratio: better than 60 db.
I.F. Pass
band flat within -L1 db over
a
"HORIZON 10"
10
14.5 kc range.
...
preamplifier control unit. $79.95
BINAURAL OPERATION
Harmonic distortion: .5%; Intermodulation: 1%. Frequency response: 20 cps -20
kc, :5
db. Power response: 20 cps -20 kc, -f- 2 db. Hum & Noise: 70 db
50 db below.' Preamp
below full output on high level inputs (low level inputs
Control has 2 high level inputs for tape and tuner. Record compensation positions
for R.I.A.A., A.E.S. and Foreign. Treble boost: 11 db and 10 db treble cut at 10 kc. Boss
boost: 15 db at 30 cps. Built -in loudness compensation.
Individual tuning condensers, volume controls and output jacks for simultaneous operation. FM free of AM
signal up to 100 times the FM signal input. AM free of
FM signal up to 100 times AM signal input.
1,/p/k
watt amplifier with
1
t
-
ationa
For complete specifications see your dealer or write to Dept. A155,National Company, Inc., Malden, Mass.
AUDIO
JANUARY, 1955
3=
www.americanradiohistory.com
AmericanRadioHistory.Com
COMMERCIAL AMPLIFIERS
Up to this point the discussion has
been general, and has not been confined
to these products of any particular manufacturer. The remainder of the section
will be devoted to descriptions of the amplifiers that are currently on the market,
with an attempt being made to point out
the characteristics that are of special
interest in the individual units. The
writer is indebted to the various manufacturers for their cooperation in furnishing photographs, schematics, and operating instructions on all of this equipment. without which this section would
have never been possible.
same tubes in the same amplifier with the
exception of the output transformer
which is changed to the Ultra- Linear
will give an output of 24 watts with the
same amount of distortion.
Altec Lansing Corporation, 161 Sixth Ave
New York 13, N. Y. and 9356 Sant..
Monica Blvd., Beverly Hills, California.
Three units constitute the line of this
company
10 -watt single chassis amplifier, model A-339A ; a deluxe preamplifier- control unit, model A -440A ; and a
35 -watt power amplifier, model A -340A.
The A -339A, Fig. 9; employs a 12AY7
as a preamplifier tube5with feedback
around the first gectiento provide the
-a
Acro Products Company, 369 Shurs Lane,
Philadelphia 28, Pa.
While not actually the manufacturer
of an amplifier, this company does provide output transformers to many amplifier manufacturers for use in the circuit known as the Ultra -Linear, which
provides a form of feedback from the,
plate to the screen of the output stage. A,.
typical circuit is that of Fig. 8. The inFig.
Altec Lansing A -339A Melodist
amplifier and record control unit.
9. The
high- frequency rolloff and with feedback
around the second section to provide the
low - frequency boost required for the
magnetic pickup input. It has four phono
equalization positions and a microphone
input. in addition to two inputs for high level sources such as inner. TV, or tape
recorder. each of these inputs having
separate level-adjusting controls. Two
sections of a 12AX7 with the tone controls and a loudness control between
them serve as voltage amplifiers, fol-
Fig.
10.
New Altec A -440A preamplifier-con trol unit.
lowed by a direct coupled amplifier and
phase splitter and the output stage consisting of two 6CM6's in push pull.
pentode connected. Output impedances
of 4, 8, and 16 ohms are provided, and
25 db of feedback hold harmonic distortion to 2 per cent at 10 watts.
The A -440A, shown in Fig. 10, is of
unusual construction, being provided
with a hinged panel on the front which
covers all the controls except that for
volume when the "door" is closed. Thus
the critical listener may open the door
and adjust controls to suit his fancy.
while the less critical listener can have
a one- control amplifier simply by closing
the door. This unit provides for two
phono inputs and three high -level inputs
each with level adjusting potentiometers.
The phono equalization requires two
controls, one for the low end and one
for the high; there are five low -frequency positions ranging from flat to a
600 -cps turnover, and five rolloff positions ranging from 0 to 16 db at 10.000
cps. The tape recorder feed is taken
from the output of the selector switch,
just ahead of the volume and loudness
controls, choice of which may be selected
Fig. 8. Typical Ultra- Linear output stage.
elusion oí a portion of the primary winding of the output transformer in the
screen circuit is said to produce lower
distortion for a given output than either
triode or tetrode connection of the same
tube. In any case, the Ultra- Linear connection has been incorporated in many
commercial amplifiers which employ the
Acrosound transformers in many instances. The earliest description of the
Ultra -Linear circuits appeared in these
pages some time ago, and the circuit may
be said to have achieved excellent acceptance since that time.
Whether or not this circuit lives up to
the claims of its inventors may be controversial, but reliable measurements
indicate that while some 15 watts may be
obtained from a conventional "Williamson" amplifier using 807's as triodes, the
e David Hafler and Herbert I. Keroes,
"An Ultra- Linear amplifier," AUDIO ENGINEERING, Nov. 1951.
Fig. 10a. Schematic of the Altec power amplifier using the new Tung -Sol 6550's.
AUDIO
34
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AmericanRadioHistory.Com
JANUARY, 1955
Did you know you
can reduce speaker
distortion by 76%
with an amplifier?
:
t-2
2 DAMPING FACT'
PATENT
I'IiNI)ING
,o
1
BOGE.
«,M1
Meet Bogen's new amplifiers
with `ultimate damping'
Now you can enjoy more hours of perfect listening without fatigue. The famous Bogen DB20 and D030 ampli-
fiers are now available with the exclusive BOGEN
VARIABLE DAMPING FACTOR CONTROL (VDFC)
which permits you to minimize speaker distortion and
eliminate system resonances.
The Bogen control is the first to offer a range from +2
through infinity to -1 ... which is that magical point,
we call it "Ultimate Damping ", at which the speaker
resistance is negated and distortion reduced to an imperceptible value.
Yes, now you can get true bass with any speaker!
It is easy to set your Bogen VDFC for Ultimate Damping ... no instruments are needed. As you can see from
the enlarged control shown above, you merely turn the
slotted shaft with a screwdriver to the desired setting
when you install your system. No later adjustment is
required.
*Acoustical measurements by an independent laboratory
using a quality hi-fi speaker system operating at 5 watts
and 25 cycles showed 96% distortion with damping
factor of 10 (typical amplifier), and only 20% with
Bogen Ultimate Damping. (Amplifier distortion itself
was well under 0.5%.)
THE DB2ODF AMPLIFIER
This is our famous Bogen
DB20 amplifier, rated ashaving "Best Overall Quality"
by a leading consumer
testing organization, with
the added feature of the
Variable Damping Factor
Control. This amplifier gives
you 20 watts of power at
0.3% distortion with a 5- position Loudness Contour
Selector, a 10-position input selector -phono equalizer,
output jack for tape recorder and non -resonant, separate
bass & treble tone controls. With Variable Damping
Factor: $108.00 (DB20 without VDFC: $99.00.)
BOGEN DO3OA POWER AMPLIFIER
This brilliant unit now features the exclusive Bogen
variable damping factor
control as standard equipment ... which adds to its
stature as the perfect companion to the all- control
tuners -such as the Bogen
R750 FM -AM Tuner where
tuning, volume, bass tone, treble tone and selector controls are all on the tuner panel. The D030A amplifies all
frequencies uniformly from 10 to 20,000 cycles within
0.2 db at rated output of 30 watts. Variable Damping
Factor Control is the same as that on DB2ODF. $99.00
SECOND PRINTING :
David Bogen Co., Inc. Dept. VA
29 Ninth Ave., New York 14. N.
"Understanding ,High Fidelity" is fast becoming a
standard manual of hi -fi theory and application. Clearly
and concisely, this new enlarged 56 page edition presents invaluable practical information to help you get
more out of any sound system. "For the Audiophile first
seeking his way ... a surprising introductory work."
says the Saturday Review. Send 250 for your copy.
Name
Address
City
HIGH
/FIDELITY
BECAUSE IT SOUNDS BETTER
AUDIO
Y.
Send "Understanding High Fidelity" (250 enclosed).
-
-
-
--
-
Zone
State
Send only free catalog and where -to- buy -it guide.
It
JANUARY, 1955
35
www.americanradiohistory.com
AmericanRadioHistory.Com
by a switch which also permits monitor-
ing the output from a tape recorder
while feeding it a signal from any of the
other inputs. The recorder output, taken
off ahead of the volume control, goes
through a cathode follower to provide
a low- impedance source. A second cathode follower feeds the normal output to
the power amplifiers. The entire unit is
self powered, using selenium rectifiers
for both plate and heater supply-all
heaters being fed with d.c. to keep hum
to a minimum.
The 35 -watt power amplifier, model
A -340A, is the first unit to appear on
the market using the new Tung -Sol 6550
in the output stage. The amplifier consists of four stages
12AY7 as an
amplifier and direct coupled phase split ter, a 12AU7 as a push -pull driver stage
and the 6550's in the output, connected
as beam tetrodes. A voltage regulator
tube serves to maintain the screens at a
fixed voltage below the plates. A control
in the output circuit permits adjusting Fig. 11. The Ampex Model 620 Amplifier Speaker combination.
the impedance of the amplifier on the 8ohm tap over a range from -4 ohms
through 0 to +4.5 ohms so as to accommodate practically any type of speaker of flat throughout the audio spectrum.
and enclosure. The networks RuFigure 11 shows the external appearance
in the feedback circuit and R.- C. in of the unit with the cover of the case
'the grid circuit of the second triode removed.
section control the input- output phase
relationship at high frequencies so
that stability is obtained with any type Bell Sound Systems, 555 Marion Road,
Columbus, 7, Ohio.
of load. Since this is the first 6550 amplifier circuit to be made public, the
One of the most interesting examples
schematic of the amplifier is shown in of the Bell line of equipment is the new
its entirely in Fig. IOa.
Model 2200C, shown in Fig. 12, particularly because of its engineering features.
This unit was designed especially for
Ampex Corporation, 634 Charter St., Redwood City, California.
those who are interested in serious home
While this manufacturer is primarily music systems or who are inclined to
known for its tape recorders, it also has experiment with audio reproduction. It
a line of high -power amplifiers in- has a rated output of 20 watts with less
tended for theater use. It does, however, than 0.3 per cent harmonic distortion and
have one unit that might find its way 2 per cent IM distortion (actual power
into a home system-the model 620 am- output, not equivalent sine -wave power
plifier-speaker. The amplifier itself con- as most measurements are made). For
sists of three stages-a 5879 direct comparison purposes, this value would be
coupled to a "long-tailed pair" type of approximately 29 watts. This amplifier
phase splitter using a 12AU7, and a uses a 6SC7 as a preamplifier, with feedpair of 6V6's in the output stage. It is back equalization over the second half,
combined with an efficient 8 -inch loud- and with a built -in rumble filter. The inspeaker in a portable carrying case, and put circuits were designed to accommotogether the amplifier and speaker pro- date high- and low -level magnetic pickvides a fairly flat acoustic output from ups, crystal pickups, microphone. and
65 to 10,000 cps. This is accomplished three high -level sources. The selector
by a frequency -selective network in the switch is followed by a loudness control
feedback circuit when the built -in and the first section of an uncompensated
speaker is being used-when an exter- volume control. The second section of
nal speaker is used, the network is out the volume control precedes the basic
of circuit and the amplifier is within 1 db amplifier and serves to keep hum output
to a minimum when reproducing sound
at very low levels. The tone controls
both employ dual pots to permit optimum
shaping of the response curves and to
ensure flat response at the center positions of the controls. The basic amplifier
is fairly conventional as to tube lineup
with a 6SN7 as amplifier and cathodyne
phase splitter, 6SL7 as driver. and two
5881's as the output stage, which differs
in that it is both plate and cathode loaded
-the latter by means of a tertiary winding on the output transformer. A chassis
mounted switch permits selection of microphone or phonograph application of
Fig. 12. Bell Model 2200C amplifier.
the preamplifier, and a d.c. balance con-
-a
trol is provided for the output stage. A
hum -balancing control adjusts the tap
on the positively biased heater circuit for
minimum hum. One additional control
permits adjustment of radio tuner signal
to match that of the phono preamp output.
This unit appears to have been designed with practical requirements in
mind. and provides in a single chassis
considerable flexibility.
Following the modern trend for compactness, the 12 -watt Model 2256 amplitier, Fig. 13, provides many of the same
features as the 2200C, but in a smaller
package and with less power output. This
unit employs two 6V6's in the output
stage, and requires fewer stages, but it
has both volume and loudness controls,
bass and treble tone controls, and five
equalization positions for phono, with
input accommodations for high- and low level magnetic pickups as well as for
crystal, ceramic, and capacitance pickups. The housing is the same size as the
Model 2255 AM -FM tuner.
Another unusual amplifier in the Bell
line is Model 3 -D, the binaural amplifier.
This unit incorporates two separate 10watt 6V6 amplifiers on the same chassis,
with selector switch, function switch
(which permits binaural, monaural, and
binaural -reverse operation) a control for
balancing the two channels, and gain and
tone controls which operate simultaneously on both sections.
The most elaborate unit in the line is
Model 2145 -A, which comes with a remote control unit which requires only
one cable between the main chassis and
the control box. all inputs and outputs
being connected directly to the main
chassis. This amplifier
30 -watt unit
will fit in with many users' requirements
where the control unit must be separated
from the main chassis. The line also includes several smaller amplifiers for
modest applications.
-a
-
David Bogen Co., Inc., 29 Ninth Ave., New
York 14, N. Y.
The Bogen line is one of the largest
in the hi -fi field, commencing with the
30 -watt D030, with variable damping
factor ; and following with 20 -watt DB20
and DB2ODF the latter also incorporating the variable damping factor ; the 15watt DB15; the 10 -watt DB110; and the
old standby, the 10 -watt DO10. In addition, a new preamplifier -equalizer has
just been announced, the PR100, which
incorporates some unusual features.
The variable damping factor feature
is of some interest, and has been intro-
-
36
Fig.
13.
Bell
Model 2256 compact amplifier.
AUDIO
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
Fig. 14. Output stage arrangement of the Bogen
D030A amplifier. The QUAD II is similar, but
uses a common cathode resistor between the
center tap of the tertiary winding and ground.
C
r5 MEG
O
MEG
o
MEG
o 2 MEG
47.000
0.27
Fig.
15.
MEG
The Bogen
"Loudness Contour
Se
lector" circuit.
duced by several manufacturers during
the past year under various names. As
used in Bogen amplifiers, the damping
factor control permits the loudspeaker
damping to be adjusted from a low positive value through infinity to a low
negative value. This control is effective
only in the frequency range below 300
cps, and permits loudspeaker damping to
be adjusted for optimum low- frequency
response. For further information on this
circuit, the reader is referred to an
earlier article' on the subject, in addition to that of reference 3. The D030
utilizes some cathode loading of the output tubes, which are KT -66's operated as
tetrodes. Figure 14 shows the output
stage with the variable damping factor
connection to the cathode of the first
amplifier stage indicated. The DO30A
is only a power amplifier, having no controls, and requiring the use of a preamplifier- control unit or a tuner with
suitable controls for complete system
-operation.
The DB20 series incorporates two
additional tubes to provide a preamplifier
and tone controls, and is thus a complete
unit in itself. The output stage emplm
6L6G's in a similar circuit to the D030,
and the variable damping factor control
is available as the DB2ODF. The tone
control circuit is basically that of the
Baxendall design, and while the volume
control is uncompensated, the amplifier
incorporates a "Loudness Contour Selector," as do many other Bogen amplifiers.
This device is, in effect, a volume control with 10 -db steps and with suitable
r Charles A. Wilkins, "Variable damping
factor control," AUDIO, Sept. 1954.
compensation so the listener sets the
control at a point corresponding to the
level at which he wishes to reproduce the
music. The calibration on the selector is
in the number of db below normal performance level that the reproduction is
to be heard, and is readily mastered by
the user in a short time. Figure 15
shows the configuration of the loudness
contour selector which is connected between the source selector switch and the
first section of the volume control.
The DB15 is slightly smaller than the
D020, but is similar in circuit design,
employing the Baxendall tone control
and the loudness contour selector. It is
normally used in a housing shown in
Fig. 16 which eliminates the need for
cabinetry in such installations where the
user might wish to place the amplifier
on a bookshelf, for example.
The 10 -watt DB110 is a relatively new
addition to the line, but it is quite complete in its features and serves well for
smaller installations where price becomes a factor. It incorporates a pre amplifier- equalizer, and the Baxendalltype tone control is used.
The DO10 has long been a popular
amplifier in the low price class. It has
no controls except a semi -fixed volume
adjustment, but provides 10 watts to 4 -,
8-, or 15 -ohm loudspeakers.
The PH10 is another 10 -watt model,
but provided with a 3- position input
selector switch, a volume control, and
a tone control with four fixed positions
It is equipped to feed 3.2- and 8 -ohm
loudspeakers.
The Challenger HF8-also built by
Bogen
an 8 -watt model which provides continuously variable bass boost
and treble rolloff controls, and has a
fader-type volume control with tuner input to the left and phono input to the
right of the center position. An equalized
preamp is included, with a chassis
mounted switch to select magnetic or
crystal and ceramic pickup inputs. It is
designed to feed 4 -, 8 -, and 16 -ohm loudspeakers.
The new PR100 Deluxe Preamplifier,
shown in Fig. 17, uses four dual con-
-is
F.
Fig.
17.
16.
Bogen
DB 15G
amplrficr
The forthcoming Bogen PR100 preamplifier- control unit.
centric controls and six pushbuttons to
provide its many characteristics. Low
and high ends are separately controllable
in the phono preamplifier ; separate bass
and treble boost and cut controls are provided ; low- and high -pass filters are
selected by a third pair of knobs; and the
volume control and the loudness contour
selector are incorporated into the remaining dual unit. Input sources are
selected by the pushbuttons. The phono
input stage is a cascode, and sufficient
gain is provided for the low -level moving -coil pickups. In addition, recorder
output and tape monitor facilities are
built in, d.c. is used on the heaters of
the first four stages, and a.c. convenience
receptacles are provided. This model
seems to offer all the features that anyone could think of, with the possible exception of a presence control.s
Brociner Electronics Laboratory, 344
32nd St., New York 16, N. Y.
eo
E.
In addition to the UL -1 power amplifier, the A100 preamplifier -equalizer,
and the CA -2 control amplifier described
in the EQUIPMENT REPORT in the November, 1954, issue, the Brociner line
incorporates two new models-the Mark
12, which is a compact single -unit 12watt amplifier, and the Mark 30 series,
which consists of a 30-watt power amplifier and a separate control center.
The Mark 12, shown in Fig. 18, provides an input for magnetic pickups,
another for crystal, ceramic, and capacitance pickups, and three high -level inputs, as well as a recorder feed which is
not affected by the loudness control
although it does follow the tone controls.
It uses two 6AQ5's as tetrodes, fed by
one half of a 12AX7 as a cathodyne
phase solitter, which is direct coupled to
the first half of the 12AX7 as a voltage
-
Fig.
18.
Front and rear views of the Brociner
Mark 12.
C. G.
McProud, "Preamp with pres-
ence," AUDIO ENGINEERING, Jan. 1954.
AUDIO
38
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
AXIETTE
8.inch
5 watts
40- 15,000 cps
$23.20
ANY AMPLIFIER
AXIOM 80
10inch
4-6 watts
20.20,000 cps
$68.50
SOUNDS BETTER
WITH A
AXIOM 150
12. inch
15
watts
30- 15,000 cps
$53.50
GOODMANS
LOUDSPEAKER
OF
tu
4,
For complete speci)ical r,,tts, write tu Dept. FA -1
Á
ROCKBAR CORPORATION, 215 East 37th Street, New York 16, N. Y.
AXIOM 22
12.inch
20 watts
30.15,000 cps
$72.95
AUDIO
JANUARY, 1955
37
www.americanradiohistory.com
AmericanRadioHistory.Com
amplifier. The loudness control may be
removed from the circuit by inserting a
pin plug into a phono jack on the rear of
the chassis. The input selector is combined with the low- frequency turnover
control, with four'phono positions, AES,
NARTB, 800, and LP. The rolloff control is separate, and provides droops of
0, 5, 10.5, 12, 13.7, and 16 db at 10,000
cps.
The entire unit is enclosed in a perforated metal case which provides good
ventilation. Outputs of 4, 8, and 16 ohms
are available, and all connections, are
made on the rear of the case. Printedcircuit wiring is used in this model,
which accounts for the small size -the
panel area being only 4% x 10N in.
Figure 19 shows the Mark 30A power
amplifier, which is also compact because
of printed wiring. It has no controls, but
is designed to work with the 30C control
center, which resembles the Mark 12 in
panel appearance. The amplifier has an
output of 30 watts with 1 per cent IM
distortion, and is 3% in. deep, 12 in. long,
and 9 in. high. The control center provides essentially the same functions as
the Mark 12, but uses a panel- mounted
switch to cut in or out the loudness
compensation, and in addition has a
switch to select one of two pickups.
Equalization curves on both the Mark 12
and Mark 30C are tailored to exceptionally close agreement with the prescribed recording characteristics.
Cook Laboratories, 101 Second St., Stamford, Conn.
Many enthusiasts have a highly developed interest in stereophonic reproduction, and in order to control the
sound sources, some special type of amplifier is required unless the user is willing to put up with the inconvenience of
handling two separate units. Cook Laboratories manufactures a dual control
unit, the BN/mn preamplifier shown in
Fig. 20. It is designed to accommodate
either two tuners or two phono pickups,
and is fitted with a selector switch to
choose between radio binaural, phono
binaural, or phono monaural, using only
the "left" phono pickup. Dual bass and
treble tone controls as well as a dual
volume control permit adjusting both
circuits simultaneously, while a "focus"
control effectively adjusts the balance
between the two halves of the unit. A
reversing switch switches the outputs so
as to accommodate various placements
Fig.
19.
AUDIO
Brociner
Mark 30A power amplifier.
Fig. 20. Cook
binaural - monaural preamplifier.
BN mn
of the two channel microphones to best
suit the listener's requirements. The unit
uses two cathode followers for the output circuits, and requires an external
power source of 400 to 450 volts at 20
nia and 6.3 volts at 1.2 amps.
The Radio Craftsmen, Inc., 4401
Ravenswood Ave., Chicago 40, III.
N.
The Craftsmen line consists of the
C350 equalizer -preamplifier, the Solitaire
20 -watt self- contained unit -the 30watt C550 power amplifier, and the 10watt model 400.
The C350, described in the December,
1954, EQUIPMENT REPORT, iS a self powered input unit which provides for
magnetic pickup input as well as three
high -level sources, and provides an output for a tape recorder which is unaffected by volume or tone controls. The
preamplifier accommodates seven recording characteristics, matching the curves
quite well. A dual volume control, which
may be connected by a panel switch so
that one section operates as a loudness
control, reduces hum to a minimum for
low -level reproduction ; the tone controls
are fed from separate stages, thus isolating them from each other to prevent
interaction. Construction is sufficiently
open to permit easy servicing, and noise
is kept to a minimum by the use of
deposited- carbon resistors in the low level stages, with the British Z729 in the
first stage further reducing noise in the
phono circuits. This unit is shown in
Fig. 21 with a filter control section which
provides cutoff of both low and high
frequencies independently to reduce rumble and undesired high- frequency disturbances.
-a
The Solitaire, Fig. 22, incorporates
the same basic functions as the C350
together with a 20 -watt power amplifier
in the same unit. It has four equalization
positions, and provides for three high level inputs. It uses the Baxendall tone
control circuit and a dual concentric
volume control -one section being uncompensated while the other is a loudness
control, It also provides a recorder out-
Fig. 21. Craftsmen C350 preamplifier and control unit with the C375 filter mounted below it.
JANUARY, 1955
put which is unaffected by the loudness
control, but is controlled by the level setting volume control and the tone controls. Three -position filter switches are
built in, permitting cutoff at 40 and 150
cps on the low end, and at 6500 and 3000
cps on the high end, in addition to the
flat positions.
The C550 power amplifier is a fixed
package of gain employing two KT66's
in an Ultra- Linear output stage. This
model is equipped with a thermostatic
time -delay switch which does not apply
plate voltage to the amplifier until the
tubes have warmed up. This is a desirable feature for high -power equipment,
since voltages are likely to be high, and
tubes may be damaged without this
protection. The amplifier circuit is similar to the Williamson, using two 6SN7's
ahead of the output stage.
The 400 is somewhat smaller, using
6V6's in the output stage, driven directly
by the phase splitter which is in turn
driven by two voltage amplifiers. It provides for 4 -, 8 -, and 16 -ohm output taps,
and furnishes its rated output from a 0.7volt input signal.
Electro-Voice, Inc., Cecil and Carroll Sts.,
Buchanan, Mich.
One of the major advances in audio
amplifier design has been introduced by
this company with its entry into the
amplifier field during the past year. This
involves the elimination of one of the
common sources of distortion in power
amplifiers when working close to maximum output.
Under these conditions, the plate current in the output transformer flows
alternately to the two output plates, since
one of the tubes is practically cut off
during the half cycle when the other is
drawing maximum current. During the
next half cycle, the position is reversed.
This results in what is termed a "switching transient," since the plate current
in each tube is "switched off" for a portion of each cycle, and because of the
leakage inductance in the transformer,
this abrupt change in current creates a
momentary transient voltage twice during each cycle.
In an effort to avoid this particular
form of distortion, the E -V amplifiers
employ a bridge- circuit configuration
which eliminates plate current from the
primary winding of the output transformer, with the simplified circuit shown
in Fig. 23. With this arrangement, one
half of the load is in the plate circuit of
each tube and the other half is in the
cathode circuit. However, the same
winding serves both tubes, so the portion that is in the plate circuit of one
Fig. 22. The new Craftsmen Solitaire
39
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THE
LABORATORY ENGINEERED BY
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featuring the exclusive patented*
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Here is what the magnificent new McIntosh amplifier gives you for your dollars invested
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Power, yes but power plus exceedingly low distortion for faithful reproduction of clean,
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For performance that really makes a difference enjoy the McIntosh, superbly crafted in
the McIntosh tradition by amplification specialists to please the most exacting listener. Advertised performance money -back guaranteed by thorough laboratory tests on each unit.
Consider this important feature: You can listen to the McIntosh for hours, not just minutes,
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For a new miracle
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AMPLIFIER
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MAX. INTERMODULATION
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TION
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QUENCY RESPONSE
30,000 cycles at 30 watts output, and within -±- 1
db 10 to 100,000 cycles at 15 watts output.
INPUT (.5 volt) .25 megohms for full output.
85 db or more below
NOISE and HUM LEVEL.
rated output.
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324
McIntosh Laboratory, Inc.
Water St., Binghamton, N.
Y.
Please send me FREE booklet
"LOST INSTRUMENTS" and detailed literature.
Name
Address
City
Zone_ State
_
type of output circuit and the same damping factor control as the A -30, and in addition has preamplifier and tone control
stages, both loudness and volume con -
trots, and inputs for ceramic and magnetic phono pickups, radio, tuner, and
tape, and it provides an output for feeding a tape recorder -the latter being
controlled by both tone and level -setting
controls. One feature of the E -V output
circuit is that it provides a 600 -ohm
output without requiring a complicated
output transformer -most transformer
engineers believing that it is practically
impossible to design a conventional
transformer which will give good response on both speaker and line windFig. 23. Schematic of bridge output circuit of
ings over the wide frequency range
E -V amplifiers to show plate supply for prerequired for modern high- feedback amliminary stages.
plifiers. The 600 -ohm output comes from
tube is in the cathode circuit of the other. taps on the primary of the output transThus there is a close coupling between former, the center tap of which
grounded.
the tubes, and by proper arrangement
Two input sets are available for use
of the power supplies, no d.c. appears in
the windings. This does require that two with the A -30 amplifier -the PRC -1
separate power supplies be used, but which will accomodate both ceramic and
since the requirements are thus halved, magnetic pickups, and the PRC-2 which
the additional complication does not in- does not have the preamp required for
crease the cost appreciably. In addition, the magnetic pickups. Both of these input
the plate supply to the driver stage is sets consist of two separate units-one
derived from the output stage in a fash- being the preamplifier unit which has a
ion which adds the signal voltage to the master on -off switch and a function
supply voltage, and the resulting voltage selector on the panel, and four individual
to the driver stage is "bootstrapped" level controls on the rear apron. The
when it is driving the output tubes the remote control unit accommodates the
hardest. The over -all result is a reduction record compensation switch with nine
positions, a level control, and bass and
in distortion, and these units have extreble tone controls, a volume -loudness
cellent operating characteristics.
Another feature of these amplifiers is switch, a presence switch which introthe employment of a dual control in the duces an 8 -db rise at 5000 cps, and a
variable- damping circuit which main- rumble-filter switch which reduces the
tains the total feedback constant, al- response 30 db at 30 cps and only 3 db
though the voltage feedback and the cur- at 70 cps. These units take their power
rent feedback are both being varied to- from the A-30 line amplifier.
gether. The arrangement that provides
Espey Manufacturing Company, Inc., 528
this feature is shown in Fig. 24.
E. 72nd St., New York 21, N. Y.
These features are incorporated in
both of the E -V amplifiers-the 30 -watt
For use primarly with their models
A -30 power amplifier, and the 20 -watt 710 and 700 AM -FM tuners, this comunit which is complete with preamplifier pany provides the Model 501 amplifier,
and control section. The A -30, Fig. 25, shown in Fig. 27. It has no controls,
uses two 6BG6's in the output stage, with being designed to work with a tuner
a 12BH7 driver and a 12AX7 as a which provides all the control facilities.
voltage amplifier and phase splitter. The The output stage consists of four 6V6's,
damping factor is adjustable from 0.1 to preceded by two 6SN7's in a conven15, and the rated output is obtained with
tional Williamson circuit. Rated at 24
an input of 1.25 volts.
watts, this amplifier is relatively small,
The A -20C amplifier, Fig. 26, proves being 12 in. long, 5 in. high, and 8 in.
the advantage of the circuit by reaching deep. It provides outputs for 4 -, 8 -, and
a power output of 20 watts from a pair
15 -ohm speakers.
of 6V6's, which are usually employed in
10 -watt amplifiers. Aside from its lower
power rating, the A -20C has the same
Fig. 25. Electro -Voice A -30 power amplifier.
Fig. 26. Electro -Voice A -20 -C amplifier-combining both power and control sections.
42
FIRST
AMPLIFIER
STAGE
9
OUTPUT TR
SEC
Rw VOLTAGE FEEDBACK RESISTOR
Ru CURRENT FEEDBACK RESISTOR
Fig. 24. Schematic showing variable voltage
and current feedback used to change internal
impedance of the amplifier.
Fairchild Recording Equipment Co., 54th
St. and 7th Ave., Whitestone 57, N. Y.
1
This company has recently announced
two units-the Model 240 preamplifier equalizer, and the Model 260 50 -watt
power amplifier. The former, shown in
Fig. 28, provides inputs for magnetic
pickups and for three high-level sources.
It uses a 12AT7 as a cascode input stage,
followed by two 12AX7's as three voltage amplifiers and a cathode follower.
The unit is self powered, using selenium
rectifiers for both plate and heater supply -all heaters being fed with well
filtered d.c.
This amplifier has an interesting design in that the knobs on the bass and
treble tone controls are, in effect, the
extremes of the audio spectrum curve,
the center range being represented by a
straight lucite bar. Thus the response
curve may be said to be flat when the
controls are in line with the center
section, and as the response curve is
changed by turning either control, the
appearance of the "curve" as indicated
on the panel is changed also. Another
interesting feature is the use of a
switch labelled LO, NORMAL, and HI
for adjusting loudness compensation for
different listening levels, at the same
time dropping the level by some 15 db
for each position down from Hr.
The Model 260 power amplifier employs two 1614's in an Ultra -Linear output stage, driven by one section of a
12AU7 as a cathodyne phase splitter,
preceded by the other section as a directcoupled voltage amplifier, and by a 6AB4
in the input stage. Both bias and dynamic balance are adjustable. To adjust
the latter, one inserts a phone plug into
a jack on the chassis. This places a high
a.c. signal on hnth output grids in phase.
Fig.
27.
Espey
Model 501
amplifier.
AUDIO
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R,,
Williamson -type
JANUARY, 1955
SWEEPING THE COUNTRY!
/tettiebi4a,/vtrt4 tee
IN AMPLIFIER DESIGN
Fig. 28. The Fairchild model 240 preamplifier,
IN TWENTY YEARS!
with "Balanced Bar" tone -control arrangement.
Adjustment of the balance control to give
minimum hum in the speaker balances
the stage dynamically. A meter plugged
into the same jack permits adjustment of
the bias control -fixed bias being used
on the output stage. The output transformer is tapped to accommodate 4 -, 8 -,
and 16 -ohm speaker loads.
Fisher Radio Corporation, 21 -21
Drive, Long Island City 1, N. Y.
FISHER
44th
Offering a complete line of equipment,
from a simple fixed -equalization preamplifier to a 50 -watt power amplifier,
the Fisher line is well reputed for its
reliability and quality. The basic preamplifier, model PR -5, is designed to
provide sufficient amplification, together
with equalization for a 500 -cps turnover.
to permit changing to a magnetic pickup
while still using an amplifier designed
for a higher -level type. It is self powered.
and employs a single 6SC7, with feedback equalization between the plates of
the two sections of the tube.
Model 50-PR is similar in circuit, but
provides variable equalization, with separate controls for low and high frequencies. The turnover control selects between
AES, RIAA (NARTB, ORTHO), 800
cps, and the old LP curve, while the
rolloff control provides droops of 0, 8, 12,
and 16 db at 10,000 cps. The unit is
housed in a small molded case, similar to
the 50 -F Hi -Lo Filter System, shown in
Fig. 29. This latter unit permits the
user to introduce a sharp cutoff at either
end of the audio spectrum to eliminate
rumble and hum in the low end, and
needle scratch, distortion, and other objectionable disturbances at the high end.
The Hi -Lo Filter is also self powered,
and employs R-C networks for the high pass filter action, and L -C networks for
the low -pass filter action where sharper
cutoffs are desirable. A single 12AX7 is
used, with the filter networks between
the two halves ; the second section serves
as a cathode follower to provide a low-
Z -MATIC
-
both are a regular and traditional
of our engineering laboratories. But never before
have we offered a technological advance so obviously needed, so
long overdue, as the exclusive FISHER Z- Matic. Regardless of
the speaker system, be it a modest 8" unit or a giant assembly,
the vast acoustic improvement contributed by FISHER Z -Matic
is instantly apparent and truly astonishing. For Z -Matic has at
one stroke eliminated the energy-wasting, distortion- producing
mismatch that has prevented the complete union of speaker and
amplifier ever since the advent of electronic sound reproduction.
Z -Matic is now standard equipment on all FISHER amplifiers.
HE unusual, the choice
1 product
What
Z -Matic
Does
Multiplies the efficiency and effective audible
range of any speaker system, regardless of size.
The continuously variable Z -Matic control
permits any setting, according to personal taste
or the requirements of the speaker system.
Eliminates need for oversize speaker enclosures and automatically corrects inherent deficiencies in speaker or speaker housing.
Z -Matic must not be confused with tone,
equalization or loudness balance controls.
A
50 -Watt Amplifier
Model 50 -A
100 watts peak! \\ orld's finest all- triode
db, 5 to
amplifier. Uniform within
100,000 cycles. Less han I% distortion
at 50 watts. Hum and ' noise 96 db below
full output. Oversize, quality components
$159.50
and finest workmanship.
1
-
Master Audio Control
Series
50-C
Radio and
"Finest unit yet offered."
TV News. 25 choices of record equalization, separate bass and treble tone controls, loudness balance control. 5 inputs
and 5 input level controls, 2 cathode follower outputs.
With cabinet, $97.50
Chassis, $89.50
Word to Our Patrons
Your FISHER 50-A or 70-A amplifier can be
readily equipped with Z- Matic. A complete kit
of parts and easy -to- follow instructions are
available at a cost of only $2.50 to cover
handling. Give serial number and model.
25 -Watt Amplifier
50 -watts peak!
Model 10 -A
More clean warts per doll
Less than V2r%o distortion at 25 watts
at 10 watts.) Response within 0.1
,
(0.05,
db, 20-
20,000 cycles; I db, 10 to 50,000 cycles. Hum
and noise virtually non -measurable!
$99.50
Prices Slightly Higher West of the Rockies
WRITE TODAY FOR COMPLETE SPECIFICATIONS
FISHER RADIO CORP.
Fig. 29. Fisher Hi Lo
AUDIO
21
-27 44th
DRIVE
L. I. CITY
1, N. Y.
filter system, model 50 -F.
JANUARY, 1955
43
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Fig.
30.
Fisher
Master Audio Control,
30 -C.
series
impedance output. Model 50 -PR -C is
identical to the 50 -PR except for the
addition of a volume control.
The Master Audio Control, 50 -C-4, is
shown in Fig. 30. This unit, which may
be had in either blond or dark mahogany
cabinets or in chassis form for installation in a larger equipment cabinet, provides essentially same facilities as the
50 -PR for phono equalization, and has,
in addition, a volume control, selector
switch, separate bass and treble tone
controls, and a loudness balance switch.
This unit is also self powered, and furnishes filtered d.c. to the heaters of the
three tubes
12AX7 preamplifier, a
12AU7 with one half serving as a cathode follower to provide a low- impedance
feed to a recorder and to drive the
volume control while the other half
serves as the output cathode follower.
The other 12AX7 serves as a voltage
amplifier to provide sufficient gain for
the tone controls. The loudness switch
cuts in or out of circuit an R -C network
connected to the volume control.
The amplifier line is completed with
two power amplifiers, the 25 -watt Model
70 -AZ and the 50-watt Model 50-AZ,
shown in Fig. 31. Both employ the new
"Z- Matic" control, which constantly and
automatically adjusts the output impedance of the amplifier to match the impedance of the loudspeaker. A variable
control permits the user to make this
adjustment himself to obtain optimum
performance and sound quality. The 50watt model is noteworthy in that it
employs only two 1614's as output tubes,
working with fixed bias and fed by two
cathode -follower drivers which are
transformer -coupled to the output grids.
This amplifier provides full 50-watt output with an input signal of 1.5 volts,
and shows an IM distortion of only 2
per cent at 45 watts.
-a
Freed Electronics 8 Controls Corp., 200
Hudson St., New York 13, N. Y.
This line consists of two amplifiers,
the 10 -watt model 910 and the 20 -watt
model 920. Figure 32 shows the former.
which employs two 6V6's preceded by a
12AU7 driver and a 12AT7 voltage amplifier and phase splitter.
Fig. 33. Model
Al -200 General Electric pre-
amplifier and control unit.
Fig. 32.
Fig.
31. Fisher
laboratory Standard Amplifier,
Model 50 -AZ.
The 20 -watt amplifier uses two 5881's
in the output stage, with one 12AU7 as
voltage amplifier and phase splitter and
another 12AU7 as driver. An additional
12A1.17, preceded by a 12AT7 preamplifier provides complete facilities-except for controls-to work with a radio
tuner which does have controls but no
preamp.
General Electric Company, Radio & Television Department, Electronics Park,
Syracuse, N. Y.
With the preamplifier and control unit
as a "front end" and a 10 -watt power
amplifier to drive the loudspeaker, this
line is small, but offers adequate flexibility for home use. The Al -200 control
unit a 6SC7 as a phono preamp, followed
by a cathode follower to drive the tone
controls, two voltage amplifiers, and an
output stage which -while not a cathode
follower-offers an output impedance of
4000 ohms. The volume control can be
connected, by means of a switch on the
rear of the chassis, to work as a loudness
control. This unit is designed to work
with a GE pickup, and if other pickups
are to be used a few changes of resistors
and capacitors must he made in order to
maintain the same characteristics, because the rolloff and cutoff controls function with the inductance of the pickup to
give the required results. The unit is
self powered, using a selenium rectifier
for plate supply, and is shown in Fig. 33.
The 10 -watt power amplifier, Model
Al -300, is a compact unit using a 12AX7
as two voltage amplifier stages, followed
by a 6C4 cathodyne phase splitter and a
pair of 6V6's in the output stage. It has
relatively low IM distortion for a 6V6
arbplifier, and provides rated output at 2
volts normally, with a minor change
making it possible to obtain full output
with an input of 0.3 volts. This unit is
shown in Fig. 34.
Fig. 34. General Electric Model
Al -300 power
amplifier.
Freed model
I
Harman - Kardon, Inc., 520 Main St., Westbury, L.
N. Y.
In addition to Model D -1000, the
Festival
deluxe AM -FM tuner with
tone controls and phono preamp combined with a 20 -watt Ultra-Linear power
amplifier, this company offers the Melody, Model C -100, which is a self-contained unit having a power output of 10
watts, and equipped with tone controls,
a phono preamp with three degrees of
equalization, and a loudness contour
selector offering six positions of compensation.
The amplifier, shown in Fig. 35, employs a 12AX7 as the preamplifier, with
feedback for equalization, and with inputs from high -level sources being fed
to the grid of the second section to
provide more usable gain. Full output
is obtained with 0.3 volts from the high level jacks, and with 8 my from the
phono input. LP, RIAA, and EUR equalizations are offered on the three positions of the selector switch, with tuner
and two auxiliary inputs occupying the
other three positions. Bass and treble
tone controls follow the input section,
and they feed the volume-loudness control. The contour selector places a resistor network across each of two capacitors in the compensating network to
adjust the amount of boost at the low
frequencies. After the desired loudness
level is set the volume control effectively
serves to adjust level.
The "basic" part of the amplifier consists of a 12AT7 as voltage amplifier
and direct -coupled phase splitter. a
12AU7 as a driver, and a pair of 6CM6's
as the output stage. Feedback is taken
from the secondary of the output transformer to the cathode of the first section
of the. 12AT7, and output impedances of
8 and 16 ohms are provided.
-a
Heath Company, Benton Harbor, Michigan.
The success of this company's kits
originally introduced to allow service
technicians and experimenters to construct their own test equipment at a
Fig.
35.
Compact Harman Kardon amplifier.
model C100
AUDIO
44
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AmericanRadioHistory.Com
910 10 -watt amplifier.
JANUARY, 1955
"Well worth careful consideration"
-HIGH
FIDELITY TITH REPORT
STENIORIANG
tairtd-AEo-fte,
12" Duplex
The superb, British made Stentorian line of High
Fidelity Loudspeakers provides types and sizes to fit
every audio purpose. Whether you select full range
coaxial speakers or extended wide range direct radiators, tweeters or woofers you'll find a Stentorian to suit
you perfectly. All models feature the revolutionary
patented Stentorian cambric cones and suspension;
Sizes 8 inches and up feature non-resonant die -cast
chassis. Stentorians are unmatched in performance,
craftsmanship and value. Hear Beam Stentorians the
Sound that "stands alone" for yourself and be
convinced.
$99.50
(twin concentric)
Response, 20 to 20,000 cps; bass resonance, 35 cps; built.in crossover;
15 watts; gross weight, 16% lbs. Series Alcomax magnet system; net
weight, 111/2 lbs.; 31,000 Gauss; two 11/2" yoke cells.
12" Extended Range Direct Radiator
$42.50
Response, 25.14,000 cps; bass resonance, 39 cps; 15 watts; gross
weight, 10 lbs.; Alcemos magnet, 51/2 lbs., 14,000 Gauss; 11/2 " V /C.
10" Duplex
-
$44.50
(twin concentric)
Response, 30 to 16,000 cps; 10 watts; gross weight, 61/2 lbs.; 3 lb. 9 oz.
Alcomax series magnet system; 25,000 Gauss; two 1" V /C.
iip)
3 way variable impedance DIRECT RADIATORS
4
-8.ms
You select the perfect impedance match
1012 U-10"
HF 912 U-9"
HF 812 U-8"
HF
L
for your system!
Extended Range Response, 30 to 14,000
cps; bass resonance, 35 cps. 10 watts.
These models also available with 15
ohms V/C only. All have 12,000 Gauss, 2
lb. 1 oz. Alcomax Magnets.
$15.95
12.55
11.95
QUALITY without Compromise
BEAM
QuAID
AMPLIFIERS
Response, 1040,000 cps; 0.5 db
20- 20,000 cps level at full 15 watts
Total Distortion, at 700 cps, less than
0.1%
than 0.4%
Max. Intermod. Distortion less
3 position Filter Slope Control; Level to
50 db/ octave
"Should Satisfy the Most Critical"
-Audio
Equipment Report
Quad II Amplifier
Q.C. II Control Unit
System Complete
Send for literature and detailed specifications on the
Beam Products described above, and on Stentorian
Speakers from 5" to 12" sizes, 5 and 15 watt pressure
horn tweeters, matching crossovers, the Stentorian 18"
woofer and Beam enclosures.
AUDIO
-
$130.00
$120.00
$237.50
The Beam QUAD is a truly superior audio
instrument, providing uncompromising quality plus unparalleled flexibility of control. Its
scarcely traceable distortion is inaudible at
any volume. Add high efficiency harmonic
filtering, push -button equalization and channel selection, plug -in pickup matching, balanced feedback throughout, 13 section output
transformer, superb British craftsmanship,
and the most functional styling in high
fidelity today and you can see why QUAD
is the recognized world leader in high quality
audio reproduction. Hear it at your earliest
opportunity.
-
BEAM INSTRUMENTS CORPORATION
350 Fifth Avenue, New York, N. Y.
JANUARY, 1955
45
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Interelectronies Corporation, 2432 Grand
Concourse, New York 58, N. Y.
The current models of Interelectronics'
Fig. 36.
Heathkit Preamplifier -one that the
user can build himself.
considerable saving over factory -built
units led them into the amplifier field.
The most popular amplifier so far has
been the "Williamson Type" amplifier,
which is available either with the output tubes serving as triodes or with the
Ultra- Linear circuit. This amplifier is
built in two parts -the amplifier proper
and the power supply. Power is furnished to either of two types of preamplifiers, with the newest model, the
WA -P2, providing complete control facilities. This unit, shown in Fig. 36. has
sepárate turnover and rolloff controls
the former with LP, RIAA, AES, and
EARLY 78 positions, and the latter with
droops of 0, 8, 12, and 16 db at 10,000.
cps. Together these provide adequate
flexibility. Separate tone controls are
provided, and the volume control is not
compensated. The three higt-level inputs
have separate level -adjusting controls,
and one flat position of the preamplifier
provides for a low -level microphone.
The new W-5M power amplifier is
built on a single chassis with the power
supply, and is equipped with a protective cover. This unit employs two KT6Ó's
in an Ultra- Linear output stage, and the
design gives improved performance for
at least one octave lower in the bass
range. and to a considerable extent at
the high end. A new balance circuit is
incorporated which makes it possible to
balance the output with only a VTVM,
instead of the usual milliammeter. The
use of KT66's in the output stage gives
somewhat greater power output, as
would be expected, and lower intermodulation and harmonic distortion is afforded, with improved phase -shift characteristics at both ends of the spectrum.
The Heath line includes several other
amplifier kits, including one which is
labeled the economy model, with a 6 -watt
output.
-
Fig. 38. Leak model TL 10 amplifier with remote control preamplifier and master control
unit.
46
amplifiers include the 40-watt "Coronation 100," and "Coronation" preamplifier- equalizer consolette. The latter is
shown in Fig.. 37.
The power amplifier consists of two
6SN7's driving two KT66's, and a
speaker damping control is a feature of
this model. This permits adjustment of
the output impedance from approximately one third of the nominal impedance of the output tap te slightly less
than zero with complete stability. This
is important, for with a total of nine
feedback loops in the amplifier, some care
must be taken to ensure stability. To
accommodate electrostatic loudspeakers
-which are probably imminent -this
amplifier is equipped with an output jack
with suitable connections.
The control consolette has separate
rolloff and crossover controls, each with
four positions. a source selector switch,
a volume control with separately control able loudness contour, and separate bass
and treble controls. For extreme quiet
in the preamplifier section, the Z729 is
used, and low -noise resistors are used
in critical circuits. All equalization
both for phono and for the tone controls
done by judicious use of feedback.
-is
b Co. Ltd., (Distributed by
British Industries Corporation,
164
Duane St., New York 13, N. Y.)
H. J. Leak
The Leak amplifier first introduced in
this country in 1949 was, for that time,
unusual in the extremely low distortion
at rated output -the name "Point One"
referred to 0.1 per cent harmonic distortion-and it is, in addition, a model of
neat and efficient construction. The
TL/10 differs from the earlier TL /12
primarily in power output, but the newer
10 -watt model has equally low distortion.
Needless to say, frequency response is
flat over the audio spectrum, so distortion remains the important difference
between amplifiers.
The TL /10 consists of two chassis.
Fig. 38-the remote control preamplifier
and the basic amplifier. The former
consists of two stages, both using EF86's
(which are equivalent to Z729's) with
feedback around the first stage for
phonograph compensation, while the
second stage, triode connected, serves as
the output tube. Four equalization curves
are provided. with close adherence to
the prescribed curves. The tone control
is of a modified Baxendall type, and the
volume control follows the second tube,
thus reducing hum and noise from the
preamplifier unit as volume is reduced.
A tape recorder feed, appearing as a
jack on the panel of the control unit. is
connected to the output of the second
stage just ahead of the volume control.
Another panel -mounted jack provides for
the input from a tape recorder -this arrangement making it simple for ti
user to connect a portable tape recorder
to the amplifier when he wishes to us,
it, and equally simple to remove it frotta
the circuit when it is not in use.
Fig.
37.
Interelectronics "Coronation"
solette.
con -
Both tuner and pickup inputs are fitted
with level-adjusting controls, and a terminal strip on the rear of the unit permits connecting 'a load resistor to suit
the particular pickup used. The input
signal required at the phono jack for 10watt output is 8 mv, while a signal of .05
volts at the tuner or tape recorder jacks
will give the same output.
The power amplifier is noted for its
neat construction, with cabled wiring,
and most of the small components
mounted on a resistor board. The tube
lineup consists of an EF86 pentode as
the first stage, a "long-tailed pair" consisting of the two sections of a 6SN7
for the phase splitter and driver, with a
pair of KT61's- similar to 6V6's but
with somewhat more linearity and considerably more power sensitivity -in an
Ultra -Linear connection for the output
stage. With four minor changes, KT66's
may be substituted for the KT61's, and
under these conditions the amplifier will
function the sanie as with KT61's. These
changes accommodate the lower power
sensitivity of the KT66's by providing
increased gain in the first stage of the
amplifier.
The basic amplifier provides a power
supply for an external tuner unit
plate
voltage of 330 at 20 ma current drain.
and a heater supply of 6.3 volts at 1.5
amps. The two sections of the amplifier
are connected by a six -wire cable, with
the input lead being shielded. The external power supply is available on the
control unit.
-a
S. B.
Marantz, 25 W. 43rd
36, N. Y.
St., New York
The \l, rantz Audio Consolette has
achieved considerable popularity since
it was first introduced. It is a three -tube
unit. requiring a separate power supply
which is a small selenium -rectifier unit.
Both are shown in Fig. 39.
The amplifier provides low -level inputs for microphone and two pickup out-
F..
>) Marantz Audio Consolette with separate power supply unit.
AUDIO
JANUARY, 1955
HEATHKIT
puts, and four high-level inputs -all being chosen with one selector switch.
Turnover and rolloff are separately
adjustable, and the recorder feed is
connected ahead of both tone and volume
controls. A loudness compensator permits adjustment for listening level, and
a four-position switch provides three
positions of low -pass filter and one flat
position. Output is from a cathode follower, with an output impedance of approximately 5000 ohms. Heaters are
supplied with direct current, and the separate power supply unit removes all a.c.
equipment from the amplifier proper,
with the exception of the power switch.
The low -level phono input has sufficient gain to work with the 1- to 3 -mv
pickups and provide full output without
the use of a transformer.
amplifier
kits
reatict(tll
WILLIAMSON TYPE
(ACROSOUND
TRANSFORMER)
This dul- chassis high
fidelity amplifier kit provides installation flexi-
Mark Simpson Manufacturing Co. Inc., 3228 49th St., Long Island City 3, N. Y.
The Masco line of amplifiers consists
bility. It features the
Acrosound "ultra-linearoutput transformer. and
has a frequency response
within I db from IO cps to 100.000 cps. Harmonic distortion
and intermodulation distortion are less than .5% at 5 watts.
and maximum power output is well over 20 watts. A truly outstanding performer. W-3M consista of main amplifier and
of two models -the 10 -watt Custom Ten
and the 8 -watt CM -8. Both employ 6V6's
in the output stage, but with several differences in the earlier stages.
The Custom 10. shown in Fig. 40, provides one phono input, with a switch to
accommodate- high - and low -level pickups, and three high -level inputs for tuner
$49.75
power supply. Shpg. Wt. 29 lbs., Express
only
i1
Model W-3 consista of W-3M plus WA-P2 Preamplifier lietedlon this page. Shpg. Wt. 37 lbs., Express
$69.50
V
only
taicttt
f'le4 44I
HIGH FIDELITY
PREAMPLIFIER
WILLIAMSON TYPE
Here is the
complete
preamplifier. Designed
specifically for use with
the Williamson Type circuit, it provides equalisation for LP, RIAA, AES,
and early 78 records, 5
switch -selected inputs
with individually preset
level controls, separate
bass and treble tone con trots, special hum control,
MODEL WA- P2
etc. Outatending in performance and most attractive in appearance. Fulfills every
requirement for true high fidelity performance.
Shpg. Wt. 7lbe
619.75
(CHICAGO TRANSFORMER)
This hi -fi amplifier is ronstructed on a single
chassis, thereby affecting
a reduction in cost. Uses
new Chicago high fidelity
output transformer and
provides the eame high performance as Model W -3 listed above.
An unbeatable dollar value. The lowest price ever quoted for a
complete Williamson Type Amplifier circuit.
Model W -4M consists of main amplifier and power supply on
oblle chassis. Shpg. Wt. 28 lbs., Exprees$39.75
Model W-4 consista of W -4M plus WA-P2 Preamplifier. Shpg. Wt. 3S lbs., Express only
;59.50
eat`eiit
Fig. 40. Masco "Custom 10" amplifier.
WILLIAMSON TYPE
and other sources. Feedback around the
first two stages provides the equalization,
with five positions being provided. The
remaining circuit lineup consists of the
compensated volume control, two voltage- amplifier stages with feedback
around them, the tone control section,
a voltage amplifier, a cathodyne phase
splitter, and the output stage. A hum
adjusting control is provided, and the
recorder -feed output is located just
ahead of the tone control network.
The CM -8 is a simpler unit, providing inputs for magnetic or crystal pickup
and for one high -level input such as a
tuner, with a fixed equalization network
for phono. A 6SL7 ,serves as a voltage
amplifier and phase splitter, with the
bass tone control in the feedback net work -the treble rolloff control being
located in the grid circuit of the 6SL7.
McIntosh Laboratory, Inc., 324 Water St.,
Binghamton, N. Y.
With the introduction of the McIntosh
circuit in 1950. a new era in high -power
amplifiers was ushered in, for with only
two 6L6's the first McIntosh model
50W -2-was capable of putting out a
50 -watt signal with IM distortion less
than 1 per cent. The basic difference
-
AUDIO
JANUARY, 1955
(PEERLESS TRANSFORMER)
This latest and most advanced Heathkit hi -fi
amplifier has all the extras so important to the
super- critical listener. Featuring ET-66 tubes.
special Peerless output transformer, and new circuit design, it offers brilliant performance by any
standard.
Bass response is extended more than a full
octave below other Heathkit Williamson circuits,
along with higher power output. reduced inter modulation and harmonic distortion, letter phase
shift characteristics and extended high frequency
response. A new type balancing circuit makes
balancing easier, and at the same time permits a
COMBINATION
W -5M and WA -P2
closer "dynamic" balance between tubes.
well. A protective cover fits over
Aside from these outstanding engineering features, the W-5 manifests new physical design as
connectors are
all above-chassis components, forming a most attractive assembly -suitable for mounting in or out of a cabinet. All
brought out to the front chassis apron for convenience of connection.
Model W -551 consists of main amplifier and power supply on single chassis with protective cover. Shpg. Wt. 31 Its
Express only
Model W.í consists of SRSM, plus WA-P2 Preamplifier shown on this page. Shpg. Wt. 38 lbs.
Express only
59.75
$79.50
%a.t.`sa
HIGH FIDELITY
H
20 WATT AMPLIFIER
This particular 20 watt Amplifier combines high fidelity with economy. Single
chassis construction provides preamplifier,
main amplifier bid power supply function. MODEL A- 98
True hi -fi performance +I db, 20 cps to
20,000 cps. Preamplifier affords 4 switch-selected compensated inputs. Pushpull 61.6 tubes used for surprisingly clean output signal with excellent response characteristics and adequate power reserve. Full tone control action.
Extremely low cost for real high fidelity performance. Shpg.
Wt. IS lbs
$35.50
EATH
COMPANY
BENTON HARBOR 25,
MICHIGAN
Write FOR FREE CATALOG AND SCHEMATICS
47
Fig. 43
Fig. 41. Simplified schematic of the McIntosh
output stage. Windings A and B are bifilar
wound, with
a
1:1
turns ratio
between the McIntosh circuit and .:onventional amplifiers is in the output
coupling system. The plates of the output stage are connected to opposite ends
of a primary winding on the output
transformer ; the cathodes are connected
to opposite ends of a second winding,
as shown in Fig. 41. Both windings
have the same number of turns, and
they are wound bifilarly-with two
turns of wire being fed onto the winding machine at the same time. Thus the
plate of one output tube and the cathode
of the other have the sanie signal potential. With pentodes, it is desirable to
have the screen bypassed directly to the
cathode, rather than to ground. By connecting each screen to the opposite
plate- through a resistor to limit screen
dissipation
is at the same signal
potential as the cathode, and at the same
d.c. potential as the plate. Each output
tube is thus operating with one half of its
load in the plate circuit and one half in
the cathode circuit. This gives excellent
efficiency and power output and, since it
represents approximately 100 per cent
feedback in the output stage, reduces
-it
distortion greatly. This arrangement
does require harder driving of the output grids, and in the 50W-2 the driver
was coupled to the output stage by a
transformer.
The newer Mc -30 amplifier, (Fig 42),
rated at 30 watts, utilizes the same output connections, but employs cathode follower drivers. While the power output is lower -30 watts
is still adequate for any home requirement, and the
distortion is held to an equally low
minimum. The Mc -30 uses one half of
a 12AX7 as the first stage, direct coupled
to a 12AU7 as a "long- tailed pair" phase
splitter followed by a 12BH7 push -pull
voltage amplifier and another 12AX7 as
the cathode- follower driver. The output
tubes are 1614's, which have a high
heater -to-cathode voltage rating. Fixed
bias is used on the output stage.
-it
rnwr
,cric
,ovrrrrr
I
10 ®
National Horizon 5 preamplifier and
control unit, which plugs into either the
Criterion tuner or the Horizon 20 power amplifier.
Fig. 44.
48
Fig.
42.
McIntosh
Mc -30 amplifier.
The output transformer has four windings-two are identical and are located
in the plate and cathode circuits; a third
winding serves as the "secondary" for
feeding the voice-coil circuit outputs;
and a fourth winding is employed only
for voltage feedback to the cathode of the
first tube. The unit is self contained, and
furnishes power to" a McIntosh preamplifier.
For those who want high power
and most particularly, for public address
or hotel installations where many speakers are to be supplied, there is the K -107
series -available with 600 /150 ohm
output in K -107F, with constant -voltage
feeds for multiple speaker installations
in K -107G, and with 4 -, 8 -, and 16 -ohm
outputs, as well as 600 ohms, in K -107H.
Each of these amplifiers is capable of
putting out a 200 -watt signal with less
than 1 per cent harmonic distortion. The
circuitry is similar, but larger output
tubes are used- 8005's -and power and
driver requirements are all necessarily
"king size."
Two preamplifiers are available-the
Model C -104 which is fairly conventional, and some two years old, and
Model C -8 which is comparatively recent. This model, shown in Fig. 43, provides extreme flexibility, since turnover
frequencies are selected by switches and
with five switches usable singly or in
any combination desired, 29 different
curves are available at the low end and
29 at the high end. This should be adequate for any possible curve now in
existence or ever to be in the future.
Separate bass and treble controls are
provided, and an aural compensation
switch adjusts loudness quality to suit
the individual. Five inputs are available
-two at high level, one unequalized at
low level for microphones, and two
equalized for phono pickups, one for
high- output models and one for low outputs. The latter incorporates a switch
which may be opened to insert a series
capacitor in the circuit for use with
capacitance pickups, and a variable load
resistor is provided so as to match any
desired pickup. A five -position rumble
switch introduces a one-, two-, three-.
and four -section R -C network progressively as it is rotated, sharply reducing
low- frequency response in the vicinity
of 30 cps.
For those applications where the pre amp is to be used with other than a McIntosh amplifier, the Model C -8P should
-
Flexible control amplifier -McIntosh
model C -8M.
be chosen, since it is self powered. The
C-8 derives its power from the main
amplifier.
National Company, Inc., 61 Sherman St.,
Malden, Mass.
This company is a relative newcomer
to the hi -fi field, but its name has long
been known for communications equipment. The line consists of a preamplifier control unit, the Horizon 5, and two
power amplifiers, the 10 -watt Horizon
10 and the 20 -watt Horizon 20.
The Horizon 5, Fig. 44, is designed
to plug into the National Criterion tuner
or the Horizon 20 amplifier, and it derives its power and all input and output
connections through a 16- terminal plug.
mounted at the rear. The unit employs
some unusual circuitry (in addition to
using printed wiring to a large extent).
having, for example, a dual volume eon trol which can serve as a binaural control, for which the tuner is equipped.
Elaborate and well tailored tone controls
are capable of giving a bass boost of 26
db at 20 cps and a cut of 19 db at the
same frequency. At the high end, the
boost is 11 db and the cut can be as high
as 23 db at 10,000 cps. The unit employs
but two tubes, both being 12AX7's, with
feedback and losser equalization serving
for the phono channel.
The Horizon 20 uses two 6L6G's in
the output stage, the circuit being arranged to work one of the tubes with a
plate load and the other with a cathode
load. This is the single -ended push -pull
configuration, and reduces the demands
on the output transformer. Distortion is
quite low, for the amplifier is rated at 20
watts yet has only 3 per cent IM distortion at slightly over 30 watts. The
tube lineup consists of a 12AX7 with
the first half operating as a voltage
amplifier and the second half as a
cathodyne phase splitter. Fixed bias is
used on the output stage, and power is
furnished to the Horizon 5 preamplifier
Fig. 45. National Horizon 20 power amplifier
When cover plate is removed. Horizon 5 amplifier may be plugged in making it a complete
self- contained amplifier.
AUDIO
JANUARY, 1955
-
AN EAR TO
'
'
'd
-
.
s.
A'
:
harman kardon
929iewce
DELUXE AM -FM TUNER
MODEL A-300
catches the spirit
of high fidelity
and expresses it in
2 magnificent
new instruments
gie)//
ULTRA LINEAR WILLIAMSON
AMPLIFIER and PRE- AMPLIFIER
MODEL C -100
The THEME Tuner and MELODY
Amplifier
not be used together. When they are,
many interesting combinations are possible.
need
If__
Illilá
artes
Sat in Bookcase
with cover panel
IÍÍIIiI
-_
llllililíililllllli
m'
YIWI
rtri7rnTrtiTtrrtrn
Set in Bookcase
built into
Side by side on
unmounted.
custom cabinet.
,
fireplace man-el
Sal vertically
on lobte top
featuring the exceptionally compact
Used with or without cabinet, this fine
tuner reflects the important new trend
toward functional, compact beauty in
high fidelity equipment. The new
harman- kardon
"flat" silhouette
The new MELODY C -100 is only 31/4"
high, 121/2" wide and 71/4" deep. This
sleek
compact
brushed copper and
black silhouette houses a remarkable
IO watt ultra -linear Wi'liamson amplifier and complete pre-amplifier The pre -amplifier incorporates the famous Harman -Kardon Dynamic Loudness Contour Control which permits
you to listen at living room volume
with the full richness you normally experience only at high volume levels.
Full selectable record equalization (including the new RIAA Curve) compensates correctly for the characteristics
of more than 30 recording labels. Separate bass and treble controls each pro-
-
carrying handle.
In every technical detail, the A-300
THEME is outstanding. Armstrong
FM with sensitivity that achieves the
theoretical maximum AM reception
which is clean quiet between stations
Precision flyand unusually efficient
wheel tuning on both AM and FM
Dramatically effective Automatic Frequency Control for ease of tuning and
freedom from drift Cathode follower
output
-
-
THEME is housed in a sleek brushed
copper cage, set off by a handsome copper escutcheon on a black display panel.
4" high, 121/2" wide and 71/4" deep, it
includes a dual purpose AM antenna
Deluxe AM -FM Tuner and Ultra Linear
"Williamson" Amplifier- engineered
-
and styled to function separately yet
matched to look and perform as a single
magnificent unit, when preferred.
vide 32db of contro-. Frequency
1
db from 10
response is flat within
to 40,000 cycles.
Price $74.50 (Zone 2: $75.50) complete.
Price $115 (Zone 2: $116.50), complete.
Harman -Kardon products are sold and serviced throughout the country by these and other leading specialists in hi-fidelity.
lasten, Mass.
RADIO SHACK CORP.
167 Woshing,en 5t.
Lafayette 33700
New Branch n .r
c.en
Sulfala, N. Y.
RADIO EQUIPMENT CORP.
147
Genesee'"(
Madison 9(76
Empire Srotrs
High Fiderr, C.
-Philadelphia,
1
-irr
Pa.
RADIO ELECTRIC
SERVICE CO.
709 Arch Street
Lombard 3 7390
Allentown a Folic, Branches
New Yak, N. Y.
ARROW ELECTRONICS, INC.
65 Cortland! Street
Digby 9 -4714
Always An Audio Fair
New York, N. Y.
LEONARD RADIO, INC.
69 Cortlondt Street
Cortlondt 7.0315
The House Built On Service
New York, N. Y.
FEDERATED PURCHASER
66 Dey Street
Digby 9 -3050
Also Newark, Easton.
Allentown, Los Angeles
New York, N. Y.
New York, N. Y.
Yonkers. N. Y.
WESTLAB
2475 Central Ave.
HUDSON RADIO
L TELEVISION CORP.
48 West 48 Street
Circle 6.4060
3 Metropolitan Area Salesrooms
Washington, D. C.
ELECTRONIC WHOLESALERS
2345 Sherman Avenue. N. W.
Hudson 3.5200
For Everything In Audio
Chicago,
ALLIED RADIO CORP.
Modison Ave. at
N. Western Avenue
Haymarket -6800
World's Largest Stocks
OI Hi -Fi Components
SOth St.
Plana 3 -0180
4 N. Y..5 White Plains Branches
Spencer 9-6400
In Westchester, It's Westlab
Walton
Whitehall 3 -1166
High Fidelity Exclusively
53 East
100
Texas
1
536 South Fair Oaks
Ryan 1.8171
4 -3560
"For Sound Advice,
See
Pasadena, California
HIGH FIDELITY HOUSE
World's Finest Music Systems
Detroit, Michigan
HACO DISTRIBUTING CO.
9730 Burnett' of Grand River
Illinois
LIBERTY MUSIC SHOPS
Chicago, Illinois
VOICE AND VISION, INC.
Los Angeles, California
GATEWAY TO MUSIC
3089 Wilshire Blvd.
Dunkirk 7-3393
Authoritative
Haco"
Chicago, Illinois
NEWARK ELECTRIC CO.
223 W. Modison St,
State 2 -2950
Write For
Hollywood, California
HOLLYWOOD ELECTRONICS
7460 Melrose Avenue
Webster 3.8208
Hi Fi Components Exclusively
Montreal, Canada
CANADIAN ELECTRICAL
Complete Hi-Fi Catalog
for Important
literature
tener
on
SUPPLY CO.
275 Craig Street, W.
University
1.2411
Toronto and Edmonton
the
"Melody"
Amplifier-Pre-Amplifier
"Theme"
HFi
Guidance
a
HARMAN- KARDON, INC., 520 Main St., Westbury, N. Y.. Dept.
"Theme" Cr "Melody" Literature
Send
Name
Address
City
www.americanradiohistory.com
AmericanRadioHistory.Com
..
...........
Zone
State
phase. If the tubes are perfectly
balanced, no hum will be heard in the
loudspeaker because of the push -pull
output stage which requires that the
signal be fed to the grids 180 deg. out
of phase. If hum is heard, the user adlusts the balancing control to reduce the
lnun to a minimum, then restores the
itch to the normal position.
Constructionally, there are several
line features in the Newcomb units.
Most of the small components -resistors
and capacitors -are firmly mounted,
with any larger than 1 -watt resistors
being supported by clips so as to avoid
strain on the leads. Another feature
which simplifies mounting in a cabinet
is the Adjusta- Panel, which is a subpanel on which the controls are mounted.
and which can be moved forward so as
to permit the shafts to extend through
panels up to 3/4 in. thick.
in
.'
Fig. 46. Newcomb Classic 2500 -R, with remote
control unit.
unit which may be plugged in to occupy
the space covered by the blank panel in
Fig. 45. Input connections to the power
amplifier itself, or to the Horizon 5 preamplifier are made on the rear apron,
and a safety switch makes it necessary
that either the preamp or the blank panel
be in place in order to turn on'the a.c.
power.
The Horizon 10 is similar in appearance, but is equipped with a simpler
type of preamplifier and control unit,
which is an integral part of the amplifier
and is not removable.
Newcomb Audio Products Co., 6824 Lexington Ave., Hollywood 38, California.
Pickering
8
Co. Inc.,
309 Woods Ave..
Oceanside, N. Y.
Primarily a manufacturer of pickups.
this company has one amplifier unit
which serves as the control point for
high -quality systems. The Model 410
Audio Input System provides one phono
input and two high -level inputs, together
with 'tone controls, equalization selector.
and a volume control. It is self powered,
and is designed on the lines of a professional unit. The equalization is
meticulously correct for the positions
provided. the basstone control provides
six positions (usi
tafFa5witch) of
bass boost, the ma iri5unrbeing 12
at 30 cps ; the trebintrol, alsoat
switch, provides one boost posi .... of
(lb at 10,000 cps, a flatrltosition, : d four
cut positions with a m iimum '. ..p of
14 db at 10,000 cps.
The unit, pictured in Fig. 48, is self
powered, and employs a 6AU6 as the
preamplifier, and three 6AB4'stwo as
voltage amplifiers and the third as a
cathode follower. A 6X4 serves as a
rectifier.
The 'Newcomb "Classic" line is quite
complete, offering some eight cofiventional amplifiers -three with remote control units
stereophonic model for
two -channel reproduction, and two Compact models. The Classic 2500 -R, shown
in Fig. 46, is typical in appearance for
the remotely controlled units, and the
Compact 12, shown in Fig. 47, is typical
of the smaller units.
There are two 25 -watt models, one
with and one without remote control ;
two 15 -watt models, with and without
remote control, a 12 -watt unit with
remote control, and a 10 -watt unit; all
in addition to the two Compacts, with 10
and 12 watts respectively. The R-7 Remote- Control Preamplifier permits remote operation with any amplifier, and
consists of two units -the control unit Pilot Radio Corporation, 37 -06 36th St.,
Long Island City 1, N. Y.
and the power supply which also incorporates preamplifier tubes to feed
Because of the completeness .of this
signals from low -level inputs through line, it would be impossible to -describe
the cable to the control unit.
all models. The most important, from the
Another interesting and useful feature user's standpoint, appear to be the inof the Newcomb line is the Audi -Balance
Model AA-903; the basis 15 -.
-an arrangement by which the user can expensive
watt Model AA -410; and its big brother,
adjust the two tubes of the output stage the 30 -watt AA -904; and the relatively
without the need for meters. Operation new and compact AA -420.
of a switch places a 60 -cps a.c. potential
The AA -903 is a single- chassis 10of about 3 volts on both output-tube grids watt amplifier providing inputs for
magnetic pickups with four equalizer
positions, and for three high -level inputs.
Separate treble and bass tone control
are used, and a dual volume control
helps keep hum to a minimum during
logy level reproduction. The output stage
uses 6V6's, and feedback is applied over
the last three stages.
The tone controls are of somewhat
unique design in that they are completely flat at the center positions. The
networks are fed from one half of a dual
triode through circuits which introduce
equal amounts of boost and cut when the
Fig. 48. Pickering model 410 Audio
Input
System.
controls are set at the center. When the
-a
50
Fig. 47. Newcomb Compact 12.
J1
slider moves toward BOOST, the cut is
decreased while the boost remains
constant, with the result that the level
is boosted. The reverse action occurs
when the slider is moved toward CUT.
This arrangement gives curves of good
listenability.
In all Pilot models, shielded heater
leads are used where necessary to reduce hum to .a minimum, and low -noise
resistors àre used in critical circuits.
-.110 is a basic amplifier using
The<
5881's 6z a6 çput stage. The circuit
consists of tworvoltage- amplifier stages.
a cathodyne phase splitter, and the output stage. This unit is designed to work
with a separate preamplifier.
Model AA -904 is a deluxe basic amplifier, with KT66's im the output stage.
It is a Williamson -tape amplifier, using
two 6SN7's with one as voltage; amplifier and phase splitter, and the other as
a push -pull driver. Dual phase- prrecting networks are employed in the feedback network to achieve good stability.
This model, shown in Fig. 49, is also
flesigned to work with an external pre $amplifier or with a tuner which incorporates tone and equalization controls.
such as the Model AF -860.
The AA -420 is a compact 15 -watt
amplifier using 5881's in the output
section, and equipped with preamplifier.
tone controls, and a compensated two section volume control. While similar in
function to many other compact units, as
seen in Fig. 50, it is essentially an AA903 on a small chassis turned on its side
and combined with a preamplifier and
control unit. It provides for a phono input, with a variable load resistor to suit
the pickup used, and with a dual- concentric switch with separate sections for
bass and treble equalization curves.
Three high -level inputs, each with
separate level- setting controls, are designed for radio, TV, or tape inputs. The
tone control section is similar to the
AA -903, but uses dual-concentric controls. Because of its small size, it is
eminently ,suitable for use in bookcase
Fig. 49.
Pilotone AA -904 amplifier.
AUDIO
JANUARY. 1955
41,
You Can Enjoy
HIGH FIDELITY
at Low Cost...
Fig. 50. Model AA -420 Pilotone amplifier.
installations, although it can be removed from the case and mounted in
another cabinet if desired.
The Pilotrol, just announced this
month, is a deluxe version of a preamplifier-control unit with a number of
unusual features which should appeal
to the critical listener who wants flexibility of control, and who indulges in
recording perhaps mixing locally
originated material, such as voice, violin, or piano, with accompaniment from
an orchestra from a phonograph record.
This unit, shown in Fig. 51, resembles
a professional console in appearance,
with the sloping panel, indicator lights.
and push -button controls. It is equipped
with a volume indicator and a switch
that selects whether the meter indicates
the recording output or the monitor
output thus ensuring that the correct
setting for the recording channel is
maintained even though the user may
change the monitor-the normal signal
output -level.
The Pilotrol incorporates two pre amplifiers -one equalized by proper
settings of push- button controls for
turnover and for rolloff, and the other
push-button
flat for microphone
group for selecting the input source
such as phono, radio, tape, and auxiliary.
continuously variable bass and treble
tone controls, a microphone control
which permits mixing with any of the
other input sources, volume and loudness controls, a meter -function switch,
and a meter -range switch. Indicator
lamps show which program source is
connected. D. c. is used on the heaters
of the preamplifier tubes for minimum
hum, and a variable resistor permits
adjusting the pickup load to match the
magnetic pickup used. The unit is constructed so that it may be installed in a
conventional cabinet, or it may simply
he used in the sloping -front cabinet
shown.
-
-a
TECH -MASTER
20
The
AMPLIFIER KIT
WATT
TECH -MASTER
Williamson -type amplifier kit
build yourself. Every component is the finest obtainable. Complete step -by -step pictorial diagrams guide your every move
right down to the last detail. All sockets, terminals, strips
and connectors are riveted to the chassis ready for wiring.
DELUXE
UL
WILLIAMSON TYPE 20 WATT AMPLIFIER KIT:
Famous Williamson circuit with modifications for increased, undistorted power out.
put. Frequency range of 8 to 100,000 cps at less than 4a% distortion for normal
listening levels. MODEL TM -15A._ _...__
_....._
Net Price $49.95
.
Ultra linear operation through
use of screen. tapped primary output transformer.
DELUXE 4. CHANNEL PREAMPEOUALIZER
KIT with CATHODE FOLLOWER OUTPUT
Provides complete equalization for virtually
employed. Input channels for radio or TV
tuner, crystal or magnetic pickup, tape re.
corder or other signal sources. Indepen
dent bass and treble boost and attenuation
controls. Cathode follower output permits
remote control operation without high fre
quency loss.
MODEL TM -15P
Net Price $19.95
Ar
All lending Radio
Parts Jobbers
and Sound Dealers
Fig.
51.
AUDIO
The audiofan's delight -the
Pilotrol input unit.
new
is a
high quality audio system you can
PROFESSIONAL SOUNDING,
TECH -MASTER CORPORATION
75 Front Street, Brooklyn 1, N. Y.
JANUARY, 1955
all recording
characteristics
now
Custom -Built
TV Chassis,
Quality
TV
Kits
and High Fidelity
Audio Equipment
51
www.americanradiohistory.com
AmericanRadioHistory.Com
employs four 6BG6G's in the output
stage, with a selenium rectifier to provide the fixed -bias supply. This unit
furnishes power for the preamplifier, and
is furnished with two a.c. outlets. The
stability if this amplifier is such that with
the load removed, a .015 capacitor may
be placed across the 16 -ohm tap without ringing on a square wave
critical
test on any amplifier. Multiple feedback
loops are used to obtain a total of 24 db
of feedback, and the output impedance
of the amplifier at the 16 -ohm tap is
0.8 ohms.
-a
Fig. 52. Grommes Model
210PA preamplifier.
Normal output level is 1.0 volts, with
rated harmonic and intermodulation
distortions both less than 0.2 per cent
at the 1 -volt ouput. Input signal for
normal output is 15 my on the microphone channel, 10 and 45 mv respectively on the low- and high -level pickup
inputs, and 150 mv on the radio, tape,
and auxiliary inputs. Outputs on both
monitor and recording channels are
from cathode followers with an impedance of 500 ohms, and a rated hum
level 90 db below 1 volt.
The experimenter will find another
use for this instrument-with the high
gain available in the metering circuits
it would serve admirably as an a.f.
vacuum -tube voltmeter, an accessory
often longed for by the hobbyist.
Precision Electronics. Inc., 9101 King Ave.,
Franklin Park, Ill.
This company, manufacturer of the
Grommes amplifiers, offers a wide range
of models ranging from preamplifier control units to 30 -watt basic amplifiers.
The most popular of the control units is
the 210PA, shown in Fig. 52 installed in
a mahogany housing. This unit uses two
6SJ7's in the preamplifier section, with
feedback around both for equalization,
and providing separate control of turnover and rolloff. One unequalized position is designed for use with a microphone input. Three high -level inputs feed
the compensated volume control, a switch
eliminating the compensation when desired. A third 6SJ7, serves as a voltage
amplifier, feeding the first section of a
6SN7, and the tone-control switches
operate to change feedback networks
around these two tubes. The remaining
section of the 6SN7 serves as a cathodefollower output stage. The tone controls
are calibrated to the actual boost or cut
at 50 and 10,000 cps. The tape recorder
feed precedes all tone and volume controls, and the entire unit requires a
separate plate and heater supply.
Models 216BA and 230BA are basic
amplifiers with 30 and 60 watts output
respectively. The 23f1RA, Fig. 53,
04
Fig
®
>5
to_41)
be
The input unit, model QC -1, for the
QUAD ll amplifier.
52
QUAD
(The Acoustical Manufacturing
Co. Ltd., Huntingdon, England; distributed by Beam Instruments Corporation,
350 Fifth Ave., New York 1, N. Y.l
A number of attractive features ap-
Fig. 53. Grommes Model 230 -BA power ampli30 -watt unit.
fiera
11
pear in the Quad II amplifier, which
consists of a compact basic amplifier and
a separate control unit, shown in Figs.
54 and 55 respectively. The basic amplifier employs two EF86's in as pentodes
in a self -balancing phase-splitter stage
driving two KT66's operating as
tetrodes in a circuit with part of the load
in the cathode circuit and part in the
plate circuit. This is somewhat similar
to the McIntosh circuit shown in Fig.
41, but in the latter the two windings
are equal, whereas in the Quad II the
cathode section is less than the plate
section. This amplifier provides a power
output of 30 watts at an IM distortion
of 1.45 per cent, although the amplifier
is rated by the manufacturer as a 15watt unit.
The advantages of cathode loading.
with the attendant feedback into the grid
circuit, is evident from the performance
characteristics of this amplifier. At 12
watts output, the total third and higher
order harmonic distortion is less than
0.1 per cent; 25 per cent tube mismatch
does not cause distortion greater than
0.18 per cent. and total distortion at 25
cps does not exceed 0.2 per cent. The
power amplifier requires a signal of 1.4
volts for 15 -watt output, and impedances
of 7 and 15 ohms are available.
The QC -II control unit is even more
unusual in construction, operation. and
performance. The phono input circuit
employs a plug -in network which is designed for different pickup load and
level requirements by varying feedback
around the first stage. Six types of plug in units are available, accommodating
pickups with sensitivities ranging from
3 to 100 mv. and matching impedances
from 2000 ohms to 100,000 ohms. Moving -coil pickups, with outputs of the
order of 3 mv, can be accommodated
without an input transformer. which
eliminates a source of hum pickup. Six
other plug-In units give the same
characteristics to the phono section,
but change one of the high -level inputs
to an unequalized low -level input to
accommodate a microphone.
Four equalization positions are provided, and two or more buttons may be
depressed at the same time to give other
characteristics, as desired.
The tone control circuits are unusual,
particularly since they are coupled with
the low -pass filter section. The filter re-
quires two knobs -the two at the right
in Fig. 55. One has a CANCEL position,
and three other positions labeled 10K,
7K, and 5K, representing the cutoff
frequencies of 10,000, 7000, and 5000
cps. When this control is in the CANCEL
position all tone controls are out of the
circuit, and the amplifier is flat (except
for the preamplifier, of course), regardless of the settings of the control
knobs. When this knob is turned to any
of the other three positions, the tone
controls are in the circuit, and affect the
response. In addition, a low -pass filter
action is evident, with a 20,000 -cps
cutoff frequency and the frequency of
maximum loss at about 35,000 cps. This
eliminates any spurious frequencies
above audibility. The second control
from the right is marked with the word
LEVEL and a series of figures from I to
50. When in the LEVEL position, the
filter is effectively at 20,000 cps, with
response flat to about 10,000 cps. As the
control is rotated, the slope of the curve
becomes sharper, the figures representing the number of db per octave of the
cutoff. This provides a wide variety of
curves, and all under the selection of the
user, yet with instant return to "flat"
simply by turning the filter switch to
CANCEL.
The unit is somewhat unusual in construction, with its die -cast front plate
ánd recessed control knobs. It is convenient to use, however, and permits
instant comparsion of quality with different curves. Mounting of the unit is
accomplished by fitting the panel section
through an opening of the proper size
and drawing the cover up tightly
against the panel, using the mounting
screws at the rear of the unit.
54. QUAD II power amplifier, an extremely compact unit rated at 15 watts, but
capable of a 30 -watt output at an IM distor
fion of 1.45 per cent.
Fig.
AUDIO
JANUARY. 1955
PILOTROL
introducing
Professional Preamplifier - Equalizer
a
byP/Qt
triumph in audio control
for the home
' /í/ú
the
4,
in
control interpreted by the exclusive
decibel meter
¿ATUFES OF PILOTROL PA-913
(C.
J.rr/u.,(
;ter level setting conical
r
X+eD(C,ef`,'
..._
.... $119.50*
ed meter for pr.r° 'cn indication of either the
,ding output leve! or
)itor output level by panel control.
:
...
...
MATCHED COMPANIONS TO PILOTROL
and loudness control.
IllfI
(F,rc /r.rirsr -1;ush button input selection with illuminated indicators.
`!
control provides five positions of treble roll-off
and five positions of bass turn-over for precise playback equalization.
&c/usire- direct
one for monitoring.
J.4-c
e
v.I
(<,+I
rlLeTeME
current supply to preamplifier tube heaters.
é rc/,.Jr..a-dual cathode follower outputs-one for recording
if
'
e/srrr e-push button
-
AA-410 PILOTONE
$49.50
AMPLIFIER
'
/.rir:e- variable
phono preamplifier input loading for precise
matching of all magnetic and variable reluctance cartridges.
i/wrirr- control for
mixing microphone with any other channel.
h°t'cltesir:e -dual monitor output jacks for multiple monitoring.
excf .rir. -- professional sloping control panel for ease of operation.
.rr /a.;iry -- chassis construction provides for either vertical
panel mounting in custom cabinet, or as supplied in attractive
mahogany sloping panel cabinet.
6orö.rrr.' -self
powered from 117 volts, 60 cycle, AC source.
Write for Free brochure A -1
'Slightly Higher West of Rockies
PILOT RADIO CORPORATION
AUDIO
AA -904 PILOTONE
AMPLIFIER
$89.50
LONG ISLAND CITY 1, NEW YORK
JANUARY, 1955
53
www.americanradiohistory.com
AmericanRadioHistory.Com
Fig.
57.
Regency
HF -350P
preamplifier
and
control unit.
Fig. 56. The Rauland "Libretto"-the backbone
of the "book" hinges open to give access to
the controls.
Rauland -Borg Corporation, 3515
Addison St., Chicago 18, III.
West
The Rauland 1826 amplifier is one of
unique design, consisting of a basic
amplifier with a preamplifier and a
cathode follower to feed a cable leading
to the remote unit, which resembles an
attractive leather -bound book, as shown
in Fig. 56. The remote unit contains
the bass and treble tone controls, as well
as equalization controls for phono reproduction. Thus the user can employ
phono -bass -boosting to a radio signal,
if he wishes. Selection of the input
signal is made at the main unit. This
could be considered a disadvantage, but
it would be necessary for the user to go
to the tuner or to a turntable to inaugurate a particular program, or even
to turn on the main amplifier, so it does
not appear to be unnecessarily complicated in operation.
A more recent amplifier, the 1811,
is a self -contained 6V6 amplifier with
an output of 10 watts. This unit has
three equalization curves, and uses
separate bass and treble controls, as well
as a compensated volume control. A
switch permits removal of the compensation if desired.
Regency Division, I.D.E.A., Inc.,
Pendleton Pike, Indianapolis 26,
7900
Ind.
While Regency introduced a $1000
amplifier a year or so ago, it has other
amplifiers in its line that are more
popular. Among them are the HF -350P
preamplifier, and the HF -350A basic
amplifier, which are designed to work
together.
The HF-350P, shown in Fig. 57, is
a self contained unit accommodating two
phono inputs a microphone. and four
high -level inputs, each with its own
level adjusting potentiometer. Seven
equalizing positions are provided on a
switch, and the unit incorporates sepa-
rate bass and treble tone controls, and
both volume and loudness controls. The
power supply furnishes d.c. to the heaters
of all four of the tubes. Cathode followers
provide low -impedance outputs, to feed
the power amplifier and a tape recorder,
the latter input being ahead of the
volume controls, but following the tone
controls.
The 30 -watt basic amplifier, Fig. 58,
employs a pair of 5881's driven by cathode followers, and with three stages
preceding those. It uses a well filtered
power supply, and has fixed bias on the
output stage.
Hermon Hosmer Scott, Inc., 385 Putnam
Ave., Cambridge 39, Mass.
Designed with a view toward optimum
performance in the user's home, the
Scott line consists of two equalizer preamplifiers, models 120 -CP and 121 -A ;
two compact table -model units, models
99 with 12 -watt output and 210 -C with
23 -watt output ; and two laboratory
power amplifiers, the 32 -watt 232 -A and
the 70 -watt 265 -A. Model 121 -A, shown
in Fig. 59, is equipped with the Dynaural
noise-suppressor circuit, as is the 210 -C,
while models 120 -CP and 99 are provided
with sockets into which an external
Dynaural unit, model 114 -A, may be
plugged. Model 265 -A is shown in Fig.
60.
The 121 -A equalizer- preamplifier employs continuously variable turnover and
rolloff controls, a volume -loudness control, input selector, bass and treble controls, and the Dynaural controls. This
latter circuit provides a sharp rumble
filter, at the selection of the user, together with a signal -controlled low -pass
filter action to limit noise and distortion.
The variable turnover control is arranged to provide an 800-cps turnover
when set at its mid position. As the
control is turned clockwise, the turnover
decreases uniformly to 250 cps, providing
an exact constant -amplitude response at
all intermediate points. When the con-
Fig. 58. Regency
trol is turned counterclockwise from the
center position, the turnover decreases
rapidly to 500 cps and then remains fixed.
Further counterclockwise rotation varies
the bass rolloff to provide an exact match
for NARTB, RIAA, old NAB, London,
Columbia, BBC, and other curves. For
rolloff a special tapered resistor is required to spread the range evenly around
the control. A switch on this same control removes all rolloff for flat treble
response.
The Dynamic Power Monitor incorporated in the 265 -A power amplifier
was designed to prevent damage to loudspeakers in case the user turns the volume up too high or inadvertently pulls
out an input plug. The 70 -watt power
output is sufficient to ruin a speaker
if the input signal becomes too high.
The Monitor reduces the long -term
power handling capacity of the amplifier
to as low as 10 watts, if desired, without
sacrificing short -time power handling
ability, which is unaffected for the first
250 milliseconds after a strong signal is
applied. Beyond that time, the power output is reduced to a point which normally
represents the maximum safe continuous
power for the loudspeaker system.
The circuit, shown in simplified form
in Fig. 61, functions as follows: When
a strong signal is applied to the amplifier, the diode Vs puts a positive voltage
on the grid of V1, which in turn controls
a series voltage -regulator tube, Vî. This
reduces the maximum power output by
reducing the plate supply voltage, rather
than simply by gain reduction -which
would be ineffective in case of an extremely large input signal. R, sets the
bias on
which is controllable by the
user to set the maximum permissible
power output, with C1RZ representing
the time -delay which permits instantaneous peaks to pass without any limiting.
Figure 62 is a simplified schematic of
variable- output -impedance
the Scott
V
Fig. 61. Simplified
Fig.
59.
Scott model 121 Dynaural
Preamplifier.
Equalize,
Fig.
60.
70 -watt
Scott model 265 -A power
amplifier.
www.americanradiohistory.com
AmericanRadioHistory.Com
circuit of the Scott Dynamic
Power Monitor circuit
the
in
265 -A
power
amplifier.
AUDIO
54
HF -350A amplifier.
JANUARY, 1955
control circuit. Potentiometer R1 provides a variable voltage feedback, and
potentiometer R2 provides a variable
current feedback. These two potentiometers are coupled together, and serve to
maintain a constant amount of feedback,
while varying the output impedance to
suit the particular speaker being used.
All of the Scott amplifiers are designed to have clean symmetrical clipping of both halves of the input signal
upon reaching the overload point, since
uniform overload of both halves of the
signal is considerably less objectionable
to the human ear than unsymmetrical
overload, which introduces unpleasant
distortion. This result is achieved by
using conservative amounts of feedback,
A
remarkable NEW development!
Fig. 62. Variable damping control used in the
Scott 265 -A amplifier.
with sharp cutoff filters at both ends of
the frequency pass band to eliminate the
possibility of oscillations arising from
the clipping.
To maintain low hum and noise levels,
a common grounding point is used rather
than conventional chassis grounds which
are likely to cause ground loops. The use
of aluminum instead of steel for the
chassis contributes further to the low
hum level, since aluminum is non -magnetic and therefore not susceptible to
eddy currents.
Sono:, Inc., 245 Sansom Street, Upper
Darby, Pa.
-
This line consists of a preamplifier control unit and two power amplifiers
the 25 -watt model 251 and the 60 -watt
model 601.
The preamplifier provides two phono
inputs, one with correct termination for
most available magnetic pickups, both
high and low level, with the other only
for low -level pickups ; two high -level
inputs are provided for tuner and tape
or TV. A recorder feed is provided, with
connection being made ahead of both
tone and volume controls. The output of
the unit feeds a power amplifier, with a
cathode follower being used to maintain
a low source impedance.
The two power amplifiers follow
closely
the Williamson- modified -toUltra -Linear output stage; the 25 -watt
model uses two KT66's, while the 60watt model uses four. Both models
supply power to the preamplifier.
8538
Warner Drive, Culver City, California.
The one amplifier offered by Stephens
is designed to work with the same company's 500 -ohm speaker systems, and
is the only unit on the market which does
not employ an output transformer. The
TIIE FAIRCHILD
50 watt
audio
An
AMPLIFIER
extraordinary guarantee!
- -less --
Now Fairchild introduces a professionaltype amplifier so infinitely stable that it is
guaranteed not to ring at any level
even where two-way or three -way speaker
systems are used.
Amazingly low intermodulation distortion
than 0.3% at 45 watts and less than
1.5% at 50 watts coupled with harmonic
distortion under 0.1% at 45 watts and
under O 5% at 50 watts -helps provide
truly breathtaking performance.
Full undistorted power is available for
crashing crescendos and other passages
which often overload ordinary amplifiers.
Yet the Fairchild 260 is a single, compact
unit, easy to install almost anywhere.
Best of all, original performance can always
be maintained! New Fairchild Balance
and it's
Control balances out distortion
easy to use at any time.
...
See the superb Fairchild 260.
-
You'll agree
there's nothing finer.
i
When you visit your audio
dealer, see, too, the NEW
Fairchild 220 Cartridge.
Listen to the only cartridge
that gives completely uni-
form response to 17,000
$14q.5o
cycles -with smooth
roll -off
beyond.
Stephens Manufacturing Corporation,
AUDIO
//BC/HI/L/DEQU/PMENT
9th AVE.
AND
154th ST., WHITESTONE, N.
Y.
55
JANUARY, 1955
www.americanradiohistory.com
AmericanRadioHistory.Com
Outstanding
noise and interference rejection
21ìì-%i
with the new
.i
360
250
Fig. 63. Output stage of the Stephens
"Citadel"
output -transformerless amplifier shown in Fig.
Lowest
ignition noise
Lowest
interference
Wide-band
detector
and limiters
Single -sweep
tuning
Interstation
noise
suppressor
2- microvolt
sensitivity
Tuning -signal
strength meter
Unique
convenience
1.
output stage consists of four 2A3's in a
series -parallel arrangement, as shown in
Fig. 63. The signal is fed to the two
lower grids from a cathode follower, and
the output is taken from the filaments
of the upper tubes-through an 80 -µf
capacitor, since this point is at a + 250 volt d.c. potential above ground. The
amplifier, shown in Fig. 1, features very
low phase shift, and employs selenium,
rectifiers throughout for plate supply.
Since no other manufacturer offers any
500 -ohm voice coils, this amplifier has
not yet achieved the popularity it de-
Quality or FM reception
k determined largely by what is not heard.
particularly in Metropolitan areas where noise.
serves.
Stromberg- Carlson Company, 1225 Clifford
interference and reflection effects are high.
The new 5I0 FM Broadcast Monitor Tuner features
wide -band circuit design permitting outstanding rejection
of ignition noise. image and other station interference.
Multi -path fading and spurious responses
(which show up as reception of the same station
at ninny spots on the FM band) are virtually eliminated.
The 2 me wide -band detector and limiters and full 150 Ice
wide flat bandpass IF characteristics make tuning
completely non -critical and drift -Free
and give essentially distortionless reproduction
at all signal levels. The 2 microvolt sensitivity
at 20 dh quieting (4 microvolt at 40 db quieting) allows
interference-free reception with full limiting action
even on weakest signals. The inter-station noise
suppressor is adjustable on the front panel and allows
complete inter -station noise elimination but also reception
of very weak stations. The fine- tuning control and
combined tuning meter and signal strength indicator
are useful for tuning weak signals and antenna orientation.
Rejection of spurious responses resulting from
cross -modulation by strong local signals is better than
85 d6. an outstanding design accomplishment. We believe
that the 310 provides the best overall design balance
possible at this stage of the art, incorporating all
significant features and refinements known today.
Unique convenience of operation,
attractive styling and moderate cost
enhance its desirability
to the serious music lover.
Ave., Rochester 21, N. Y.
Three amplifiers comprise the Strom berg- Carlson line -the 10 -watt AR -410,
the 25 -watt AR -420, and the 25 -watt
remote control model AR -425. The AR410 is a small self -contained unit employing a 12AU7 as a preamplifier, the two
sections of a 12AX7 as voltage amplifier
stages, a 12AT7 as a phase splitter, with
6F6's in the output stage. The circuit
of the power section is fairly conventional, although feedback from the output
transformer is taken from a tertiary
winding, which is wound to have less
leakage inductance than usual low -impedance secondaries.
The AR -420 shown in Fig. 64, incorporates continuously variable turnover
and rolloff controls, together with bass
and treble controls, and a volume -loudness control with a switch to remove the
loudness compensation. It accommodates
high- and low -level magnetic pickups,
high- and low -level radio tuner input, as
well as two auxiliary high -level inputs.
The output stage consists of a pair of
6L6G's, and feedback again comes from
a tertiary winding.
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cscs}v
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Elti {orupYOfIOM,°i ;o/ und E
°nd IM
H. H. SCOTT inc.
I.9LE BOOKLET
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Fig.
385 PUTNAM AVENUE,
CAMBRIDGE 39, MASS.
64.
Stromberg Carlson
AUDIO
56
www.americanradiohistory.com
AmericanRadioHistory.Com
model
AR -420
amplifier, with continuously variable turnover
and rolloff controls.
JANUARY, 1955
The AR-425 amplifier has a separate
control unit which derives all operating
voltages from the basic chassis which is
similar to the AR -420 in circuit. The
remote unit accommodates low- and
high -level magnetic pickups and a microphone, as well as a low- and high -level
tuner input and a high -level auxiliary
input. Three equalization curves are
provided, and a three-section volume
control gives loudness compensation. A
BRILLIANCE control introduces a low -pass
L-C filter into the circuit with cutoffs
at 3, 5, 9, and 20 kc. The output is a
cathode follower, permitting operation
up to 31 feet from the power amplifier
section.
Tech -Master Products Company, 75 Front
St., Brooklyn I, N. Y.
Tech -Master has long been the leader
in television kits, with suitably simplified
construction data so that anyone can
assemble a TV set and make it work
usually better than many commercial
units. It was only natural that this company would enter the audio -amplifier
market with a kit.
The amplifier consists of model TM15A. a combined amplifier and power
supply on one chassis using 5881's in
-
TANNOY
TANNOY "AUTOGRAPH"
PRE-AMPLIFIER
.. with four switched in-
puts, and switched correction
for all major recording characteristics.
$95
..with polished wood and
metal enclosure for stand
mounting,
TANNOY HIGH- FIDELITY
POWER AMPLIFIER
The perfect complement to
TANNOY DUAL
CONCENTRIC SPEAKERS
12 "unit complete with CI' oSsover,
$1à0
15" unit complete with Crossover,
$159
the Tannoy "Autograph" Pre Amplifier,
$150
$110
TANNOY VARILUCTANCE TURN -OVER
with dual diamond styli,
$65
This pickup represents a technical advance of
some magnitude. It
has no
uncontrolled
resonances whatsoever, the lateral to vertical
compliance ratio has had particular attention,
and the damping arrangements are ideal. These
factors, combined with very low effective dynamic mass permit a completely safe tracking
weight of six grammes at all speeds. The turnover mechanism is simple and positive, and the
styli assemblies are independent.
CARTRIDGE
TANNOY (CANADA) LTD.
TANNOY (AMERICA) LTD.
36 WELLINGTON ST., EAST,
TORONTO
Fig.
65. Tech- Master
kit -type preamplifier.
an Ultra- Linear output stage, and model
TM -15P, the remote control preamplifier- equalizer. The former is a Williamson-type unit of conventional design, but
engineered to make it possible for the
home constructor to make it work properly. The preamplifier, shown in Fig. 65,
employs a 12AX7 as a feedback -equalized
preamplifier, and a 12AU7 with the tone
controls between the two sections. Three
equalization curves are provided for'
magnetic pickups, and three high -level
inputs will accommodate tuner, tape, TV.
or crystal or ceramic phono pickups.
United Transformer Company. 150 Varick
St., New York 13, N. Y.
Primarily a transformer manufacturer,
this company is currently offering a 25watt power amplifier, model MLF -for
Multiple Loop Feedback -in a semi -kit
form, shown finished in Fig. 66. Most of
the amplifier construction is completed
when the user buys the kit, since the
sub-chassis is a printed- circuit unit incorporating all of the resistors and
capacitors correctly connected. All the
user has to do is to connect the power
and output transformer leads to the sub chassis, install the power switch and
pilot light, insert the tubes and he can
be playing the amplifier. As to performance, this model has eliminated most
AUDIO
The
1,
ONT., CAN.40
CARNEGIE HALL
.VEW YORK 19, N. Y.
4
O,d0,
preamplifier
C/)
marantz
.0 0!3
QUALITY DESIGNED
by
C
There wos o clearly defined purpose in developing the Marantz Audio
Consolette: to create a control unit embodying advanced design thinking coupled with the best available components and finest construction
technique. The results have more thon justified this extra effort and
core. For practical efficiency...for sheer quality of performance, the
Morantz Audio Consolette is unmatched by any unit on the market.
These are the features: 7- position Selector Switch Continuously Variable Bass
and Treble Controls Independent Turnover and Rolloff Controls Loudness Compensator (does not affect volume), High Frequency Cutofl Selector Frequency
Response: 17 to 40,000 cycles ± db
Negligible IM Distortion (less than .03
at 2 -volt output).
1
$155
U°ser's Net Price complete w th tubes and cabinet
Chassis (less cabinet) available at lower cost
Wherever Fine Audio Equipment
is
Sold
Write for Complete Details:
Si.
b. marantz
JANUARY, 1955
44 -15 Vernon Boulevard,
1.
I.
C.
1,
N.
Y.
57
www.americanradiohistory.com
AmericanRadioHistory.Com
which employs several feedback loops,
this is a very desirable feature, because
minor changes in wiring and in parts
placement could easily make a considerable difference in the performance
of the finished amplifier.
il
sheer
musical
magic'
Conclusion
There are other amplifiers on the
market -some undoubtedly on a par
with those mentioned -and the omission
of the products of any particular manufacturer does not mean that those products are not considered suitable for a
high -quality home music system. Such
omissions have been the result of a
lack of information from the manufacturer or the necessity of shortening
some of the material because of the large
number of amplifiers available.
Selection of an amplifier for each
individual's own particular applications
should not be particularly difficult, even
though the various units may appear
to be somewhat complicated. It is not
necessary that the user be thoroughly
familiar with what happens throughout
the circuit of a modern amplifier to
enjoy the entertainment which a good
music system can give. Even the lowest
priced high -fidelity amplifier is so far
superior to the average music reproducing system sold as a radio -phonograph
combination that almost anyone would
notice the difference immediately. True,
there are grades of amplifiers, just as
there are grades of speakers, tuners,
tape recorders, automobiles, or even
such a commonplace product as a loaf
of bread. No one can say, without risk
of being challenged, that any one
-a
"semi -kit" unit
Fig. 66. UTC amplifier
employing a printed wiring panel which comes
with the small components already in place.
of the troubles encountered by the home
model
1811
full
12
watt
high fidelity amplifier
NOW, at moderate cost, you
can own and enjoy a quality
of musical re- creation virtually
Indistinguishable from the original
performance. Here is the ideal
"heart" for your home music
system, capable of reproducing the
full musical range from vibrant
bass through thrilling treble with
the full emotional depth and
meaning of the original music.
Here is the finest audio achievement,
designed to bring you the
ultimate in enduring listening pleasure.
builder who assembles a Williamson type amplifier, and performance at extremely low frequencies -less than 10
cps, for example-and at frequencies
above 50 kc has been improved because
of the multiple feedback loops. The circuit of this amplifier -originally published in the June issue with one or two
minor ( ?) errors in it, is reproduced
correctly in Fig. 67.
The use of the printed- wiring panel
ensures that the "dress" of the wiring
will be identical in every amplifier of
a given design, simplifies the location
of any of the components in case of
failure, and-in the case of the MLF
amplifier -makes it a very simple unit
for the home constructor to finish,
since he is required to connect only 17
wires leading from the filter choke and
the power and output transformers to
the printed- wiring subpanel, insert the
tubes, and the unit is completed and
ready to play. In the case of a circuit
UTC
UTC R1051
R201-8.1
22008,2018ME
F
B.
RESISTOR
IMPEDANCE RESISTOR IRE)
OUTPUT
338
Sa
7Sa
.
5V46
1111111111
with every desirable feature for
63V
superb musical reproduction...
TO
68e
300
1008
5081 CATHODES
-1-vw
8/450V
1/2
Response, : 0.5
Full 12 watts output
db, 20- 20,000 cps. 3 Response Curves
fidelity
in all types
full
out
the
to bring
and makes of records Microphone input
for entertainment and recording Separate
Choice of
Bass and Treble tone controls
regular or "equal loudness" control
Inputs for GE or Pickering cartridge,
tape, tuner, and microphone Removable
47K
iss
12 AX7
O1MEG
o 51MEG
25
5881 ETC
6 AU6
1E-4
180
o
82
panel for easy mounting...
every other desirable feature
to create a new dimension
In sound for your home.
0 22
PLUS
MEG
f
02
rn
25
V2 12A%7
o
o
/
t7
vo
Hear the
RAULAND 1811
HI-FI dealer, or writ*
for full details.
8.3
I6pyK1
C.
Chicago 18, III.
BA50
0111^6
O 51 MEG
R6
(SEE FEEDBACK
RAULAND-BORG CORPORATION
3515 W. Addison St., Dept.
ñ
oo
o
m
o
=
Amplifier at your
1OMEG
W
W
CHART)
in
Fig. 67. Corrected schematic of the UTC MLF amplifier. This circuit was published
June, 1954, issue in a form that wouldn't work.
AUDIO
58
www.americanradiohistory.com
AmericanRadioHistory.Com
the
JANUARY, 1955
amplifier is "the finest on the market,"
for there are so many excellent ones on
the market that a person could almost
telephone his distributor and say, "Send
me an amplifier costing about x dollars."
There are differences in features, of
course -some use tetrodes, some use
triodes, some use the Ultra- Linear circuit. Some amplifiers provide as few as
three equalization controls for phono
reproduction, others are so flexible that
they can accommodate as many as 25
or 30 curves. Some are designed for
only one or two inputs, while others
have provision for five or six in addition
to feeding a tape recorder.
The final choice should be based on
two questions : "How much money can
I afford to spend for an amplifier ?"
and "How am I going to use this
amplifier in my home ?"
Obviously, you are likely to get more
features. higher output power, greater
flexibility, and-possibly-lower distortion at the normal listening level
with an expensive amplifier than with
the units in the lowest price bracket.
But you must ask yourself if -for your
own requirements
these particular
features are important. If you have a
small apartment and expect to feed only
one speaker with radio programs, for
example, you do not need the 100 -watt
Super- Roarer with 40 phono equalization curves, dual tone controls for
both bass and treble, and three separate
channels so you can listen to a stereophonic program while you record
another monaural program at the same
time. You should he able to get along
with a fairly simple unit without any
phono preamp at all.
If, on the other hand, you have an
enormous record collection extending
back to the days before electrical recording, with representative discs from
a dozen foreign countries and some
two hundred domestic recording companies, you will do well to select your
amplifier from those which do give you
sufficient flexibility to match any recording curve ever used and four others
that haven't even been thought of.
By all means, make sure that you
select the best amplifier your budget
will allow -skimp a little on some of
the other components at first, if you
must, but be sure that the amplifier
is of top quality. Amplifiers are not
like automobiles -they do not have to
be traded in every year or so (unless
you simply have to keep up with
your friend who does have the Super Roarer). Transformers last practically
forever, resistors and capacitors are
almost invariably used well below their
ratings, and tubes can be replaced. The
writer is still using a power supply
built to go with the Residence Radio
System built in 1948 (the amplifier has
been modernized a number of times
since then, but it hasn't been touched in
over two years) ; and the first 6AS7G
amplifier described in these pages in
May, 1948, is still working an average
of eight hours a day -and it has never
had a single failure since it was built.
Tuhes have been changed, to he sure,
to Flawless Music...
in Your Home
TRUE FIDELITY
SPEAKERS
STEPHENS
Created by one of the world's foremost
High Fidelity engineers. Tru -Sonic
Speakers are internationally famous for
their flawless clarity and full, rich mellow tones.
Years of thrilling ... emotionally satisfying... listening pleasure are yours
when you choose Tm -Sonic Speakers by
-
AUDIO
BY
STEPHENS.
The International Standard
Write for descriptive literature
STEPHENS MeunreeTURINO CORPORATION
PRICED FROM $30.00 TO $600.00
S531 WARNER DRIVE
CULVER
CITI, CALIF.
THE ORIGINAL
z
KT66
The name
GENALEX on the
tube and carton is
your guarantee
that you are buying
the original
... world.
famous power
tetrode, often
referred to as the
finest audio tube
ever made! The
KT66
GENALEX KT66 is
the hallmark of the
finest amplifiers.
It is supplied as
original equipment
in Williamson,
Radio Craftsmen,
Leak and Heath Kit
products. Identical
pins and
connections as
6L6 tubes.
Only $3.50 net.
For complimentary
fact sheet, including
circuit diagrams,
write Dept. Al.
Quality endorsed
product ot the
British Industries Group
BRITISH INDUSTRIES CORPORATION
164 Duane Street
JANUARY, 1955
New York 13, N.
Y.
59
www.americanradiohistory.com
AmericanRadioHistory.Com
Buy PEERLESS
and KNOW
you're right!
The PEERLESS Catalog is
constantly improved
but not a resistor, capacitor, trans fomer, or choke has ever given a minute's trouble.
An amplifier that may cost $200 today
should certainly be in service ten years
from now, at a cost of 5% cents per day,
and even then it isn't likely to collapse
like the one -horse shay -you'll still be
using it.
Once the potential purchaser is convinced of the reliability of high -grade
modern amplifiers, he can go about the
serious business of making his final
choice. Not all amplifiers will sound the
sanie, even with the same program
sources and the same loudspeaker system.
While we can measure frequency response, distortion, transient response,
output impedance, and most of the other
characteristics of an amplifier with a
high degree of accuracy, there still remain some characteristics which we
we
do not know how to measure
assume that we know what those characteristics are. For any audio engineer
will tell you that it is possible to run
a series of tests on two amplifiers and
find them to have practically identical
frequency response, distortion under one
per cent, the same output impedence and
damping factor, yet when subjected to a
listening test these two amplifiers may
not sound alike at all. We can guess at
what causes the difference but we may not
be able to measure any perceptible difference in the two units. Therefore,
even if the specifications measure up to
what you want in an amplifier, do not
fail to listen to it, preferably in direct
comparison to one or two others, and if
at all possible, with the same loudspeaker
and enclosure that you intend to use.
It is well to select as subject material
-if
Obsolete items removed
Consistently the highest
quality in the industry
a record with which you are thoroughly
familiar, because you should not introduce more than variable at a time. Listen
to the same music on two or more ampli-
fiers- change nothing but the amplifiers
as you switch back and forth-under no
condition should you listen to two separate systems if you are attempting to
pick only an amplifier. The sanie advice
would apply if you were choosing a
speaker-try a number of speakers in
direct comparison, always using the
sanie amplifier, phono pickup, and source
material.
Even the source material is important.
for you won't always be listening to a
symphony orchestra, a string quartet,
or a jazz combo. Get some variety into
your source material. Remember too
that you may listen to the radio sometimes, and that the human voice will
have to be reproduced. This is an important test, too, because certain tone
controls may introduce too much "chestiness"-the term applied to the range
between 100 and 200 cps which makes
the voice sound barrel -like.
And finally, while you may ask advice
on what quality differences there may
be in different amplifiers, you should
not ask anyone to tell you which amplifier sounds best. You are the person that
is going to listen to it, and you are the
one who will have to be satisfied -you
and your family, perhaps, but certainly
no one else. So if you are sure of the
integrity of the manufacturer-and you
may well be in the case of any of the
high -quality audio components -base
your selection on how the unit sounds
to your own ear. Then buy it, take it
home and put it to work, and . .
Happy Listening.
.
The manufacture of quality trans-
formers is
a
long- standing habit
with PEERLESS. Typical of PEERLESS
products are the famous 20-20 and
20-20 PLUS lines, the logical choice
when superlative performance is re-
quired. Every PEERLESS product is
a
quality product. Keep your PEERLESS
Catalog and latest price list handy.
It's
up -to -date.
It's DEPENDABLE.
If you don't
have the latest PEERLESS
Catalog, write for it today!
PEERLESS
Electrical Products
A
DIVISION OF
9356 Santa Monica Blvd., Beverly Hills, Calif.
161 Sixth Avenue, New York 13, N.Y.
"Yes, it's something new
.
AUDIO
60
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
Equipment Report
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Harman -Kardon "Festival" Tuner and Amplifier, Model D -1000
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ComsmiNG in UIIC chassis a sensitive
AM -FM tuner, complete with preamplifier for magnetic or crystal pickups, tone controls, and a 20 -watt power
amplifier, the Festival-newest and most
complete of the Harman -Kardon line -provides in one unit all the elements necessary
for a home music system, excepting, of
course, the loudspeaker and its enclosure.
From the measurements, it appears that
nothing has been sacrificed by the combination, for the curves compare favorably with
separate units and distortion in the UltraLinear output stage is under one per cent
up to the 20 -watt point, reaching 2 per cent
at about 22 watts. As with most properly
designed feedback amplifiers, the break
point is well defined, and distortion increases
rapidly at higher outputs.
The tuner section consists of separate
front ends for the AM and FM sections,
with ferrite -cored built -in antenna for AM
and provision for external antennas for both
AM and FM. When the Festival is used
with a grille cover, the built in antenna is
removed and mounted on the rear, with a
jack on the rear apron into which the leads
are plugged. The FM sensitivity is estimated to be better than 5 tv for 30 -db
limiting, and on AM all local stations (up
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Fig.
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(Continued on page 70)
IO
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to 30 miles) were received with the loop.
The audio portion of the Festival has
some interesting features, one of which
makes it easy for the tape-recording enthusiast to connect to the tuner circuits or the
phono preamp. Many modern recorders are
provided with a switch which shorts the
input and output leads when the recorder
is not in use, thus permitting the recorder
to be connected permanently between the
signal sources and the audio-amplifier section of the system. This is particularly useful with a three -head recorder, for the
user can feed a radio (or in this case, a
radio or phono) signal into the recorder,
and monitor direct or from the tape, at
will. This is a comparatively simple operation when separate units are used, but
this is the first combination tuner-amplifier
that has been observed so far to have this
feature. The output from the selector switch
-through one stage of amplification-is fed
to a Der OUT jack, and can thus be connected
to the input to the tape recorder. The output
from the tape recorder is fed to the AMP IN
jack. In case the tape recorder is not provided with the necessary switching facilities,
a switch is provided on the rear apron which
88K
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47K
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470
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270K
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ALL CAPACITOR VALUES WITH
DECIMAL POINT IN MFD
27K
ALL CAPACITOR VALUES WITHOUT
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AUDIO
12K
IN MMF
mr
JANUARY, 1955
61
www.americanradiohistory.com
AmericanRadioHistory.Com
EDWARD TATNALL CANBY*
the combination. We haven't begun to explore the possibilities as yet.
Albums -Plus
significant development
in records these last few months is not
disc hi -fi, which (advertising aside)
is moving forward in more or less established channels, but a new merchandising
stunt which has already had far more than
mere sales effect -the introduction of more
and more spectacular "audio-visual" albums, adding the appeal of eye -material of
an astoundingly wide variety to the existing
ear-appeal of the record itself.
Eye -appeal isn't new, of course. It began
after the war, when the formerly sedate and
plain albums for ye olde 78 -rpm discs blossomed out in colors. Cover art was born
and has, on the whole, prospered ever since.
It has, indeed, become a serious art -form
in spite of itself, under the fierce goad of
competition-involving some of our biggest
artists of the day and of the past. At first,
the brightest colors sold the most albums
but very soon the eye- splitting glare of
every conceivable garish color lay-out took
the sales appeal clean out of mere color
and so, ART crept in, necessarily! Not
necessarily good art or bad art but the principle of Art itself-the use of shapes, forms,
designs, to appeal to the eye. That is how
art has always operated; and in most centuries, remember, art has been just as practical, just as competitive as in the era of
record covers.
And now -the insides of the albums go
visual, to much more spectacular lengths.
Not only art, but documentary photography
and, most of all, words -text. The old "album liner" is now expanded to 40- or 50page books of information and inspiration.
In fact, things have already gone so far
(see below) that in a good many cases I,
for one, find the visual material a good deal
more interesting than the audible! Maybe
some of these new albums -plus should be offered alternatively at a lower price minus
the records (or the lone, single record that
many of them boast).
But don't let me give the impression that
this move is to be taken lightly or without
due appreciation. The good and the bad are,
and will be intermixed as always; but the
potentialities for good, the possibilities in
the way of a wholly new form of product
midway between the poles, art, literature
and music, are fascinating. For a good
many years there have been sporadic attempts to coordinate books and records, or
art and records, but these new albums -plus
mark the first really successful formula for
BY FAR THE MOST
-
*780 Greenwich St., New York 14, N.Y.
Ballet
"Hommage à Diaghilev." Including music
from "Parade" (Satie), "Spectre de la
Rose" (Weber), "Afternoon of a Faun"
(Debussy) , "Daphnis and Chloe" (Ravel) ,
"Swan Lake" (TchaikowskyI, "Les Sylphides" (Chopin) , "Good Humored Ladies"
"Three- Cornered
Scarlatti- Tommasini),
Hat" (De Falla), "Pas D'Acier" (Pro kofieff), "Kikimora" ILiadov), "Pe(
trouchka" (Stravinsky)
; 35 -page booklet,
color prints, drawings, photos, information.
Philharmonia Orchestra, Markevitch.
Angel 3518C (3)
The plain difficulty In listing this album, as
above, is testimony to its revolutionary character.
The records, fine as they are, constitute merely
one part of a beautifully organized "exhibit" of
sight and sound; the music is conducted by a
member of the Diaghilev "circle," Igor Mar kevitch; the illustrations are virtually all by
famous names in the same great inter -art group
Picasso, Cocteau and the like -and even the
written commentary stems from the same unified
source, as do the extremely interesting informal
snap -shot -type photographs- Stravinsky and Debussy in the latter's apartment taken by Satie;
Prokofieff, Stravinsky, Ansermet, and Diaghilev
in a London street (1921) and many others.
If these names mean little to you, the album, granted a curiosity on your part, will still
prove of great interest ; for the brilliant group of
assorted artistic creators in various fields that
collected about the massive Diaghilev (a kind of
elevated Barnum and Billy Rose combined) was
surely one of the most productive assemblages of
hi -IQ art -makers since the Italian Renaissance,
and it was the sparkling impetus of Diaghilev, the
great entrepreneur, who made it all go.
Our latter-day Greenwich Village bohemians
-
..
look pretty sad beside these titans of eccentricity
They were that -but they delivered the goods and
their stuff, as anybody can see and hear in this
album, has had an enormous influence on every
artistic field -and many commercial fields
this very day.
The best virtue of this album is that its at first
seemingly helter -skelter assemblage of an astounding quantity of drawings, photos, color reproductions, testimonials, quips, epigrams-and music
actually is, in toto, a perfectly splendid indirect
reflection of the whole feeling and purpose of the
great Russian- French movement, in art, in music
and in dance, of those years 1908 to 1929, Diaghilev's artistic reign. This is a genuine modern
documentary, radio -TV style applied in the very
best sense to this new record -album -plus medium.
And so I find I simply cannot review it merely
as a recording. Indeed, I come last of all to the
music, which is in part ultra -familiar (the more
credit to Diaghilev and associates . . .) in part
strange, and all rather beautifully played and
superbly recorded. Markevitch was a youth in the
Great Days but he took up the feeling and the
sense of those artistic times and one senses here a
decided authority in the interpretations, an ease,
-to
-
fluency, that comes from good musicianship plus
direct, first -hand experience of the original performances. A great tradition, passed on directly.
The music in most cases is not complete-but
this album is not a recording of ballet scores as
such. A few, the less well known, are given in
Coto- Prokofieff's unfamiliar "Pas D'Acier"
(Dance of Steel)
machine-age ballet from the
hard- bitten Twenties that I found surprisingly uninteresting, for this usually warm and human
composer-and Satie's surprisingly jazzy "Parade." The "Afternoon" and other familiar scores
are played with gorgeous musicality if in a few
cases the experts may question tempi and the like.
This is no child's ballet album; it's not recommended for starry -eyed youthful balletomanes
whose urge is hero -worship l But for any adult
with an eye for line, for color, a mind for interesting documentary history and an ear for ballet
music-this is it.
And don't tell me this review is long. It ought
to be twice as long. So also with many another
item of this sort. just stop for a moment and
think of the combined talent and time that went
into (a) the original productions of these many
works-dance, staging, music-and (b) the rec.
ording of eleven utterly unlike musical scores, and
(c) the extraordinary job that must have been
done to assemble and arrange the text and unique
art work in this album itself. Years!
-a
The Ballet. "Les Patineurs" (Meyerbeer) ;
"The Incredible Flutist" (Piston) ; "Fire
Bird" Suite (Stravinsky) ; "Daphnis and
Chloe" Suite #2 (Ravel) ; "Invitation to
the Dance" (Spectre de la Rose) (Weber) ;
"Sylvia," "Coppelia" (Delibes) ; "La
Valse ' (Ravel) ; Bacchus et Ariane ' Suite
#2 (Roussel). Boston Pops, Boston Symphony, NBC Symphony, Stokowsky Symphony, assorted conductors. 18 -page booklet, full -page photos.
RCA Victor LM 611313 )
Here is RCA's counterpart and, were it not
for the superbly high standard set by the above
Diaghilev album, this would surely rate very high.
In a sense it is a budget job, since the recordings
are not newly made but constitute a collection of
handily available RCA playings-note that several
are not the ballets themselves but the concert
suites derived from the original scores for symphonic performance. No objection, except that
there is a divergency of style, interpretation and
recording acoustics (and quality) that is mildly
disturbing.
The booklet is handsomely bound -in with a good
looking plastic ring binding, decorative and functional; the full -page ballet photos, borderless and
tinted in misty cool and warm shades, are superb
of their sort. The long text by Robert Lawrence,
in three divisions -"Ballet with Accent on Music," "Some Words on Listening," and a brief
comment on each ballet, are useful and easy to
read.
This is the album to give to the budding balletomanes! The pictures will enchant, the comment is not difficult (nor unusually profound), the
whole approach is in the tradition of ballet and
opera glamor that has such a wide appeal. The
musical selections, be it noted, are nicely comple-
AUDIO
62
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JANUARY, 1955
mentary to those of the Diaghilev album, with only
one duplication and an overlap (parts of "Daphnis"). In both good and bad respects a more
conventional album than the Angel opus.
Room 686-Los Angeles Audio
Fair-February
10th through 12th
A Midsummer Night's Dream, Old Vic
1954 Production; B.B.C. Symphony, SarLM 6115(3)
gent.
This is the now -standard quick release on records of an important "Broadway" production, a
technique that is applied gratifyingly to every
thing from new musicals to grand opera and
straight drama. The much-heralded all -over British production of Shakespeare and Mendelssohn,
here recorded, combined in one show music,
speech, acting, ballet and general spectacle.
As far as the actual show was concerned most
opinion here felt that it was an anticlimax, somewhat of a hodge -podge, undigested, over -long,
inconsistently styled. The recorded version, of
course, merits its own separate judgement and.
actually, is altogether different in effect. The
whole of Mendelssohn 's score is here, but in a
scrambled order with some rather odd tempi (evidently to fit the stage doings -of -the moment) and
clearly not as originally intended by Mendelssohn
-if
that matters. The speaking-acting is strictly
manner, which will
satisfy most listeners and annoy some.
I'd suggest that, even with an excellent explanatory booklet to put it together, this production
falls between the stools; too much music for the
Shakespeare people, too much dialog for the
music -lovers. Musical plays in the time of Schubert, Mendelssohn, Beethoven, were clearly far
removed from any conceivable music -speech combination familiar to us today and it is bound to be
as difficult for us to recapture the unity of that
theatre style as it might be for us to enjoy the
then concert style -involving three or four hours
of heavy music at a stretch! Times have changed.
in the expected Shakespearian
SEVERAL B'S
SYSTEMATIC
Bach: Brandenburg Concertos #1 thru
#6. Chamber Orch. Vienna State Opera,
Prohaska.
Bach Guild 540/1/2
Here is a wonderful study in tone colors, and
perhaps the closest approach to the originally intended sound of these six varied concertos so far
put on records. Each work is in itself a study in
tone color, an exercise in virtuoso tonal orchestra.
tion with the widest variety of instruments of the
period. It has been clear for a long time that the
restoration of the original instruments, without
"modern improvements," leads to far greater
listenability in these works
any listener,
trained or no. But the Bach instruments are not
easy to find and to play, the fabulous techniques
of Bach's day have been largely lost and are only
gradually being recovered.
Prohaska's carefully painstaking versions of
the Brandenburgs are superbly recorded with utmost instrumental clarity, from the standpoint of
tone -color. The rich play of color- contrast from
-for
one concerto to the next is wonderfully evident,
from the sharp, thin sound of the baby violitto
piccolo-"little violin," and the ploppy high
pitched horns, in the First Concerto through the
turtle -dove chortles of the pair of recorders in the
Fourth, the edgy dark string tones of the Sixth,
the multiple overlapping string choirs of the
-
Third.
The chief glory of the set is in the famed "Bach
trumpet" of the Second Concerto, here played by
Helmut Wobisch, one of the men who have restudied the lost trumpet techniques of the 18th
century to cope with this extraordinary kind of
trumpet music. The clarino, the small valveless
trumpet of Bach's day, was, it seems, relatively
light in tone rather than loud and piercing as
are most modern small trumpets, which explains
the odd combinations that Bach uses
this con.
certo, a trumpet, a recorder and a violin as the
solo group. Most earlier high- trumpet recordings
have featured loud trumpets; this is the first in
which the elanfno part is correctly balanced
against the other instruments, its tone relatively
light, though still climbing those dizzy heights
of pitch which take it up into the highest flute
range. (The part used to be played an octave
lower by an ordinary modern trumpet, a very
-in
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Prohaska's Bach is earnest, sincere, a bit on
the inflexible side, but these concertos seem to me
more fluently played than the earlier Prohaska per.
formance of the four Bach Suites (also in "restored" versions) on Vanguard.
Another new recording of the Brandenburgs,
from Vox, will be reviewed later.
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Bach: Art of the Fugue. Gustav Leonhardt,
harpsichord.
Bach Guild BG 532/33 (3)
Bach: Goldberg Variations. Gustav Leon hardt, harps.
Bach Guild BG 529
The Art of the Fugue, Bach's last work, is not
easy to explain to those who haven't "fallen" for
Bach by dint of sheer musical enjoyment. To
those who do feel sense in Bach's musicwhether they are trained musicians is beside the
point -the Art of Fugue speaks for itself and
many an ignoramus has found its music thrilling,
fugues or no.
The difficulty lies in two aspects. First, it is a
treatise on the art of writing fugally, and as such
it is archaic in style even for Bach's day, harking
back to a long tradition of musical "mathematics"
treats a single very short theme to every
-it
trick of counterpoint, imaginable, including mirror
fugues, fugues that play backward, combination of
three and four subjects, plus a vast array of sheer
"development" illustrating the maximum that can
be done with an extremely simple and elementary
idea. All of which is pedantic, dull in a way, and
yet being Bach is at the same time tremendously
powerful and imaginative
you can hear it.
And the entire work, secondly was written for
no specified instrument at all, but was merely set
out in open score (four separate lines) as pure
pitch and rhythm.
Now this is no puzzle at all to anyone who has
had even the most elementary training in composition. But it has continued to baffle music listeners used to music written "for" some direct
medium. And so theories continue to pop up, new
mediums are tried -string quartet, two pianos,
string orchestra, organ, full orchestra, and finally,
in this version, the harpsichord.
My ear says no-but I suspect that part of the
trouble is in a certain rigidity in the Leonhardt
playing that, especially in a supremely difficult
and vast musical edifice such as this enormous
-if
piece, quickly sends the ear to sleep. I've tried; I
can't take more than a side or less of this version
without running to turn it off. Sorry. And I've
known the "Art" for a long time, too.
The Goldberg Variations, a far more informal,
brilliant. idiomatic piece very specifically written
for harpsichord virtuosity, confirms the point. The
Landowska version on RCA Victor, faint, tinny
and from 78's, is marvellously more pliant and
alive, though one cannot directly criticize Leon hardt for the slightest clumsiness, bad registration or other obvious fault. Another recording by
this player, on the organ, "17th Century Organ
Music" (Vanguard VRS 452) shows once more
the same strangely rigid, dogmatic playing, outwardly impeccable but strangely deadening to the
senses. It would seem to be a matter of musical
personality.
How many times a not too -confident listener
must have thought, in listening to performances
of this sort-"something must be wrong with
me." I I'm an enternal optimist in these matters.
I am sure that any listener, no matter how untrained, will get to enjoy a really good performance, even of old man Bach himself, given a
little
time.
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Only the B -J arm holds the stylus
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A non -communicative playing will register just
as low a reading on the untrained ear as on the
trained -but the beginner, not knowing any better,
blames himself ; the informed listener says "bad
performance" and feels smug and virtuous, knowing how right he is! But both ears are right.
Orchestral Music of Brahms. New York
Philharmonic, Bruno Walter.
Columbia SL 200 (4)
A conservatively styled album-plus,
but
one
of the finest to hit the market this season nevertheless, this offers all four of the Brahms Symphonies in such beautiful readings as you will
rarely hear again; also included are major separate works for orchestra.
Yes -others can conduct Brahms, but there is
scarcely a man alive now who can give such a
beginning to the end of the record.
wholly natural, moving, convincing, intuitive playing of this fast-aging music. Not our younger
conductors, by and large; the " feel" for Romantic
music of this kind is disappearing and no amount
of instrumental virtuosity will bring it back. I did
a recent detailed comparison of one of these recordings with the same music as conducted by
Leonard Bernstein for Decca-the same players,
too-and the differences were startling, for any
listener.
If you are, again, one of those not -too-confident
listeners to the classical, this is the album for you.
For this music will talk directly to you and convince you in its own terms, and it won't need
advertising and publicity to help it, either. You
can't miss.
The album is most tastefully bound in a handsome Victorian -style gold and black fabric and
there are 13 pages of full size pictures and com.
mentary as well.
Berlioz: The Damnation of Faust. Soloists,
Harvard Glee Club, Radcliffe Choral Soc..
Boston Symphony, Munch.
RCA Victor LM 6114 (31
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heartfelt performance with much excellent work in
it, notably from the choral singers (no slight intended upon the solos and orchestra but choruses
are so often lackadaisical and uninspired!) but
there is, necessarily, a rather distracting mixture
of styles here
kind of international performance, like the French opera at the Met and the
New York City Center. This is not good, in the
long run, for the highly stylized drama of Berlioz;
it is inevitably better in a wholly French performance, especially in the singing department.
This is exciting and well worthwhile, (though
you'll find it a pretty long pull), but you'll discover a really better performance in the old
ording from France, Columbia SL 110 (3).
Sample it, if you can, before you commit yourself to this one. RCA Victor wins by a mile as to
.
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Menotti: Amelia al Ballo (Amelia at the
Ball). La Scala, Milan, Production. With
booklets.
(II
you have ever enjoyed Menotti's English
operas, notably the light- hearted "The Telephone"
and the spooky "The Medium," this early opera
will please you equally, though it is sung in
Italian. It is a farce, in one act, preposterous and
AUDIO
www.americanradiohistory.com
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Angel 35140
If
JANUARY, 1955
amusing; the complete text in Italian and English
in the accompanying booklet (another booklet
describes La Scala and its history) makes following the story pleasant and easy, and the music is
skillful, tuneful and unpretentious, persuasively
performed under the composer's supervision.
Superior recorded sound, too.
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(Corelli: Concerto
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One of a new series of HMV albums -plus, (His
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Victor), this lovely recording features the well
known Roman group in two of the now -familiar
type of early 18th century concerto and a symphony of the early 19th century, rediscovered only
recently, by a man whom every piano student
knows for his piano works, big and little, Muzio
Clementi. This last is the prize on the record,
though the other items are excellent material.
Clementïs symphony, a first hearing for virtually
everybody, is of the Beethoven period but in a
conservative vein as of that time; there is much
of Mozart and Haydn in it, but tempered with a
Romantic lushness that is not far from Mendelssohn.
The new HMV series is boxed with a fancy
removable color print in a window in each album,
this one being a beautiful Madonna and Child by
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Mozart: The Complete Works for Piano
Solo. Walter Gieseking. Angel 35188 (11
The killer. diller to date -eleven LP records and
)
one of the top pianists of our time. The review
copy problem was a dilly here, and Angel solved
it by making up a special sample album for us
folks. It has the blue moiré silk cover, genuine,
and the 24 pages of excellent notes, but only one
record. That one is a bit erratic; some of the
sampled Mozart is superb, some is not quite as
successful as it might be, which is perhaps an
indication of the nature of the other ten discs.
Gieseking's Mozart, of a very high order,
nevertheless is just a bit on the cool side; it lacks
the enormous vitality of his incomparable Debussy.
I can't help feeling that the much younger
Badura.Skoda can do a few things with Mozart
that not even this great pianist can match. All of
which doesn't much lessen the value of this collection as a unique complete survey, Pianists
who think Mozart is easy (and probably play him
badly for that reason) can learn a vast amount
about good pianism and musicianship here. Listeners can revel for years in it. Go to it
you
have $75 handy.
-if
The Confederacy. Essays by Bruce Catton,
Clifford Dowdy; extensive photographs,
facsimiles Lee's Farewell to the Army of
Northern Virginia; Music by Richard Bales
based on music of the South, 1861-65.
Soloists, Nat. Gallery Orch., Cantata Choir,
Luth. Ch. of Reformation, Bales.
Columbia SL 220 (1)
This album marks the ultimate in the opposite direction -all the above material, 32 pages
of booklet and only one record! I list the contents
in order of interest (for my ear and eye, anyhow) and solemnly state that I would be glad to
purchase this album without any record in it at
all; for the material presented in the large
bound -in book at the beginning is absolutely fascinating, on a par with that in the "Diaghilev"
album reviewed earlier and an equally thorough
job of amassing information, creating a sense of
the time and of history. The lavish pictures are
profuse and extremely interesting, as is the comment.
As for the record -well, after all, what is there
to hear about the Confederacy Precious little.
Mr. Bales has collected a batch of sentimental
ditties, mostly on the order of "Johnny Get your
Gun" of another time, or "Silver Threads Among
the Gold," and has dolled them up for orchestra,
with solo singers of considerable pretentiousness.
General Lee's Farewell, read by a cousin named
Lee, is convincingly Southern- accented, but,
withal, very short and mainly appropriate platitudes. It is no Gettysburg Address. Even the
record's handsome special label, with a Confederate
stars and bars in place of Columbia's usual blue,
doesn't help much.
In short, this is a record album to be seen and
not heard-and well worth the cash, too ! Who'd
á thought we'd come to this,
I
(Continued on page 78)
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THREE - CHANNEL PREAMP - MIXER
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this condition the input line is terminated
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AUDIO
66
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JANUARY, 1955
ABOUT MUSIC
(Ironn
page 10)
nitely not the way to go about it, unless
you have an independent income and can
remain glued to your phonograph night and
day for months or even years. A good
beginning would be the Brandenburg Concertos, some of which, by the way, turn up
consistently on "Favorite Compositions"
polls conducted by WQXR among its audiencè. The reason for their popularity seems
to be that these half dozen "concertos" Bach
wrote for "His Royal Highness, Monseigneur Christian Ludwig, Margrave of
Brandenburg" are closest in spirit and content to orchestral music as we know it today than any other works of the period.
You might investigate the Münchinger set
on London ffrr for a buoyant and kinetic approach to the music. Karl Münchinger and
his Stuttgart Chamber Orchestra have been
criticized for "rhythmic inflexibility."
There is drive and propulsion here, but no
rigidity to these ears. With a steady pulse,
Münchinger achieves remarkable dynamic
effects, linear texture, and a fine sense of
tonal balance.
For those of you accustomed to the soaring tones of a typical cathedral organ, the
sound of a Baroque organ may come as
something of a surprise. At first, the reedy
quality of the upper register will strike you
as "tinny," the volume too inadequate, and
the general tone devoid of lushness. But
once you've become acclimated, so to speak,
you'll begin to notice other things about this
type of organ, most important of all, its exquality so essential
traordinary lucidity
to the music of Bach. Each line can be followed like (to use an analogy appropriate
to this publication) lines on a schematic.
Decca's recordings of the blind German
organist, Helmut Walcha, are models of
acoustical clarity,
There are now over half a hundred Bach
cantatas in the LP catalogue. That's approximately a fourth of all Bach's works in
this form available in print. As a beginner,
try Cantata No. 4 "Christ Lag in Todesbanden," No. 140 "Wachet Auf," or No. 82
"Ich habe genug." The Bach Guild Chorus
and Orchestra have recorded the first two
of these. Their interpretations, under the
baton of Felix Prohaska, are well conceived. The tempo of the opening of No.
140, majestic and promising, immediately
sets the mood for the entire work.
And speaking of sure rhythmic impulses,
no musician is more gifted in this respect
than the seventy- five -year-old wizard of the
harpsichord, Wanda Landowska. There is
nothing tentative about her playing, her
attacks are clean, her phrasing unerring,
and her love of Bach and his times shows
itself in everything she interprets. Mme.
Landowska has recently completed her
"last will and testament"; that is how she
describes her monumental recording of the
complete Well- Tempered Clavier for RCA
Victor. She has been heard to say: "Bach
and I, we understand each other; we make
a happy couple." With the help of recordings such as these, you too may find "living
with Bach" a happy and rewarding experi-
-a
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carefully selected and matched. Simple
plug -in installation. System includes: quality Knight 12 -Watt Amplifier (featuring
The super -value high fidelity system.
Top quality matched components at a
remarkably low price. Complete system
3- position record compensation,
calibrated
bass and treble controls, loudness- volume
control, response ± 0.75 db, 20-20,000 cps
at 12 watts) in black -wrinkle metal case
only 3% x 13 x 10%'; Webcor 1127 -270
Three-Speed Changer (9 x 14 x 14') with
G. E. RPX -050 triple -play magnetic cartridge (dual -tip sapphire stylus); Permoflux "Diminuette" speaker system (3
speakers in modified bass reflex enclosure,
for bass, middle range and treble reproduction), 11 x 23% x 12', choice of mahogany or blonde finish. System comes
ready to plug in. Hi -fi demonstration
record included. Shpg. wt., 56 lbs.
94 PA 129. Net only
$ 156.50
93 SX 312. Knight 12 -Watt "Space Saver"
Amplifier only. Shpg. wt., 14 lbs.
Net only
$59.50
....
EXPERT HI -FI HELP
inputs, separate bass and treble controls), satin -gold finish, 8 x 14 x 9'; famous Garrard RC -80 Record Changer;
deluxe G. E. RPX -052 triple -play
"Golden Treasure" magnetic cartridge
with dual -tipped stylus (diamond LP
tip, sapphire standard tip); ElectroVoice 12TRX 3 -way speaker with 3
coaxially mounted sections (response
t 5db, 30- 15,000 cps). This superb system is complete with all plugs, cable and
hardware, plus hi -fi demonstration record-ready for plug -in connection. Shpg.
wt., 92 lbs.
4
94 PA 134. Net only
SEND FOR FREE CATALOG
Write today for ALLIED'S 308 page 1955 Catalog -your
complete guide to the world's
largest selections of Hi -Fi
to help you select
components and
systems to satisfy your
listening desires at
the lowest possible
cost to you.
home music systems, amplifiers,
tuners, speakers, enclosures,
changers, recorders and
accessories. If it's anything in
Hi -Fi, it's in stock at ALLIED.
EASY TERMS
Hi -Fi is
$261.75
935X321. "Golden Knight" 24 -Watt
Hi -Fi Amplifier only. Shpg. wt., 30 lbs.
Net only
$79.50
Our Hi -Fi consultants
are always available
ALLIED
available from
RADIO
ALLIED on easy
payments: only 10%
down, 12 months to
pay. Write for details.
Everything in Hi -Fi
1
ALLIED RADIO CORP. Dept. 17 -A -5
100 N. Western Ave., Chicago 80, Ill.
Send FREE 1955 Catolog
Send FREE Hi -Fi Booklet
Ship the following:
enclosed.
5
9/l.e6 Send for our
16 -page illustrated
booklet: "This Is
High Fidelity"
ence.
AUDIO
includes: "Golden Knight" 24 -Watt
Amplifier (3- position record compensator, response ± 0.75 db, 20- 40,000 cps,
Zone
State
,1
JANUARY, 1955
67
www.americanradiohistory.com
AmericanRadioHistory.Com
NEW PRODUCTS
Fairchild Amplifier. The Fairchild 50watt hi -fl power tftnpllfler is the smallest
50 -watt chassis now on the market, measuring only 12 "w x 7 "d x 7%"h. It has exceedingly low intermodulation and harmonic distortion, excellent signal -to -noise
ratio and is guaranteed not to ring at
any revel regardless of load power factor.
A unique balance control, permits adjust-
Frequency response is 40 to 13,000 cps. A
single control selects tape direction, fast
forward, standard forward, rewind, and
stop. Other controls govern playing speed,
Deluxe Table
Phonograph.
Built
throughout of high -fidelity components,
the new deluxe "Encore" highlights the
Pilot line of table -model phonographs. It
features a push -pull 8 -watt amplifier with
less than 1 per cent distortion, a Garrard
RC -80 automatic record changer with GE
variable reluctance cartridge, and 3 -step
equalization control for all types of recordings. The two -way speaker system
consists of an S -In. woofer and a 6 -in.
tweeter enclosed in an acoustic chamber.
-
ment for minimum distortion, proper phase
inversion, and dynamic balance of the output tubes to be made aurally, without test
equipment of any type. The amplifier is
exceptional in its stability under varying
load conditions. Further data may be
obtained by writing Fairchild Recording
Equipment Company, 154th St. and 7th
Ave., Whitestone, N. Y.
Square Ware Voltage Generator. This
instrument permits calibration of an
oscilloscope so that voltages may be read
directly from the face of the CR tube. In
operation it generates a square wave with
a constant frequency of 1 kc /sec. and an
amplitude which can be varied continously
from 0 to 50 volts. A display of this signal
on a 'scope appears as two parallel horizontal lines. The distance between the two
lines is equal to the desired voltage. The
record /playback, and volume. The unit
incorporates two high- impedance inputs
a jack for microphone, and a terminal
strip for phonograph pickup or tuner. For
playback the 212 must be fed into an
external amplifier. Write Webster Electric
Company, 1900 Clark St., Racine, Wis., for
Bulletin R8A1.
Trans- Linear Tone Arm. Distortion due
to tracking error is practically eliminated
by the new Trans -Linear tone arm which
is now being manufactured by Karl Products, 1704 Walnut St., Philadelphia, Pa.
The arm performs in a manner similar to
that of professional record cutting equ'pment, the stylus traveling across the surface as the record is played. The angle at
which the stylus touches the record is
unchanged as the playing progresses from
The mahogany finished cabinet is smartly
styled with the new "Solareed" grille
treatment. The Encore may be adapted
to chairside use by means of easily
mounted wrought -iron hairpin legs which
are available as an accessory. Pilot Radio
Corporation, 37 -06 36th St, Long Island
City 1, N. Y.
outside to center. Pin -point indexing,
which greatly facilitates cueing, is afforded by means of a calibrated adhesive backed index strip which is supplied with
the arm. Two models of the Trans -Linear
arm are available, one for 12- and one for
16 -in. turntables. Folder on request.
Tape Threader. The chore of threading
tape on a blank spool is eased by this
device which is manufactured by The
Fl:, ban Con. tinny, 7517 Pelham Drive,
a
is a sturdy metal unit
to the reel for the
Dynamic Studio Microphone. The latest
addition to the Capps line of high- quality
microphones is a dynamic unit designed
primarily for reproducing large sound
bodies such as orchestras, choirs, and
organs. Designated Model DM -2050, the
microphone has a frequency response of
50 to 15.000 cps. Impedance is 50 ohms.
Extremely compact, it measures anly 134
in. in diameter and is but 4% ins. long.
I
amplitude of any other signal then displayed may be read directly in volts by
comparison with the calibrator signal.
Signals of unknown amplitude may be
measured by comparison with the calibrator dial. The range of the Instrument is
covered in nine steps from .005 to 50 volts
full scale. Manufactured by Shasta Division, Beckman Instruments, Inc., P.O. Box
296, Station A, Richmond, Calif. Requests
for information should specify Model 402.
Tape- Recorder Mechanism. Designed for
custom installation, the new Ekotape
Model 212 Symphotone tape recorder mechanism reproduces and records at 3% and
7% ips with a twin -track recording head.
first few turns, then can
tt..r be -.,iped
off or left in position to serve as a .r:tk.
The threader can be used on any size
spool up to 7 ins. and fits all makes and
models of recordera which are equipped
with standard spindles. It can also be used
on any standard 8 -mm motion picture reel.
68
It is available in either high glosa finish
for broadcast application, or matte finish
for television. Each microphone is supplied
with an individual calibration chart.
Further information will be supplied by
Frank L. Capps & Co., Inc., 20 Addison
Place, Valley Stream, N. Y.
AUDIO
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
The NEW
1
NEW
SI
CRAFTSMAN
TAPE RECORDER
With Servo -Controlled
Isimetric Drive for
33/4 & 71/2 or 72I & 15" /sec.
High Fidelity
óILL
<A
t,
f
FM -AM TUNER
The first significant improvement in tape handling mechanisms. A multi
poled Alnico VI magnet whirling freely within two drag cups is positioned
axially by a sensitive feedback system to apply balanced relative torque to
the reels for constant tape tension and continuously variable drive and
instant brake oction. No frictional clutches or brakes employed. Tape
front and control system embodying a sensitive tuner for both
reception, record preamplification and equalization, and tone
compensation. Inputs ore provided for tape recorder, TV, phono, or other
sources for program material. FM Section has 3 my sensitivity for 40 db
quieting, and 2 my for 30 db of limiting. Effective AFC circuit simplifies
and assures accurate tuning. Defeat switch on front panel permits AFC
cut off. AM Section provides both broad and narrow bond reception, the
latter for greater selectivity and sensitivity and the former for higher
fidelity. A front -pone) switch permits selection.
Four equalization positions cover most recording characteristic requirements. Separate bass and treble controls permit up to 15 db boost or
attenuation at 50 and 10,000 cycles respectively. Two cathode- follower
outputs ore provided: one for feeding main amplifier, and the other, bypassing the tone- control circuit, for tope recording. Frequency response:
FM -20 to 20,000 cycles ± Vs db, and AM -20 to 5000 cycles ± 1/2 db.
A complete
FM and AM
tension presents constant load to capstan of all times and maintains uniform
speed from beginning to end of reel.
A single knob controls Start, Stop. Reverse, Record and Play. Tape travels
in same direction as knob is deflected. At high speeds (skip and rewind)
tape lifts automatically from heads establishing contact only at intermediate
speeds for locating or editing. Tape can be hand-cued by merely turning
one reel in either direction. Automatic motor shut -off with lost tension
eliminates 'spills' and 'brooks.' Dual speed hysteresis synchronous motor.
Change of speed automatically changes equalization. Simple single -line
threading. Has separate heads for erase, record end playback- monitoring
with provision for mounting up to six heads,
Specifications: Frequency response: ±4 db 30- 15,000 cps ( ±2 db 40.
10,000 cps)
Signal -to -Noise Ratio: over 55 db
Flutter and Wow: below
0.2% at 71/2" /sec.
Playback Timing Accuracy: 11/, sec. for 30-minute
recording
Start Time: approx. .05 sec. to full speed
Max. Tope Travel
after stop: 11/2" at IS" per sec. Rewind: less than
min. for 1200' reel
Inputs: low -level, high -level
Playback output: 5v across 10K ohms
Distortion: less than /2y IM. Has record and playback level controls. More
complete specs on request.
151 Recorder Mechanism with 3 heads, and record and playback
preamps (specify full or halftrack and speeds desired).___
:39600
151 Tape Player with
head and playback preomp (specify full or
half -track and speeds desired)
333.00
- - - -Portable Carrying Case for either of above units
34.00
101/2 Reel Adapters for either of above units
33.00
-
-
-
-
-
-
Complete with
tubes........_....._.
30 -WATT
1
AMPLIFIER
Model C550
1
Designed for critical listening, the new C550 delivers 30 watts of audio
power with only 1/10 of 1% harmonic and 1/2 of I% intermodulation distortion. Frequency response extends from 20 to 20,000 cycles ± .1 db, and
from 5 to 100,000 cycles ± 2 db. Effective gain permits amplifier to be
driven to full output with only 1.5 volts input.
A special thermal delay circuit protects power supply and other components by insuring proper warmup before high voltage is applied. Damping factor is 30:I, and internal output impedance, .57 ohms at 16-ohm tap.
Output taps are provided for 8 and 16 -ohm speakers. Employs KT 66 output
tubes in push -pull.
NEW
JENSEN CONCERTO
2 -WAY REPRODUCER
Model CT -100
Complete with
An extremely flexible control control system designed for use with highest
quality audio components. Has 4 inputs for magnetic phono pickups, tuner,
TV and tope recorder, each with independent level control. Seven positions
are provided for phono equalization covering the entire range of record
characteristics. Separate controls permit boost and attenuation of bass up
to 15 db, and treble, + 13 db and -15 db. These controls operate a hinged
circuit with fixed turnover points, thus eliminating distortions due to sharp
....168.00
'shelving'.
Write for the NEW HARVEY Audio Catalog
Two cathode follower outputs are provided: one for main amplifier, and
the other, bypassing the tone -control circuit, for tape recording. A loudness
control with disabling switch permits setting for desired listening quality
at all levels. Power supply is built in.
s1295o
Complete with tubes
WEATHERS
Debonnaire
NEW HARVEY
TIME PAYMENT PLAN
Model K700
FM Record Player
on purchases of $150 or over
fidelity manual record ployer designed to operate into any
high quality power amplifier. Has built -in self- powered preamplifier with
A complete high
controls for volume, boss and treble boost and attenuation, and turnover.
Also has auxiliary input and selector switch for tuner, TV, tope recorder, or
other program source. Additional volume control sets level for these units.
Employs the famous Weathers FM pickup cartridge and tone control. Frequency response extends from 20 to 20,000 cycles. Player is mounted on an
attractive Formica base finished in either blond or mahogany.
Complete with tubes
_.
NOTE: Prices Net, F.O.B., N.Y.C.
_._._...
.._...
-...
..
$
Subject to change without notice
AUDIO
I
.
Write for Details
HARVEY RADIO CO., Dept.
1
-A 103 W. 43rd St., New York 36, N.Y.
-7
Please ship the following
JU 2
money order for S- ._..._.
I enclose
check
shipping charges. Unused surplus will be refunded.
Sends
RADIO COMPANY, INC.
103 W. 43rd Street, New York 36
r
Up to 12 Months to Pay
124 SO
ESTABLISHED 1927
HARVEY
:10950
_....__.__...._..
EQUALIZER
Model C350
:16450
Mahogany
Blonde Korina
tubes__.. .__.........._ ................_
PREAMPLIFIER
A complete 2-way speaker system employing the
new P12-NL (12 ") low frequency speaker and the
RP- 102H -F high frequency tweeter. Both speakers
ore mounted in the new Boss- Ultrafiex enclosure,
acoustically designed to give smooth response from
the low fundamentals to the upper limits of audibility. A H -F Balance
Control is located of the side of the cabinet to permit balancing perform
once to room acoustics. Impedance is 16 ohms, and power handling
capacity, 25 watts.
CT -100
...:17950
...._....._...._........_......
--
1
UNITS
-Model C1000
-1500
Nome__...
_...
including estimated
1955 HIGH FIDELITY CATALOG
Details of your TIME PAYMENT PLAN
......_._
_....._....
_...
Address
City ......._.
_.
_...
JANUARY, 1955
_
....Zone
_....
State
69
www.americanradiohistory.com
AmericanRadioHistory.Com
Audio Fair Los Angeles
Annual West Coast event readying for capacity attendance at the Alexandria Hotel, with
first six floors devoted to the activities of the Fair and the Audio Engineering Society.
the first Annual Western
Banquet of the Audio Engineering
Society as the opening activity, the
third Audio Fair-Los Angeles gets under
way on Wednesday evening, February 9.
The technical sessions start the next day
in the Grand Ballroom on the mezzanine
floor and continue through Friday and
Saturday.
The Fair itself opens Thursday evening,
with "Trade Night." Since it is nearly
impossible to separate qualified "resellers"
from persons who are affiliated with the
trade, the Advisory Committee decided
that it would admit anyone who had read
about the Fair in the trade magazines,
whether engineer, audiofan, or dealer. The
official opening announced to the general
public -not those in the know about audio
FEATURING
-is
2:00 p.m. on Friday, February 11.
The show continues until Sunday evening,
so many who could not otherwise attend
will be able to come in on their day off.
Representing a change from previous
audio shows throughout the country, this
year's Audio Fair -Los Angeles is open
only to the manufacturers of audio components-and not to packaged "high- fidelity"
radio sets and phonographs. This is a step
in the right direction, for entirely too many
manufacturers of packaged equipment have
entered the high fidelity market simply
by applying the name "high-fidelity" to
their products, without any apparent real
effort to produce equipment which came
up to the as- yet-unspecified standards which
are well knnwn by anyone in the audiu corn-
ponents business and by audiofans who are
acquainted with high -quality products, but
which have never been reduced to a complete and reliable set of standards which
could be used to evaluate equipment on a
"go-no go" basis. With the restriction
placed on exhibits, the public is sure to
get an honest picture of what is truly "high
fidelity," and need not go away with the
feeling that a complete home music system
can be had for "49.50, including ten records
of your own choice," which is the trend
in the fringes of the industry.
The list of exhibitors who will show at
this year's Audio Fair-Los Angeles includes most of the big names in the audio
industry, as would be expected. The preliminary list follows:
Altec Lansing Corporation
Ampex Corporation
Audio Devices, Inc.
Audiogersh Corporation
Avow Magazine
Ralph Auf der Heide
Bell Sound Systems, Inc.
David Bogen Co., Inc.
Berlant Associates
Bradley Mfg. Co., Inc.
British Industries Corporation
California Record Distributors
Capitol Records Dist. Corp.
Conrac, Inc.
D & R, Ltd.
Daystrom Electric Corporation
Electro- Voice, Inc.
Fairchild Recording Equipment Co.
EQUIPMENT REPORT
(from page 61)
shorts these two jacks together, giving a
normal circuit arrangement.
Phonograph equalization is provided for
the three most useful curves, as shown in
the top section of Fig. 1. A built -in high pass action reduces extreme low- frequency
response to eliminate rumble. Connection
of a crystal or ceramic pickup is made
through a small capacitor and a series
resistor to the input of the preamplifier,
and equalization is then correct as indicated
on the selector switch.
The loudness contour switch places less
and less shunting resistance across the compensating capacitors of a conventional twotap compensated volume control. As the
resistance is increased, the amount of corn pensation increases, as shown in the center
section of Fig. 1, along with the tone -control range. This arrangement affects the
maximum amount of correction available,
and permits the user to set the control for
the average reproduction level, then controlling the volume in the normal manner.
The lower section of Fig. 1 shows the
distortion of the power amplifier. Note that
distortion is less than 1 per cent at the
Fig. 3. The
Harman - Kardon Festival, Model
D -1000.
rated 20 -watt output. Two rectifier circuits
are used-the output stage, together with
the entire audio amplifier obtain plate supply
from the high -voltage winding on the power
transformer, using a 5U4GA rectifier, while
the tuner section derives its plate supply
from a lower -voltage section of the transformer and a 6X4 rectifier. Separate filtering circuits ensure a minimum of hum and
of interaction between the two sections of
the unit. Figure 2 is the schematic of the
audio portion of the Festival.
The a.f.c. action of the FM tuner section
is remarkably effective, holding the station
in tune over a dial spread of about one-
70
Fenton Company
Fisher Radio Corporation
Ferranti Electric, Inc.
General Electric Company
Harman-Kardon, Inc.
High Fidelity Magazine
International Electronics Corp.
Jensen Mnaufacturing Co.
Karlson Associates, Inc.
Klipsch & Associates
James B. Lansing Sound, Inc.
London Records of California
Magnecord, Inc.
McIntosh Laboratory, Inc.
Minnesota Mining & Manufacturing Co.
Newcomb Audio Products Co.
National Company, Inc.
ORRadio Industries, Inc.
The Pentron Corporation
Perlmuth- Coleman & Associates
Pilot Radio Corporation
The Radio Craftsmen, Inc.
Radio Electronics Magazine
Rek -O -Kut Company
Reeves Souncraft Corp.
Revere Camera Company
The Sargent -Rayment Company
Hermon Hosmer Scott, Inc.
Stephens Manufacturing Corporation
Technical Tape Corporation
Telectrosonic Corporation
The Tetrad Company, Inc.
Thorens Company
Tung -Sol Electric, Inc.
University Loudspeakers, Inc.
Webster Chicago Corporation
Westminster Recording Co., Inc.
quarter of an inch, and with a minimum of
quality change throughout the deviation.
The a.f.c. circuit is defeated by pressing
inward on the tuning knob, which is a
logical location.
Sensitivity of the audio circuits is such
that an output of 1 watt is obtained from
an input of 0.15 volts at the Aux jack, and
only 3 my from the phono jack. The AMP
IN jack requires a signal of 0.4 volts for
the 1 -watt output, and the same magnitude
of signal is available at the nez OUT jack
to feed the tape recorder.
With the volume control at maximum,
the hum and noise output is 53 db below
1
watt, but this is not a true figure in
practice because the operating position of
the control is about 30 db below maximum.
With the volume control at minimum, the
hum and noise output is 78 db below 1 watt,
which is practically inaudible.
For the user who has a minimum of
space and who still wants high -quality
reproduction, the Festival might be the
answer, for there does not seem to be any
evidence of compromise to achieve cornpactness. The simplicity of the controls
would appear to the non -technical user,
and especially to those whose interest is
solely in good reproduction without any
desire for gadgetry.
AUDIO
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
Only the
U
"
I
}rc.
MIRACORD
XA -100
has the
Edward ratna11 Canby
WSG;'
Voice of the People Department
The only spindle that
let me quote some
pieces of mail, excerpted, as recently
received by this department. Sometimes
a phrase or two in a letter can bring out a
point of general interest better than a whole
article. Two, in this letter:
ease from the sounds of the older machines
but who-quite rightly-deplore the ugly
sounds they have heard coming from equipment that is technically top -notch. They are
very, very right in their basic hurt But
their conclusions are not valid.
Dear Mr. Canby,
. I have a technical problem
the
best means of reproducing the very low bass
from let's say 20 to 200 cps. My specific
question concerns the value of the "air
All the technical publications
coupler"
have given ample space to the virtues of the
exponential horn and its variations; for instance, I believe I could build the Jensen
horn in the October (1954) Aunlo without
much difficulty. But (few publications)
have written on the air coupler, either for
or against. Is it as good as (they say)
below 60 cps? Is it any good at all?
"In my case I could better house an 8foot air coupler than I could a Jensen horn,
but which would be better for that bottom
octave? I'm quite a lover of the pipe organ
so I want to reproduce 32 cps and Cook's 16
cps is a new challenge."
That's a slightly doctored version, but it
represents the writer's questions pretty
well. Here's an excerpt from my answer
on two points :
"As far as I'm concerned, the air coupler
died a peaceful death some years ago and I
really didn't expect to hear from it again.
Though I'm not a technical expert on such
matters, common sense tells me that the
idea of a resonating column is not good, and
unnecessary today, and a lot of
. engineering opinion that I have heard seems
pretty well to bear this out.
. I would suggest, however, that the
excitement of hearing a 16-cps note is not
very profound. It's not music and it's not
much of anything else but a slow vibration.
Even the 32 -cps pitch is practically nonexistent in music, and though it is certainly
desirable to have a solid musical bass, the
strictly musical importance of the very low
fundamentals is slight indeed."
"All of which doesn't mean that you
should give up your search for low bass;
but don't take it too seriously. There are
other much more interesting tones to listen
for, in the long run."
Next, a representative of the old school
of thought that prefers the good old -fashioned phonograph to these new fancy hi -fi
noise -makers. It seems to me that the
trouble in arguments like the following is
simply a misplaced emphasis, a faulty train
of reasoning, based on right feelings. Most
people who think this way are good listeners, often with highly musical ears, who
not only can interpret musical sense with
"Mr. Canby :
.. I write concerning your opinions of
commercially built "hi-fi phonographs, especially as you have regarded them in the
July 1954 issue of this magazine. Frankly I
don't think you're being fair. I own and use
extensively a
affair which com-
NDER THIS
HEAD,
U
...
...
-
AUDIO
1
pletely satisfies me.
"My cousin was happy with oil lamps and
a woodburning stove-until he came to the
city. But, at one time, I owned a [complete
and expensive hi -fi system] ; it was stolen
in toto, diamond and all, and in the meantime I rented a demonstrator
. The
superbly balanced sound and the complete
lack of fussing with solder and knobscrews
quickly led me to pay in full for the machine, my entire $150 plus $16.75 for a diamond stylus, its only lack.
"I admit that I am primarily interested
in music, but isn't that the case with nine
tenths of all record purchasers? Do we
need the remarkable qualities of modern
sound equipment when we can have pleasant
music so easily and cheaply?
.. Please do not misunderstand me; I
own a very large and quite varied all -LP
library, in very fine condition. All of my
Olympians [Mercury] and a few other
isolated records, such as Gieseking -Debussy-Angel [Piano works of Debussy]
actually sound quite startling. I'm a happy
man."
My answer in part was as follows :
"The trouble with good phonograph
equipment is that the better it is the more
tricky it is to use and the more easily can
it be misused to make hideous rather than
good sound. I think that is the problem as
far as you are concerned.
"The more expensive equipment, after all,
does reproduce more closely the original
sound as picked up by the microphones.
"I admit immediately that recorded music
is a sound unto itself and that one can't
exactly reproduce a concert hall, in any
case. Nevertheless, the better equipment is
capable of bringing out more of the musical
values in a recording, and so I still feel that
it is the thing to have-even for a music
lover."
There's no doubt about it, we need a lot
more education on how to use hi -fi equipment for best effect. Tin -ear or no, there
are ways to get the best out of records
even recorded railroad trains and steam
calliopes! As noted here last month in con-
-
JANUARY, 1955
treats your precious
records with the care
''\
they deserve. No more
"out -of- round" center
holes. No rumble;
no wow.
See
the
MIRACORD XA -100
AT
NNRUEV
-
.411pl J°"G
I
PI,"s
PUSH BUTTON CONTROI
operation of this remarkabie
changer is simply controlled by four
push buttons
Every
Plms PAUSAMATIC
Now you can automatically preset the
time lapse between record changes,
from 5 seconds to 5 minutes
Phis
ALL THESE FEATURES
No Wow.
No rumble.
Intermixes 10" and 12" records.
Interchangeable plug -in heads.
Ball- bearing- suspended turntable
and tone arm.
Adjustments without tools.
Rubber matted turntable.
All 3 speed settings controlled
by single knob.
Shipped complete with leads and
plugs, ready to play.
HARVEY RADIO
COMPANY, INC.
103 W. 43rd Street, New York
36,N. Y. Nielson 4.1500
71
www.americanradiohistory.com
AmericanRadioHistory.Com
-Built to the FAMOUS
WI LLIAMSON Specification
PARTRIDGE WWFB
Output Transformer
Built to the famous Williamson specification,
the PARTRIDGE
WWFB covers full A.F.
range with lowest distortion. Secondary windings are brought out to eight separate sections
of equal impedance. Power Rating
continuous
steady
tone.
Stock
types comprise 0.95, 1.7, 3.6 and
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nection with the Audio Fair, some of our
professionals could learn a bit too, along
with the customers.
Finally, a letter from an overseas serviceman and Audio subscriber who, after asking about a mail -order portable phonograph
marked "best" in a well known catalogue
that features a single point for all records
(my answer will, of course be-stay away
from all "all -groove" points, "best" or
otherwise, if you want to treat your records
fairly, with the single possible exception of
the Weathers cartridge), goes on to describe record collecting in France as a
tough proposition. (It's even tougher for
Frenchmen, who must pay what is for them
fabulously high prices for records and
equipment.)
"I suppose there are some really fine hi -fi
German and maybe even French records
that we should be adding to our collections
here, but no one seems to know just which
companies in Europe do dependable work.
As listening booths and pre -trials are unheard-of in the smaller towns where we are
stationed, the problem of knowing which
records are good is difficult indeed.... It
is a shame that the "Stars and Stripes," our
official overseas newspaper, has never gotten around to running columns on records
or music in general. Cameras are discussed
in full, you can find out the HP of every
new European vehicle on the road, but here
in the home of so much great music it is
impossible to find a single worthwhile critical article on instruments, records, orchestras, etc. Even tourist books ignore the subject in favor of best brands of perfume,
gloves, etc. to carry home. For that reason
many of us can thank you for helping us
through the maze of new recordings and reissues which we never even have a chance
to hear or read about."
I wish someone would help me through
the maze. But be that as it may, I can only
remark as I did after the summer of 1953
when I was in Europe, that the place to buy
European recordings is in the U.S.A.
Though our own musical activity has
been picking up as far as records go, there
is still a vast quantity of European -played
music issued here on LP records, or shipped
here in special editions for the U.S.A., as
with Angel and London records. Most
American companies now have European
affiliates and vice -versa. Records are far
cheaper to buy here and, I suppose, cheaper
to make. Quality in many cases-not all
tends to be better as far as the record plastic material is concerned, English discs
being the outstanding exception.
True, many new European recordings are
issued on both American and European
labels and so are available in Europe. But
the high cost of recorded music over there
often means economies in the making, such
as close grooving ; some items that are 12inch LP's here are crammed onto 10-inch
discs in Europe. But the clincher, for
American servicemen, at least, is the price.
Records shipped from America are I would
guess bound to be far less expensive than
the local product. (The European citizenry,
of course, would have to pay a steep import
tax that would remove the profit entirely.)
As for music criticism and information, I
suggest that perhaps if this soldier were
stationed in one of our own small country
towns he might find himself in the same
box. Useful and informed criticism of records and music, up- to-date information and
understanding concerning hi -fi equipment,
are matters for the big cities, here as in
Europe.
I'll never forget trying, a few years ago,
to buy a GE replacement stylus on that
highly civilized vacation spot, Cape Cod.
-
AUDIO
72
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
Long distance calls to every town within
thirty miles produced nothing; they'd never
heard of the thing. Finally a local GE
toaster -gadgetry outlet sold me a complete
cartridge at full list price. He didn't aim to
carry any damfool things like extra needles
and if I wanted one I could have the cartridge. I took it. No alternative, short of
New York or Boston.
Records for Overseas
The best bet for overseas servicemen is
as follows. (1) Study record reviews, to
taste, sent on from the U.S.A. or in European journals. (2) Acquire a late issue of
the monthly Schwann Long Playing Record Catalogue, from a record dealer in the
U.S.; or the Long Player, also monthly.
(For information, write Schwann at 131
Clarendon St., Boston 16, Mass., The Long
Player at Box 346, New York 19, N.Y.
Year's subscription to the Long Player,
overseas, $4.). Both carry monthly listings
of manufacturers' suggested prices (i.e. list
prices, minus discount). (3) Order from
local U.S. dealer or from one of the larger
big -city dealers, most of whom now given
discounts up to 30 percent from the list
price. Almost any dealer will ship overseas.
These two cumulative catalogues between them list just about every LP available in the U.S., marking the newest
releases for quick identification ; heavy advertising by the various record companies
gives an added label -by -label cross section
of new material. They are invaluable as an
adjunct to reviews.
For those who are stationed in Latin
American countries, note that a Spanish language Mexican monthly on LP and
Hi -fi, "LP" ( "La mejor musica del mundo
Para discotecas selectas") gives quite remarkable coverage to most major U.S. LP
issues and to most of the current hi -fi equipment as well. Brief reviews, in Spanish, big
ads for new records and equipment. A separate section is called "Alta Fidelidad"
which in the last issue I received included
a glossary of hi -fi terms in Spanish, with
English equivalents in parenthesis. Might
come in very handy. Subscription, $3 U.S.,
for foreign mailing. Address: Editor, Otto
Mayer -Serra, Apartado postal 8688, Mexico, D.F.
Gadgefizing: 1. Micro -Poise
I'm as intrigued by an ingenious gadget
as the next man is -even by what one might
call a hopeful gadget ; that is, one that is on
the right track even if it doesn't work out
too well. There are lots of hopeful gadgets
in hi -fi and I'll admit that I've praised a
number of them in the past, even though in
the long run I have put some of them aside
as not really very practical.
One of the most fruitful areas for well intentioned devices in audio has been the
stylus -weighing department.
Everybody
wants to know how much his or her stylus
point "weighs," but in the past nobody has
been able to decide for sure, thanks to those
complexities of pickup geometry, the arcs of
travel, the side -pull and what -not, that
make readings in grams singularly inaccurate on most devices.
I mentioned the Weathers weighing
gadget some time back -and noted at the
time that its ingenious suspension principle
at least got around the difficulty of the
point's vertical arc of travel ; but the arrangement of detachable levers on this little
springless weigher, as then noted, was
perfectly .designed for quick misplacement.
In no time at all I had lost essential parts
of the device (behind the radiator or up the
vacuum cleaner hose) and that settled that.
Moreover, I had already come to feel that,
AUDIO
even though the elimination of springs was
a big step towards practicality, there were
still friction problems which might make
the Weathers scale something less than
accurate, at best.
Now the indefatigable Maximilian Weil
has come up with another stylus weigher
which, at ldttg last, really works. I don't
think anybody will improve on it. The
Micro-Poise goes straight back to the most
ancient and the simplest principle of all, the
balance, see-saw style. Put the pickup on
one side of the see -saw or teeter -totter, put
a small brass weight on the other and see
what happens. A collection of small weights
of varying sizes will allow you to figure
stylus pressure by process of elimination.
Of course this device is somewhat trickier
than a teeter -totter. The ingeniously machined central pivot is a pleasure to see, the
product of a lot of experiment and some
very sharp old- fashioned know -how. The
inscribed "record groove" on the pickup
side of the balance, into which you slide the
stylus, is another tricky idea, and much
better than the cups and depressions in
some other devices. The small brass weights
that fit over a pin complete the arrangement-two of them in convenient sizes.
Rest your pickup stylus in the groove, put
on a likely weight, and the device immediately tells you, with only a quarter -inch or
so of motion, whether you are heavier,
lighter, or the same as the given weight.
What seems to me good about this gadget
is, first, the good geometry, which makes
for the best possible positioning of the
stylus, in the normal playing location, and,
better, requires but an extremely small arc
of motion to give a "reading," thereby
reducing a major source of error ; and second, the absolute minimum of friction inherent in this see -saw balance approach.
This is one gadget I expect to keep on
using.
The Micro -Poise isn't cheap -none of the
point -pressure gauges is cheap-but a bit
of close inspection will convince you that
the machining and calibration of weights is
of a high order here, and worth a bit of
cash.
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2. Static Eliminators
Another area of perennial hopefulness in
the record gadget field is static removal. It
was one of the first, after the introduction
of the plastic record, and many a reader
will remember the excitement over the
radioactive poloniurir activated static brushes
which a lot of nervous people immediately
decided were by- products of the atomic
bomb and at least as dangerous. (They
wern't)
Static still has to be removed via gadgetry, the static -free plastic record being
still a rarity. Some of it goes away via the
residue of one or another of the wipe-on or
.
spray -on fluids. Some gets wiped off clumsily via a damp cloth.
Some still goes via ionization of the adjacent air, as with the polonium static
brush, but there are much more practical
ways of doing it now. The newer radioactive gadgets last a large number of lifetimes, instead of losing 50 per cent of their
efficiency in a year or so.
I reported, back awhile, on the Mercury
Disc Charger, a tiny bit of radioactive material embedded in plastic that clips onto one
side of your pickup and "scans" the record
as it plays, removing static ahead of the
stylus. Since then another and very similar
device has appeared, the Eby Stati -Mute,
and I have had this one inconspicuously attached to my playing arm for some months.
I must report that it works, and this goes,
too, for the Disc -Charger. (That is an un-
JANUARY, 1955
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The original audio anthology is still
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Just learned about the book. Contains
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2nd audio anthology continues
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fortunate name, I'd suggest! One would
almost think it charged the disc up, instead
of discharging it.)
The main criticism I've heard suggested
concerning these static- removers is that
they merely loosen, but do not remove the
dirt and grime which is held to a plastic
disc by the bonds of the static charge. In
practice this is not, it seems to me, a serious criticism.
It is true that if you play a very dirty
record under the static "scanner," much of
the lint and dirt will ball up under the
stylus and some grinding of the groove may
occur, I suppose. But obviously the thing to
do with such a dirty record is to clean it
first; then on subsequent playings it will
remain static -free under the scanner and
pick up a minimum of new dirt. Clean records, new records, fare very well under the
scanning beam, as I have good reason to
know. And so I recommend both of these,
the Disc -Charger and the Stati -Mute as a
painless and automatic means of keeping
discs free of static. Nothing in the way,
nothing to use up. (And if you want to reset your stylus pressure to compensate for
the slight additional weight, pull out your
Micro - Poise, above.)
3. GE "Baton" Arm.
General
Electric's pickup arm has
reached me a trifle late, a couple of years
or so, but I still have some comments on it
that are of current application, since the
arm is still very much on the market.
The "Baton" arm (two sizes, 12 -inch and
16-inch) is a handsome twin -tubular affair
with a counterweighted section up front.
somewhat like that in the Pickering arms.
But unlike Pickering, GE has a balance
scale built into a visible counterweight shaft
that exten.s back from the cartridge shell.
Because everything is visible about this
front -end assembly, I find that there is
much less danger that an unknowing or
absent -minded user will grab the main arm
and drag the cartridge point across the record than there is in the nicely streamlined
Pickering models, where the vertical -moving head assembly is concealed under the
end of the main arm, which moves only
sidewise.
The GE arms are clearly intended for the
GE cartridge and that is that. The scale is
calibrated to match the weight of that cartridge, for one thing. More important, the
slide -in cartridge holders are intended basically for the GE and are not very- well
adapted to most other makes, mainly because the two contacts in the rear of the
receptacle, reached through a snap -in kind
of spring arrangement, are not too easy to
hit.
Don't worry, if you have other cartridges
in mind: I've got an E -V Ultra -Linear
ceramic in my GE arm now. Most adaptations can be made with a bit of ingenuity
But I should think that, as a general principle, a regular "shell" with its own contacts into the arm, as in many changers,
would be a useful adjunct to this and other
arms for those who want to be able to use
a wide variety of cartridges, or who use two
separate cartridges for one -mil and three mil playing.
Cartridge Mounting
An increasing difficulty, incidentally, in
cartridge standardization as to size and
mounting is the rapid drift away from the
once-universal horizontal pin connections at
the cartridge rear. Numerous cartridges
still have them, but many newer ones have
vertically placed contacts, one above the
other, and the distance between the pins.
vertical or horizontal, gets less and less as
AUDIO
74
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
cartridges get smaller. and smaller. A universal arm to match all present types of
cartridge contacts in plug -in fashion is no
longer possible. The Clarks= arm for example, which a few years ago would take
just about any cartridge on the market with
a quick twist of its set -screw clamp, now
will not accept many new cartridges. (It
has two horizontal spring -loaded contacts
against which you push the rear of the cartridge.) The shell arrangement, with loose
slip -on wire connections inside, to slip over
any cartridge's pins, plus its own external
prongs, is now the best answer to universality, for any arm or player.
Which brings up another question of
minor but intriguing importance. What of
the half -inch mounting holes, now standard
(with varying screw sizes) for American
use? As cartridges have grown smaller, the
once universal pair of screw holes at this
distance (RCA's and a few others were
slightly different) and the familiar large size head
or shell become daily more
anachronistic. Most new cartridges are so
small that the mounting gear is in the form
of "wings," spread out from either side of
the tiny cartridge itself, clearly a makeshift adaptation of a small unit to an overlarge space.
The miniature cartridge first hit the popular market in a relatively large way with
the original Philco- Columbia LP player
and its small crystal "sugar- lump" cartridge, with special small arm to match. This
department then hailed it as a coming and
presumably standard size; but the idea
didn't go over widely, though Astatic's
model U crystals and their special arms are
still extant today as an outgrowth of the
old LP player. The large cartridge receptacles and the wide-spaced mounting centers, half-inch, continued standard for the
United States.
We now still use the large heads, big
enough to fit the biggest and clumsiest of
old-style cartridges, though the plain fact
is that a large proportion of the newer cartridges are miniature in size and more
miniatures appear every month. Recent
major recruits are the tiny Pickering magnetics (mounted on relatively huge and
clumsy adapters for the big shells), the
Sonotone, Astatic, and Shure ceramics, and
the Dutch Ronette crystals. All of these
are now equipped with wings or other devices to fill the empty spaces in the standard cartridge head.
But in a few years, we can guess, the
large shell will have to go. Then the miniatures will move, properly, into miniature
heads in new slim arms, like those long
used for the Zenith "Cobra" pickups, or the
special Ronette tubular arm now available
in this country. (You take off the Ronette
wings; the small cartridge just fills the
head.) Fine -we can use smaller, lighter,
less bulky arms. But what will the new
"standard" mounting arrangement be, I
ask ?
So far I haven't seen the slightest indication of any forthcoming agreement. Has
anybody given the matter a thought ? True,
it's not exactly a basic matter and I can see
how most manufacturers, thinking purely of
their own product would never give it their
attention. They should. For as usual, the
poor goat -the consumer -will in the end
be the one to suffer if, in abandoning the
present semi- universal U.S. standards for
cartridge mounting, we move into an area
of simple chaos, where every cartridge requires its own special adapter and every
arm, changer or non -changer, likewise, and
an audio parts dealer in order to match all
the leading cartridges to all the leading
arms will need a vast carload of adapter
fittings! Could happen, and it probably will.
AUDIO
Isn't it time to investigate a practical
new miniature cartridge standard right
now? Maybe it's already too late-for present designs are radically unlike in the essential respects. It's not too late to try.
What is needed is a compromise smaller
adapter shape, to which the present small
cartridges could practically be adjusted, as
they now are to the large -size standard
mounting. It would take ingenuity, but we
have plenty of that around, if only the cartridge designers would get together in a
Standards Committee-as the tape equalization people finally have done.
Ronette
Following this continuing stream of
thought, herewith some words on the
above- mentioned Dutch- import Ronette
crystal cartridge. I got a sample load of
these units, plus the Ronette arm, last winter from Holland. (The separate cartridges
were, of course, equipped with standard
half-inch mounting wings as per above.) I
did not then know that these cartridges
were to be widely used on coming U.S.
equipment, notably the 1955 Columbia
phonograph line and several others. Thanks
to this, and to their general availability, the
Ronette line is now of considerable importance in the United States.
These are plain "old fashioned" crystals,
and many will turn up noses. But don't do
so until you investigate the kind of performance these units give. There are some
very interesting points to note. And among
them the most interesting to me is the audible effect of extreme high compliance, as
widely claimed in Ronette literature; for
this reminds me of an old battle in these
pages, Circa 1948, when, unaccountably, the
new Columbia -Astatic crystal LP cartridges played new LP records without
"buzz" in the loud parts, where many existing expensive magnetics made nasty noises
at every loud passage. The magnetics were
flatter in :esponse, but the high -compliance
crystal sounded better.
Our magnetics have long since overcome
this trouble and the newest magnetics are
outstandingly good as compared to earlier
models. The point I have to make is slightly
different, for today.
The Ronette, as sold in the U.S., comes
in two models, the OV or "standard" grade,
very cheap, and the P or professional cartridge, outwardly the same in looks but with
higher standards of response, a different
curve. (More of that in a moment.) I've
been trying both, and my interest went immediately to the cheaper cartridge, the OV,
since that one is to be used in many a low priced "hi-fi" phonograph. It appears, for
instance, in the new Columbia 3-speed
player attachment, which sells for about $17
and is thus the cheapest player available
with minimum quality requirements, including two sapphire needles. (No "all-groove"
points, no precious metal.)
It may seem crazy, but when I connected
the two Ronettes straight into a high -level
amplifier input, unequalized (as one does
with the new ceramics) it was the cheaper
OV that sounded the best -and indeed,
though its response is relatively limited,
with a practical top of under 10,000 cps, it
reproduces hi -fi recordings with far better
sound than it has any "right" to, according
to its description.
I can give you two interesting reasons
why. First -compliance. The outstandingly
good compliance of this unit gives it a tone
quality that is smooth and natural to the
ear with a minimum of metallic "crystal"
sound and a particularly nice clarity in the
loud passages. Even with a slightly restricted frequency range -remember that
JANUARY, 1955
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constant-amplitude curve that is normal
for them. They have peaks and they fall off
above or below some peak frequency. The
Ronette OV model has a curve of response
that is decidedly not flat. But its general
shape, nevertheless, follows the constant
amplitude curve as to tonal balance, high
and low. Therefore, as played into a flat
amplifier (with proper termination), unequalized, it matches pretty closely the now
semi- standard record playback curve, highs
boosted and lows rolled off.
This has been and still is the principle of
operation for all the newer wide -range
quality crystals (including ceramics) in the
U.S. The E -V Ultra- Linear is advertised
as adhering to the RIAA- New- Orthophonic
curve within close tolerances the CAC
cartridge was designed to match the old LP
curve without equalization.
But the professional Ronette P cartridge
has a special curve. It has, with proper
termination, a constant velocity response
over most of its range. (See EQUIPMENT
REPORT, Dec. 1954.) Over this area of its
response, then, it acts like a magnetic cartridge. Too strong highs, unequalized
reproduces the recorded high boost without
the built -in compensating roll -off of other
crystals. As far as I can figure it (and I
admit that I am not entirely out of the
underbrush of confusion in these matters)
the lower end of the Ronette P model still
boosts the bass more or less normally according to the constant amplitude curve
when working into a high load resistance, 1
meg. or more. Anybody with a little know how and some basic curiosity can equalize
;
-it
Acknowledged the Leading Publication
in the Field of Sound Reproduction
AUDIO
the upper highs arc mathematically very
close, 8000 cps to 16,000 cps being only one
octave -the basic sound of this unit is excellent. It reproduces, let's say, 99 per cent
of the significant musical material on a
record.
But there's another reason. Why did it
sound better than the professional model P
Ronette, under the same conditions? Because of equalization.
Few crystals are really anywhere near
flat in response, even to the theoretical
the P for good results, and I managed it
quite handily. But not most unknowing listeners especially if they are not warned in
advance.
Common sense tells me that unless the
clear difference in type of response curve is
made very, very plain in Ronette literature,
many people-and plenty of service men
too -are going to find themselves dismally
confused. I'm getting a headache already,
thinking about it.
NEW PRODUCTS
(from page 68)
Packaged
Circuits Utilizing Etched
Circuitry. Of particular interest to engineers and designers is a new departure in
packaged multi -component units which
use circuits etched on impregnated Teflon.
own*
IL)
g
AUDIO for the nest
print
Name
Address
Zone
State
City
Subscription price: U.S.A., Possessions, Canada and Merici
year $4.00; 2 years $7.00, all other countries 55.00 per ye
1
AUDIO
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY. 1955
Manufactured by Audio Products Corporation, 2265 Westwood Blvd., Los Angeles
64, Calif., and sold under the trade name
"Pakaps," the new line is offered in three
serles having many applications in computer and airborne instrumentation, laboratory equipment, and high -fidelity audio
amplification. Standard serles 100 and
miniature Series 200 units perform such
functions as low -, medium -, and highspeed binary scalers, cathode followers,
multivibrators, pulse formers, pulse
shapers, ring counters, and gates. Series
300 Pakaps are multistage amplifiers available In three ranges of amplification; 20,
40, and 60 db, flat from 20 cps to 40 kc.
Overall size is 31/2" high x 11/2" diameter.
MODEL C8W
8"
Soaotone Ceramic Cartridge. Exceptionally fine performance characteristics are
inherent in a new single- stylus high fidelity ceramic cartridge recently announced by Sonotone Corporation, Elmsford, N. Y. Known as the 1P, the cartridge
features high compliance and extended
now...Adjustable
Speaker Networks
by
balance your system
speaker combination
your present system
To
To suit any
To improve
For the first time, networks and filters, so designed as to provide a wide selection of popu-
lar crossovers al various speaker impedances
-So engineered as to expand, without waste
obsolescence,
o
he
reproduction
sound
of
2- way and c 3 -way systems. The built -in versatility of these units allows you to assemble
systems that suit your own taste, operating
conditions, and budget.
LOW FREQUENCY
REPRODUCER
Ideal for assembling a compact,
limited space, high quality system
perfect too, as mid -range
unit in low cost three-way system.
Can also be used in multiples
...
as
N2A
expanding woofer.
Eight ohms impedance,
25
L/C DIVIDING NETWORKS
ADJUSTABLE
watts power capacity
N-2B
As 2-way network:
MODEL N -2A
MODEL
C12W
12"
ADJUSTABLE
RESPONSE
WOOFER
Contains exclusive built -in facilities
for limiting high end response
to 700, 2000 or 5000 cycles, thus
suiting crossover requirements
of most tweeters. Overall response
40.6000 cycles. Handles 30 watts,
impedance 8 ohms.
MODEL C15W
Impede
once
8
Ohms
16 Ohms
4 Ohms
frequency response. It does not require
an equalizer or preamplifier, making it an
ideal unit for improving older phono installations: Output is one volt from microgroove records. Because of its small size
it will fit into an unusually large number
of tone arms. The unique replacement
stylus snaps into place and is available
with either diamond or sapphire tip.
Conaro Record Changer. Many improvements which add considerably to the user's
convenience have been incorporated in the
new Collaro Model RC-54 three -speed
changer. Automatic intermix permita
stacking of 7 -, 10 -, and 12 -In, records in
any order of play without any adjustment
or pre -setting. provided they are of the
same speed. The complete changing cycle
of the RC -54 requires only six seconds,
regardless of the speed at which records
Ask
For
AUDIO
KENSICO AVENUE.
WHITE PLAINS. N. Y.
Progressive Speaker
Expansion
2500, 5000
2500
5000
4 Ohms
-
16 ohms to 1250,
2500, 5000 cycle
crossover;
8
ohms to 2500,
5000, 10,000 cycles;
4 ohms to 5000 and
10,000 cycles.
MODEL N -3 THREE -WAY
CROSSOVER NETWORK
Complete
with
built in
continuously
variable
"presence"
and
"bril-
liance"
con.
trots. For 8 ohm 3 -way
systems using 350 and
5000 cps crossovers. Adjustable
4.8 ohms and 10-16 ohms.
LOUDSPEAKERS, INC
16 Ohms
MODEL N -1 ADJUSTABLE
HIGH PASS FILTER
Built-in continu-ously variable
high frequency
control. Matches
-
50 SOUTH
1250, 2500,
12db /oct 2 -way networks
and in combination as 3 -way
networks.
girder construction for lifetime
trouble -free operation. Adjustable
voice coil permits match to
For descriptive literature write desk 45
Selections
Ohms
as
Acme of attainable perfection in
the specific reproduction of low
frequencies. Two spiders for positive
piston action. Greatest axial
voice coil depth and excursion
Six lb. Alnico 5 magnet. Die-cost
Another engineering achievement of
Crossover
once
8
units can be used singly cs
6db/oct 2-way L/C networks, singly
12db
/oct L/C filters, in pairs
as
15"
Defies obsolescence.
watt systems.
350, 700
350, 700
700
!mood-
These
DUAL
IMPEDANCE RANGE
SUPER WOOFER
For 50
MODEL N -28
Crossover
Selections
are being played. Mechanical features include: A powerful 4 -pole motor with dynamically- balanced rotor; a weighted steel
turntable which runs on a cushioned ball
thrust for rumble -free operation; automatic idler disengagement when the
changer switches to "off"; automatic
switch -off when last record has been
played, and automatic muting switch
which shorts out the pickup during the
change cycle. The new RC -64 is considerably smaller than its predecessor, measuring only 12 x 181 in. Further information
may be obtained by writing The Collaro
Division of Rockbar Corporation, 216 E.
37th St., New York 16, N. Y.
JANUARY, 1955
mounting arrangements.
For descriptive literature
write desk 45
Another engineer mg achievement of
LOUDSPEAKERS,
80
Ask
INC
SOUTH KENSICO AVENUE, WHITE
For
Progressive
PLAINS. N. Y.
Speaker
Expansion
77
www.americanradiohistory.com
AmericanRadioHistory.Com
CLASSIFIED
"SOUND" PRINCIPIES
worn page 20)
Rata: 10o
per
adyortismenh;
word
25.
per Insertion fer nenenmerded
word fer eemmerelal
ados.
not
and ne discounts will 1
per
bates are
Its manifold possibilities are apparent tisomenh.
allowed. Cory most be arcompanlod y remittance lw
airport, transportation termifill. and mut roach the New Merl Mies by Ss
nals, store, hospital, stadium, office,
5nf .1 the month prwodins the dab of iue.
school, church, arena, conference hall, in
all facets of industry, commerce and recTILE AUDIO EXCHANGE has the largess
reation. They await only the vision, selection of new and fully guaranteed used
Catalog of used equipment on reenergy and determination of more men equipment.
quest. Audio Exchange, Dept. AE, 159-19 Hill.
side Are., Jamaica 32, N. Y. OL 8- 0-145.
like Nathan D. Reiss.
in factory,
AUDIO EXCHANGE EXCHANGES AUDIO
DOES THE IMPORTANT JOBS
DIAMOND NEEDLES : Custom re- tippins
of your phonograph needle or cartridge with
broadcast quality diamond. For information
and price write to : Transcriber Company
(Diamond Stylus Manufacturers), 70 Pine
NO OTHER TAPE CAN DO!
St., Attleboro, Mass.
Revolutionary new Soundcraft LIFETIME®
Magnetic Recording Tape takes over where
others fail. This high- fidelity tape:
Banishes program timing problems due to tape.
Preserves priceless recorded material for
a lifetime.
Stores perfectly in any climate.
Is a third as strong as machine
steel.
Will never break, cup, curl, tear,
dry out or grow brittle.
To the best of engineering knowledge,
LIFETIME Tape will last forever. Newest in
Soundcraft's quality tape line, its remarkable Micro- Polishedv oxide coating anchored to DuPont "Mylar" polyester base
FM ANTENNAS. Standard and Special
types. Installation Accessories. Wholesale
Supply Co., Lunenburg, Mass.
ALLIED 16 -in. Professional Recorder, (same
as Presto 6N), like new, bargain. Box CJ -1.
AUDIO, P. O. Box 629, Mineola, N. Y.
makes it the finest tape money Can buy. At
dealers everywhere. Start using it today.
For Every Sound Reason
REEVES
SOUNDCRAFTCORP.
DEPT. B -1
10
52nd St., New York 22, N. Y.
E.
The Soap Box Derby, famed focus of juvenile
ingenuity and prowess, annually attracts some
65,000 spectators. Thorough coverage requires
careful engineering and considerable experience.
quality control of
JIM
LANSIN-
RECORDS
(from page 65)
speakers
BI testing
One of the final Inspections given all Jim Lansing Signature Speakers
Is made with a BI tester. This instrument gives
a direct, accurate measurement of each unit's
electrical quality.
Magnet
size and
flux
density alone do not determine speaker efficiency. The force available
to move the dynamic
assembly in any speaker
is proportional to:
the
flux density surrounding
the voice coil, the length
-
of conductor uniformly
subjected to lines of
force, the current flowing through the wire.
This total relationship
(131
Offenbach: Laité Parisienne. Meyerbeer:
Les Patineurs. Boston Pops, Fiedler.
In the Signature B1 tester a speaker's ability to
support a known weight
is read directly on a
JAMES B. LANSING SOUND. INC.
manufacturers of precision transducers
FLETCIIER DR. LOS ANGELES 39. CALIFORNIA
PRECISION MAGNETIC HEADS
Erase-Record-Playback
STANCIL-HOFFMAN CORPORATION
Hollywood 38, California
FOR SALE : REK -O-KUT "Challenger"
Deluxe disc recorder, $350 ; Wagner -Nichol*
Microgroove 33% r.p.m. disc recorder, 2100;
Presto TL-10 tape mechanism, 7%- and 15-ips
capstans, $100 ; General Electric 5-in. oecllliecope, CRO -SA, 14 tubes, voltage -regulated,
$100. All excellent condition, priced FOB.
Sold on money -back guarantee. V. R. Hein.
418 Gregory, Rockford. Ill.
RCA Victor LM 1817.
The Pops, Arthur Fiedler and Offenbach, in
"New Orthophonic," i.e. RCA's up-to -date recording: need I say more? A grand and glorious
sound, very hep and peppy.
SELL : UTC 3A equalizer ; new Fairchild
650-C1 preamplifier. Will sell to best offer.
Eugene Browne, 44 Clement Ave., West Roxbury, Mass.
Additional Classified Ads
PORTABLE DUAL-SPEAKER unit with
Bell amplifier and University and GE speakers, in two -piece traveling case, $95. GRAY
AUTOGRAPH 1'S -1, DC -AC CONVERTER;
input 105 -125 volts, d.c. output same, a.c.,
$10. CORNELL- DUBILIEÌt POWERCON VIBRATOR CONVERTER, Model 110 -RIO; 110 volt d.c. Input ; 110 -volt a.c. output ; 100 -150
watts ; $15. ATR DC -AC INVERTER, Model
RHB ; 110 -volt d.c. input ; 110 -volt a.c. out put ; 225-325 watts with voltage regulator ;
$15. PINCOR ROTARY CONVERTER, Type
output 110 -volt
K -20 ; input 115 -volts d.c.
a.c. ; $25. Prices all for FOB, N. Y. Cash with
order. BURTON BIGELOW ORGANIZATION,
274 Madison Ave., New York 16, N. Y.
factor) can be meas-
ured by applying a voltage to the voice coil
and measuring the force
exerted by the dynamic
assembly.
calibrated watt meter.
No other commercially
produced speakers have
a higher Bl factor than
do Signature units with
their edge -wound wire
ribbon 4" voice coils.
And, before being released, every Signature
Speaker must meet the
same high standards.
2439
d
WILL SELL AS A UNIT ONLY: Two
Presto 6 -N three -speed disc recorders in 4 -B
studio cabinets. One has cutter lift-off for
masters. Both have Van Eps heads, special
suction Jets, hot -stylus kits, W.E. 9A and Gray
playback systems. Included are two Alter
AMC 75 -watt recording amplifiers, one custom line amplifier with corrective equalization for recording heads, selective equalizers
for flat recording, AES, and NAB curves. Also
included are eleven outside-in feedscrews
2-186, 1 -176, 1 -224, 1 -272
2 -88, 2 -96, 2 -112
lines per inch. Original net cost $3260. Asking
$2360, which is $900 below our cost. Demonstration by appointment. Reco -Art Sound Re.
cording Company, 1305 Market Street, Philadelphia 7, Pa.
CUSTOM -BUILT HI-FI : Speaker, Bass
reflex, 15 -In. coaxial ; amplifier, triode high gain, UTC components ; Jensen Customode
cabinets, blonde mahogany (rare at any price) ;
turntable, Rek -O -Kut 8 -speed : dual Livingston
arms, G.E. broadcast, including packing and
crating. Price $1050. R. C. K. Chadwick, The
Manor, Alden Park, Philadelphia 44, Pa.
FOR SALE : Electro -Voice Peerage equipment console, mahogany. New, in original carton, $65. J. Klein, 235 Lyons Ave., Newark,
N. J. Phone WA 3-3025.
RECORDING SERVICE. Hi -fi discs cut from
your tapes. Send for free timing chart. SOUND
SERVICE ENGINEERS, 1778 Fulton Ave.,
East Meadow, N. Y.
FOR SALE : Demonstrator Grommes deluxe
amplifier, 215BA and preamplifier 210PA, almost new, $140. Box CJ -3, AUDIO.
IT'S FUN to SPLICE TAPE with GIBSON
GIRL Cutter -Splicers. At your dealer or write
Robins Industries Corp., 82 -09 251st St., Belle rose 26. N. Y.
:
NEW U -L Williamson amplifier, dual chassis, all Peerless transformers, oil filters, $74.50.
New Altee 820A system, $399. Box CJ -2.
AUDIO.
SELL Rek -O -Kut turntable, $56. B. Black.
934 First St., Manhattan Beach, Calif.
.
;
WANTED: Western Electric 640AÁ microphone heads. Also Ampex tape machines,
series 800, 350, 400. State condition and price.
P. Turetsky, 9033 Wilshire Blvd., Beverly
Hills, Calif.
RECORDING FANS
where. details free. Box
1,
California.
-
www.americanradiohistory.com
AmericanRadioHistory.Com
tapes everySan Francisca
-
Save
AMAZING BARGAINS : Amplifiers
Accordions, Pi50%, Tremendous savings
anos, Organs, Typewriters, Movie Equipment,
Binoculars, Recorders, HI -Fi systems. ABELMART, 466 Belmont, Paterson, N. J.
AUDIO
78
Swap
1404
!
JANUARY, 1955
.9Ka.abil
PROFESSIONAL
DIRECTORY
"W"
MAVEIT
N.1.
COEarONlA1S ExCIUSIVELY
HOLLYWOOD
ELECTRONICS
AVE.
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Irving Greene has resigned as vice- president of New York's Asco Sound Corporation to become advertising and sales promotion and sales manager of University
Loudspeakers, Inc. His place as Asco sales
manager will be filled by Ozzie Reiter . .
Jack Earns, executive vice -president
of
Recoton Corporation, vacationed in Florida
during the Christmas holidays
. Jane
Proms= is the latest show business celebrity to be bitten by the hi -fi bug -her new
music system incorporates a two -way
Lansing speaker, a Marantz preamplifier
and a McIntosh 30 -watt amplifier
University Loudspeakers, Inc., sales executive Larry Epstein vacationed in Mexico
after illness ... A bout with a bug bedded
Victor Brooiner of Brociner Electronics
Laboratory
George C. Daleo has resigned as chief cabinet engineer for CBS
Columbia -after a short vacation he will
open shop as a manufacturers' representative in New York
Recent additions to
sales division of Electro- Voice, Inc. announced by Lawrence L. Le8ashman, vice president in charge of sales, include
Cullen Macpherson as assistant manager
of the reproducing components division
George R. Riley as assistant manager of
the distributor sales division, Lloyd
Loring as sales engineer, and Everett W.
E.
Leedom as advertising manager
Charles A. Hansen, having completed his
assignment to build a distributor sales
organization
for
Gramer
Transformer Corporation has -Halldorson
returned to
California to conduct his own manufacturers' representative firm
Dr. Jerrold
R. Zacharias, professor of physics and
director of the laboratory for nuclear
science at Massachusetts Institute of
Technology, has been elected to the board
of directors of National Company, Inc....
John E. Hogg has been named manager
of
field sales for the instrumentation division
of Ampex Corporation.
.
SALE! 12" LP
SUPER-FIDELITY
.
...
HIGH- FIDELITY HOUSE
Offering the World's Finest Home
Music Systems, created by experts
with years of experience.
High Fidelity is our only business
not a sideline. Complete stock of every
worthwhile component at all time&
536 South Fair Oaks. Pasadena I, Cal.
-
SY
5-4118
RY
1
-8171
ORGAN RECORD
...
"EVERYTHING IN HIGH FIDELITY"
From Primary Components
to Completed Custom Audio Equipment
KIE
F
Sound Corp.
820 West Olympic Blvd.
Richmond 7 -0271
Los Angeles 15, Calif.
ZEnith 0271
Custom -Built Equipment
U. S. Recording Co.
Vermont Ave., Washington 5, D. C.
Lincoln 3-2705
1121
i
CANADA
High Fidelity Equipment
Complete Lines
Complete Service
HI -FI Records
Components
and Accessories
-
6LECTROi)O10E
141
SOUND SYSTEMS
TnonNT(r rnNo¡s-.
DUNDAS ST. WEST-
SPLICES MAGNETIC TAPE
Neatly
- Quickly - Easily
kit Incfudea plastic splicer which adheres to recorder or work.
tatW. (loemos supply of pro -cut tape splicing tabs, handy blade,
Instructions and plastic case. Only $1.50 postpaid. If your dealer
can't supply you. order from ...
7557
COIISINO, INC.
rase. B, Ohla
Magban Ans.
NEw!
for everything In Electronics?
1440 page MASTER
Renard ,mrn
item,
15,000
Full
Ash
UNITED CATALOG
AUDIO
1
dr,,,iprien,
5.5 00
Illo,.
Fully indeed
War. 6
9S at host electronic
PUBLISHERS, INC., 110
lbs
parts
u
distributors. List
$6.50
Lelaryrre St., IL T.
13
EIGHT
Adam Hamme,
ORGAN
SMM, performs on
a 3- manual Aeolian
Skinner pipe or-
CLASSICS!
Reiss eee
Purdue University has installed 27
Magnecord record -playback machines for
use in its foreign language laboratory,
according to Carroll W. Hoshour, products
manager for Magnecord, Inc. It has been
found that regular use of tape recorders
in the teaching of foreign languages is
from two to five times faster than other
methods. The machines are installed in
sound -proof booths in which a student
hears, through headphones, instruction
material emanating from another machine
which serves as the master unit. The
master tape has frequent intervals of
silence, during which the student speaks
into a microphone and attempts to duplicate the sounds he has just heard. The
student's recorder records both what he
has heard and said. In this manner the
student and his instructor
are enabled to
compare the instruction pronunciation
with the student's own. The Purdue language laboratory was established in 1950
and is under the direction of Dr. Elton
Hocking.
To publicize the opening
its new
sound laboratory at Pittsfield,ofMass.,
the
General Electric Company's power transformer department is using a "talking" ad
-an
advertisment that is both a recording
and a regular printed ad. Contrasted
on
the recording are sounds recorded inside
and outside of the laboratory's anechoic
chamber. A reader can hear these sounds
by merely punching out the paper record
and playing it on home phonograph equipment. The ad is produced by Sound 'N'
Sound Enterprises, Inc., of New York.
Shure Brothers, Inc., manufacturers of
microphones and acoustic devices, has announced plans to begin construction of
a modern one -story plant in Evanston,
Illinois, a suburb of Chicago. The new
building will provide 80,000 sq. ft., with
room for expansion on the industrial property covering 220,000 sq. ft. The plant,
which is expected to be completed in the
Spring of 1956, will serve as the new
home for the entire Shure organization.
A new engineering laboratory for the
development of electronic fire- control
systems for military aircraft will be established next month in Waltham, Massachusetts, by Radio Corporation
of America.
A portion of the Waltham Watch Company
plant, 225 Crescent Street, was leased to
house the new operation, which will be
equipped with the latest in research test
equipment and scientific computing devices.
JANUARY, 1955
tan.
8
famous
works by Farnam,
Karg- Elert, Dupre,
Vierne, Mulet, Main, Brahms, Widor.
Made by authentic sound recording specialists, this high -fidelity demonstration recording displays the great variety and range of
a 2872 -pipe (plus harp, chimes) organ from
the lowest Bourdon note of 32 cycles to
the limits of hearing.
COMPLETE
AUDIBLE
RANGE!
The
better your
music system, the
mose you'll enjoy
the 100% custom
quality of this 12"
331/3 rpm LP. The
dramatic price reduction is due co an exclusive special purchase by Radio Shack. Mail orders filled
promptly! Dealer inquiries invited.
REGULARLY $5.95
SALE PRICE $
Add 35e Postage -Handling
Order No. 11-703011f
4
`1.85
OUR EXCLUSIVE
TAPE BARGAIN!
1200 F-e. x 1/4"
PLASTIC BASE!
7 -INCH REEL!
Order No. R- 7101HF
Add 35c Postage
RADIO SHACK CORP.
Washington, Boston 8, Mass.
230 -4 Crown, New Haven 10, Conn.
167
79
www.americanradiohistory.com
AmericanRadioHistory.Com
HIGH -FIDELITY
ADVERTISING
INDEX
wont to neat
FA I R (' I 11. I)
MAGNETIC SOUND HEADS
1
Allied Radio Corp.
Ampex Corporation
Audiogersh Corporation
280 SERIES
TRANSCRIPTION ARM
67
Cover 2
11
45
Beam Instruments Corp.
Bell Telephone Laboratories
Bogen, David Co., Inc.
Bozak, R. T. Co.
14
35
63
80
22, 59
Bradmatic Limited
British Industries Corp.
78
79
Classified Advertisements
Cousino,
Inc.
Electro- Voice, Inc.
Electro -Voice Sound Systems
The Series 280 new-type transcription arm permits
the cartridge alone to lift all the tone color from
high fidelity recordings-eliminates the adverse
effects of arm resonance. Dual pivoting, plus a
precision engineered offset provide continuous
midgroove tracking, while an automatic built -in
arm rest safeguards the stylus. Designed for any
standard cartridge. A Fairchild professional quality achievement!
$2400
1
.
esa
I
l('IIILD
220 CARTRIDGE
1,
Fisher Radio Corp.
43
Electric Co.
Coodmans Industries, Ltd.
37
General
Harman -Kardon, Inc.
Harvey Radio Co., Inc.
Heath Co.
-
roll -off beyond giving smooth natural
sound. identify the NEW Fairchild 220
by its sparkling silver finish, symbolizing peerless performance.
it)
..
lye:
47
Hollywood Electronics
Hughes Research and Development
Laboratories
Hycor Co.. Inc.
79
Interelectronics
31
Kierulff Sound Corporation
79
Lansing, James B., Sound, Inc.
Leonard Radio, Inc.
Lowell Manufacturing Co.
78
65
72
Inc.
10
9th Ave. and 1S4th St.. Whitettone. N.
$11.00
59.50
59.50
$9.50
*A
standard
shove prices apply to heads fitted
type stems as illustrated. Alternatively. our "Commercial" friction type can lu fitted at 60 cents
vitra cost. This type is easily adjusted for height.
LOW IMPEDANCE HEADS CAN
BE
SUPPLIED TO ORDER
57
73
33
Cover 3
SCREENING CANS
(Suitable for above heads)
$1.20
$1.35
Mumetal (unplafed)
Mumetal (plated)
Steel /Mumetal
651
79
BRADMATIC LIMITED,
Radio Shack Corporation
Radio Craftsmen, Inc., The
Rauland -Borg Corporation
Recoton Corporation
Reeves Equipment Corp.
Reeves Soundcraft Corporation
Rek -O -Kut Company
Rockbar Corporation
79
Station Road, Aston, Birmingham, 6.
ENGLAND
13
We specialise-that is why recorder
manufacturers standardise our heads.
53
9
WRITE FOR DETAILS (Private or Trade)
25
58
74
76
78
5
66
3
56
4
59
57
51
75
6
Tung -Sol Electric, Inc.
WHIM EQUIPMENT
fidelity
Type 5RP (Record /Play)
Type 5R (Record)
Type 5E (Erase)
The
40, 41
Thorens Company
r
Type 6RP (Record /Play)
Super
2
72
60
Tannoy (Canada) Limited
Tech -Master Products Co.
Terminal Radio Corp.
United Catalog Publishers, Inc.
United Transformer Co.
University Loudspeakers, Inc.
U. S. Recording Co.
These Fairchild products are now
aailablee at better audio dealers.
STANDARD HEADS
(High Impedance -Half track)
Partridge Transformers, Ltd.
Peerless Electrical Products
Pickering & Company, Inc.
Pilot Radio Corp.
Presto Recording Corporation
Professional Directory
Inc.
Sargent -Rayment Co.
Scott, H. H., Inc.
Sonotone Corporation
Stephens Manufacturing Corporation
$3ZSO
49
69, 71
64
79
ORRadio Industries,
-
7
HI- Fidelity Distributors, Inc.
High -Fidelity House
National Company, Inc.
sharp cut -offs! Completely uniform
response to 17,000 cycles and slow
79
Fairchild Recording Equipment Corp. 55, 80
Marantz, S. B.
McIntosh Laboratory, Inc.
Milo
An unparalleled achievement in high
fidelity cartridge design. No peaks! No
28, 29
8
79
Cover 4
77
79
°a
IF YOU ARE MOVING
Please notify our Circulation Department
at least 5 weeks in advance. The Post
Office does not forward magazines sent
to wrong destinations unless you pay additional postage, and we can NOT duplicate copies sent to you once. To save
yourself, us, and the Post Office a headache, won't you please cooperate? When
notifying us, please give your old address and your new address.
Circulation Department
RADIO MAGAZINES, INC.
P. 0. Box 629 Mineola N. Y.
Y.
AUDIO
80
www.americanradiohistory.com
AmericanRadioHistory.Com
JANUARY, 1955
FERRO-SHEEN
the sensational
iiih
NEW
TAPE
BRAND
Extended Frequency
Range
...frequency
response
limited only by the recorder you use.
Reduced "Drop-outs"
virtually eliminated.
Reduced Head
reduction.
... nodules
Wear
Unexcelled Adhesion
...
...
Permanently Plasticized
imbrittlement with age.
Long Playing
and agglomerates
from 40% to 100%
no shedding
...
of oxide.
complete absence of
FERRO -SHEEN
irish
Tape
new super
DuPont's
Strength.
Base:
Higher Tensile
On Mylar
strength film.
Resistance.
(',realer Tear
user net
reel
$300 user net
plastic
on
900'
reel
lactic
1800' on plastic
standard P
Base: The
On Acetate
industry.
recording
user net
hase of the
reel_...... $3.00
net
900' on plastic
4.95 user
reel.........
1800' on plastic
THE
irish
FERRO-SHEEN
PROCESS
Recently, after four years of research and
development by our Tape Research Laboratories, irish revealed the most important
magnetic tape development in six years, the
exclusive, irish patented, FERRO -SHEEN
process.
Irish's big story is the FERRO -SHEEN
process. A completely new concept in the
art of tape manufacture. A new oxide and
binder treatment, a new magnetic surface
material and an improved plastic base,
which results in the strongest bond
the
highest uniformity of oxide particles
and
the smoothest surface ever attained in reSo,
-
In
addition to SHAMROCK 30.
and SOUND -PLATE 220 we ar
featuring ..
.
long Playing
FERRO -SHEEN
Irish
cording tape manufacture.
FERRO -SHEEN gives you Extended Frequency Range The FERRO -SHEEN process
results in a smoother, glassier surface than
any polishing process can give. This permits
vastly improved contact with the magnetic
head, utilizing all the response available in
-
the magnetic medium
... all
the highs
...
all the lows. Frequency response
limited only by the recorder you use.
FERRO -SHEEN gives you Reduced
outs"
on new thin base.
now
"Drop-
by momen- "Drop- outs" arethe caused
full surface of the
tary loss of contact of
tape with the recording head, due to nodules
and agglomerates. New, high uniformity in
distribution of the magnetic materials by the
FERRO -SHEEN process virtually eliminates
Nodules and Agglomerates.
FERRO -SHEEN gives you Drastic Reduction in Head Wear The mirror sheen surface produced by the FERRO -SHEEN process
-
frictionless and free from abrasives
that head wear is reduced from 40% to
100 %. FERRO -SHEEN Tape has "built-in is so
lubrication".
The FERRO -SHEEN process results in almost
homogenuity between the magnetic oxide
and the plastic film base. This treatment also
results in a complete absence of imbrittlement with age. irish FERRO -SHEEN Tape is
Permanently Plasticized.
Tape
NOW you get 50 % longer playing time o
the same size reel. Available on eithe
Mylar or Acetate lase at your dealers today
is
So, When You Buy Recording Tape, Remember
only irish has the FERRO -SHEEN Process.
.. .
Available of all leading sound dealers.
ORRADIO Industries, Inc.
Opelika, Alabama
Export Division: Morhan Exporting Corp., New York, N. Y.
In Canada: Atlas Rodio Corp., Ltd., Toronto, Ontario
ied
YOU/V
in llniinutes..
'LINEAR STANDARD'
20 -WATT PRE -FAB AMPLIFIER
THE
)econdfa
Akne
acé
Yes, just tighten 17 screws, in 17 minutes, connect your completed
UTC Pre -Fab Amplifier into your Hi -Fi system, then sit back and enjoy
the most spine -tingling tones you ever heard through your music
system. And all you have used is a screwdriver.
The UTC 'Linear Standard' is the first pre- engineered, pre- fabri-
cated, pre -assembled amplifier kit ever offered to the home building
audio fan, that employs the latest and most advanced techniques
including the printed circuit. You needn't know a tube from a condenser, just how to use a screwdriver.
More than a year of top level UTC engineering has gone into this
amplifier to produce the cleanest, purest, response you have ever
heard. It's absolutely linear: no positive feedback, hence no response peaks at either end of the spectrum. Excellent damping and
transient response . . no hangover on low frequencies to cause
no high frequency ringing. In short, just pure, clean,
boominess
true -to -life response that sounds as good as it tests on the meter.
...
.
And it's the only amplifier with a feedback circuit so stable that any
one of the tubes can be replaced and still be perfectly matched to
its twin, with no critical circuit readjustments necessary.
amplifier you can own, and you can proudly say,
it myself."
It is the finest
"I built
N I T E D
150 VARICK
STREET
TRANSFORMER
NEW
YORK
C O.
13, N. Y.
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