true -fidelity organ reproduction
APRIL. 1956
ENGINEERING
MUSIC
SOUND REPRODUCTION
Increasing interest in the use of transistors, particularly
in low -level circuits, makes this article with all its detail
especially valuable. See Transistor Preamps, page 31.
Studio -Type construction is
key to flexibility in this author's system. See page 23.
TRANSISTORIZED PREAMPS
PROFESSIONAL HI -FI HOME MUSIC SYSTEM
SIMPLITRONICS -Simplified Electronics
TRUE-FIDELITY ORGAN REPRODUCTION
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E.
40th St., New York 16, N. Y., CABLES: "ARLAB"
THE
g
BRITISH INDUSTRIES
A
I
message
to the
Quality - minded
Consumer
Claims.....
Claims !
It must be very confusing to the
consumer to read the claims of different manufacturers. It's a bit
confusing to us.
Thumbing through one of the publications devoted to our field, I recently came upon no fewer than
seven Turntables of one kind or
another being offered to the audiophile. Not one of these acknowledged
in any way that it was even possible
for any other Turntable to be superior, or better value for the
money A recent edition of the New
York Times carried a Sound
Studio's advertisement showing
four record changers (in the same
advertisement, no less) and each
one of these four stated quite
calmly that it was simply the best
made! The cheapest, the most shoddily constructed, make the same
claims, in vague, non -specific terms,
as the finest
I almost yearn for the automobile type salesmanship, which makes
the strongest possible claims for a
six -cylinder Ford, but at least has
the decency and good taste not to
claim that it is every bit as good as
the Lincoln Continental. Each has
its place in the market, but they are
!
!
two separate places!
No such modesty, however, ham-
pers the record -player maker Thus,
one manufacturer blandly undertakes to "objectively" evaluate a
Turntable versus an Automatic
Changer but neglects to point out
the small fact that he only makes
one of the two! Well, if I were to be
influenced on the choice of a blue
suit versus a black suit, I would like
my information to come from a
manufacturer who made both. That
might make the analysis somewhat
objective
!
!
www.americanradiohistory.com
AmericanRadioHistory.Com
I notice
that some manufacturers
are showing "rumble" figures in
their advertisements
just figures, that's all. Any competent engineer will confirm that these are
utterly valueless, if not intentionally misleading, unless they are distinctly related to a given test. How
was the test made? How was the
turntable mounted? Which amplifier was used? At what frequency
was the test made? Which independent laboratory, if any, conducted the test? Was the unit
tested taken from inventory or was
it a specially selected unit?
.
these are but a few of the questions
which could very well be asked.
Yet -despite all the confusion surrounding these products, there are
reliable yardsticks available to the
equipment buyer:
First, there is the length of time
the manufacturer's products have
been accepted on the market. Here,
GARRARD stands alone. It has
been acknowledged the leader in
the field for nearly 35 years. No
come -lately are we, trying to climb
aboard a band wagon. On the contrary, we are proud that we are one
of the pioneers of the industry.
Second, there is the basic reputation of the manufacturer. Here
again GARRARD stands alone, because our products are known
throughout the world as just about
the best that can be made. No compromise is made with quality. No
mass-production methods are employed. That, of course, is the
reason why Garrard Changers and
Transcription Turntables are not
always in stock at your Sound
Studio, for delivery that very day.
We are catching up with the demand, but not at the expense of
quality control.
I suppose the correct phrase to employ in considering this question is
"Caveat Emptor ". You don't (or
shouldn't have to) buy a Record
Changer or Turntable very often;
why not get the best when you do?
...
Leonard Carduner is President of British
Industries Corporation, Port Washington,
New York. BIC is an American company
which offers yo ii the finest of audio equipment . . . fully guaranteed, with service
and spare pat- :available throughout the
country.
The B.I.C. Group
consists of the following
products:
d Record Players
Leak Amplifiers
Wharfedale Loudspeakers
R -I Enclosures
River Edge Cabinets
Genalex Tubes
Ervin Multicore Solders
G
c.:
www.americanradiohistory.com
AmericanRadioHistory.Com
APRIL, 1956
VOL. 40, No. 4
for the
discriminating
listener
Successor to RADIO, Est. 1917.
hErrna
AU D IC
F7s1.1\1
ND
-11
THE CLASSIC
NAME IN
HIGH FIDELITY
presents a group of high
,presents
REPRODUCTION
.
G. McProud, Editor and Publisher
components
enry A. Schober, Business Manager
arrie K. Richardson, Associate Editor
ewis C. Stone, Associate Editor
mery Justus, Canadian Editor
lorence Rowland, Production Manager
dgar E. Newman, Circulation Director
featuring superiority of
sound reproduction and
elegance of appearance.
They may be used
together for a completely
integrated system, or
individually as
improvements in
existing installations.
Sanford L. Cahn, Advertising Director
Special Representative
H. Thorpe Covington,
7530 Sheridan Road, Chicago 30, Ill.
Mid West Representative
Th
Sherwood
-
_Treu
/NC'
S
-2000
FM -AM TUNER
I V,
-
µe coecode FM
sensitivity
AFC and 1ty wheel tuning
wide and narrow AM selectivity
exclusive AM hi-II circuitry
with infinite
Sanford R. Cowan, 67 West 44th St.,
New York 36, N. Y.
impedance detector
outstanding
West Coast Representatives-
oil stability
low IM distortion
James C. Galloway and 1. W. Harbison,
on FM cold AM
6535 Wilshire Boulevard, Los Angeles 48, Calif.
Choir, of cabinets
Sherwood
.
.
$139.50
!rpm
5 -1000
AMPLIFIER
20 wolf ultra- linear outpu
push-butto, record equalicotion
CONTENTS
Audio Patents- Richard H. Dorf
Letters
About Music -Harold Lawrence
Coming Events
London Letter- Richard Arbib
Z729 low noise phono preamplifier
new 'center -set' loudness control
rumble and scratch filters
Choice of cabinets ... from $99.50
2
6
8
..
Editor's Report
A Professional Hi -Fi Home Music System- Oliver Berliner
True- Fidelity Organ Reproduction- Julian D. Hirsch
_.
Siinplitronics-Harold Reed
Audioclinic- Joseph Giovanelli
Transistor Preamps -H. F. Starke ._
Power Amplifiers- SOUND, Chap. S -Edgar M. Villchur
Equipment Report-Ferrograph Tape Recorder- Rogers Developnitnts Ltd.
"Cambridge" Amplifier-Fentone B&O Velocity Microphone
Audio ETC -Edward Tatnall Canby
Record Revue -Edward Tatnall Canby
New Products
..
.
_
.
.
10
14
18
23
26
29
30
31
49
Industry Notes and People
54
60
64
74
77
86
Advertising Index
SS
Be Your Own Record Critic
__
Forester
LOW- DISTORTION
THREE -WAY SPEAKER SYSTEM
Performance
comparable to
systems costing
TWICE AS MUCH!
0.5'
IM distortion
at 10 watts
!1/2 ft. horn -loaded
12" woofer
separate 8
mid -ronge unit
full
12 db
/actuve,
300 cps: 5000
i
cps
crossover
5" tweeter
response to 15KC
choose
ontemporary (shown),
c
trcditionol, or French
Model SFC
31 SO
00 complete
Pro wincial cabinets, or
Do -It- Yourself Lits
at $139.50
WRITE FOR FREE DESCRIPTIVE LITERATURE
(title registered U. S. Pat. Off.) Is published monthly by Radio Magazines. Inc., Henry A. Schober, President;
O. 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. $7.00 for two years all other countries, $5.00 per year. Single
copies 50e. Printed in U. S. A. at Lancaster. Pa. All rights reserved. Entire contenta copyright 1956 by Radio Magazines,
Inc. Entered as Second Class Matter February 9, 1950 at the Post Office, Lancaster, Pa. under the Act of March 3. 1879.
AUDIO
C.
RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y.
AUDIO
APRIL, 1956
Dept.
44
2802 W. Cullom Ave., Chicago 15, III.
1
www.americanradiohistory.com
AmericanRadioHistory.Com
AUDIO PATENTS
I1o41d
RICHARD H. DORF*
îze904.
Vane Ajze ...
the
NEW
American e'501"
Series Microphones
Lightweight, rugged, easy to handle ...
true -to -life in fidelity of voice pickup.
The new American "501" Series presents a complete line of dynamic or
carbon hand microphones to improve
all types of voice communications.
The attractive styling is completely
functional
the gently curved case
fits easily into the hand. Positive operation under all conditions is provided
by a specially designed cantilever
switch. The case is made of die cast
aluminum to assure durability and
minimum weight.
...
There's a model for every need:
Mobile
Communications
Police
Ship -to -Shore
Aircraft
Amateur
To be heard and understood
...start with an American Microphone. Write for Complete
details and specifications today. Ask for Bulletin 501.
ELECTRONICS DIVISION
ELGIN NATIONAL WATCH COMPANY
370 Soath Falr Oaks, Pasadena 1, Calif.
of using a coil to cover a
roost with electromagnetic waves at
audio frequencies, and then picking
them up with portable receiving equipment,
is well known. its uses are numerous -front
cueing in television studios to simultaneous
translations at the United Nations. So far
as this writer knows, however, -just about
all of these systems require electrical gear
of one sort or another. Sonic have abbreviated equivalents of ordinary radio receivers
which pick up, detect, and amplify radio frequency signals; others have hearing -aidtype systems which amplify audio picked
up inductively.
Victor Albert Foot, a British inventor,
has cone up with a magnetic sound transmission system which requires no electronism-no tubes, no resistors, capacitors, or,
in fact, anything but one or two specially
built earphones. The patent covering this
(a U. S. patent) is 2,721,896 and no assignment of it is noted.
The system begins with an audio amplifier which feeds a wire loop strung around
the room, of which more details later. The
wire, one or more turns, is strung around
the walls, floor, or ceiling in such a way
that amplifier output causes a magnetic
field to be set up in the room.
The special headphones used for reception are shown in the two drawings of Fig.
I. (A) is a cutaway side view and (B) a
cutaway front view. We reproduce here the
actual drawings from the patent specification, contrary to our usual practice, simply
because this is probably the clearest way
to show what is largely a mechanical invention. When we refer to the part symbols,
look at them in both drawings to give yourself a clear idea of what exists.
The symbol C' indicates the earphone as
a whole, which, at least from the outside,
greatly resembles a standard one. There is
a casing 11 with a cover E which carries a
conical diaphragm F. The center of the
diaphragm F is secured to a reed -like armature G which at its outer end (sec the front
view) is fastened rigidly to the casing D.
The reed G is directly over -but not
touching -the gap between a pair of pole
pieces H. These pole pieces are composed
of a highly permeable material (one which
carries magnetic flux very easily) and extend in opposite directions from the armature. They are shown here emerging from
the ease and are about the only visible features (from the outside) which would make
the earphone look abnormal when it is in
THE TF.CIINIQUE
When the phones are worn, they are adjusted so that the normal direction in which
the pole pieces run is in line with the flux
produced by the transmitting loop. This
means, of course, that if the wires run
around a baseboard, say, the pole pieces
would be vertical. The pole pieces, being so
very permeable (material not specified),
collect and concentrate the magnetic flux
in their vicinity. A good deal of flux, therefore, passes through the air gap between
the two pole pieces and, of course, through
the reed -like armature G. This causes the
armature to move and the cone attached to
it to push air, so that the sound is reproduced. The permanent magnet functions in
the normal way to superimpose some steady
flux and prevent reversal of the force exerted on the armature.
Contrary to usual practice, the cover E of
the earphone is held by the headband (it is
usually the case which is held), and the
cover and case are held together in such a
way that the case, and with it the pole
pieces I1, eau be turned about the axis of
the diaphragm to orient the pole pieces exactly in line with the magnetic flux in the
room. This allows adjustment for maximum
signal and also gives a sort of volume control.
If the permanent magnet offered low
reluctance to varying flux it would tend to
short -circuit the pole -piece gap and reduce
sensitivity. The inventor suggests either using a material with low incremental permeability for the magnet (low permeability
for varying flux: or using two permanent
magnets, one alongside each pole pieces,
with their circuit completed by leakage flux
from their outer ends.
The inventor also suggests arrangements
using coils to aid the sensitivity of the
headphones. If interested, you can obtain
a copy and read those details for 25 cents;
address The Commissioner of Patents,
Washington :5, D. C.
(Continued on page 69)
UM.
The pole pieces H are bridged by a permanent magnet. In (B) of Fig. 1 the permanent- magnet arrangeaient is shown as
the magnet itself J and two soft -iron pole
pieces J'; but a C-shaped magnet might be
used instead.
' $55 W. 84th St., New York $4, N. Y.
Fig.
AUDIO
2
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AmericanRadioHistory.Com
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APRIL, 1956
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LETTERS
Criticism
for use where
Small
Controlled
Reluctance
Microphones
space is limited
stability is essential
intelligibility is important
These rugged, magnetic microphones are designed for use in transistor -type
Slit
Harold Lawrence 's piece on critics is the
fairest ever to hit print. It might be added
that the function of the record critic, like
that of many another kind of writer today,
is to entertain. Your own Mr. Canby, for
example, does a bang -up job as proxy listener for thousands of phono enthusiasts
who'd enjoy wringing all those wonderful
new releases through their own hi -fi rigs
but who lack both the time and money required to slake such an enviable degree of
:
hobby- riding possible.
hearing aids, small amplifiers and transmitters, dictating equipment,
magnetic recorders ... wherever size and weight must be kept at a minimum.
SHURE microphones based on this same design principle have been used
extensively by the Armed Forces in many military applications where
severe operating conditions are encountered.
J. M. KUCERA,
1280 Pine St.,
San Francisco 9, Calif.
Disagreement
SIR
MC20
with Mr.
This microphone measures only 'Me x '/i" x 3Á ", and weighs 9/2
grams. Its rectangular shaped case simplifies placement of other
circuit components, and permits an appreciable reduction in the
size of the equipment using it.
Output Level: 75 db below one volt per microbar (0.56 x I0"'
watts for one microbar-at 1,000 c.p.s.for 1,100 ohms impedance).
Frequency Response: 400 c.p.s. to 4,500 c.p.s.
Impedance: 1,100 ohms (at 1,000 c.p.s.). Other impedances available on special order.
MC
10
One -inch diameter microphone, less than 0.4" thick, weighing
only Il grams. Similar in construction to the MC20, for use
where amplifier gain is at a premium, and a more sensitive
microphone is needed.
Output Level:
71 db below one volt per microbar (approximately 10-10 watts for one microbar
1,000 c.p.s. for 1,000
ohms impedance).
-at
Frequency Response: 400 c.p.s. to 3,000 c.p.s.
Impedance: 1,000 ohms (at 1,000 c.p.s.). Other impedances
available on special order.
R5
Where a still higher output is required and space is not so limited,
the R5 is an ideal unit. It is "ht" thick and l'351" in diameter.
weighing only 4 ounces. Encased in its rubber mounting ring the
R5 measures I:á" thick and 2'?l." in diameter.
Output Level: 51.5 db below one volt per microbar
1,000
c.p.s. for 14,000 ohm impedance.
Frequency Response: 100 c.p.s. to 9,000 c.p.s.
Impedance: 14,000 ohms at 1,000 c.p.s. Other impedances available on special order.
-at
The SHURE Engineering staff will work with you in confidence to adapt these and other Controlled Reluctance
microphones to your specific applications. Write on company letterhead to our Sales Department- explaining your
requirements.
SHURE
SHURE
222
:
I would like to express my disagreement
BROTHERS, INC.
HARTLEY AVENUE, EVANSTON,
ENGINEERS:
Escellent employment opportunities
available for men having Methods
and Standards experience, Research
and Development ability in Magnetic Recording, Microphones, Transducers, Phonograph Reproducers.
Write Chief Engineer, Shure Brothers,
Inc.
ILLINOIS
Stephens comments on loudspeaker efficiency that appeared in this column in February.
Mr. Stephens attempts to link speaker
inefficiency to poor performance in the
form of hangover by reasoning that (a)
hangover is prevented by magnetic damping, and (b) that efficient speakers have
heave magnets and good damping; by inference. inefficient speakers have small
magnets and poor damping.
The weight and material of the speaker
magnet is only one of many factors that
determine efficiency. Our own AR -1 woofer.
for example, using a 3,3 -1b. Alnico V magnet and ti lbs. of Armco iron, has far lower
over -all efficiency than many speakers with
6.8 -oz. slugs. The choice here was between
efficiency and the low- frequency limit of
the 11:1s's-band; sacrificing response blow
5t) cps and allowing the mechanical V of
the speaker to be increased-thereby, inci-
dentally.
introducing
hangover -would
have allowed the efficiency to be significantly inerensed.
If one applies the etfieieney rating of a
speaker to the low bass portion of the
sound a !meet rum as well as to the mid-band
spectrum, the picture is likely to dhange
quite a hit. 'We at Acoustic Research were
interested to note that the Audio League
(Pleasantville, X. Y.; reported in issue
No. 11 that the absolute efficiency of the
AR -l. at _- ens, t.ccee,led that of :1 justly
famous speaker system rated as having 5o.
times the overall -ltieienev of the AR -1.
Speaker efficiency, or the hick of it, can-
not be taken as :tll index of quality, any
snore than the output voltage of a phonograph pickup (representing its efficiency
as a transducer) can be taken as :m index
of pickup quality- I consider that it is as
useless to compare loudspeakers without
making some adjustment for equal sound
level as it would be to compare different
phonograph eartridges without adjusting
amplifier gain.
EIx:.tR M. Viii.t'nt-R.
Aeuustic Research, Inc..
35
Thornlike St.,
(:nubridge
(Thal ought to
be smjjieient
41, Mass.
to con-
furl
lino(' this controrers¡l. It would appear
that efficiency can not b. rated al any mina,
frequency, but shoal,1 p, rlutps be inte.apeetnnu. ED.
grated over the nr..
-.
AUDIO
6
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AmericanRadioHistory.Com
APRIL, 1956
It it's
worth an Engineer's time...
... it's worth
an Engineered Cable
Belden
microphone
cables
Whatever the installation,
whatever the requirements,
there
is an
accurately
rated Belden Microphone
Cable built for the ¡ob.
(ßeldcn
W IREMAKER FOR INDUSTRY
SINCE 1902
CHICAGO
1001
.UDIO
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t
WIRES FOR EVERY ELECTRONIC NEED
APRIL, 1956
7
www.americanradiohistory.com
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TUBELESS
AUDIO
HAROLD LAWRENCE
COMPENSATION
only 14 db!
insertion loss!
The Model
izer
4201 Program Equal-
has been developed to provide
utmost versatility for the compensation
of sound recording and broadcast
channels. High and low frequencies
may be boosted or attenuated while
the program is in progress with negligible effect on volume levels. It may be
switched in or out instantaneously to
permit compensation at predetermined
portions of the program. This feature
is especially useful in tape dubbing
work.
By
Any Other Name
THE CLASSICAL sales manager of a
large record company which of the
ASK
following Mozart symphonies are
Ir to outsell the others: Nos. 38, 39,
40, and 41, and without even checking his
sales figures he will tell you: Nos. 38 and
41. He will also inform you the Beethoven's Violin Sonata, Op. 24, stands a
better chance of attracting sales than Op.
30 no. 2, always assuming that the interpreters are the same or of comparable
quality. What makes him so certain? There
seems no clear-cut musical reason for placing No. 41 above No. 40, or 38 above 39.
As for the Beethoven sonatas, they are
vastly different in conception; the first is
a lyrical work of classic proportions, the
second a forceful , impassioned expression.
Both are prime examples of the composer's
violin literature. The answer to this baffling state of affairs can be summed up in
one word: "title." Mozart's 38th and
41st are named "Prague" and "Jupiter,"
respectively; Beethoven's Op. 24 is called
''Spring.',
In the society of musical compositions,
Model 4201, Program Equalizer
the untitled piece is often lost in the
shuffle. With nothing to identify itself but
a dull opus number or key signature, it is
outshone by its more colorfully labelled
counterparts.
FEATURES:
Equalization and attenuation in accurately calibrated 2 db. steps at 40,
100, 3000, 4000 and 10,000 cycles.
Insertion Loss: Fixed at 14 db. with
switch
"in"
or
"out."
Impedance: 500/600 ohms.
Low Hum Pickup: May be used in mod
erately low-level channels.
rend for Bulletin E for complete data
Net Price $195.00
F.O.B. North Hollywood
Model 4201 Program Equalizer is also
available for the custom builder in kit
form with complete wiring instructions.
Send for Bulletin TB4.
Representatives in
Principal Cities
IYCZNI
Division
International Resistance Company
12970 Bradley Avenue,
Sylmar 3, Calif,
There are exceptions, of
course. A few that come to mind are Beethoven's Fifth, the Brahnss Symphonies,
and Mozart's piano concertos. Nevertheless, in sales and popularity, titled music
generally leads the field.
The predilection for titles flowered in
the nineteenth century but actually dates
back to the Renaissance and the birth of
modern instrumental music. Elizabethan
keyboard pieces were given such fanciful
titles as My Lady Carey's Dompe, His
Humour, The King's Jueil, and The New
Sa -Hoo. Later, in France, court composers
devised an enigmatic language of their own
to clothe their miniature pieces with an
aura of mystery. This piquant nomenclature rubbed off on Fram;ois Couperin in
his harpsichord works. Here are a few examples: La Zénobie, Les Fastes de la
grande et ancienne Mxnxstrxdxsx, Le tictoc -choc, Les Culbutes Jxcxbxnxs, and La
Petite Pince -sans-rire. Your knowledge of
French will get you nowhere with these,
by the way. Other Couperin pieces, however, were authentic miniature tone poems
whose names seem to have preceded rather
than followed the music's creation. Even
such a nonsensical designation as Le tictoc -choc is not as remote as one would
think from the character of the piece with
its light staccato effects and sparkling wit.
Couperin's contemporaries in Central
Europe regarded the art of the French
clavecinistes as too unsubstantial for their
serious tastes. The frills and ornaments,
unconcern for weighty and sober construction, and brevity were foreign to their ears.
26 West Ninth Street, New York 11,
N. Y.
Solidity was the primary quality they
sought to express. Titles were therefore
strictly functional: partita, sonata, concerto grosso, sinfonia, toccata, fugue, etc.
The late 18th century composers, in their
preoccupation with classic forms and the
development of the orchestra gave little
thought to descriptive titles. The terms
symphony, sonata, serenade, divertimento,
and concerto were therefore seldom qualified wtih picturesque phrases. The public,
however, bestowed titles left and right to
its favorite works. The symphonies and
quartets of Haydn are a case in point.
Symphony No. 96 in D is subtitled,
"Miracle," because of an incident that
took place at the première. According to
a contemporary report, "Part of the audience pressed forward to look at the popular
musician at close range, leaving a vacant
space in the concert room. Hardly had they
moved when a chandelier crashed down
upon this empty spot. There were cries of
' A miracle, a miracle,' because no one was
killed or hurt by the accident." The quartets have been assigned such colorful names
as "The Razor," "The Frog," "The
Joke," "The Lark," "The Sunrise" and
"A Dream."
Carrying the circumstantial principle to
a logical conclusion, why not call Schumann's Symphony No. 1 (as one English
critic put it) The Rusty Pen Symphony,
since it was written with a rusty pen which
Schumann picked up on Beethoven 's grave
during a trip to Vienna?
With the dawn of romanticism, trivial
associations of this sort gave way to words
or phrases that would embody the heart
and soul of a composition. Thus, the
Pathétique and Appassionata Sonatas and
the Eroica and Pastoral Symphonies. As
the 19th century progressed, critics and
music lovers thought they saw a "program" not only in a ballade or symphonic
poem, but in many a piece of abstract
music. Countless "stories" of the great
symphonies appeared. The publishers
eagerly catered to public tastes; to enhance the sales potential of a new edition,
they would often provide subtitles of their
own. Of the nine Beethoven piano sonatas
with tag names, only three ( "Pathétique,"
"Les Adieux" and "Hammerklavier ")
were given by the composer. The "Moonlight" Sonata, for example, got its name
from a critic who compared the first movement with shimmering beauty of Lake
Lucerne, a lake Beethoven had never seen.
The "Tempest" Sonata grew out of a question a friend asked Beethoven about the
meaning of the work. Beethoven, in what
must have been a hasty reply, said, "Read
Shakespeare's Tempest." It is more than
likely that the composer had not yet read
the play himself. Had he done so, he would
never have linked it with the sonata.
Nearly a century after Beethoven, a
Frenchman named Erik Satie anticipated
friends and critics by providing virtually
all his piano pieces with not only titles,
AUDIO
8
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AmericanRadioHistory.Com
APRIL, 1956
The system shown -like every Altec
System -is made of components proved
in rigorous studio and theatrical use.
See your Altec Lansing dealer soon for
a demonstration of this or other complete Altec high fidelity systems ranging
in price from 8324. to $1180.
305A AM Broadcast
fidelity
gives highest
Tuner
AM reception
exceptional
outstanding sensitivity
mahogany or
blond hardwood cabinet'
ideal tuner for areas
lacking FM broadcast
$99.00
stability
...
901B MP110011H,4i.
Record Reproducer
utilizing exceptional Altec 3398 amplifier
finest
English -made 3 -speed changer
magnetic pickup
three inputs: one low level, two high level
powerful enough to drive any size speaker; comprises a complete music system
finest record
reproducer -amplifier- preamplifier available
Mahogany or blond hardwood cabinet'... $237.00
GUARANTEED PERFORMANCE
With Altec Lansing High Fidelity Components
415A
bi f ex Speaker
I
guaranteed frequency response 30- 14,000 cycles
15" Cone using multiple concentric compliances
outstanding efficiency
extremely low distortion
smoothest speaker response at an economy price
$60.00
The exclusive Altec Lansing Performance Guarantee is your assurance that
every Altec home music component you buy will meet or exceed its published
technical specifications. This guarantee is made possible by the engineering
integrity, proud craftsmanship, and product testing that goes into every Altec
Lansing component. In addition to quality performance Altec offers beautiful,
smartly designed cabinets that bear the Fine Hardwoods Association Seal.
N\'hen you check the specifications on Altee equipment, remember that these
are conservative figures that will be exceeded in actual performance.
...
ALTEC FIDELITY IS HIGHEST FIDELITY
':111 Afire furniture -finish cabinets bear
the seal of the Fine Hardwoods Association
AUDIO
Dept. 4 -A
9356 Santa Monica Blvd., Beverly Hills, Calif.
Sixth
Avenue,
New
York
13,
New York
161
ALTE E
9
APRIL, 1956
www.americanradiohistory.com
AmericanRadioHistory.Com
but "programs" for his essentially abstract conceptions. In the first movement
of Chapitres tournis en tons sens (Chapters
Turned Evert-Wit i eh- \Coy) entitled, "She
Who Talks Too Much," he wrote the fol. signs of the imlowing 'narration': "
patience of the poor husband
. Let nie
speak!
I'd like a hat of heavy Mahogany
. Mrs. Thing has a bone umbrella
Miss What's-Her-Name married
a man as dry as a canary
Well, listen
...
...
to me!
his ribs
tion."
.
...
...
.
.
the eoneièrge has a pain in
the husband dies of exhaus-
Satie's art was
reaction against the
was poking fun
at the prosaic realism of such scores as
"Siufouia Botuestica" which charted a
day in the life of a typical German
bourgeois family, including baby 's noisy
awakening, the bath, playing with the child,
p.rents' argument, and yes, a love scene
a
"music illustrators." Ile
too.
upon program music
Brahms frowned
of any kind. To him the noblest musical
BOTTOM VIEW
WITH COVER REMOVED
PRECISION WORKMANSHIP
THROUGHOUT
TH f
]E'ISH EK
ALL - TRANSISTOR
Preamplifier-Equalizer
ARE PROUD to announce the new FISHER All- Transistor PreamplifierEqualizer. Model TR -1. This little giant is the result of four years of
research and development and represents one of the greatest achievements in
the long line of FISHER FIRSTS. We believe the TR -1 is the first all- transistor
product of any kind in the high fidelity field. Its development was no accident,
but rather the fruit of twenty years of leadership in audio technology. The
TR -I has NO hum. We repeat: ABSOLUTELY NO HUM. Second, it has
NO microphonism. Other unique features of the TR-I are listed below. The
initial demand for this revolutionary device may exceed the available supply.
To avoid disappointment, may we suggest that you place your order now.
expression was to be found in the classic
vein. It would have warmed his heart to
know that posterity would not provide
more than a handful of his works with
nicknames.
Like Braluus, the purist would certainly like to abolish all titles not assigned
by the composer to his own music. He might
even want to eliminate all but the most
necessary formal heading for each composition, particularly for abstract works.
On the other hand, there are those who
maintain that without the "Moonlight,"
Beethoven's Sonata in C Sharp Minor, Op.
27 no. 2, might have passed unnoticed by
the majority of music lovers. Titles, they
say, serve two purposes: (a) they 're fine
for quick reference, and (b) they arouse
interest and pave the way for a more receptive audition. After all, even the nonobjective modern painter invents poetic
names for his latest efforts.
Every once in a while the controversy flares up again. A music critic writes an
article, his readers send urgent letters pro
and con to the editor, and soon other critics
become embroiled in the dispute--a storni
in a teacup. What was that Shakespeare
said about a rose?
WE
Outstanding Features of
THE FISHER
Model
1
Power Volume. Cartridge Impedance Selector, Phono- Microphone Selector Switch.
Uses three transistors. Printed wiring throughout.
Fully shielded chassis with
bottom cover.
Attractive control designation plate. sizt: 2" by 4" by 41i" deep.
wsuan: 12 ounces.
Price Only $24.95
WRITE TODAY FOR COMPLETE SPECIFICATIONS
21
-29 44th DRIVE
L. I. CITY
Manufacturers Federation Show, Grosvenor House. London, England.
13 -15 -11e London Audio Fair 1956.
\\'ashiugton Hotel, Curzon St., London,
England.
April
16, 18, 19- Broadcast Engineering
Conference, in conjunction with the 34th
:annual Convention of the National Association of Radio and Television Broad casters. Conrad Hilton Hotel, Chicago.
April
TR -1
Can be used with any existing amplifier, audio control, or sound system.
Battery
powered. Power consumption only 0.033 watts. Battery will last as long as it would
when lying idle on a shelf
Can be used as a phonograph or microphone preamplifier.
Uniform response, within 2 db. 20 to 20,000 cycles.
Built -in switch selects cartridge impedance.
Handles all popular magnetic cartridges including very low -level
type. Does not require transformer with the latter.
Hum level: absolute zero!
Noise level. 65 db below 11) my input for high impedance cartridges. Better than
60 db below 2 my for low impedance cartridges.
Incorporates RIAA equalization,
now standard on all records.
Permits output leads up to 200 ft.
Three Controls:
FISHER RADIO CORP.
April l0 12-Radio Electronic Component
tronics. Meeting,
tronic Progress.
Bostons, Mass.
,
N. Y.
'
England Radio -Elee-
"Stoektaking of Elec-
Sheraton -Plaza Hotel,
29 -May 4 -79th Convention of the
Society of Mution Picture and Television
Eugimieers, Hotel Statier, New York
April
City.
April
1
23 -24 -Nein
April
23 -May
6- British
Industries Fair.
Earls' Court, London, England.
(Contina,vl on pane 8.3)
AUDIO
10
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AmericanRadioHistory.Com
APRIL, 1956
Only the
PRESTO SR -27 Tape Recorder
Mtc
Professional Performance
,
.el
or idler pulley. Compare the features of the companion amplifier: 10 watt output at 16 ohms, self contained power supply, separate preamps and VU
meter and two playback speakers. You can monitor the tape during recording. This professional
performer is yours for just $588 complete.
The top performance features of the finest PRESTO
-27
units are yours in this 2-unit combination
tape recorder and A -920B amplifier. Check the
features of the recording unit: 3 -motor drive;
separated record, erase and playback heads; fast
forward and rewind. There's no take-up reel clutch
-R
PRESTO
,Pollette
T -18
NEW
TURNTABLE
PRESTO
finest low- priced professional turntable has
world- famous flick shift -one sideway flick selects
K -11 DISC RECORDER
any speed.
improved professional version of PRESTOS all favorite K-10-incorporates revolutionary T -18
Net price $396.00
turntable
There is no finer, smoother-running or easier -to- operate
instrument for control room, studio or hi -fi system than the
Pirouette T -18-the PRESTO achievement that sets a new
high :n turntable design. You select any speed -331A, 45
or 78 rpm -with a sideway flick of the exclusive PRESTO
3 -speed shift. You engage the proper idler for the speed you
want with one motion. There are no bothersome arms or
shift cams. And check the extras you get: extra heavyweight wide-beveled table, deep -well bearing, sleek styling
in telephone black and hru.hed chrome.... Net price
Net price $117.00.
S66.00. With hstere.i. motor
time
.
.
.
K -11 is the smart new disc recorder you can fit into your
or use as an on- location recorder. It's
sound system
featherweight with a completely new pick -up arm, fully
encased hi -fi speaker, smart new panel design with push
button controls and the dependable PRESTO cutting head.
You get excellent broadcast-quality fidelity. For those times
when a disc recorder is preferable, the K -11 is your best
-
bet. Cuts discs up to 131/4 inches in diameter. Three-speed
.
Net price $145.00.
operation. With hysteresis motor
.
RECORDING CORPORATION
PARAMUS, NEW JERSEY
Export Division:
Canadian Division:
I
I
25 Warren Street, New York 7, N. Y.
Instantaneous Recording Service, 42 Lombard St., Toronto
WORLD'S FOREMOST MANUFACTURER
AUDIO
OF
PR
ECISION RECORDING EQUIPMENT AND DISCS
APRIL, 1956
11
www.americanradiohistory.com
AmericanRadioHistory.Com
What do you
from a
Extra playing time?
At economy price? Famous acetate -backed
"Scotch" Brand Extra Play Magnetic
Tape 190 also offers 50% more recording
time
much as found on 13 reels of
standard tape. New, high-potency oxide
coating assures recordings of increased
frequency range. New economy price
saves you 28 %.
-as
0
Economy?
The favorite tape of sound engineers,
the world over, famous "Scotch" Brand
Magnetic Tape 111 cuts tape wear in half,
thanks to exclusive silicon lubrication.
Tape glides smoothly over recording heads
to give flawless sound reproduction time
after time. Buy it now at a special new
low price!
The term "Scotch" and the plaid design are registered trademarks for Magnetic Tape made in U.S.A. by MINNESOTA
MINING AND MFG. CO.. St. Paul 6, Minn. Export Sales Office: 99 Park .Avenue. New York 16, N.Y.
AUDIO
12
www.americanradiohistory.com
AmericanRadioHistory.Com
APRIL, 1956
want
magnetic tape?
A^
High Fidelity?
'
Extra strength?
New "Scotch" Brand High Output Magnetic Tape 120 guarantees greater dynamic range recordings ... with harmonic
distortion reduced to a minimum. 133%
more output permits brilliant sound reproduction. A must for hi fi fans. Also
available with Polyester backing at slight
extra cost.
New "Scotch" Brand Extra Play Magnetic Tape 150 is made to take even hardest wear thanks to its tough, durable
"Mylar plastic, backing. In addition
to super- strength, new .150 Tape offers
50% more recording time on a standardsize reel, and famous "Scotch" Brand
recording quality.
"-
"Mylar" is a registered DuPont trademark.
SCOTCH
Magnetic Tape
AUDIO
""
APRIL, 1956
www.americanradiohistory.com
AmericanRadioHistory.Com
The ULTIMATE In
HIGH -FIDELITY
SPEAKERS
3Jrntiniu
3Jxttr
WADI
Combining
RICHARD ARBIB
OUTSTANDING
TONE QUALITY
AND ECONOMY!
AMAZINGLY
REALISTIC
TONAL
RANGE
AUDIO
IN
l'N;I,xD
should
receive a
great impetus by the presentation of
the first British Audio Show. This
will be occupying three floors of the Hotel
Washington in London by .about the time
you read this Letter. Although there are
three exhibitions or shows held in. England
each year in which audio equipment is exhibited this is the first attempt to have an
Exhibition which has the title "Audio
)''air" and which has quite frankly been
patterned upon those whirl) have been such
a sweeping .success ill the i'nited States.
Previously the show which was devoted
nmst exelusicly t :nuli. equipment bas
been the annual exhibition of the British
Sound Recording \..uei:ition but whilst
this has been an interesting exhibition it
has been on a comparatively small scale
and it is hoped tbnt tIi new Audio Fair
will attract to in o I3r wore visitors. Of
course, these numbers annot compare with
the Radio Show tthieh bas more than a
quarter of a million patrons every year. As
.
LONG
LASTING
PRECISION
c
4
PERFORMANCE
31 nllirorc Sohl, r... Ltd., lirtm
stead, Hurls., England.
l
Hemp-
London Audio .'how will follow immediately after the British Radio Components Show, it is likely to be patronized
by a Humber of visitors from Overseas.
If this :,udio Show berumes an annual
event, it will fulfill one very useful purpose in providing a focal point each year
for Audio equipment manufacturers to pre
sent their new products. During the past
few mouths there has been little new in
this field 1'tur even some of the items I have
described in previous Letters have not yet
reached the production stage, but no doubt
these will be seen by the public for the first
time at the Audio Fair.
the
New Tape Recorders
lu the field ut' tap. recorders there are
only really three new pieces of equipment
of interest tu the audio enthusiast and
probably the most interesting of these is
the new Ferrugrapl, titi which is a complete
unit of a tape deck. amplifier, and preamplifier, built in such a way that if a hole
I.i
Iti" is eut in a board the unit can
drop in complete. It incorporates switches
Imported from Western Germany, these
quality-perfect WIGO Hi -Fi Speakers are
unmatched for range and realism. Full
bodied bass, balanced mid -range, and silky smooth highs, blend together to produce the
ultimate in musical perfection. Skillfully
engineered . . . with exclusive fiberglass
centering construction . . . designed to
satisfy
a
DELUXE
lifetime!
12" EXTENDED
FULLY -SHIELDED
GONE TWEETERS
RANGE SPEAKERS
$10.95
$59.50
8"
GO- AXIALLY
MOUNTED
SPEAKERS
$51.00
12"
GO- AXIALLY
MOUNTED SPEAKERS
$89.50
Write for
Specifications
and Names
of Nearest
Authorized
Dealers
'
8 " -10" EXTENDED
RANGE SPEAKERS
$14.40 to $26.50
16 -INCH DELUXE
WOOFERS
$159.50
0
AU
wO PROp
...
1i//
"...,,,++
UNITED AUDIO PRODUCTS
(Olv. of United Optical Mfg. Corp.)
202 East 19th St., N. Y.
C.
3, N. Y.
Close -up of the steel drawer in which are contained the tape recorder, amplifiers,
tuner unit, crossover network, and a felt-lined recess for a microphone. On the right
con be seen the transcription turntable and pickup.
AUDIO
14
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AmericanRadioHistory.Com
APRIL, 1956
rb
k `vn stSe.1°t
áv i
6ri oo
cts
108U
ks °
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p
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<
eet
ettdsua8c
e8
0'well
aVetÓQm
*
A
AIR FORCE, NAVY AND AIRFRAME
CUSTOMERS RECEIVE FULL -TIME SERVICE
Sas
AND INSTRUCTION ON FIRE CONTROL
mpNdó
vtet
SYSTEMS AND GUIDED MISSILES.
Hughes maintains a highly trained organization of expert
engineering support to the armed services and airframe manufacturers
using the Company's equipment, wherever operational bases or plants
are located. Each of the engineers devoted to this work holds a degree in electrical
engineering or physics, and is experienced in electronics equipment maintenance
or design. These men are assigned to five separate divisions of the department: Engineering
Writing, Training School, Field Engineers, Technical Liaison, Field Modification.
A
completely staffed and
equipped school is operated
qualified military and company
to train
personnel in maintaining
Hughes
equipment. Instructors
are graduate engineers
or physicists with
backgrounds in development
work or university instruction.
4.4 48ry
feSP
4:r
yr
pyd..
'a
°?. y9'ri
4ky.
/%
9.Pry, córyT/P/'
ti
6
%/i
p
%
J°j°p` yorri4
.Oy/
Pó
ENGINEERS
s! ''óyP
r
v
AND
PHYSICISTS
it you feel that tou are Qualified
for any of the above
positions. send us your resume
and Qualifications.
SCIENTIFIC
STAFF
RELATIONS
HUGHES
RESEARCH
AND DEVELOPMENT
LABORATORIES
Hughes Aircraft Company
Culver City,
Los Angeles County, California
AUDIO
15
APRIL, 1956
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AmericanRadioHistory.Com
Your answer
to a low -cost,
well designed speaker!
NEW! Isophon
ELECTROSTATIC
TWEETERS
* Better performance in higher
frequencies (7000 -20000 cycles)
* Extremely low cost
* Compact, space- saving
* Easy Installation for single output
and push -pull amplification
* Remarkable brilliancy of sound
1111111111111M'
STHB7
Diaur: 2.76"
Thickness:
0.55"
5TH 5/16
Size:
that a pick -up, microp one and tuner
can be permmnentlyconaeat d,,fnd this can
so
"1411
Thickness:
0.787"
kutitoecb
I
E.
ARNHOLD
CERAMICS, INC.
57th Street, New York 22, N. Y.
Musical Industries, Ltd., in New
-
How to Obtain English Record Catalogues
Write for details
and spec. sheet A -4
&
York.
,
known companies such as Quad, Leak, Pye,
Pamphonie, Trix, R.C.A.. Rogers, and
Tannoy.
Although sales of high fidelity equipment
are still good, it is surprising that during
the last six months the demand for radio
gramophone combinations has been much
depressed despite the fact that sales of records have exceeded all previous figures.
1.97"
x 6.30"
Electric
virtually form the heart
The disc lover who would like to see one
n411 high;
fidelity iatitallatien-and the more all bitious British catalogue is recommended to get
user taut connect -to' it á larggr amplifier the H.M.V. which includes twenty pages of
taking the output from- the Ferregraph details of composers including dates of
before it reaches the output stage. This their births, deaths, and nationalities, a
machine 'i available in two forms, wkU most excellent proatinciatien guide, and a
tape spee6 of 7t and 15 ipe or 3t and-7P .,.lossarÿ of musical terms.
ips, and I am advised that the first deliverThe Decca catalogues probably contain
ies were made to the United States. One a` math larger quantity of L.P. records
particular advantàge -of this machine is than E.M.1. because Decca were issuing
thát as it uses 8i -in. reels; 1 hour 10 'min- L.P. rè'eords two years before the first
utes playing time can be obtained at 74 ipe
one appeared. Copies of the Decca
without changing a reel and 2 hours .0 catalogues are obtainable from London
minutes on both tracks of one reel.
Records, Inc., in New York. The main cataAnother new model made by an old es- logue contains details of over 2,000 long
tablished British tape recorder manufac- playing records, nearly 250 medium -playing
turer is the Simon S.P. 2 which incor- records, about the samep}imber of extended
porates a 10 -watt amplifier and is stated to play 45 rpm records, and over 700,of the
have a frequency response of 50- 12,000 standard length 45 rpm records. 'Whilst
cps ± 3 db. This is a self- contained model E.M.I. issue separate catalogues for each
which can be carried about reasonably of their marks, the Decca catalogue covers
easily.
all its labels, including Brunswick, London,
Specto, Ltd., who have previously con- Felsted, Telefuuken.
fined their activities largely to home cinema
While both groups of companies issue
projectors, are now producing two tape re- monthly lists of their releases, the Decca
corders both of which incorporate the Rud- people issue every quarter a comprehensive
man Darlington tape deck which has a catalogue in a stiff backed cover covering
variable speed control. Whether or not this all the records issued under their various
idea of a variable speed control is a good
marks during the appropriate period. Opera
one is a debatable matter but it must have lovers can buy the most excellent libretti
very intriguing possibilities for high fidel- giving the original language in which an
ity enthusiasts wishing to dub tapes and opera is recorded and an English translavary speeds.
tion side by side, and similar booklets are
One of the models produced by Specto is available for most recital records. Details
a stereophonic one designed for reproduc- of these booklets, which are quite inexpening the H.M.V. and Columbia stereosonic sive, are given in the appropriate catatapes. It is rumoured that in the near fu- logues.
ture, E.M.I. will have at last produced a
The record enthusiast who wishes to keep
high- quality tape recorder and reproducer up to date with British record releases canfor home use. This has been promised for not do better than obtain copies of .Tito
nearly two years.
Gramophone which is probably the oldest
Both E.M.I. and "Scotch -Boy" are now
journal in the World which has been excluproducing "long- play" tape and despite sively devoted to records. It is published
the present economic position, there is still monthly and costs only $3.50 a year.
a brisk demand for amplifiers of the well
High -Fidelity Home
Elaborate built-in high -fidelity installations of the kind only too well known in the
United States are a comparative rarity in
this Country and consequently, you may be
interested in details of your correspondent's equipment which is illustrated on
the cover and in a more detailed view here.
Behind the grille on the left is a 1.4 cu. ft.
sand -loaded enclosure in which is mounted
a 15 -in. bass speaker. Mounted above are
American enthusiasts have asked me for an 8 -in. and a 3-in. speaker in a simple
details of catalogues of British records and baffle that is open at the sides and rear.
it is as well to remember that probably 85 The main equipment is housed in a pull -out
per cent of sales of records in England are drawer which weighs nearly 250 lbs. It comachieved by the E.M.I. and Decca Groups. prises a tape recorder, amplifier and preE.M.I. issue annually four international amplifier, AM /FM tuner, recess for microcatalogues covering the H.M.V., Columbia phone, crossover network with adjustable
Parlophone and M.G.M. marks. These cata- potentiometers, and a sub -control panel.
logues cover in all 1,318 pages. Whilst they
This panel enables signals from the reare of course available from England, it corder or amplifier to be fed into the three will probably be simpler for the American way loudspeaker system and /or the extenenthusiast to get them in the United States. sion loudspeaker network. Signals can be
H.M.V. record catalogues are available fed to the recorder from the tuner or pickup
from R.C.A. Victor; Columbia are obtain- or from a television receiver which is situable from Columbia Recorde Inc.; Parlo- ated in another side of the room. A main
phone through American Decca; and the switch is provided which switches off all
catalogue of Angel records which now in- -the equipment simultaneously. On the right
clude the discs issued in England under >the band side the only part of the equipment
(Continued on page 69)
Columbia trade mark can be obtained from
AUDIO
16
www.americanradiohistory.com
AmericanRadioHistory.Com
APRIL, 1956,
The British Electronics Industry is making
giant strides with new developments in a
variety of fields. Mullard tubes are an
important contribution to this progress.
Another
Mu /lard contribution
to high fidelity
The Mullard EF86 audio frequency
pentode is one of the most widely used
high fidelity tubes in Britain today. It
has been adopted by the leading British
manufacturers whose sound reproducing equipment is enjoying increasing
popularity in the United States and
Canada.
The marked success of this tube stems
Principal Ratings
6.3V, 0.2A
Heater
IW
Max. plate dissipation
Max. screen dissipation
0.2W
Max. cathode current
6mA
Characteristics
Plate voltage
250V
Screen voltage
140V
Grid voltage
-2v
Plate current
3mA
Screen current
0.6mA
Transconductance
1800
p. mhos
Base
Small button noval 9 -pin
from its high gain, low noise and low
microphony characteristics.
By careful internal screening, and by
the use of a bifilar heater, hum level
has been reduced to less than 1.5,..V.
Over a bandwidth of 25 to 1,000c's
equivalent noise input approximates
2 .LV.
Supplies available
When operated below t,000c's, internal resonances of the EF86 are
virtually eliminated. Even at higher
frequencies chassis and tube socket
damping are usually sufficient to make
vibration effects negligible.
Supplies of the EF86 are now available
for replacement purposes from the
companies mentioned here.
from:
In the U.S.A. International Electronics Corporation,
Dept. 44,
81
Spring Street, N.Y.12,
New York, U.S.A.
In Canada Rogers Majestic Electronics Limited,
Dept. NH,
Toronto
11
17,
-19 Brentcliffe Road,
Ontario, Canada.
Mullard
DULLARD OVERSEAS LTD., CENTURY HOUSE SHAFTESBURY AVE., LONDON, ENGLAN.)
Mullard is the Trade Mark of Mullard Ltd. and
in most of the principal countries of the world.
AUDIO
is
registered
ELECTRONIC TUBES
OS' N~I.:'141triAtifeirOfWt
U
['RnN'1
APRIL, 1956
17
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EDITOR'S REPORT
FLEXIBILITY AND CONVENIENCE
AY BACK ill the early days of hi-fi, we remem-
ber how most of us housed our home installations so as to look as much like a radio station's
control room as possible. Lucky was the man who had
either a very coöperative helpmate or sufficient intestinal fortitude to preempt adequate space to install a
six -foot rack for amplifier, power supply, tuner, control unit, volume indicator panel, and a few rows of
jacks, and who located his turntable in a two -footsquare cabinet as nearly identical as possible to those
alongside the master control of the local radio station
-even to lacquering the cabinet the usual gray, now
almost universally called the "utility" model. Those
were the "good old days."
And while we still long for the flexibility of that
type of installation (and surreptitiously attempt to
hide a few jacks of the telephone type -they are the
only ones that can be camouflaged by flush mounting
on a limed oak panel -on a cabinet that is seen by all
and sundry who chance to come into our diggings) we
can't help but admit that with few exceptions the
permanently installed group of necessary components
serves the household with a sufficiency never dreamed
possible by the long-time audio fan. When we use the
term "permanently installed" it must be construed
in the looser sense
will not be changed daily, even
though it may be reorganized upon receipt of each
quarterly dividend check (unless that happens to coincide with an outgoing check destined for a city on
the Potomac).
The real experimenter who is always trying out a
different amplifier, speaker system, tuner, pickup, or
other component needs the flexibility, to be sure. We
do feel that it is desirable to have facilities for substituting various components without having to move
too much furniture. We like the idea of being able to
"patch in" a filter, another amplifier, or different
speakers whenever we get a chance to compare -the
credo of the real hobbyist. One simple solution might
be to install a row of jacks underneath the cabinet,
perhaps set far enough back to be reasonably out of
sight yet not so far as to make them completely inaccessible. Then one has the flexibility of the professional
system with the acceptable appearance of a custommade cabinet. Suggested treatment would be to have
jacks for output of pickup, input to preamp, output
from tuner, high level input to control unit, output
from control unit, input to main amplifier, and several more pairs of jacks to accommodate amplifier
outputs and speaker lines. If tape recorder, TV set,
or other auxiliary inputs are being used, a pair of
jacks for each would do the trick. With contacts normailed, the "system" plays just like any permanent
installation; with suitable cords patched in, all kinds
of combinations can be tried.
Mr. Berliner's article on a Professional Hi -Fi Home
Music System reflects the thinking of one who has
long worked in studios, yet not every home can be
-it
adapted to accept such an installation. There are manyadvantages to the professional type of construction,
not the least of which is the pride of showing it off.
But when listening is the prime reason for the array
of equipment, the flexibility must result from some
sort of compromise.
Fortunately for the industry -and even for the real
hobbyist, since it provides him with a wider range of
equipment to choose from -listening is the prime
reason for most sales of hi-fi equipment. We still feel
that many of the improvements that have resulted
from the activities of the home experimenter have
made hi-fi as important as it is today.
Just as improvements to automobiles are the result
of experience at Indianapolis, Daytona, and Le Mans,
so the improvements to audio equipment often get
their start because of the insatiable curiosity of the
experimenter and his quest for perfection. Long live
the experimenter!
LOOK IN THE BOOK
Purchasers of any equipment -power lawn mower,
electric razor, air conditioner, or what not -are
usually exhorted by the manufacturer to read the
instruction book before installing or using the product. We recently heard what we consider a classic in
this regard.
Large, respected manufacturer receives record
changer for evaluation. Makes tests. Rejects changer
as not meeting specifications claimed with respect to
rumble by as much as 15 db. Returns changer.
Changer manufacturer rechecks sample, finds it perfectly normal. Suspicion dawns. Replaces wooden shipping block wedging motor to chassis and rechecks.
Figures duplicate those of manufacturer who rejected
unit.
Instruction book specifically cautions user to remove
block before using. But nobody read it. We think that
is a real good joke. On somebody.
DEADLINES
We were so pleased with Jean Shepherd's first
column on Jazz, expected confidently to continue
monthly. New (to us) author not sufficiently acquainted with need for meeting deadlines. Better luck
next time.
OVEROPTIMISM
Seems we erred somewhat in stating that the attendance at the Philadelphia show was around 17,000. The
correct figure, we have been told by some more careful
observers, should have been 8000-all paid admissions.
Our original informant seems to have caught the
virus which is manifested by counting feet rather than
faces
not uncommon affliction, it appears, from
some of the figures we have heard given out for shows
that we have had the opportunity to observe person-
-a
ally.
18
AUDIO
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APRIL, 1956
and for the first time!
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APRIL, 1956
19
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ENGINEERS AND MANUFACTURERS OF
Widest choice makes it easy to enjoy
TRUE HIGH FIDELITY
Whatever your space and budget, you find the exact answer in the
complete selection of E -V 2, 3 and 4 -way speaker system components
Your enjoyment of high -fidelity reproduction depends largely on the efficiency of your
loudspeaker system. For only with properly engineered speaker components can you
obtain the range, the cleanliness of tone, the realism you want.
With today's most complete line, ELECTRO-VOICE makes it easy for you. You can
start with an economical, integrated 2 -way coaxial or 3 -way triaxial speaker...and expand it
as you desire to a multi -way system with the E -V Building -Block Plan. Or, you can
choose now a complete, separate a -way, 3-way, or 4-way speaker system which more
efficiently reproduces each section of the audio spectrum.
In E -V speakers, you have the advantage of heaviest, most powerful magnets,
edgewise-wound voice coils, scientifically treated cones, and many other features that
provide highest efficiency with the least discernible distortion.
What's more...the exclusive E -V Radax principle of high-frequency propagation...
the exclusive E-V mid-range coaxial diffraction driver-homs...the exclusive E -V Super -Sonax
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That is why your friends will recommend ELECTRO -VOICE. Look...and listen...
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sizes
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Low -Frequency Drivers (Woofers) for separate multi way speaker systems in Economy and Super Series
...in 12 -inch, 15 -inch and 18 -inch sizes
...from $29.70 to $90.00 net.
Mid -Range Coaxial Driver -Horns for separate multi way speaker systems... in 12 -watt and 25 -watt sizes
...from $29.70 to $48.00 net.
Mid -Bass Driver -Horn Assembly for long -path indirect radiator applications
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Treble Diffraction Horns from $16.20 to $21.00 net.
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Tweeters) in Economy and Super Units
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High- Frequency Level Control for adjustment to
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Crossover Networks for separate multi -way speaker
...from $8.40 to $72.00 net.
systems
Building -Block Kits of matched components for expansion of existing economy speaker systems
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All components are designed for
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ENCLOSURES, DO-IT- YOURSELF KITS, MICROPHONES AND PUBLIC ADDRESS EQUIPMENT
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t
PP
Vibrations of the sound "or" in the word "four." Pattern represents nine
of the "pitch periods" which originate in puffs of air from the larynx
when a word is spoken.
An intrstng
exprmnt
in spch
f
Some day your voice may travel by a sort
of electronic "shorthand" when you telephone. Bell Laboratories scientists are experimenting with a technique in which a
sample is snipped off a speech sound -just
enough to identify it -and sent by wire to a
receiver which rebuilds the original sound.
Thus voices can be sent by means of fewer
signals. More voices may economically share
the wires.
This is but one of many transmission techniques that Laboratories scientists are exploring in their search for ways to make Bell
System wire and radio channels serve you
more efficiently. It is another example of the
Bell Telephone Laboratories research that
keeps your telephone the most advanced on
earth. The oscilloscope traces at right show
how the shorthand technique works.
BELL TELEPHONE
An electronic sampling of the "or" sound. One "pitch period" in three
has been selected for transmission. This permits great naturalness when
voice is rebuilt. Intelligible speech could be sent through a 1 in 6 sampling.
The selected samples are "stretched" for transmission. They travel in a
narrower frequency band than complete sound.
Using the stretched sample as a model, the receiver restores original
frequency. In all speech, sounds are intoned much longer than is needed
for recognition even by the human ear. Electronic machines perform
recognition far faster than the ear.
LABORATORIES
-
World center of communications research
Largest industrial laboratory in the United States
t
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The receiver fills in gaps between samples. recreating total original sound.
Under new system. three or four voices could travel at once over a pair of
wires which now carries only one -and come out clearly at the end!
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A Professional Hi -Fi Home
Music System
OLIVER BERLINER
A marriage of high fidelity and broadcast audio equipment has resulted in an extensive but essentially simple home entertainment center for the advanced audiophile and tape recording enthusiast.
PURPOSE OF T IIE SYSTEM described
herein is to provide high -fidelity
sound reproducing facilities plus a
provision for tape recording of various
types of material. For ease of description
the system will be separated into listening and recording facilities.
Virtually every form of audio programming available in the home is incorporated into the listening portion of
the system. As a result, the following
components were included : an FM /AM
tuner, a three -speed record changer, and
a remote -controlled television set. The
tape recording requirements resolved into recording from radio or from television, and the dubbing of records to
tape. For these purposes the following
equipment is used: a professional tape
recorder, a broadcast type mixer. a three speed transcription -type playback turntable, a phono cueing amplifier, and a
TV -sound tuner.
The needs of the installation do not
stop here, for some method of coordinating this equipment is necessary. Two
identical preamplifier- master audio controls serve perfectly, and added to this
is a power amplifier and loudspeaker,
thus completing the equipment lineup.
In order to mount these components in as
compact a manner as possible, the vertical mounting plan was selected and every
possible item is placed in a rack, as
shown in Fig. 1.
The location of the equipment in the
rack is of some consequence, and it is
placed as shown with one purpose in
mind -ease of operation and easy access
to critical controls. From top to bottom,
the components are: master power panel,
magnetic tape recorder, FM /AM tuner,
Oberline TV /FM tuner, record changer,
and the two master audio controls. The
McIntosh 30 -watt amplifier rests on the
floor of the rack, behind the master audio
controls. The Conrac television set and
RCA loudspeaker system (Fig. 5) are,
of course, separate. The transcriptiontype playback, Fig. 2, contains a Rek0-Kut turntable, Fairchild pickup arm,
and an Oberline cueing amplifier. The
T,
1007 No. Roxbury Drive, Beverly
Hills, Calif.
AUDIO
space below the amplifier houses 16 -inch
transcription records.
The careful observer will undoubtedly
notice that there is some duplication of
equipment, for there are two FM tuners
and two TV tuners in the line -up. This
is a matter of personal preference and
convenience and is not unavoidable. The
two FM tuners (one combined with AM,
the other combined with TV (audio) )
provide a safety in the event of failure
of one of them. The two TV tuners (one
with FM, and the other the television
set itself) serve two purposes : onesafety; the other
record one television program while watching another.
No duplication exists in having both a
record changer and a manual player,
for they serve two purposes : convenience
in the case of the changer; and ability
to handle 16 -inch transcriptions and all
other discs with the ultimate in reproduction, in the case of the straight
-to
player.
Figure 3 is a block diagram of the
components hook -up, the solid lines represent audio circuits, while the dashed
lines show power supply connections.
Where power suppliers are not shown, it
indicates that those units have their own
self- contained power supply on the same
chassis. Careful examination of the diagram indicates that the system hinges
around the two master audio controls
and the two- position toggle switch. S,.
Circuit Description
Fig. 1. Front view of the equipment rack.
Locotions of the various components must
be carefully selected to provide ease of
operation.
APRIL, 1956
Each of the master audio controls has
three inputs: the TV /FM tuner, FM /AM tuner, and transcription turntable
on one; the television set, tape recorder
(playback output), and record changer
on the second. This is by no means a
haphazard arrangement, for you will
notice that the input units used for both
listening and recording are all connected
to Control 1, whereas the units used for
listening only are connected to Control 2.
When the two section toggle switch,
S, is in the normal position, the program sources connected to Control 1 are
fed to the recorder and those connected
to Control 2 are fed to the monitor system. However, when S, is thrown to the
other position, Control 1 goes directly to
the monitor amplifier and Control 2 is
completely out of the circuit, providing
listening facility without the need of
feeding through unnecessary equipment.
To make a recording, S, is placed in
normal position, (as shown in Fig. 3). The
selector switch on Control 1 is set for the
23
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AmericanRadioHistory.Com
desired program source-AM /FM tuner,
TV /FM tuner, or transcription turntable -which is fed to the program
amplifier. This amplifier serves two purposes. It converts the high-impendance
output of the master audio control to
600 ohms and to the proper level for
driving the tape recorder; also it contains a volume indicator meter for checking recording volume level.
After passing through the recorder
where they are put on tape, the signals
are fed to one of the selector switch positions on Control 2. If the selector is set
to pick up the tape recorder, it will send
the signal on through to the monitor
amplifier and loudspeaker for listening.
Now here is where the versatility of the
system makes itself available. As shown
in the diagram, Control 2 may select
either the record changer or the television set (audio) for listening, in addition to the tape-recorder output, without
disturbing the other equipment. Therefore, it is possible to record a radio program, for example, while listening to
records or watching television- simultaneously, and without interaction or interference between the two.
This feature is extremely handy when
one has two favorite shows that he wishes
to hear or watch at the same time. One
may be recorded (and played back at
any convenient time) while you listen to
the other. Both go through the hi -fi audio
system, yet do not interfere with each
other. The secret, of course, is in having
//
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more than mere program source selection
and gain control, for each has a set of
bass and treble controls. Therefore, it is
possible to compensate for deficiencies in
the response of a signal being recorded,
such as an AM radio broadcast or a telecast; or to adjust for room conditions or
listening preferences when just listening.
In addition, phono equalizers are also
provided -one for the transcription
turntable, the other for the record
changer.
The Program
Amplifier
The program amplifier (Fig. 6) used
in this installation, was one designed for
general portable use and has more facilities than are needed here. Although
only one (high- level) input is actually
necessary, this mixer has three, plus a
master gain control. In this manner, up
to three separately controlled microphones may be fed to the tape recorder
and monitor when the recordist wishes to
make a live tape recording at home, or
in the field. Additional niceties, such as
u current metering switch for self-contained tube testing; a meter on -off
switch; and a master audio line on -off
switch have also been incorporated into
this mixer /program amplifier.
A great deal of time could be spent
discussing the tape recorder and tape
recording, but that is not our purpose
here. Let it suffice that this unit accepts
up to 101/2 inch reels; operates at 15 or
171/2 inches per second tape speed; has
Broadcast type turntable with
equalizer and cueing facilities on pedesFig.
2.
tal. Mercury switch eliminates "popping"
on motor starts and stops.
two master controls; and in connecting
the proper program sources to each one.
Remember, one control unit is used for
recording and /or just plain listening;
the other for listening only. With this
arrangement, the program sources on
Control 1 may be connected directly to
the monitor, as do those on Control 2,
without the necessity of going through
the program amplifier and tape recorder.
The master audio controls provide
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ANTENNA COUPLER
TV(FM) ANTENNA
TV(FM) TUNER
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RECORD CHANGER
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INPUT TRANSFORMER
TUNER and MC -I POWER SUPPLY
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MC -I REC/MON MASTER CONTROL PI
MC -2 MONITOR MASTER CONTROL R2
Fig. 3. Single -line block diagram of professional hi -fi home music system. Correct hook -up of each component is essential to provide for the desired features.
24
AUDIO
www.americanradiohistory.com
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APRIL, 1956
separate record and playback gain controls; and has three heads so it is possible to monitor from the tape during
recording.
The VU meter may be used to check
erase and bias currents, and also indicate record and playback volume levels.
Sinee the meter on the program amplifier is suitable for indicating record
level, the meter on the tape -recorder
may be set to indicate playback level.
Thus it is possible to watch recording
and playback levels simultaneously without having to switch from one to the
other. With the mixer mounted on top
of the rack, the meters will be in line
with each other for minimum eyestrain
and easy comparison.
A word about volume indication. In
order that meter readings may be quickly
and accurately compared, the meters
should be identical in appearance and
operation. Four-inch, front illuminated
VU types with equal ballistics are recommended. Certain tape recorders use a
vacuum tube voltmeter callibrated in
volume units. The action of such a meter
is different from that of the standard
VU meter, and makes readings much
more difficult to compare, and even inaccurate. The meter scales should also
be the same, either type "A" (VU cali-
brations predominate) or type "B" (per
cent modulation predominant) ; the latter is preferred by the writer.
Equipment Rack
The main equipment rack is mounted
on a dolly, and may be swung around
for servicing, as may the transcription
turntable. This allows the equipment to
be placed near the wall and eliminates
the need for walking space behind. The
turntable is a 12 -inch model, but it has
a pick-up arm capable of handling up
to 16 -inch transcriptions, either wide or
fine groove. A four -position broadcast type equalizer switch at the turntable
may be used, if it is desired to connect
the pick -up arm directly to the mixer.
Otherwise, the equalizer on Control 1,
to which the arm is normally connected,
is used (see Fig. 3). The former is handy,
especially when one wishes to mix turntable with microphones in a live pick -up.
A small cueing amplifier located on the
shelf just below the turntable plate allows the recordist to locate any exact
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spot on a record without interfering
with the regular recording or monitoring
channels, as in standard broadcast operating practice. This may be any good
small amplifier.
The TV/FM tuner deserves some description. It is buit around a DuMont
"front end" which has been designed to
tune in the FM broadcast band in addition to television channels 2 to 13.
The frequency modulation band of 88 to
108 megacycles is located between television channels six and seven. Only the
sound i.f. and audio stages of the television receiver were constructed with
just enough audio amplification included
to deliver about one volt to the input
of the Master Control. A green "magic
eye" tube for precise tuning was ineluded. The circuit is shown in Fig. 4.
The AM /FM tuner has two "magic
eyes," one for the AM band and the
other for FM tuning. Each tube glows
only when you have selected its particular band, which also serves as an indicator for band switching.
The record changer is housed in a
pull -out drawer located just below the
(Continued on page 84)
6AÚ6
33
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AUDIO
APRIL, 1956
"front end."
25
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AmericanRadioHistory.Com
True -Fidelity
Organ
Reproduction
JULIAN D. HIRSCH'
Edgar Hilliar, organist at the Mt. Kisco church, during the
making of one of the recordings used at the demonstration.
IT
IS UNUSUAL to find two persons in
complete agreement on the meaning
of the term "high fidelity ". Individual
tastes vary so widely that it is hard to
find a music system so poor that it will
not meet someone's quality standards, or
so excellent that it cannot be validly
criticized. However, when sound is reproduced with such accuracy that it cannot
be distinguished from the original, this
is indeed "high fidelity ". Perhaps "true fidelity" would be a better description of
such an accomplishment.
As the high fidelity industry has
grown, there have been many public
demonstrations in which live and recorded sound have been compared. These
are frequently staged by equipment
manufacturers, who are naturally interested in showing that their products are
capable of functioning as parts of a
true -fidelity reproducing system. Since
certain musical instruments are much
easier to reproduce than others, it is not
surprising that the most successful and
popular demonstrations have involved
solo violin or cello, or small chamber
groups. In Carnegie Hall last fall, Mr.
G. A. Briggs achieved virtually perfect
realism in reproducing the sound of a
woodwind quintet, in direct comparison
with the original sound. He was possibly
less successful in matching the tonal
quality of a pipe organ.
There are four basic characteristics of
a sound which must be duplicated for
true -fidelity or facsimile reproduction.
Since only one note at a time is being
generated, problems of intermodulation
distortion are minimized. A solo instrunient has an acoustic output well within
the capabilities of most good -quality
loudspeakers and amplifiers, even at
peak levels. Finally, the entire sound
comes from a rather limited area, comparable in size to many practical home
speaker systems.
The preceding statements apply, in
lesser degree, to the reproduction of
small groups of instruments. Fortunately, chamber players are usually located in a rather tightly knit group, not
too much larger than most good speaker
systems. Thus, by using a single microphone and speaker system, it is still possible to duplicate the spatial distribution
of the sounds of a quartet or quintet
with remarkable fidelity. It is usually
unnecessary to resort to stereophonic
recording techniques to simulate the
sound of such a group.
The successful reproduction of a full
symphony orchestra has yet to be accomplished. The frequency-range requirements are not too difficult to meet,
although it is possible that accurate reproduction of the waveform envelopes of
some massive orchestral sounds requires
the systems to respond to the upper
the pipe organ, and possibly the piano, and lower limits of the audible specthey have relatively restricted frequency trum. Due to the multiplicity of inranges. A system with a range of 40 to struments, the intermodulation distortion
12,000 cycles can do a creditable job of of the entire system, from microphones
to speakers, must be extremely low if the
The Audio League, P.O. Box 55, reproducing almost any solo instrument,
whether it be string, woodwind, or brass. resulting sound is to be completely natPleasant ville, New York.
ural. This order of perfection, while attainable, permits no compromise with
quality in any part of the system.
Description of techniques and instrumentation used in recording
The enormous acoustic output of a full
and playback of pipe organ performance in A -B comparison with orchestra, together with the large size
the live sound, in the continuing search for audio perfection. of the concert hall in which it plays, calls
These are:
a) Frequency range. The full frequency
range of the sound source must be
reproduced, without significant distortion of any kind. Reduced to essentials, this means that the entire
recording and reproducing chain,
from microphone to speaker, must
have a flat frequency response and
negligible non -linearity.
b) Dynamic range and sound level. The
playback must create the saine sound
pressure at the listeners' ears as did
the original sound. The reproducing
system, therefore, should be capable
of producing as much acoustic power
as the original sound source.
c) Spatial distribution. The various
components of the reproduced sound
must originate from the same physical
locations as their original counterparts. It is imperative that the microphone and loudspeaker be located as
close together as possible.
d) Acoustic environment. In order to be
played back in the room in which it
was made, a recording must be as
"dead" as possible. If room reverberation is audible in the recording,
realism is destroyed.
Let us now consider these four requirements in relation to the reproduction of
certain specific instruments.
It should be apparent that solo instruments in general are the easiest to reproduce successfully. With the exception of
AUDIO
26
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APRIL, 1956
for the use of a number of speakers and
a correspondingly large amplifier power
output. If published data on the acoustic
output of musical instruments is correct.
it is unlikely that completely faithful
reproduction of a full orchestra can be
accomplished with a reasonable amplifier
power. However, recent public demonstrations, notably the Philadelphia
Soundorama, showed that 300 watts can
be quite satisfactory when used with efficient loudspeakers. In fact. G. A. Briggs
did a respectable job in Carnegie Hall
with only 60 watts and with speakers of
ordinary efficiency.
In the writer's opinion, the chief obstacle to true -fidelity orchestral reproduction has been the spatial distribution
problem. On the face of it, stereophonic
recording and reproduction would seem
to solve this difficulty. However, the
microphones used in orchestral recording are usually located in front of the
orchestra and well above it. There may be
valid and compelling reasons for this
choice of microphone placement. There
are usually even more compelling reasons
why the speakers cannot be mounted in
this manner.
In the playback process, it is customary to use two speakers, or groups of
speakers, which cannot possibly duplicate the sound of the orchestra when fed
with signals derived from microphones
placed many yards away. Under ideal
conditions, it may be possible to get a
sound which is very much like an orchestra, but a direct comparison with the
original orchestra will show up the differences in instrumental balance and
spatial distribution.
Fig. 3. Recorder
and amplifier setup. Left is John
McKnight
of
Armed Forces
Radio Service, operating the Ampex
350. Assisting him
is Milton Weiss of
The Audio League.
The Pipe Organ
The "King of Instruments" shares
many characteristics of other solo instruments and a full orchestra, with a few
additional problems peculiar to itself. IYY
physical size, it is considerably more
compact, although its pipes are frequently
located in two widely spaced groups. The
Position of the Bozok and
speakers under the smaller
pipes of the organ. The E -V 655C
microphone for recording is seen in the
circle.
Fig. 2.
Janszen
pipe organ spans a wider frequency
range, on fundamentals, than the entire
orchestra. The problem of reproducing
it is complicated by the fact that its
pedal notes generate tremendous acoustic
power at frequencies of 32 cps or lower.
Few speaker systems can generate these
frequencies at appreciable levels without severe distortion. The harmonics of
the upper organ fundamentals extend
throughout the range of human hearing
and beyond, also with considerable amplitude.
Although the equipment specifications
for organ recording and reproduction are
more severe than for orchestral recording, there are two compensating advantages. First, the physical arrangement of
the pipes makes the use of two -channel
stereophonic recording easy and unusually effective. Second (and not to be
minimized), the organ is played by one
man. Many hours of experimenting with
microphone and speaker placement are
necessary for demonstrations of this
type, and the expense of keeping a 100 man orchestra on stand -by for such a
period would be prohibitive. On the other
hand, if a cooperative organist is available, it is possible to conduct a serious
investigation of the recording and reproduction problem on a limited budget.
Events Leading to This Experiment
Fig.
Three AR -1
speakers and a
Janszen
electrostatic tweeter set
up in front of the
1.
great organ for
the public demonstration.
AUDIO
APRIL, 1956
The Audio League, basically concerned
with testing and evaluating high -fidelity
components, is staffed by enthusiastic
audio hobbyists. For some time we had
observed the various attempts at true fidelity sound reproduction, and had
formed some definite ideas as to the most
desirable techniques for accomplishing
this. Independently, another audiofan,
Richard W. Burden of Mount Kisco,
N. Y., had been studying the same problem. He proposed, as a program for the
local amateur radio club, the Harmonic
Hill Radio League, to record the new
27
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Aeolian- Skinner organ of St. Mark's
Episcopal Church in Mount Kisco and
reproduce it in the church itself.
Mr. Burden and The Audio League
joined forces at this point and we pooled
our equipment and ideas. Fortunately,
we had the complete cooperation of St.
Mark's Church and of Mr. Edgar Hilliar,
their organist. Mr. Hilliar spent many
hours working with us during our preliminary tests, and without his patience
and skill the experiment could not have
succeeded.
Early Trials
The Aeolian- Skinner organ at St.
Mark's is a three -manual and pedal instrument, containing 38 stops, 53 ranks,
and 3000 pipes. The larger pipes are located behind a wooden grillwork on the
right (as one faces the altar), and the
smaller pipes are in a cluster above an
arch on the left side of the church.
Initially, all recording was done monaurally on Mr. Burden's Ampex 350. Two
microphones were used, with electrical
mixing. An Electro -Voice 655C dynamic
microphone was placed as close to the
treble pipes as possible, and an Altee
21C condenser microphone was placed
directly in front of the great organ.
Our first problem was to select the
speakers to be used in the playback. Obviously, it was desirable to use speakers
capable of reproducing the entire frequency range of the organ with minimum
distortion. Inasmuch as no corners were
available, folded horns were out of the
question. Infinite baffle systems appeared
to be the only ones capable of doing the
job. Several combinations of speakers of
different makes were tried. Fortunately,
the one which sounded most like the
organ was also the smallest and lightest.
We selected the Acoustic Research AR -1
system, on the basis of A -B listening
comparison with the live organ.
It soon became apparent that a single
AR -1, driven by a Heathkit W5M amplifier, was not capable of maching the acoustic output of the organ during any but the
softest passages. The results of the first
test were so promising, however, that we
decided to enlarge our installation and
try again. At this point, we found it
necessary to seek the cooperation of a
number of manufacturers and other outside agencies, since the cost of the equipsevment we planned to use amounted
eral thousand of dollars.
For the second trial, an impressive
array of equipment was on hand.
Through the cooperation of the manu
facturers, we had five Fairchild 275 75watt amplifiers, four AR -1 speaker systems, a Bozak B -305, and a Janszen 1 -30
electrostatic speaker. Atlantic Records,
Inc. loaned us a stereo Magnecorder with
two Telefunken 1;47M microphones. Tom
Doud of Atlantic Records operated the
stereo machine in this test and in the
final demonstration.
I
-.
Since most of the acoustic output of
the organ came from the great organ, we
set up three AR -1 speakers directly in
front of the grillwork (see Fig. 1). At
this point, the advantage of the AR -1's
small size was brought home to us, since
it would not have been possible to mount
a large speaker enclosure so close to the
organ pipes. The fourth AR -1, the Bozak
B -305 and the Janszen tweeter were located underneath the bank of treble
pipes as in Fig. 2. A separate amplifier
was used for each speaker, with the exception of the Janszen, which was paralleled with one of the AR -1 systems. The
E -V 655C microphone is visible directly
in front of the pipes (in the circle). Behind the speakers is one of the Telefunken microphones used for the stereophonic recording, only the stand showing.
An Altec 21C was placed as close to the
organ pipes as we could get it. The Telefunken microphone used on this side was
similarly located. Both Telefunken
microphones were adjusted for a cardioid
pattern.
Microphone Placement
Note that our microphone and speaker
placement puts them close to each other
and to their respective groups of organ
pipes. This technique minimizes the effect of room reverberation since the
recorders can be operated at low gain
settings. The proximity of the speakers
to the organ pipes enhances the realism
of reproduction, even with a monaural
system.
A considerable amount of experimenting with the exact placement of speakers
and microphones was required to approximate closely the sound of the organ.
After each change, Mr. Hilliar would
play a short selection which was recorded
and played back for comparison with the
live sound. To our surprise, our major
problem was excessive bass. The apparently random orientation of the
speakers in Fig. 1 was actually the result of hours of experimentation. A valuable tool in achieving proper balance
was the variable damping factor adjustment of the Fairchild amplifiers. By
varying the damping factors of the individual amplifiers, we were able to
tailor the bass response of the speakers
to match the sound of the organ.
For some inexplicable reason, there
was an apparent source of bass in a
corner of the church where no organ
pipes were located. To fill in this region
during playback, we pointed the Bozak
B -305 opposite to the other speakers,
facing the corner.
As the second trial proceeded, the realism of the reproduced sound became uncanny. Frequently, we are unable to tell
whether we were hearing the live or
recorded sound, even when monaural
recordings were played. The conviction
grew upon us that what had started out
to be a simple program for the local ham
club was likely to be of interest to a
much wider segment of the population.
We decided, therefore, to hold a public
demonstration, in which live, monaural,
and stereophonic reproduction would be
compared.
The Final Performance
The public demonstration was held on
March 2. Although only a limited amount
of local publicity was given to the event,
over 450 people filled St. Mark's Church
nearly to capacity. The equipment was
essentially as described earlier, with the
addition of a second Janszen 1 -30
tweeter and a Fisher 50AZ amplifier
(loaned by Fisher Radio Corp.) which
was used to drive the Bozak speaker system. The second tweeter was placed near
the great organ as shown in Fig. 1. Figure 3 shows the recorder and amplifier
set-up.
Although the St. Mark's organ is a
relatively low pressure instrument and
consequently does not produce very high
volume levels, we had some doubts about
our ability to duplicate it with only 425
watts of amplifier capacity. The speakers
used were all of rather low efficiency, and
we could not expect to develop more than
four acoustic watts of output.
Our recording and playback levels
were set up as follows : Mr. Hilliar
played the loudest passages to be used
during the program. The recorder gains
were adjusted for maximum recording
level, and were not disturbed for the
duration of the demonstration. While
these passages were being played, the
sound pressure was measured about two thirds of the way back into the church,
using a calibrated Altec 21BR150 microphone. The maximum sound pressure
measured at this point was 84 db. When
the test passage was played back, the
playback amplifier gains were adjusted
to produce the same sound level at the
measuring point. Final adjustment was
by ear, with less than 2 db of gain padding needed to produce identical sound
levels from live, monaural, and stereophonic systems. Once set, the adjustments were not changed during the
demonstration. These level settings were
made with the church empty, and no readjustment was required when the audience was present. Rough measurements
of power delivered to the speakers indicated that the loudest passage required
20 watts per speaker. Obviously, some
dipping must have occurred in the amplifiers, even though they can deliver 150
watts instantaneous peak power. This
clipping was not audible, however.
A control box was constructed which
switched the amplifier inputs to the appropriate recorder outputs, and shorted
all inputs when the live organ was playing. Additional contacts on the switches
operated signal lights which informed the
audience whether they were hearing live,
(Continued on page 81)
AUDIO
28
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APRIL, 1956
of V,,_{ connected at the junction between R_, and Rf0. The feedback voltage
is the voltage drop that appears across
Rt7 and is applied to the cathode of Km.
The bias of V,A iS still determined
mainly by the value of R20-the shunting
effect of
and the transformer secondary being very slight.
Actual measurements made on the portion of the amplifier as shown in Fig. 1
are as follows : with the feedback resistor
disconnected from the output
winding of the transformer and a 1000 eps signal from an audio oscillator applied between the grid of V,A and
ground, a 0.23-volt signal from the
oscillator fed to the input gave a 9 -volt
signal across the output transformer. See
simplified schematic of (A) in Fig. 3.
A 9 -volt signal across the 16 -ohm output
winding is approximately 5 watts output.' Therefore, the voltage gain without feedback is equal to the output voltage, 9, divided by the input voltage, 0.23,
or 39.
R
R
With Feedback Connected
Fig.
1.
Typical small power amplifier used for example worked out in the text.
Simplitronics
Electronics Simplified: Feedback Voltage
HAROLD REED
there is still a
need for electronics articles written
in a down to earth manner, but not
over-simplified to such an extent that the
THE AUTHOR BELIEVES
audio experimenter, hobbyist, or student
is informed only that a certain arrangement of component parts and circuit design is employed because they produce
certain results; and yet, not presented
with mathematical analysis not understandable to the reader without clarification.
For instance, concerning feedback
the subject of this article
is usually
found that the simplified literature will
state that negative feedback is used in
an amplifier circuit to improve its operation and stability without giving any
information concerning the feedback
voltage. More advanced technical writings may state the same thing and then
include mathematical equations or for-
-it
° 3917
AUDIO
-
Madison St., Hyattsville, Md.
mulas to explain these statements without explaining the equations. Under the
title SIMPLITRONICS it is proposed to
present articles in this magazine to
bridge the gap between these two extremes.
The reader is probably aware that
feedback is the process of applying some
of the output voltage of an amplifier
back to the input of an earlier stage in
the circuit. This is shown in Fig. 1 which
is a schematic diagram of a straight
voltage amplifier VA, phase splitter
V,,ei and push -pull output stage V4, V,.
This circuit arrangement is given because
it is found in a number of hi -fi amplifiers and will be familiar to many readers.
The feedback resistor is R,7. If we
simplify and redraw the portion of the
circuit under consideration as shown in
Fig. 2, we see that R27 and R20 are
actually across the amplifier output and
form a voltage divider, with the cathode
APRIL, 1956
If the feedback resistor is now connected to the 16 -ohm tap of the transformer winding, it is found necessary
to increase the audio oscillator signal to
1.4 volts to again obtain 9 volts of 1000 cps signal across the transformer output.
Refer to (B) of Fig. 3.
The voltage gain, then, with feedback
applied to the cathode of V,A is equal
to the output voltage, 9, divided by the
new input voltage, 1.4 or 6.43. In other
words, the voltage gain has decreased
from 39 to about 6.
As it required an input of 0.23 volts
without feedback and an input of 1.4
volts with feedback to obtain a constant
9 volts output, the feedback voltage
must be 1.4 minus 0.23, or 1.17 volts
which is negative, and therefore opposing
the original input signal.
We can now express these results by
-
Power = E2 /Z. E (voltage) is 9; Z
(output impedance) is 16. Thus power is
92 or 81 divided by 16, which is approximately 5 watts.
((`f,uti,,
u
,1
Fig. 2. Simplified arrangement of outpu
transformer secondary and the first tube
of the amplifier of Fig.
1.
29
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Phono Switch "Pops"
What are the best methods of suppressing the "pops" heard in a sound system
when the a.c. switch of a record player is
turned on or of? Donald F. Sampson, Central City, Nebraska.
A. In the better grade of record changers,
the cartridge is shorted out during all portions of the cycle until the needle strikes
the record surface, after which the short is
removed, allowing the cartridge to feed
into the amplifier in the normal way. Because of the very low impedance at the
input of the amplifier at the time the motor
is turned on or off, the high induced voltage
around the motor windings cannot introduce too much of the unwanted "pop"
sound into the system.
Excellent results may be had by wiring
the motor of the record player in accordQ.
are sometimes made of a plastic which
can be attacked by the carbon tetrachloride,
completely ruining the switch. Carbon
tetrachloride should, in fact, be used as
little as possible in cleaning electronic
equipment; other agents can usually be
used which will be at least as effective and
which will endanger the equipment on
which they are used to a far smaller extent.
Volume Controls: To quiet a noisy volume control, first remove the knob and
arrange the equipment so that the shaft
of the control faces up; then, with the eyedropper, pour a little of the cleaning liquid
into the control at the point where the
shaft enters the body. While doing this,
rapidly rotate the shaft so that the cleaning agent will be spread over the entire
surface of the element and slider contact.
If this treatment does not produce the
AUDIOCLINIC
JOSEPH
?
GIOVANELLI
ance with the schematic shown at (A) in
Fig. 1. The capacitor, C placed across the
switch,
effectively puts a load across the
motor winding. (Because of the fairly low
impedance of the a.c. line circuit, the capacitor is actually in parallel, not in series,
with the motor, as will be seen from examination of the schematic.) When an inductance transfers energy into a load, the
Q of that inductance is lowered. In this
instance (large capacitive load), it is
lowered substantially, resulting in a much
smaller induced voltage which, in turn,
causes almost complete elimination of the
S
annoying "pop ".
It may also be possible to combine the
two methods, as shown at (B). To make
this method really effective, S, must operate in the following sequence: When the
record player is turned on, S,, must close,
turning the motor on; then, S,e must open,
permitting the pickup to feed the amplifier; when the player is turned off,
must close, preventing the pickup from
feeding the amplifier ; then S,,, must open,
turning the motor off.
If the player is a record which already
has the shorting feature previously outlined, all that need be done is wire the a.c.
circuit as shown at (A) in Fig. 1. If, however, it is a manual player or a changer
S
lacking this feature, the schematic of (B)
should be followed. Since it may be difficult to obtain a switch which will operate
like 5,,,-5,,, it may be necessary to resort
to using two separate switches operated in
the prescribed manner; however, it might
be somewhat annoying to have to fuss
with two switches when your mind is on
listening rather than tinkering.
Noisy Volume Controls
Q. How can
?
I quiet
noisy volume controls
and switches? F. Goldman, Providence,
R. L
A. This can be done with the aid of an
eyedropper and a cleaning agent such as
No-Noise or Quietrol. Carbon tetrachloride
may be used in place of either of these, if
necessary. However, this substitution should
not be made if the switches to be cleaned
are of the wafer type since such switches
desired result, it should be repeated. If
the second application of cleaning liquid
fails, it is an indication that the control is
beyond help and should be replaced.
Switches: Wafer construction usually
necessitates removal of the equipment from
the cabinet. To clean this type of switch,
apply the cleaning agent directly to the
contacts and then rotate the switch so that
the liquid will be thoroughly spread over
them. If it is a toggle switch that is to be
cleaned, pour the liquid into it at the point
where the handle enters the body, moving
the handle back and forth to distribute the
cleaning agent.
Decibels
Q. What is meant by the term decibel?
James Larkin, Wheeling, W. Va.
A. A decibel is not a concrete unit like a
watt or a volt. It represents a ratio of
two powers. The power ratio is expressed
by the formula:
Output Power
Power Ratio =
Input Power
loss of 20 db, there is a net gain of 10 db,
or a power ratio of 10 to 1.
As has been previously noted, a decibel
indicates a power ratio. Sometimes, however, a piece of equipment is said to have
a power output of so many db. In order
for such wording to be meaningful, 0 db
must be assigned a specific power level,
such as 1 milliwatt, and when 1 milliwatt
is the reference, it is indicated by using
"dbm" instead of db. Let us say, for example, that a particular amplifier has au
output of 30 dbm ; 30 10=3, the log,, of
the power ratio ; the antilog of 3 is 1000,
and so the power ratio is 1000 to 1. Since
0 dbm = 1 milliwatt = .001 watt and the
output of the amplifier is 1000 times this
figure, it is easily seen that the power output is 1 watt. However, it should be noted
that there are at least two other reference
power levels, 6 milliwatts and 12.5 milli watts; actually, any power level can be
used although these are the most popular
ones. It is necessary, therefore, to know
to what power level 0 db refers if the
power output of a piece of equipment is
to be meaningfully expressed in db.
:
Piezoelectric Effect
Q. What is the Piezoelectric effect! Les
Salvage, Jacksonville, Fla.
A. When a crystal of a material such as
Rochelle salts is bent, or stressed, a voltage appears across its faces. When the
bending motion ceases, the voltage disappears; when the bending motion proceeds in the opposite direction, the voltage
which appears is of opposite sign. Conversely, when an a.c. voltage is applied
across its faces, the crystal will be bent
in accordance with the amplitude and polarity of that voltage. This is the Piezoelectric effect. Most materials will behave in this manner to some degree; however, in the case of a metal such as steel,
the impedance of the substance is so low
that very little voltage will be developed;
it is possible, though, to observe the presence of some voltage if the proper detector is used.
Even when a crystal of Rochelle salts.
(the most common material used) is at
(Continued on page 70)
TURNTABLE
MOTOR
=
0.1 l,r
P,
Originally, the unit used was the bel,
simply defined at the time as the log of
the power ratio. It was discovered that one
mile of standard telephone cable had an
attenuation of 0.1 bel at a frequency of
886 cps; it therefore became more convenient to think in terms of the decibel:
10 x log of the power ratio. It was because of the ease with which logarithms
may be used that the decibel came into
use as a means of discussing these power
ratios; it is far simpler to add all the
logarithms in a given problem and then
find the antilog in a table which exista for
this purpose than it would be to do all
the multiplication that would be required
if the power ratios themselves were used.
e.g. A system has an amplifier whose power
ratio is 1000 to 1; log 1000 = 3; 10 x 3 =
30; the amplifier thus has a gain of 30 db.
The line into which it feeds attenuates it
from 1.0 to .01; the log of this ratio is -2;
10x- 2 = -20; the line thus has a loss of
20 db. Since there is a gain of 30 db and a
-
(A)
t-
TURNTABLE
MOTOR
MAKE BEFORE -
BREAK
0.1
y
AMPLIF
CRYSTAL PICKUP
(B)
Fig.
AUDIO
30
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IER
o.l
1
APRIL, 1956
Transistor Preamps
H. F. STARKE`
A discussion of practical considerations involved in the design of preamplifiers for phonograph reproduction -with their attendant low- frequency boost -and flat amplifiers for microphone applications.
may be
PREA Al PI, IF IERS
classified broadly according to their
RANSISTOR
-
T various
in fact, it
applications
alight be better to say that they must be
so classified because (1) frequency discrimination networks are, in general,
somewhat more difficult with transistors
than with tubes and (2) the input resistance varies enormously with circuit
configuration, operating current, and
transistor alpha (a). The present account will be concerned mainly with two
general types of amplifiers: those having
flat responses and intended as dynamic
microphone preamps or as impedance
transformers, and those designed as preamps working from an inductive pickup
into an otherwise flat main amplifier.
Values have been published for the
new standard record curve (RIAA) to
the nearest millibel.' A straight line between the extremes at 30 and 15,000 cps
has a slope of very nearly 4 db per octave and if this line is raised a trifle it
does not depart more than 1.6 db from
the RIAA at any point (Fig. 1). Although it must be seriously doubted
whether the most critical observer could
distinguish between the two, the point is
largely of academic interest because, as
it happens, an amplifier with a slope of
4 db per octave throughout the entire
band would be more difficult to design
Raytheon Manufacturing Company,
Semiconductor Division, 55 Chapel St.,
Newton 58, Mass.
"The Proposed AES Disc Standard,"
(RIAA curve). J.A.E.S., Jan. 1954.
than one having RIAA response with its
slight 1,000 -cps flattening. This is because resistive -reactive networks are
characterized by slopes of 6 db per octave- obviously too much for a nine octave band.
In general, it is a mistake to interpose
a resistive element between the transistor
input and the generator for the purpose
of obtaining frequency adjustment if a
primary objective is that of providing
the highest possible signal -to -noise ratio.
The special case of a preamp designed
for working from an inductive pickup,
however, may be considered as a practical exception only to the extent that the
designer would like to mitigate the severity of the input impedance problem
at the expense of some degradation of
the signal -to -noise ratio.
One form of the phono preamp is
shown in Fig. 2 in which the following
features may be recognized:
(1) No frequency networks between
pickup and input.
(2) High- frequency rolloff by controlled input resistance.
(3) Low -frequency boost by means of
a negative feedback loop from collector
to collector. This technique is, of course,
similar to the plate -to -plate loop of the
vacuum -tube amplifier.
(4) Bass flattening by adjustment of
the interstage blocking capacitor.
With an inductance of 0.52 Hy, the
cartridge used during the development
of this amplifier requires an input resistance of 6200 ohms for RIAA re-
shoo.( when used with a vacuum -tube
amplifier. This drops very little for the
transistor amplifier because the d.c. resistance of the cartridge is less than
500 ohms.
If the crossover point appears to require adjustment, this can be most readily accomplished over a reasonable range
by changing the operating current of the
first stage. It will be noted that the base
divider for this stage consists of equal
values of resistance in order to keep
the parallel impedance of these elements
as high as possible. The adjustment of
operating current should accordingly be
made by changing the emitter resistor
rather than the 1 to 1 ratio of the base divider elements. If the required current
change turns out to be considerable, it
will be necessary to modify the load
the general objective being to maintain
a collector voltage between 1.5 and 2
volts in this stage from a supply of 6
to 7 volts.
The low- frequency boosting network
with a crossover of approximately 500
cps works from a source consisting of
the second -stage collector load (20,000
ohms) in parallel with the output imand
pedance of that stage, Rß(1
works into a load made up of five impedances in parallel :
-
a),
(1)
(2)
(3)
(4)
(5)
First -stage output impedance.
First-stage collector load.
Second -stage upper base resistor.
Second -stage lower base resistor.
Second -stage input impedance.
R
Fig. 1. RIAA playback characteris.o
line)
tic
(solid
plotted against a
straight - line response curve having a slope of 4
db per octave
(dotted line).
a
I
.i
p
iQ
3
a
x
,w
Ir
laue
'°°°°
FREQUENCY IN CYCLES PEN SECOND
AUDIO
Fig. 2. Transistor phono preamp in
initial
stages of design.
31
APRIL, 1956
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It will therefore be recognized that this
network cannot be predicted to the same
exactitude that will be found in vacuum tube circuits unless at least the alphas
of the two transistors are known and
their values of R0 and Rb are not too far
from average for the operating current.
Also, if a substantial change is made in
the first -stage operating current for the
purpose of correcting high -frequency
rolloff, the corresponding change in first stage output impedance will have some
effect upon the low- frequency -boost network although the converse effect is
much less. Both input and output impedances vary inversely with current,
of course, and when the first -stage current is reduced the slopes of both high
and low networks are increased. For a
given change, however, the effect is
more pronounced for the LR network
because R in this case is a single impedance (the input impedance of the first
stage) while in the other case the first stage output impedance is only one of
several impedances in parallel.
Accordingly, if the first frequency
run on the completed amplifier deviates
from the standard by more than an acceptable amount in one or two places,
the preferred order of adjustment would
be:
(1) High- frequency rolloff.
(2) Low -frequency boost.
(3) Bass flattening.
The standard calls for a 3 db flattening at 50 cps and most of this is obtained
from the rather low value of interstage
coupling-the remainder being due to
the emitter bypasses (250 µf) which have
enough impedance at this frequency to
drop the gain 0.6 or 0.7 db. More or less
flattening is readily obtained by altering
the value of the coupling capacitor with
little effect upon the rest of the curve.
elect to use a battery in view of the low
current demand and this is a value that
provides 5 or 6 volts of output. On the
other hand, if the supply is obtained
from a 250- or 300-volt plate supply in
the main (vacuum -tube) amplifier by
means of a divider, there is no particular
reason for setting the tap higher than
30 volts. The bleeder current in this
divider should be at least four or five
times the total current taken by the
transistor preamp so that the voltage at
the tap will not rise unduly if the preamp is switched off separately.
The 1000-cps voltage gain of this amplifier is approximately 52 db and if
this is somewhat in excess of what is
required, the first stage collector load
may be tapped down without much effect
upon over -all frequency response provided the low boost network is left at
the collector.
In terms of comparative physical size,
the 250 of emitter bypasses stand out as
the largest components physically, on
the list. If an amplifier of this type is to
be built into the pickup arm, it accordingly becomes desirable -because of both
size and weight -to eliminate these capacitors. This leads to the form of preamp shown in Fig. 3 which uses the type
of regulation circuit in which the base
divider feeds from the collector instead
of from the battery. Compared to the
.01
39,000
Practical Considerations
Since a two -stage amplifier with phase
reversals in each stage has a final output in phase with the amplifier input,
the input base divider should be decoupled. The filter serves the further
purpose of dropping the supply voltage
to the first stage and -as used here
leaves only the second -stage collector
supply at the higher voltage. An earlier
version of this form of preamp used 6
volts to both stages and resulted in a
design which gave adequate performance
in gain, noise level, and frequency response, but which was deficient in the
matter of maximum undistorted output
voltage. This has been corrected in the
present amplifier by raising the secondstage supply and holding the emitter resistor to a reasonable value.
It will be recognized that no particular
importance attaches to the value of 221/2
volts other than the fact that some may
-
Fig. 3. Amplifier of Fig. 2 is modified
to avoid use of large emitter bypass
capacitors.
first circuit, this form has somewhat less
regulation and (because of the negative
feedback from collector to base) lower
stage gain. The feedback also has the
effect of reducing both the input and the
output impedance of each stage apart
from the rather low value of the resistor
from base to ground. This latter can be
increased only at the expense of achieving a poorer regulation factor.
The over -all combination proved to
have an input impedance somewhat too
low for the inductive pickup with a
first -stage transistor having a current
gain of 50. As an alternative to increasing the impedance by reducing the operating current
procedure discussed
-a
32
in connection with Fig. 2-a small resistor was placed in the first-stage emitter. Although either scheme appears to
be workable and would probably result
in approximately the same reduction in
gain (other things being equal) it should
be noted that the slight reduction in battery current must be balanced against
maintaining or slightly improving the
regulation factor.
The gain of 40 db at 1000 cps-although 12 db lower than the gain of the
previous amplifier -is still adequate for
the purpose. Since the second-stage collector supply is the same, the maximum
output is also the same : 15 or 16 dbv.
The impedance of the low-frequencyboost network is not much more than
one-half that of the corresponding network of Fig. 2 because it works between
the lower impedances resulting from the
negative feedback. The 2 -uf capacitor
for bass flattening has sufficient effect
with no augmentation from emitter bypasses-again because of lower impedance.
Adding Other Curves
For the benefit of those who would
like to provide, by means of switching
in other networks, a choice of frequency
responses, the following practical difference between transistor and vacuum
tube circuits may be noted :
Although, in general, a reactive impedance must equal the sum of the resistive impedances on either side at the
crossover frequency, it is common practice in vacuum tube circuitry to disregard the source impedance (usually a
plate load shunted by the plate resistance) and consider only the much higher
following impedance -i.e., a grid leak
shunted by the grid impedance. In direct
contrast, the transistor circuit -because
of the choice of circuit configuration or
the use of feedback -may show a preceding impedance higher than, the same
as, or lower than the following impedance and both must be taken into account.
At 15,000 cps, audio-frequency
transistors will show some loss of gain
due to frequency cutoff of alpha. On a
flat amplifier, such as will be described
in connection with dynamic microphone
preamps, this can result in a response
that is down 3 or 4 db at 15 or 20 kc
in two stages. On the RIAA type of response, the effect may be noticeable as
a convexity (facing up) of the portion
of the curve between 2,000 and 15,000
cps. In brief, if the response is down by
the correct amount at 15,000 cps, it will
be 3 or 4 db too high at one octave
lower or, conversely, if it is down by
the correct amount at. 7 or 8 kc, it will
be 3 or 4 db too low at 15,000 cps. To
determine how much alpha cutoff correction is required, it is of course inAUDIO
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formative to run the curve to 20,000
cps despite the fact that the standard
stops at 15,000 because-unlike the other
end of the band where the 6 db /octave
response due to low- frequency boost is
severely modified by bass flattening -the
slope of the high -frequency end of the
RIAA curve is rather well defined.
The simple, low-impedance network to
accomplish this correction will be discussed in connection with the flat -response amplifiers. For the present, it
may be noted that the circuit of Fig. 3
will require less alpha cutoff correction
than that of Fig. 2 because, as might be
expected, the presence of negative feed hack independent of frequency reduces
the drop.
Frequency responses for these amplifiers have not been included for the simple reason that the conformity of an
to
amplifier of this type to RIAA
any of the older curves for that matter
largely either a question of patience
for the individual experimenter or of tolerances to the commercial designer. It
seems safe to say that the desired gain
(32 to 35 db minimum) and frequency
response can be obtained with transistors having common- emitter current gains
af at least 30 or 35 although the preferred range would appear to be between
70 and 100. The choice between the tw
circuits is a matter of deciding whether
or not the large emitter bypasses are too
much to pay for the extra stability. In
this connection it may be worth noting
that the quantity S (stability factor) as
now used is not particularly informative. In the first place, since a larger
number denotes a more unstable circuit,
the correct term would appear to be "instability factor." Of more importance,
however, is the fact that, with transistors
having current gains of 15 to 150 available for various purposes, the S- factor
alone does not give a clear indication of
circuit stability in terms of the improvement effected over the use of a unit
having the same current gain in an unregulated circuit. For example, transistor A with a current gain of 100 is used
in a circuit giving an S- factor of 20-an
improvement ratio, obviously, of 5 -1.
Transistor B with a current gain of 30
is used in another circuit having constants resulting in an S- factor of 10 or
an improvement of 3 to 1. But because
the latter is a lower S-value, the erroneous conclusion can be made that B is the
better circuit. Since the factor is intended to describe the stability of the
circuit and not the stability of the transistor, it would be more informative to
quote the ratio illustrated above and call
it "regulation factor." In this notation
unity describes, of course, an unregu-
-or
-is
lated circuit and the higher numbers are
the more stable circuits.
The two phono preamp circuits show
values as follows: (B is the common emitter current gain)
Figure
2
Stage
1
2
3
3
s
100
70
50
50
S
2.9
7.3
2.6
14.2
sis
34.5
9.6
19.2
3.5
This matter of regulation and designing circuits for a reasonable temperature range cannot be dismissed lightly.
Too many designs have appeared in the
recent past showing unregulated circuits
although their designers must be aware
of the fact-since no one has tried to
keep it secret-that transistors are temperature responsive. In the present instance, a rise of 10 or 15 degrees Centigrade would produce, on an unregulated
phono preamp, a frequency response
only distantly related to RIAA or any
of its forebears. With rising temperature (and rising collector current) transistor impedances will drop and if the
degradation of frequency response is
too great to accept, the designer must
improve regulation to the point where
the deviations are tolerable for the temperature range over which the equipment is intended to be usable.
For example, a 50 -ohm microphone will
require a common base stage and if this
must work into a low- impedance line
(say 250 or 300 ohms) because of frequency and line capacitance considerations the stage gain will be less than 10
db since the gain of the common base
connection is derived from the ratio of
the load to the source.
It is a mistake to suppose that a
"cathode follower" (i.e. grounded collector) type of input stage can be used
for these applications as a sort of universal input device capable of working
from a few tens of ohms to a few tens
of kilohms with the real gain derived
from the following stages. Those who
think along these lines exhibit only a
slavish adherence to vacuum -tube circuitry in the face of the demonstrable
fact that low (and approximately equal)
noise factors are possible for all three
common-electrode arrangements only
when impedances are matched or at least
approximately so. They would like, in
short, to enjoy the enormous advantages
of transistors without paying the necessary (and not unreasonable) price of
learning to think of the transistor as a
power device.
Impedance Adjustment
Flat Preamplifier
Preamps to be used with dynamic
microphones and having flat responses
must generally be designed for a specific application with due regard to
microphone impedance, line impedance,
phyical size and the input characteristics of the main amplifier. In the situation most prevalent at present, the latter will be a vacuum -tube amplifier with
either a high- impedance (direct to grid)
input or a line -to -grid transformer. To
obtain the advantages of operating the
line at a higher power level (i.e. higher
than the level of the unaided microphone) and with a fairly wide choice as
to impedance, it is necessary to build
the transistor preamp either into the
microphone case or in a small cylindrical
housing which can be interposed between
the cable plug and the microphone receptacle. This is practically the same, it
will be noted, as saying that the transistor preamp may be regarded as an impedance transforming device which could
conceivably replace the transformer now
used for this purpose -the important
difference being that gain may be obtained along with the transformation at
little or no cost as far as signal -to -noise
ratio is concerned.
For these purposes, the actual gain
obtained in the input stage should be
considered as secondary to obtaining the
required impedance because it is always
possible to add a second stage without
an excessive increase to the size, weight
and battery drain of the preamplifier.
34
Fortunately for present purposes, it is
possible -as already intimated
cover
a very wide range of input impedances
-to
by the selection of transistor alpha, circuit arrangement, and operating current.
The selection, furthermore, may be made
to show some overlap in the transition
from one circuit to another although the
region of the overlap will usually favor,
for one reason or another, the common
emitter. A few illustrative examples may
serve to clarify this point, for the benefit of those who have not hitherto given
much thought to this problem.
Let us assume that the designer, in
addition to the choice of circuit, has
available the following:
(1) Maximum operating current : 2
ma.
(2) Minimum operating current: 50
Pa.
(3) Maximum transistor beta: 90
(types 2N65 and 2N132).
(4) Minimum transistor beta : 22
(types 2N63 and 2N130).
It
will be understood that these maximum and minimum beta values are not
absolute but merely representative of
the types indicated. Also, the beta at
50 pa will be typically about 50 per cent
of the 1 -ma value and the following estimates are based upon this reduction.
The minimum possible input resistance (grounded base, short- circuit load)
is:
Ri=Re+R6(1a) =Re+R6
AUDIO
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APRIL, 1956
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35
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At 2 ma:
R{ =12 +400 (.011) =16 ohms
For maximum with grounded base
(current 50 pa, beta 11) :
R,= 500+ 1200 (.083)=600 ohms
The input resistance of the grounded
emitter is :
R+ =Rb +R4(0) (1i-0)
For the minimum, the current is 2 ma
and the beta 22:
Rt = 400 + 12 (23) = 676 ohms
For the maximum (4= 50 pa ; ß = 45) :
Ri= 5000 + 500 (46)=28,000 ohms
The final values have been rounded because the Rb quoted for each case is
simply the most probable value and the
actual Rb may differ since this parameter, for a large number of units, has its
own distribution.
The important parameters, then, for
the control of input resistance are alpha
(or beta) and base resistance. For either
the equipment designer who must be prepared to accept a reasonable parameter
dispersion or the experimenter who must
perforce take his chances as to the exact
values of the few units he is willing to
purchase, the common emitter circuit
would appear to be preferable because:
(1) The minimum R, for a given beta
and emitter current (as, for example, the
676 ohms quoted above) can be still further reduced by the use of collector -tobase feedback.
(2) This type of feedback will reduce
the range of input resistance caused by
a given range of transistor current gain
and base resistance.
(3) Negative feedback is extremely
difficult to apply to the grounded-base
circuit because of its characteristically
low input resistance and the severe losses
in gain -lower than the grounded emitter to begin with -caused by the shunting of the load. It will be understood
that we are speaking not of the case
where the designer considers it no particular hardship to use 22 %- and 45 -volt
B batteries, but of the more practical
case where the desired results are obtained with a minimum of supply power.
Variation of Operating Parameters
In elaboration of the foregoing, a digression at this point may be permissible. While it is true that the phono
preamp already described uses a 22-volt
supply (for the output stage only) it
must be recognized that this was done
for one specific purpose: that of providing approximately the same maximum output voltage as may be obtained
from the vacuum -tube preamp without
resorting to the use of an output transformer. As far as its performance otherwise is concerned, the transistor preamp
can be built with a 4-cell, 3 -cell, or possibly even a 2 -cell battery.
The higher voltage, as already noted,
is of course available from the power
supply of the main amplifier. This is
also true of many other transistorized
units intended to be used with vacuumtube equipment already on hand. We
are in a period of what might be called
"hybridization" in which the transistor
is relegated to the role of performing
only those functions where it is demonstrably preferable, for one reason or
another, to the vacuum tube. In many
of these cases design problems would
actually be simplified if the entire equipment were transistorized. Since it appears likely that some equipments now
line operated will take the form of battery portables by the full exploitation
of transistor capabilities, it may be recommended that designer and experimenter alike begin to channel their
thinking away from 45 -volt B batteries
and toward low -voltage operation.
The phrase "without resorting to the
use of an output transformer" which
appears above has a similar explanation.
High-quality transformers, in addition
Fig. 4. Simple form of one -stage ampli
fier for
use
with dynamic microphone
to being rather costly, are usually much
larger and heavier than the rest of the
components put together, including the
transistors. Consequently, if the end result can be achieved without using transformers, it seems probable in the long
range viewpoint that their use will decline in miniaturized applications. In
fact, it may be recalled that part of the
present discussion will be devoted to an
examination of the feasibility of using
transistors as impedance transforming
devices.
To return to the main subject : Of relatively less importance is the fact that
the upper limit on Rt for the common emitter circuit can also be extended by
the use of external emitter resistance
feedback because these higher impedances (above 25,000 ohms) are also
available with the common-collector circuit at normal operating currents and
also because the emitter type of feedback gives virtually no improvement in
restricting the range of input resistance.
The grounded- collector input resistance
is extremely sensitive to output loading
and values ranging from something like
10,000 ohms to several hundred thousand
ohms may be obtained with loads not in
excess of 20,000 or 30,000 ohms.
"Flat" Amplifier Circuits
For the flat amplifiers we will describe
first a unit intended to work from a
high -quality dynamic microphone into a
tape recorder. Many low- and medium priced recorders are designed to operate
from crystal microphones and consequently are not equipped with line input
transformers. If the owner of such a recorder wishes to use a microphone of
better quality and also to be able, on occasion, to place the microphone at some
distance from the recorder (very difficult
with the high -impedance crystal microphone because of line capacitance) he
will find a satisfactory solution to his
problem in a transistor preamp at the
microphone.
Let us assume the following factors:
Microphone impedance : 500 ohms.
Microphone power: 95 db below 1
watt/microbar.
Microphone response : down 3 db at
50 and 12,000 cps.
Amplifier input : direct to grid.
Microphone cable : 50 ft of single
conductor at 70 pp4 /ft.
Battery : one or two cells.
Figure 4 is typical of the simplest
sort of one -stage amplifier that might be
seriously considered for the purpose.
With the omission of the output blocking capacitor (since this would be included with the tube -amplifier input)
the circuit shows three resistors, one capacitor, one transistor, and one cell. The
combination of load and collector current leaves 0.6 to 0.85 volts at the collector according to whether a mercury or a
carbon cell is used. By connecting the
base divider to the voice -coil return instead of directly to the base, the feedback normal to this type of regulation is
made practically zero and the power
gain of the stage is approximately 17
db. This does not sound very impressive
(unless viewed in relation to the paucity
of components) but it may be instructive
to take a close look at just what we have
before leaving it.
The power from the microphone, at
500 ohms, is given as
95 dbw per
microbar. This is 3x 10.10 watts for a
sound pressure level of 74 db. The same
microphone with a built-in transformer
to raise the impedance to 25,000 ohms
will deliver 5.5 millivolts to an open grid
for the same pressure. The cable in this
case, it should be noted, must have a
capacitance no greater than approximately 525 µµf for response to 12,000
cps.
The original microphone power (3 x
10-1) watts) plus 17 db (the preamp
gain) is 1.5 x 10-8 watts which is 5.75
millivolts in 2200 ohms. The maximum
AUDIO
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tolerable capacitance across the latter is
nearly 6000 µµf. The net practical comparison, then, is that we have the same
voltage at the grid with this extremely
simple preamp, working from the 500 ohm mike over a line more than 12 times
as long, as we would have from the high impedance mike.
With a transistor alpha of 0.975, the
input resistance of this stage in the absence of feedback is approximately 3500
ohms and a mismatch of this order may
yield a noise factor 1 or 2 db higher
than the minimum value possible for a
given transistor. To the perfectionist this
may sound a trifle alarming but this
particular microphone has an inherent
signal -to-noise ratio of 68 db in a 74 db
sound field and it is consequently of little practical importance in this particular case whether the noise factor of the
transistor is 4 db or 7.
To a microphone which is down 3 db
at 12,000 cps, it matters little whether
or not the transistor is down 1.5 or 2 db
at 20,000 cps because of frequency cutoff of alpha. There is accordingly no
need for a compensating network and
this is true, in general, for most preamps for dynamic microphones although
this factor deserves more attention if
for some special purpose considerable
gain with several stages is built into the
preamp.
For the second ease involving a microphone preamp, let us assume that the
owner of the tape recorder has a low
impedance mike of 50 ohms and finds
that when he tries to use it the recorder
gain must be forced to the point where
the quality of the resulting recordings
is very dubious because of hum and
microphonics -the latter being due to
the tape reel motor. A similar situation
can be encountered (although somewhat
less annoying) if the mike is of medium
(250 ohms) impedance.
We will therefore assume:
Microphone impedance : 50 ohms.
Microphone power: - 79.4 dbm /microbar.2
Microphone response : 50 to 10,000
eps.2
Amplifier input: direct to grid.
Preamp supply: one cell.
Microphone cable : two -conductor.
Although the length and capacitance
of the cable are relatively unimportant
because of the very low impedance, the
two- conductor cable is usually supplied
to balance out hum pickup. This in turn
calls for a balanced input at the amplifier and if the necessary input transformer has not been provided the only
makeshift solution is to operate with
an unbalanced line and reduced cable
length. This difficulty disappears with
the transistor preamp because the hum
2 Manufacturer's
data on Model 556S
(Shure Bros.) Cardioid.
picked up by an unbalanced line of almost any reasonable length will be, in
effect, down by an amount equal to the
preamp gain.
The input impedance of 50 ohms indicates a common -base input stage with
a transistor having rather high current
gain (100) so that the Rb(1 - a) portion
of the input resistance may be held to
10 or 15 ohms thereby allowing an emitter resistance of 35 or 40 ohms for a
current of 600 or 700 pa. Figure 5 shows
a two -stage amplifier with a power gain
of approximately 28 db and an output
impedance of 2200 ohms. The corresponding output voltage for an input
power of 1.15 x 10-11 watts ( -79.4 dbm)
is 4 millivolts or - 48 dbv. This compares
to - 60.5 dbv (open circuit) for the same
type of microphone at 35,000 ohms.
For any microphone supplied with a
?,
:N'32
R1
^'
:N65
2N133 or
N1JC
5
d
of
_vc
1
=2
:
:
39,000 to 68,0v3
47,0e0 to 100 ,u00
11p
- c5ci
u.
300
'
pc.
i
y.
amplifie
with a power gain of 28 db and the
comparatively low output impedance of
Fig. 5. Two -stage microphone
2200 ohms.
two -conductor cable the preamp designer is under no particular compulsion
to package the cells with the preamp because the change to the unbalanced line
makes the second conductor available
for supplying power. Alternatively, if
the designer elects to change to a single conductor cable with the battery in or
near the preamp, the switch usually supplied for grounding a single -impedance
mike can be made to serve as an ON/OFF
switch for the battery. If the preamp is
built into a cylindrical housing plugged
into the mike receptacle, the size of such
a package will of course be considerably
smaller than that of the housing now
commonly used for the cable transformer. The diameter, in fact, need be
no longer than whatever is necessary to
accomodate the connectors; with a
length of two or three inches according
to the number and type of cells and the
mechanical arrangements for their replacement.
For the benefit of those who are unduly impressed by statements which still
appear on some rating sheets for junction transistors to the effect that:
(1) The transistor should not be in-
38
serted into the socket with the power on
or (2) Switching transients should be
avoided; (3) Capacitor discharge surges
should be avoided; (4) The socket should
be designed so that, upon insertion of
the transistor, the collector makes contact last
may be noted that statements of this kind represent little more
than survivals from similar statements
appearing on ratings for contact types.
With currently available junction types
having avalanche voltages usually well
in excess of 50 volts, switching tests
conducted at voltages well below this
value must be run into the hundreds of
thousands before significant changes in
major parameters may be ascribed to
switching alone.
To return to Fig. 5: the capacitor
from base to ground of the input stage
may be described somewhat beyond the
mere statement of its value. At first
ight, it might be supposed that this
value should be several hundred microfarads to avoid attenuation of low -frequency response in view of the 50 -ohm
input. Since such a capacitor would be
by far the largest component in the preamp, it is fortunate for purposes of miniaturization that such is not the case.
klthough called, by precedent, a "bypass" condenser (since it bypasses the
lower bias resistor) it shows up in an
,equivalent circuit as an impedance in
series with Rb and, as such, in the common base circuit its impedance is reduced by the same factor (1-a) as Re,.
Consequently, the effectiveness of this
capacitor in relation to low- frequency
cutoff is increased as if its value were
multiplied by 1 /(1 -a) or (ß +1).
For the marginal case where only a
small amount of gain is required, the
first stage alone will give a power gain
of approximately 11 or 11.5 db with
a corresponding voltage gain (50 ohms
to 1000 ohms) of 18 or 18.5 db. With a
sound pressure level of 74 db at the
microphone, the preamp output in this
case is - 78 dbv. This gain for this stage
is, of course because common -base gain
must be obtained from RL /4Rr and the
load has been reduced to 1000 ohms to
provide the 50 -ohm input with one cell.
The addition of the second stage as
shown results in an over -all power gain
of approximately 28 db-the output
voltage varying according to the value
chosen for the collector load and line
impedance.
-it
Design of Microphone Preamp
Let us now assume that the microphone on hand is of the "high impedance" class. As used with dynamic microphones, this can mean anything from
20,000 to 40,000 ohms, although the
value most often encountered is 25,000.
We will therefore assume:
AUDIO
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AmericanRadioHistory.Com
APRIL, 1956
Martin Block's
Make Believe
\`'
&
Ballroom
Here's how recording tape made with "MYLAR"
solves
a
that "Mylar "*
polyester film gives to recording tape
solved a production headache for radio
personality Martin Block.
In the past, aging and temperature
changes weakened ordinary tapes on
which Mr. Block pre-recorded portions
of his popular program
sometimes
caused them to break on air time. He
solved the problem with tapes made
with Du Pont "Mylar ". They're virtually unbreakable, unaffected by changes
in temperature and humidity, can be
stored indefinitely.
Tapes made with Du Pont "Mylar"
offer you a combination of advantages
never before available in recording tapes.
Besides being unbreakable under normal operating conditions and requiring
The lasting strength
...
AUDIO
problem for Martin Block
no special care in storing, tapes made
with "Mylar" mean longer playing time,
extra economy. With high -strength
"Mylar ", tapes only two -thirds as thick
as most ordinary tape can be used, giving essentially a reel and a half of tape
on one reel.
All leading tape manufacturers now
have tapes made with "Mylar" in their
line. Most leading dealers are featuring
your favorite brand made with "Mylar ".
So -take advantage of all the important
extras found in tapes made with
"Mylar ". Next time you see your dealer,
ask him for a reel or two of your favorite
made with "Mylar".
brand of tape
E. I. du Pont de Nemours & Co. (Inc.),
Film Dept., Wilmington 98, Del.
...
Pont's registered trademark for its brand of polyester film.
Du Pont manufactures the base material "Myla r" -not finished magnetic recording tape
."Mylar" is Du
DU PONT
MYLAR®
POLYESTER FILM
APRIL, 1956
IU POO
AEG.U.S.cT.OfL
BETTER THINGS FOR BETTER LIVING
.THROUGH CHEMISTRY
39
www.americanradiohistory.com
AmericanRadioHistory.Com
Microphone
impedance :
25,000
ohms.
Microphone voltage (open circuit)
:
60 dbv.
Microphone power (into 25,000
ohms) : 10 -11 watts/microbar.
Frequency response: 50 to 10,000
cps.
Amplifier input : direct to grid.
Microphone cable : single-conductor.
Figure 6 is representative of an amplifier adjusted to an input impedance
of 25,000 ohms. Because the resistance
in this case depends predominantly upon
the product of ß and
it is necessary
to obtain the major portion (say, 20,000
ohms) by operating at a rather low
R
emitter current. Alternatively (or supplementarily) the product can be raised
to the required level by increasing Re
with an external resistor. However,
whether the 25,000 ohms is obtained by
reducing the operating current, by increasing the external emitter resistance
or by a combination of the two, the gain
will be about the same for a given beta
in the first stage. The actual gain realized is not of overwhelming importance
because another stage will be required
in any case because with a high source
impedance and a low load impedance
the voltage gain will be considerably less
than the power gain.
For most general- purpose a.f. transistors, maximum beta occurs at an
emitter current of 1.0 or 1.5 milliamperes and, although the peak is very
broad on a linear current scale, the
value will be down about 35 per cent at
100 pa and 50 per cent at 50 pa. As in
the ease of the phono preamp, in lieu of
measuring RC1 Rb and ß at several operating currents and computing the resulting impedance, a simpler and more direct
method is the familiar one of supplying
a known current signal through a resistor much larger than the expected R4
and measuring the ensuing voltage at the
input. Since a 2 to 1 mismatch loses only
0.51 db in power gain and the noise
factor will not worsen appreciably until
the mismatch becomes gross, any value
between 15,000 and 40.000 should be
acceptable.
1.3
.
2N133
a
In
0
RI
adjusted for le
=
100 pa.
R
adjusted for le
=
500pa.
Fig. 6. Transistor microphone amplifier
with an input impedance of 25,000 ohms.
With a type 2N133 having a current
gain of 50 to 100 i a in the first stage
and a 2N132 showing a gain of 70 at
500 pa in the second stage, the power
gain is approximately 40 db, assuming
average base resistance. The voltage
gain (25,000 ohms to 1000 ohms) which
is of greater immediate interest if the
output must work into a transformerless
tube input is less according to:
VG(db) = PG(db)
+ 10 log RL/4Ro = 26 db
If some other output impedance is selected to meet some particular requirement, the second -stage current should be
readjusted if possible to drop about 0.5
volts across the collector resistor. Similarly, if the first -stage current must be
changed from the indicated value to
meet the input impedance requirement,
the collector resistor of that stage should
be changed. The object in both cases is
to obtain the highest possible regulation
factor from the single cell without operating at a collector voltage too close
to the knee of the collector characteristic.
sw
T
1
o
Fig. 7. Common -emitter input stage with
a
very high input impedance.
High -Impedance Sources
Most difficult of all is the situation
where the amplifier is required to work
from a high-impedance capacitive source.
A good example of a particularly difficult case is that of the Western Electric 640 -AA condenser microphone. This
unit, with a capacitance of 50 ppf, is
commonly worked into a cathode follower of at least 200 megohms for sound pressure measurements of 20 cps with
little or no correction and if used for
ordinary a.f. purposes to 3 db at 80
cps must still see 40 megohms. Since
these impedances are not available with
germanium transistors, we may at least
examine briefly the much more common
case of the 500 Aid pickup or microphone.
The common-base connection is, of
course, completely useless and for either
the common collector or the degenerated
common emitter a major cause of the
difficulty is the fact that the bass potential must be fixed by the divider
which cannot be placed in the low side
of the source as in some of the circuits
500 ppl
1
Fig. 8. Circuit of Fig. 7 modified by use
of diode as lower base resistor to pro-
vide temperature compensation.
already discussed because there is no
d.c. current path. In the equivalent circuit, the divider elements are in parallel
with each other as well as in parallel
with the input.
Although in this instance the use of an
input transformer appears to be the obvious and low -cost solution, there still
remains the problem of primary resonance and the necessary correction of
the frequency response in subsequent
stages of the amplifier. Here again the
transformer may be rather large if the
resonant point is made at least an octave
below the lowest frequency of interest.
There appear to be only two possibilities of obtaining the required impedance (3.2 megohms for
db at 100
cps) without the use of a transformer.
Neither is particularly encouraging
they are included in this account only to
illustrate the difficulties involved.
Figure 7 is a common -emitter input
stage with a rather large emitter resistor
and a 45 -volt supply. The input impedance of the transistor is approximately
OR. or 6.4 megohms for 13= 160 and the
same impedance would be available with
a common collector by taking the output
from the emitter and bypassing the collector resistor. There is a practical difference in favor of the common emitter,
however, because here the collector load
may operate into almost any reasonable
value for the following -stage input while
the common collector must work into
something considerably greater than 40,000 ohms to avoid excessive shunting of
the emitter resistor upon which the input impedance depends.
The latter is now 3.2 megohms but
the cost is almost prohibitive. The beta
of 160 (at approximately 55 pa) would
certainly represent some selection but
even more serious is the very poor regulation factor under conditions of collector voltage and current such that a very
good regulation factor is strongly indicated. The entire circuit, in fact, is
scarcely better than if we had used a
betta of 80 in the first place and had
omitted the base divider entirely.
Figure 8 is similar except that the
lower base resistor has been replaced by
(Continued on page 71)
3
AUDIO
40
www.americanradiohistory.com
AmericanRadioHistory.Com
T
-
APRIL, 1956
1
HIGH
FIDELITY
has come of age...
at HARVEY's
AU
DlOtorìum
It is not surprising that America's most modern
high-fidelity store -the one store that completely reflects
-
the many recent changes of trend in high fidelity
should be a creation of the Harvey Radio Company.
Founded in 1927, during the real infancy of radio and
electronics, HARVEY'S grew up with the new industry
learning its new ideas as they were developed and teaching
it some new ideas in turn. Commercial broadcasting,
"ham" radio, public address, electrical recording
and many other new electronic developments became
associated in their earliest stages with HARVEY'S
merchandising program and services.
-
And so it has been with audio. It took HARVEY'S -the
store that sold selected audio components to the pioneer
audio experimenters of the 1930's to come up with the
the 10,000- square-foot Auniotorium, the store where
high fidelity has now, in its modern sense, come of age.
-
Continued on next page
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AmericanRadioHistory.Com
ARVEY
HIGH
FIDELITY
has come of age...
3 great new GARRARD changers!
HARVEY'S was in the high -fidelity
business long before the term "high
fidelity" gained currency. When
those "in the know" began to build
home music systems, more than 20
years ago, from the separate amplifiers, loudspeakers, pickups and
GARRMD
...there's a
now for every high fidelity system
B.I
other components developed for
broadcasting, sound film and public
address applications, HARVEY'S was
there to help them with their selections. When quality audio components for home use assumed the
aspect of a major hobby under the
name of "hi -fi" shortly after World
War II, HARVEY'S was among the
first to carry a complete line. As the
hi-fi movement spread, HARVEY'S
made history with the first audio
comparator panel for side -by-side
ear -testing of hi -fi components.
And now
just as hi -fi is beginning to be regarded as an expected
feature of every American home ...
HARVEY'S is again setting the pace
with the new AUDIOtorium. For the
first time, there is an entire building
on one of the main thoroughfares of
the House of Aud
They're all at Harvey
manual players to
C.
ENDORSED
OUALIrY
THE WORLD'S
FINEST!
PERFECTION!
-
mit undisturbed simultaneous
listening by a number of customers,
eliminating the frequently heard
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high -fidelity stores. The sales staff
of the AUDIOtorium has been selected
for its thorough mastery of the
technical end of high fidelity. Its
recommendations will apply to complete, packaged hi-fi systems as well
as individual components.
The entire concept of HARVEY'S new
AuDiotorium is based on the premise
MIR ATWINe rtridge
Newest Advance in
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Cartridge consists of
two Independent car-
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New York City devoted exclusively
to the needs of the hi -fi shopper and
outfitted in the streamlined style of
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Nothing has been spared to make
the AuDiotorium the nation's outstanding hi -fi showplace. Some
15,000 feet of wire went into the
construction of the AUDiotorium's
three huge new demonstration
panels, designed for instantaneous
switching between endless thousands of possible high -fidelity combinations selected from more than
350 basic components all of them
pre- tested by HARVEY's experts to
meet the HARVEY standard.
Separate sound -proofed demonstration studios at the AUDiOtorium per-
tridges, for
NEW
MIRAPHON XM -110A
It', Automater!
MANUAL RECORD PLAYER
MIRACORD XA-100
TRANSCRIPTION -QUALITY FEATURES
Constant.Speed 4-pole motor
Rubbermatted, balanced turntable
Special
spring mounts
Plug-in head
7 -speed
drive
Ball -bearing mounted tone arm
...PLUS ALL THE PERFORMANCE -PROVED
BASIC RECORD -PLAYING FEATURES OF THE
WORLD -RENOWNED MIRACORD SA400!
Shipped completely assembled with plugs and leads attacked ready fer operation
with DE RPX-050A Cartridge
XI. 7.50
$44.50
OYal- Purpose,
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USHBUTTON
With "MAGIC WANG"
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-
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Amaring wide -range
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Perfect
Instant
Replacement
of Styli!
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output
frig
RECORD CHANGER
LP
Standard r ecord s,
mounted back to
back in a turnover
Higher
Easy mount.
tits any tone
SPINDLE
TWO in ONE
Precision Instrument
Pushbut-
ton Automatic Changer, Pushbutton Manual
Player
'Magic Wand" Spindle intermixes
ID" and 12" records
Pushbuttons for Repeat, Pause, Filter, Start Beautifully Styled
Compact
Shipped completely assembled
with all plus and leads attached, ready for
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with GE RPX -050A Cartridge
$74.50
(67,50
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MST-2D
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over Cartridge with two Sap-
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_.
*4-5.00
$22.50
MEMBEcR
tmtttntt
The GRAY High Fidelity Turntable, Built Like
a
high fidelity turntable, like a battleship, must be rugged, heavy,
... yet easy to control. Both must he completely dependable, smooth in performance, andyuiet in operation.
Imagine the pound by pound advantages
found only in Gray's turntable assembly
designed exclusively for High Fidelity
recordings:
A i.," steel motorboard for complete
A
massive
Battleship!
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MAW,
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rigidity.
An 18 lb. flywheel action turntable with
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A turntable and motorboard assembls
that is lU times the mass of the motor,
prevents the transference of all mechanical
disturbance.
a
that the modern high -fidelity
shopper wants full- fledged retail
service, just as if he were purchasing furniture or clothing or automobiles. Typical big-departmentstore features such as an efficient
and cheerful adjustment, exchange
and refund service
an extra large inventory of spare parts and
accessories ... shipment on the same
day as an order is received are a
matter of course at HARVEY's. High
fidelity is no longer just an interesting technical hobby but an important
part of American living -it has
come of age . . - and HARVEY'S, as
always, is meeting the new trend
head -on at the new Auntotorium.
-
...
-
-
... from
professional turntables,
each unit, in its class ...
Audux
H i-Q7
Magnetic Pickup Cartridg
In music listening quality is everything ... The
diamond AUDAX Hi -Q7 has it to a
degree not equalled by any other pickup
But,only YOU can tell what sounds
best. That is why AUDAX is today in the home of practically every Maestro. Come
in, HEAR it yourself
there is NO other way.
Also see the new AUDAX compass -pivoted arm and the remarkable new AUDAX
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...
-
Hi -Q7 Chromatic Diamond Cartridge
Compass- Pivoted Arms (less cartridge)
www.americanradiohistory.com
AmericanRadioHistory.Com
$4750
From $32.00
.
ÿ
for the Finest
in Audio Equipment
AUDIO
COMPONENTS
,VeWec?iìuy
%02
Engineer's choice: ESL
Record manufacturers, radio stations, and audio engineers are switching to the sensational new ESL Professional and Concert Series electrodynamic cartridges. Here's why:
Inherent linearity of performance with ESL's exclusive D'Anossval movement
2) Frequency response exceeds human hearing: s 6 to beyond 30,000 cps
3) Extraordinary lateral compliance: 6.8 x so-6 cm /dyne
4) Minimal dynamic mass at stylus:.00s grams
Jay4
ideh
aieeac Ysfaem4
!MN?.
1)
5)
6)
7)
8)
Highest fidelity: distortion immeasurable with finest instruments
Least hum pickup and needle talk: no resonances within audio range
Superb, trouble -free performance
Record and stylus life is greatly prolonged by the ESL
No matter how respected nor how recent your pickup may be, you're missing plenty until
you switch to ESL -the world's most advanced phonograph cartridge.
PICKERING
/uwa/vi_PICKUP
The PICKERING "Fluxvalve" Turnover Pickup is
designed for use in the finest professional
equipment. With this revolutionary new pickup,
tracking distortion, record and stylus wear are
reduced to new low levels. The "Fluxvavle" provides the first flat frequency response beyond
20 kc. and features replaceable styli from three
mil down to less than one mil radii.
With -mil diamond and 2.7 -mil sapphire $4950
1
C:®
-11F
chain is no stronger than its
weakest link ... a fleet is no faster
than its slowest ship ... and a hi-fi
system no more capable of perfect
reproduction than its least perfect
component. Any and every audio
component adds some distortion to
the signal it reproduces - the best
units in just barely measurable and
scarcely audible quantities, the more
modest units in sufficient amounts to
be audible, though still quite acceptable, to sensitive ears. A nearly
distortionless component would be
wasted on a system having other
components that produce considerably more distortion. For example,
it would make very little sense to
use an amplifier costing over $300
to drive a nice little $20 eight -inch
speaker. The resulting sound would
be nearly indistinguishable from
that of a good $60 or $75 amplifier
in conjunction with the same eight inch speaker - which can be very
agreeable sound indeed.
There is very definitely a hi -fi system for every ear and budget, but
it must be properly matched -and
that's where HARVEY'S audio comparator panels and audio consultants comb in. It is, of course,
desirable though by no means
absolutely essential - to have some
idea of the process of selecting suitable audio components even before
coming to HARVEY'S AUDlotorium.
Hence the following brief pointers.
A
-
WALCO
WALCO
L:UG (
STATI -CLEAN
unti- static record
spray; eliminates de-
«
struetive dust. Less
nit
PRODUCTS
usi40
3,y
than a penny per disc.
WALCO
-
and
dum
st
; protect
ord st
against dust, mois
turn, fingermarks.
WALCO
LfpK7
Balanced Seed In
Round Brush
Accurate
Camel's hair record
brush; clips to ton
Revel
PIOtwe
Plastic protective rec-
An
brushing away
ahead of the
needle.
Wal co
PHONOGRAPH NEEDLES
SAPPHIRE
DIAMOND
-
turntable
level; precision stylus
pressure gauge. Elim,
cater excessive rec
ord wear.
The World's
OSMIUM
Finest
THE FISHER
view of the enormous accumulated
repertory now available on high fidelity long- playing records. The
first requirement of successful record
reproduction is that the record be
turned at an absolutely constant
speed -331/3, 45 or 78.26 revolutions
per minute with the barest minimum of fast -slow -fast fluctuations
(wow and flutter) or random low frequency vibrations (rumble) and
with complete freedom from extraneous noises of any type. Transcription turntables are designed with
this, and only this, end in view and
can therefore be constructed with
-
MODEL FM -40
with all that the name
FISHER FM Tuner
for only $99.50. Through the years it has been
implies
our policy to bring equipment of FISHER calibre within the
reach of the widest possible audience. Rarely has that objective
been more spectacularly attained. For the FM -40 represents
one of our greatest values in almost two decades. It is a superb
combination of engineering excellence and dazzling performance at moderate cost. Its specifications, conservatively outlined
below, are your best index to the quality of this instrument.
Professional FM Tuner Onty $99.50. Mottos. es Ilene. Cabinet: $14.95
instruments.
For the innumerable people who insist on the convenience of an automatic record changer, there are now
a number of de luxe models of very
high performance. The more expensive of the new Garrard changers
and the Miracord XA -100 fall into
Continued
H
-
EERE IT IS, a
OUTSTANDING FEATURES OF THE FM.40
Sea Meter for micro- seeurate tuning.
Uni3 uy for 20 db of quieting.
form empanne, ±I db, 20 to 20,000 cycle.
encode RF stn {e.
3 IF sages and
2 outputs: Detector/Multiplex plus caSelf -powered.
thode follower. 8 tubes.
Brown-and- gold brushed brass panel.
sui: 12s4' wide, 4" high, 8 %" deep.
SHIPPING WEIGHT: 15 pounds.
One of the most important high fidelity program sources today is
the phonograph record, especially in
maximum ruggedness, simplicity
and precision. They have always
been and remain the perfectionist's
choice. One look at the Garrard 301
or the new Gray turntable will tell
Professional FM Tuner
eitivity:
The Phonograph Assembly
.
-
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AmericanRadioHistory.Com
the story. They are precision
l
HARVEY
the House of Audio
AUDIO
COMPONENTS
Yelechny
this category. Both of these manufacturers also make a manual record
player. The final choice depends on
the purchaser's type of record collection, technical demands and budget. Wow, flutter and rumble should
be carefully checked for in any
event they can be quickly spotted
in listening tests. Wow affects the
pitch, and flutter the tone quality
of reproduced music; rumble blapkets the lowest notes at high volume
levels. All three should be conspicuous by their absence in top -quality
units.
The other all- important component
to come in contact with the record is
the pickup cartridge. Its function is
to translate the zig -zag of the record groove into an electrical signal
corresponding to the recorded sound.
To do this without altering the quality and balance of the sound is one
of the most difficult jobs in audio,
and as a result there are greater
audible differences among cartridges
of different manufacturers than
among all other hi -fi components,
with the single exception of loudspeakers. A good high -fidelity pickup should respond with equal
sensitivity to any part of the audible
range of frequencies -in other
words, it should have "smooth" frequency response. Its stylus should
have as much side -to -side "give"
(compliance) as possible, so that it
can closely follow sudden sharp turns
in the record groove. These characteristics show up in listening tests
smooth frequency response results
in a natural overall sound quality,
without exaggerated highs, lows or
middles; high compliance makes for
realistic reproduction of "transients," the sudden, sharp, fleeting
sounds that begin a drum tap, cymbal crash or string pizzicato.
The finest pickup cartridges on the
market today are with very few exceptions of the magnetic type in
each the motion of the stylus is converted by the cartridge into an electrical signal by means of a magnetic
generator system. Most of the top
cartridges such as the Audax, the
new Miratwin and the Pickering
'Fluxvalve'- utilize a magnetic design of the so- called variable
reluctance type; a few other outstanding cartridges such as the
Electro -Sonic series -are of the
moving -coil type. All of these cartridges have high compliance and
function best in conjunction with a
high-quality, manually operated
transcription pickup arm. The Audax and the Miratwin may also
be used in well- designed record
changers; the Pickering 'Fluxvalve'
and the Electro -Sonic 'Concert' and
'Professional' are generally used
only in transcription arms -the last named only in the special arm it is
sold with. The Audax may also be
had with its own special arm.
In choosing a pickup the thing to
listen for is, above all, natural sound
-the type of sound you would hear
at a live concert. Your HARVEY audio
continued
(3-faired by
1-(arvy as
"'uncktc,s1-íana6y
-
PRECEDENT
Features:
Micro -Meter for precision tuning
-
on
FM
and
Dual limiter and discriminator circuit
Better than 1.5 av FM sensitivity for 20 db
quieting
Continuously variable amplified AFC
2 -stage IF amplification for broad and sharp
AM
10
KC filter
Better than 2av AM
plus
sensitivity
3 inputs and 2 cathode -follower
outputs
Independent equalization controls provide 5 roll -off and 5 crossover positions
AM
FM-t
Model
-
TUNER
AF -860
with built -in phono preamp and dual tone
controls. Offers you the ultimate in FM and
AM reception with complete facilities for
record equalization plus bass and treble
Cabinet Optional
1 V
tone controls.
-
-
TM tuner
ever mack
9
Cordovan Mahogany $15.95
Limed Oak 16.95
esos cabinet
Mark 10 Integrated Amplifier and Control Center by
BROCINER
_
... as
February AUDIO Magazine says: "In
a field
which includes dorcns of medium-powered amplifiers,
there is always room for one more,
particularly when its specifications and performance
come up to the standards exhibited by the Brociner
Mark 10. On the whole, the amplifier
is designed along good engineering principles
and does not rely on 'gimmicks'
"ASTONISHED
for its performance!"
ME."
-B. H. Noggin, "The Nation"
$75.00
net.
-
marantz
Power Ampbbfer $189
A power amplifier
which meets the unusually
high performance
standards
set by the
maranIz
control pre`amplifier-equalizer
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Preamplifier $162 (with cabinet)
the Finest in Audio Equipment
AUDIO
COMPONENTS
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he art of
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passed
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TI
s
consultant is in the best position to
advise you as to the best pickup
selection for a completely balanced
IIt4nfo9h
MC-60
$198.50
system.
True high -fidelity record reproduction also depends to a significant
degree on the condition of the record.
The grooves must be clean and free
of deformation due to wear or careless handling. Record cleaning and
preserving accessories, such as those
made by Waco, are therefore very
useful items to have on hand.
The Radio Tuner Section
Radio broadcasts are another im-
CLEAN, BRILLIANT
portant source of high -fidelity
90-111
<0.1.11r2
H. H. SCOTT SOUND
211
CONTROL
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Veal
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A SUPERB HIGH -FIDELITY RECEIVER FEATURING:
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sensitivity 2.5 µv for 30 db quieting on 70 -ohm Input
Harmonic distortion under 0.5% at rated output
Frequency response within 0.5 db, 16- 30,000 cycles
"Zero-In" precision tuning meter
FM -AM
FM
RR550
d
INN
CH
;is
En,-
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TIM,
5- position record equalizer,
famous Bogen Loudness Contour
Selector, speaker selector switch, high and low filter switches,
bass, treble, volume, tuning, and function selector controls
Bogen Variable Damping-with new light indicator
Inputs for phono, tape, other program sources
Beautiful, compact styling
Simply connect the RR550 to a loudspeaker and enjoy the very
finest in musical reproduction.
luxe FM -AM Receiver
&
legs
$220.00
8.00
tone
when high fidelity stopped being machinery
and became a new kind of musical instrument!
The Festival combines all the electrical elements of a
de -luxe system on one well organized, compact chassis.
It is at once a sensitive AM -FM tuner, a professional
quality preamplifier and a 30 watt ultra linear power
amplifier. Each element is of highest quality and they
are mated for optimum performance. This is no glorified radio, but a system which commands the professional's respect. With a suitable loudspeaker and record
player a high fidelity system of incomparable performance and unique good looks is yours.
Optional Model DC cape.
$19995
Slightly higher
in
hywN
Ask for technical data sheet D5D1100 for complete specifications.
harman kardon
IN COMP OMatFD
Westbury,
L. 1., N. Y.
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aye
listening fare. FM programs have
inherently greater fidelity than AM
broadcasts, in addition to freedom
from "static" and other interferences characteristic of AM. In urban
areas, most of the major AM stations duplicate their programs on
FM, so that it is not always necessary to incorporate both AM and
FM reception in hi -fi systems.
Where there are no FM stations,
high- fidelity AM reception can come
close to FM quality if the best equipment is used.
It is the function of the high-fidelity
tuner to take a radio signal out of
the air and convert it to an audio
signal of the same type as the output
signal of pickups, which can then
be fed into the next component in
the "chain" that makes up the hi -fi
system. The finest FM tuners have
lower distortion, Iower background
noise content and wider audio frequency response than the more
modest units, but perhaps the principal difference among FM tuners
is in sensitivity, which is the ability
to respond with full fidelity to weak
radio signals. Those who live at a
distance from FM transmitters, or
else in the few weak -signal areas
near transmitters, should invest in
a highly sensitive FM tuner. AM
tuners exhibit similar differences the best have somewhat better frequency response, lower distortion
and more sensitivity than the next best.
For those with Rolls Royce tastes.
there is an FM -only tuner which is
entirely in a class by itself - the
REL 'Precedent.' It is the most uncompromisingly designed, most
sensitive, most distortion -free and
by far the most expensive FM tuner
available. In an altogether different
price category but retaining many
de luxe features is the new Fisher
FM -40, an FM -only tuner with sufficient sensitivity and fidelity for
very high -quality hi-fi systems. In
still another category is the Pilot
AF -860, a combined AM -FM tuner
of excellent sensitivity and fidelity,
which incorporates on the same
chassis a very good preamplifier.
The
Amplifier System
This brings us to another vital link
in the high -fidelity system the amplifier. It is the one component connected to all other components in
the system. Its basic function is to
continued
-
the House of Audio
HARVEY
AUDIO
COMPONENTS
.VWee/iiw
Illll\
\I. COMA writ.-.
"Atlantic:
in
"1 could not quite get the AR woofer and the Janszen tweeter into
phase and balance one with another, though there were tantalizing hints
that, could I hare done so, I might have had at my disposal the best loud speaker system I had encountered."
The problem of matching the AR and Janszen speakers has now been
take the relatively low -level signals
produced by other components like
the pickup or the tuner and raise
these signals to a sufficiently high
power level to "drive" the loudspeaker. It must do this without
distorting the signal in any way
whatsoever. This is a reasonably
simple and straightforward function, which can be accomplished to
near -perfection by present -day
electronics. Nearly all of the highfidelity amplifiers made available
within the last three years are
therefore remarkably good, but
there are still important differences
as regards power output, flexibility
and other factors.
All hi -fi amplifiers consist of two
sections the preamplifier section
and the power amplifier section.
These are built on two separate
chassis in the more elaborate amplifiers and on the same chassis in more
compact designs. The preamplifier's
function is to apply certain corrections to the signal while giving it its
first "boost"-the corrections being
necessary not only to adjust bass
and treble response to suit the listener's ears and room acoustics
but also to "equalize" the "recording
characteristic." The latter is an unavoidable but controlled "twist" in
the bass -treble balance of recorded
music, which must be "untwisted"
in the playback. The degree of flexibility and versatility with which a
preamplifier can apply these corrections will determine its size, complexity and price and it is here
that one of the greatest differences
among amplifiers will be found. As
far as the power amplifier section is
concerned, its sole function is to step
up the power of the signal passed on
by the preamplifier. The maximum
undistorted power available from today's amplifiers may be anywhere
from 10 watts to 60 watts or more.
The advantage of a high- powered
amplifier over a low- powered one is
not so much a gain in volume, which
is not very great, but rather the
ability to drive the bass end of any
loudspeaker system to full output.
Ask HARVEY'S audio consultants
about your own requirements. The
things to listen for in evaluating
amplifiers are, above all, clarity in
heavy bass passages and a "sweet,"
unstrained quality on the high end,
especially in loud string passages.
For those who want a very compact
single- chassis amplifier with moderate but fully adequate power and
practically every feature currently
found in top designs, the Brociner
'Mark 10' is hard to beat at its low
price. One step up on the price scale
is the larger, more powerful but still
compact Scott 99 -B -a 22 -watt
single-chassis job with complete controls. In the no- holds-barred category are two of the world's finest
power amplifiers, the 60 -watt McIntosh and the 40 -watt Marantz.
These are for perfectionists. The
latter is complemented by the 'Audio
Consolette,' a particularly fine and
elaborate preamplifier.
sohed through cooperatise efforts of the Iwo manufacturers. No
external erossoser network is needed, and grille cloths and wood
finishes are the snnn-, Suggested driing power, at least 30 walls.
AR -1W acoustic suspension woofer:
continued
\SZE\
-30 push -pull electrostatic tweeter:
1
189.00
145.00
Walnut
Mahogany
Birch
132.00
Utility
161.00
Walnut
Mahogany
Birch
154.00
Utility
145.00
Literature
ACOUSTIC RESEARCH, INC.
184.00
179.00
JANSZEN LABORATORIES, INC.
on request
The Purest Voice for a Fine Music System
-
-
J
-
quality of its associated equipment, the more vital is the role
for it is the speakers that, in the end, determine
of the loudspeakers
the listening ease and realism of your music system as a whole. A Bozak
Speaker System in an infinite -baffle mounting, with worthy associated equipment, will assure you the closest approach to realism and enjoyment that
grows through the years. Each Bozak, from the B -207A ($83.85
without enclosure) to the magnificent B -310, represents in its
class The Very Best in Sound.
The higher the
ASK FOR NEW
yoke GUIDE
TO HIGH -FIDELITY LOUDSPEAKER SYSTEMS
Tells how to choose
any space,
and why
budget.
and
decor
-for
ougtz -in r Speakers
Tweeters
Components
NEARING IS BELIEVING.
TB -1
1P312
1P312
12" WIDE -RANGE SPEAKER
549.50
r
/
TB -1
Lorenz Wide -Range Speakers and Components are
adaptable to and improve all sound systems! 75
years of Lorenz craftsmanship assures crisp, accurate sound reproduction, regardless of budget or
space requirements. Years -ahead Lorenz engineering assures you complete musical satisfaction.
you'll underLet your ear be the final judge
stand why ..
...
.
TB
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TWEETER ASSEMBLIES
Coaxial L Diaslal
L TB -2
Fit across any 12" speaker
TB -1
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10.2
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$21.69
MOST PEOPLE WHO LISTEN TO LORENZ, BUY LORENZ!
1P31í.112" COAXIAL SPEAKER
LP208
B" WIDE -RANGE SPEAKER
$22.50
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With
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LP312 -2 12" 01 -AXIAL SPEAKER
with NP -1 Crossover x71
Pass Filter
79
Nigh
for the Finest in Audio Equipment
.f kiii'ay AUDIO
Fortunately, the photographer can use his
art to describe his reaction to a University
speaker. We can use only words, yet find
them so inadequate. How can mere words
convey the quality of concert -hall realism...
or describe the way University captures the
naturalness of the bassoon, the richness of
the clarinet and the brilliance of the triangle'. They can't! Yet University speakers
and systems do have all these.
Whatever your taste, P S E University's
,Aer?'
(
1
1.
When
it
sounds like this
...instead of this ...
Progressive Speaker Expansion Plan makes
it possible to start an excellent basic system,
at low cost, and add to it later, while enjoying immediate listening satisfaction. Thus.
your speaker or speaker system can never
become obsolete.
IT'S TIME FOR
THE ULTIMATE IN LOUDSPEAKERS AND SYSTEMS
Whether you plan to build a system or
hull it complete, come in and ask us about
University's P S E -their famous do-it.
!ourself "KwiKit" speaker enclosures-and
their incomparable speaker systems. FREE
literature available on request.
COMPONENTS
noteworthy trend in hi-fi is the
ultra -compact, unified system, and
A
it is best exemplified by two unusual
units - the Bogen RR -550 and the
Harman -Kardon 'Festival.' Both of
these incorporate a high -class AMFM tuner, a versatile preamplifier
and a large power amplifier - all on
one chassis. Just hitch up a speaker
and out comes the music.
The Loudspeaker System
The loudspeaker is perhaps the most
important and certainly the most
controversial of all the components
to be selected for the hi -fi system.
Being the last link in the chain
the component we actually "listen
to "- it can distort a perfectly distortion -free signal fed to it by all
the preceding components. Having
the most complex and least well understood function of any audio
component to convert the electrical
impulses furnished by the amplifier
into sound waves -the speaker can
be (and is) designed in as many
ways as there are designers. Choosing a loudspeaker is therefore
purely a matter of listening the
speaker that sounds most like your
recollection of actual, live music is
the speaker for you. To be perfectly
honest, though the more expensive
sound best to most people.
If you want a simple, moderately
priced speaker system of very high
-
elf
3
-SPEED TAPE
RECORDER
The Bell model RT-75 is the ideal machine for
most recording requirements since it operates at
71/2, 33/4 and IN ips. Up to eight hours of recording are possible on a single tape reel, making it
ideal for business meetings, etc. Full -range response for music recording at higher speeds. Fast
forward and rewind, control- button speed -changer
with automatic equalization, three inputs, two outputs, self- contained amplifier and speaker, microphone, attractive carrying case with ample storage
for extra tape, mike, reels, cables, etc. Write for
complete data and full -color photograph.
Those who demand the finest in "living reproduction" always choose tell.
-
-
-
quality, try the new Lorenz
ffagnecord
NEW
RECORDER
JUST ARRIVED
-
-
One of the finest precision -built tape recorders of the century
with
new VU meter
power amplifier, speaker and microphone
in handsome genuine cowhide carrying case. For home or
away at work or ploy.
7
-
-
$(00
-
speakers. If you want to invest only
a small initial amount into an excellent speaker and later expand it
into a superlative system, you would
do well to investigate the University
line. Another justly famous line that
includes all sorts of speakers from
modest -but -good all the way up to
price -no-object-but-sensational is
Electro- Voice. Bozak also has an
enviable reputation among hi-fi enthusiasts for making moderately
priced speakers that sound fine as
well as large systems that sound
terrific. And for those willing to try
something really new and different,
there is the combination of the
Acoustic Research low -frequency
unit and the new Janszen electrostatic speaker an extemely compact, smooth and wide -range system.
-
The Tape Recorder
HARVEY has a
complete line
of Cabinets
to meet any
Component
Requirements
www.americanradiohistory.com
AmericanRadioHistory.Com
The time has come when no hi-fi
system can be considered really complete without a tape recorder. The
best pre- recorded tapes often sound
even better than the best records
and home recording can open up entirely new areas of satisfaction to
the hi -fi enthusiast. Fine music recorded off the air from live broadcasts can be built into a unique,
individual tape library. The new
Magnecord 'Citation' should be
investigated by everyone shopping
for a de luxe tape recorder it is a
unit with very high- quality features
at a surprisingly reasonable price.
The Bell RT -75 should satisfy the
needs of all those who want a more
modestly priced unit that still retains the features expected in a
high -quality tape recorder.
-
You get more than just good components
... when you buy Hi -Fi at
o
o
AUDIOtorium
HARVEY's
High fidelity means more than
just a number of separate, highquality audio components suitably connected. It is possible to
spend many hundreds of dollars
on an assortment of loudspeakers, amplifiers, pickups and
other components -and end up
with a system that is good for brand -name dropping but
most uncomfortable to listen to. It is also possible to
spend what is a reasonable sum to your purse and obtain
immediate and lasting aural delight from your system.
It's how, where and with whose help you select the
components that makes the difference ...
At HARVEY's new AUDIOtorium, you will be met by someone from HARVEY'S unique staff of audio consultants
all of them members of the Audio Engineering Society
-and briefed on the possible component choices for your
kind of listening room, musical preferences, hearing
characteristics and budget. Then you will be escorted to
one of HARVEY'S soundproofed, living -room sized demonstration studios and asked to listen to and compare the
components under consideration. HARVEY'S three huge
demonstration panels designed for instant switching
from any one of many hundreds of components to any
other and for hooking up many thousands of combinations will enable you to ear-test as many complete
systems, part by part or assembled, as you wish. And
when you have made your choice, you will be given the
-
-
-
opportunity to make your purchase on a time-payment
plan or to trade in used components against your new
equipment.
All of this in a spacious, streamlined, relaxing decor
reminiscent of the top department stores and specialty
and that's not all. In your own home, your
shops
enjoyment of your new equipment will be increased by
...
the secure knowledge that HARVEY'S integrity and know how follow every sale. Components sold at the
AuDlotorium are pre-tested by HARVEY'S experts and
a leading manufacturer's reputation stands behind each.
You buy the finest and most complete high -fidelity service in the world ... when you buy hi -fi at HARVEY'S new
-
AUDIOtorium.
t
HARVEY
RADIO COMPANY, INC.
1123 AVENUE OF THE AMERICAS (SIXTH AVENUE) AT 43RD STREET
YORK 36, N. Y.
www.americanradiohistory.com
AmericanRadioHistory.Com
Udson 2-1500
JUdson
Power Amplifiers
An analysis of power amplifiers -their function,
important characteristics, and how they work.
SOUND -Chapter
8
EDGAR M. VILLCHUR
NOTE: While Chap. 6 appeared in the
March issue, this is actually Chap. 8 as
it will appear in the book of this series
to be published this coming September.
Some rearrangement of chapter numbers
will be made. En.
the term "power
amplifier" refers to the output stage
of an amplifier. This stage receives
signals of relatively high voltage but
negligible power, and releases signals of
the same wave form but of sufficiently
high power to drive a loudspeaker. In its
less restricted meaning, however, the
term is used to represent the entire group
of stages (other than preamplifier and
control stages) which are housed on the
power- amplifier chassis. The chassis
usually includes a general -purpose voltage amplifier or amplifiers, a phase
splitter, and the output stage itself, plus
a "power supply" for all of these stages.
A detailed description of the functioning of different audio circuits is not
considered to be within the scope of this
work. Rather it is intended to provide
a general understanding of the function
and working of the stages listed above.
STRICTLY SPEAKING,
Voltage Amplifiers
A typical commercial power amplifier
(the term used in the free sense as described above) is designed to produce its
Acoustic Research, Inc., 25 Thorndike
St., Cambridge 41, Alass.
GENERAL
AMPLIFIER
PIJRPOS
VOLTAG
PHASE
SPLITTER
AMPLIFIER
15v.
os.
03mw
I.
Fig.
3m
VOLTAGE
GAIN
8
-1.
10
+
VOLTAGE
GAIN =3
+
POWER
GAIN
=
30,000
Block diagram of voltage and
power amplifiers, showing voltage and
power gain.
AUDIO
rated power output at an input signal
of one -quarter to one-half volt. But the
output stage proper needs a much higher
signal voltage at its grids to be driven
to its rated output. Most pentodes, under
their usual conditions of operation require signal voltages in the range between 15 and 25 volts for full power output, and a triode such as the 6B4 requires as much as 70 volts. The amplifier
must thus provide the facility for amplifying the relatively weak input voltage,
a characteristic called voltage gain. With
an input signal of 1/4 volt, and the requirement that a driving signal of 20
volts be applied to the output stage
grids, a voltage gain of 80 must be
available.
A limited amount of voltage gain can
be secured from a step -up transformer,
but it is impractical to use transformers
for large amounts of voltage gain ; this
gain must be provided by one or more
vacuum -tube stages in the amplifier. The
difference between voltage and power
gain should be clearly understood : the
amount of voltage gain in or preceding
the amplifier has no bearing on its power
capabilities. Once the input signal voltage has been increased to the required
amount, further voltage amplification
will merely serve to overdrive the output
stage into the distortion region.
A block diagram illustrating the difference between voltage and power gain
appears in Fig. 8-1. The voltage amplifying stages provide a total voltage gain
of 30, so that the input signal is increased from 1/2 volt to 15 volts at the
output stage grids. The power at this
point, however, is only of the order of
a milliwatt, one -thousandth of a watt;
the power gain of the first stages has
been incidental.
The output stage of Fig. 8-1, on the
other hand, supplies real power gain,
and can drive the loudspeaker with 30
watts. The power gain available has
thus been thirty thousand, from .001
watt to 30 watts. Any voltage gain in
the output stage is incidental : if we
measure the output voltage at the plates
of the tubes we will find a moderate gain,
while if we measure the output voltage
at the speaker itself we may, depending
on the impedance of the speaker, find
that there has actually been a voltage
loss.
Voltage amplifiers and power amplifiers differ in quantity rather than
quality. Where the signal output must
have high voltage but does not need appreciable power, a vacuum -tube circuit
such as that illustrated in Fig. 8-2 is
used. The input signal causes the electrical charge on the grid to vary, in step,
which in turn varies the current flow
through the tube and through the load resistor RL. This variation of current
through RL necessarily creates the same
pattern of variation in the voltage
"drop" across the resistor. Since the
greater the drop across the load resistor
the smaller the voltage appearing across
the total output (shown as VOLTAGE
ouT), the signal output of this stage of
amplification is reversed in phase, that
is, instantaneous voltage peaks are reproduced as troughs, and vice versa.
Although power amplifiers do not
usually have resistive loads, it would not
be possible to tell, from Fig. 8-2,
whether the circuit was that of a power
amplifier or of a voltage amplifier, without knowing the tube used and the circuit component values. Tubes designed
for voltage amplification have limited
maximum current flow, and are used in
O
O
ó
Fig. 8 -2. A
general purpose voltage
amplifier. Varying current through the
load resistor R, creates the output signal
voltage, which has been amplified and
reversed in phase relative to the input
signal.
49
APRIL, 1956
www.americanradiohistory.com
AmericanRadioHistory.Com
AMPLIFIER
>TAGE
¡
HAMPLIFIER
STAGE
h
Fig. 8 -3. Two types of vacuum -tube distortion. (A) Distortion due to saturation
(B) Distortion due to cut -off.
conjunction with circuit values which
provide the desired voltage gain, under
the required conditions of bandpass
(range of frequency response), distortion, and absolute values of signal voltages that must be handled.
The proper functioning of a voltage
amplifying stage involves intelligent design and layout rather than expensive
parts. Cheap parts may indeed interfere
with optimum performance-capacitors
may be leaky, resistors noisy or inaccurate in value -but the cost difference
in going to high quality parts is normally
measured in cents rather than dollars.
Vacuum -tube Distortion
Although vacuum -tubes do a fine job
of amplifying without distortion they
are not perfect, especially when high
powers are involved. Let us follow a
simple sine -wave signal through the
vacuum -tube to see how it can be changed
from the original during the process of
amplification.
When the signal on the grid changes
in the positive direction the current
through the tube and through the associated output circuit is increased. The
more positive the instantaneous value
of the input signal the greater the current. Now there is obviously a limit to
the amount that the current can increase.
After the current has been driven to
this limit (saturation), no further increase of positive input voltage will increase the current flow. This condition
is illustrated in (A) of Fig. 8-3, in
which the input voltage covers too great
a range, in its positive peak, for the
current to follow accurately. Further,
the picture is not in simple black -orwhite, where the tube is either saturated
or not. Before complete saturation is
reached the changes in current flow begin to lag the changes in voltage, so
that distortion of a less graphically obvious nature is introduced.
A similar condition exists on the negative peaks of the signal. The smallest
amount that the current flow can be reduced to is zero (cut-of), and if the input signal continues to go more negative
after cut-off has been reached, the value
of current flow in the tube is helpless to
follow. This is illustrated in (B) of Fig.
8-3. Here, again, distortion of a less
drastic nature begins to introduce itself
before the actual cut -off point is reached.
In order to minimize the distortions
described above, the operating point (an
index of the no- signal current flowing)
is chosen carefully, so that maximum
current swing is allowed. The operating
point is determined by the value of a
fixed negative voltage applied to the
grid, called the bias voltage. The valve
of input signal is then limited to the
non -distorted regions of operation.
The wave -form distortion that we
have been describing can be analyzed
into spurious harmonic components, at
frequencies which are integral multiples
of the original, and is thus called harmonic distortion.
Push -pull
Operation
Certain elements of the distortion
introduced by vacuum-tubes are reduced
or eliminated by using two tubes in a
circuit configuration referred to as push pull.
A close analogy to push-pull operation
can be constructed, using a situation in
which a person is engaged in the task
of sawing through a log. Let us consider
his back-and -forth motion analogous to
the up-and -down current changes in the
vacuum -tube, and let us further consider
that the condition of no distortion is
represented by a back -and -forth motion
in which the saw is pushed forward
from its neutral position (operating
point) exactly the same distance as it is
pulled backward from this position.
It would be conceivable that, for one
reason or another, the operator of the
saw cannot push as hard as he can pull,
and that while he pulls the saw back a
foot the best he can do on the push, with
the same maximum effort, is half a foot.
We will use this condition to represent
Fig.
8
the fact that the tube current flow can
follow the direction of the input voltage
on the increase, but is unable to do so
in the negative direction due to cut -off
characteristics of the tube.
We now introduce a handle at the
other end of the saw, and a second
woodsman (subject to the same limitations on the force of his push relative to
that of his pull), who pushes when our
first operator pulls, and vice versa. What
will happen? Each motion of the saw is
subject to two unequal forces, a pull
from one direction and a lesser push
from the other, but the sum of these two
forces will be the same for each direction
of motion. The saw must then move the
same distance coming and going. It is
being operated in push-pull.
In the case of our tubes, the total output current during each half of the
cycle is made up of two parts, one full
(corresponding to maximum current
flow in one tube) and one incomplete
(corresponding to operation of the other
tube past the cut-off region), as illustrated in Fig. 8-4. An analysis of the
operation of a push-pull stage will show
that, with perfect balance between the
two halves, the part of the distortion
that is eliminated is that represented by
spurious even harmonics only. It is
possible to take advantage of this fact
by choosing the operating point of the
tubes to produce very low harmonic
distortion, at the expense of allowing
higher even harmonic distortion, and
then to cancel out spurious even-order
harmonics by push -pull circuitry.
The force of each of our sawyers was,
from the point of view of time, applied
out of phase one with the other. But
these forces were also applied to the
saw out of phase from the point of view
of direction. There were thus two phase
reversals, and the forces combined to
create a final power equal to the sum
of the separate parts. Similarly, each
of the tubes in push-pull are driven out of- phase, and their individual outputs
are out -of-phase from the point of view
-4. Combination of two distorted
signals in push -pull operation to create undistorted output.
AUDIO
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APRIL, 1956
6,6eri
erekk,
teø'*# jenen...TRIAXIAL
ífß
ki J-tv
(ele
Six years ago Jensen introduced the TRIAXIAL which combined into one
unitary assembly a special "woofer" and two horn -loaded compression -drive
"tweeters" to span the audio frequency range with an entirely new smoothness and realism unmatched by any other loudspeaker for listening quality.
It is a fact that only Jensen makes a unitary true three -way loudspeaker with
three electrically and acoustically independent speaker systems. Today the
TRIAXIAL is still the unchallenged peer of "all -in -one" loudspeakers.
'TRIAXIAL
is a registered trademark of Jensen Manufacturing Company
en4enMANUFACTURING COMPANY
Division of The Muter Company,
So.Laramie Ave.,Chicago 38,111.
In Canada: Copper Wire Products Ltd., Licensee
6601
WORLD'S QUALITY STANDARD FOR MORE THAN A QUARTER CENTURY
AUDIO
APRIL, 1956
51
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CURRENT
IN THIS
DIRECTION
INCREASING
s.
e
OUTPUT
c
URRENT
CURRENT
IN THIS
DIRECTION
DECREASING
Fig. 8 -5. How the out -of-phase halves of
a push-pull circuit are combined in- phase.
of time. The two output currents are
combined in such a way, however (as
shown in Fig. 8-5) that the direction
of flow in the output transformer constitutes a second phase reversal, and the
final output power is equal to the sum
of the powers available from each tube.
Push -pull circuitry is universal in
modern high-fidelity audio amplifiers. It
can be used for both voltage and power
amplifier stages: it is common in the
former and universal in the latter.
The Phase-Splitter
Push -pull stages must be driven by
two signal voltages which are identical
except for phase -one must be in its
positive half of the cycle at the same
time that the other is in its negative
half. There are various ways of splitting
the signal in this manner, and the stage
which does the job is called the phase splitter.
One type of phase-splitter, called a
split-load stage, is illustrated in Fig.
8-6. It will be seen that the currents
through the two load resistors are in
opposite directions relative to ground.
The output voltages across these resistors, taken in each case relative to
ground, are thus out of phase with each
other, as required.
Negative Feedback
The application of negative feedback
in amplifier circuitry, as an additional
method of reducing distortion, is so important that a separate chapter is devoted to the subject. (Note: this has
already appeared in an article in the
June, 1955 AIIDIO)
Amplifier
Amplifier output terminals are labelled according to the speaker impedance to which they are to be connected: 4 ohms, 8 ohms, 16 ohms, or etc.
A mis -match downwards (from an 8 -ohm
tap, for example, to a 4 -ohm speaker)
will usually not affect quality appreciably but will reduce the power capability
of the amplifier -how much depends on
Source Impedance of the
the amplifier itself. A mismatch upwards, however, from a lower-impedance
tap to a higher-impedance speaker, can
usually be used with impunity. The fact
is that the amplifier is "mismatched" to
the speaker in an upward direction, in
any case, over most of the frequency
spectrum. We will see that the rated or
nominal impedance of the dynamic
speaker holds over only a small frequency band, usually in the 150-400 cps
region, and that the actual speaker impedance increases manyfold at the frequency extremes.
The source impedance or internal resistance of the output stage (which is
the source impedance of the amplifier)
is an entirely different thing, although it
is sometimes confused with the ratings
of the output taps. The terms are
synonymous, and refer to the resistance
that the speaker "sees ", looking back at
the amplifier, rather than to the load
that the amplifier is designed to see.
The source resistance is effectively in
series between the amplifier and the
speaker, as the internal resistance of any
generator is in series between it and
the load. If the value of this source resistance is high, relative to the nominal
impedance of the speaker, it effectively
controls the relative voltage fed to the
speaker at different frequencies. When
the speaker impedance is high, as at the
extreme frequencies, a maximum of
voltage will be fed to it. This tends to
create a combination of boominess and
shrillness. Such used to be the case, as a
matter of fact, in the old pentode power
amplifier without negative feedback, and
this was the main reason for the generally acknowledged superiority of
triodes in the output stage prior to the
general use of feedback.
The source resistance has another
significance relative to amplifier performance. If the speaker is set into
vibration, especially at some low frequency near the natural resonance of its
mechanical system, it will tend to continue to vibrate after the signal has
stopped (an action referred to as hang over). Such a tendency is common to
any mass -elasticity system that has received a mechanical stimulus.
The tendency to hangover in speakers
is controlled by damping, of which there
are three kinds; mechanical, acoustical,
and magnetic or electrical. The last of
these is a function of the source resistance. When the speaker voice -coil
undergoes vibrations it acts as an electrical generator, and the vibrations are
braked electrically by the source resistance. Electrical energy created by
motion of the voice coil is dissipated in
the source resistance, which the speaker
generator sees as a load, and vibrations
unauthorized by the signal are brought
to an abrupt halt.
With speaker systems which are horn-
loaded, or which are in resonant -type
enclosures such as the bass -reflex, it is
generally desirable to have the source
resistance as low as possible (although
once the source resistance is one -fourth
or less of the value of the load there is
not much further damping action). With
speakers mounted in the wall or in
totally enclosed cabinets, however, the
value of optimum source resistance may
be higher, in some cases as high as the
impedance of the speaker. The proper
value depends on the speaker used, and
on where it is mounted in the room. Too
low a value may attenuate the bass, but
in any case a very high source resistance,
corresponding to the old pentode -without- feedback, is never desirable.
The source resistance of an amplifier,
relative to the speaker impedance, is
also expressed as a ratio called the damping factor. A high damping factor represents a low relative value of source resistance : a damping factor of one represents a source resistance equal in value
to the rated impedance of the speaker
to which the amplifier is connected.
Many modern amplifiers have variable
damping factors for adjustment to different speakers and conditions, which
means that their source resistances (or
the effective values thereof) are variable.
The Power Supply
The amplifier requires certain operating voltages -tube filament supply (normally a.c.), plate and screen voltages
(d.c.), and in some cases fixed grid voltages (d.c.). These are provided by the
power supply, which step the power company's voltage up or down as the case
may require, and rectifies and filters the
input a.c. (converts it to a smooth d.c.).
This power supply should be hum -free,
rugged, and stable. The voltage should
not change when large current demands
are made by the signal, or distortion will
be increased.
The requirements of a power amplifier
(Continued on page 85)
5
5
o
Fig.
8
--6. Split -load phase -splitter stage.
AUDIO
52
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APRIL, 1956
VITAL
NEW
harman kardon'
N S TR U M E NTS
NOWT
READY
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Nuaute AM-FM Tuner
I
An altogether new and brilliantly engineered tuner,
tuned RF
designed to mate the Prelude amplifier
Meets
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stage on FM
Automatic Frequency
FCC Radiation Specifications
mv. FM sensitivity for 20 db
Control AFC Defeat
quieting Printed Circuits throughout AM Ferrite
Brushed Copper EsLoopstick Built -in Antenna
cutcheon Matt Black Cage Dimensions: 121/2" wide
x 4" high x 9" deep.
-
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Model T -10
(complete with cage)
-The Ro .do
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$79.50
AM -FM Tuner
The ultimate development of the famous Harman Kardon silhouette in a fine new tuner, designed to mate
Tuned RF stage on FM
the Melody amplifier
Exclusive new FM Rumble Filter Cathode Follower
Output Ferrite Loopstick and 10 KC Whistle Filter
in AM
Meets FCC Radiation Specifications AutoPrinted
matic Frequency Control and AFC Defeat
Only 3s/S" high x 131/2" wide x
Circuits throughout
8R/" deep.
-
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Combined AM -FM Tuner
$95.00
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A beautiful and complete high fidelity system on one
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and at a remarkably modest price. The Solo
combines the tuner characteristics of the new Overture,
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of the Prelude, PC -200, amplifier in a brushed copper
and black enclosure only 4" high x 131,4" wide x 13"
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chassis
Model TA -10
(complete with cage)
$129.50
All prices slightly higher in the
Write Dept. pc-4 for free Technical Data Sheets
harman kardon
INCORPORATED
520 Malte Street, Westbury, L.
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1.,
N. V.
West
Equipment Report
The Ferrograph Tape Recorder -Rogers Developments Ltd.
"Cambridge" Amplifier-Fentone
of every
audio enthusiast is to own a good tape
recorder. Unfortunately, a good tape
recorder is likely to cost as much 'as many
a complete system, presuming that the
individual is, perforce, budget conscious or
is especially efficient in his purchasing department. The serious enthusiast is not
likely to settle for the common "consumer type " recorder that is offered at bargain
prices because he is too conscious of hum,
poor frequency response, flutter and /or
ONE OF THE ULTIMATE AIMS
RESPONSE PROM
AMPE X 5563 STANDARD TAPE
o
d am
TONE CONTROLS AT MININOM
1r`
-20
RECORD -PLAYBACK RESPONSE
EEO
7%2
IPS- O.
IPS
- --
m
.o
Fig. 1. Performance curves for the Ferro graph tape recorder. Tone controls were
at "10" for both of the lower curves.
B
&0 Velocity Microphone
wow, and many of the other ills that seem
to be indigenous to the low- priced tape
recorder. True, such machines fulfill the
same need for many families that the inexpensive box camera does, but the real audio
fan is in the Leica class, and demands much
more from a recorder.
Fortunately there are a few tape recorders that approach the professional models in
everything but price, and when one of them
is introduced into a system, the user
unless he has had considerable experience
with the true studio -type recorder
more
than likely to be fairly well satisfied with
the performance. The Ferrograph appears
to be in this class. It is not strictly in the
top -bracket studio class, yet its performance is well above the average -we would
call it a "semi- professional" model, which
is not intended as "faint praise" at all but
serves to set it apart from the box -camera
class. In all departments, it performs sufficiently well to warrant giving it a place
in even the best home systems.
Reference to Fig. 1 shows how the Ferro graph performs from the frequency -response standpoint. The upper section shows
the output from an Ampex Standard Tape
#5563, which most closely fits the curves
employed in all recorded tapes we have
observed so far. With tone controls at the
maximum position-which is 10 on the dial
-the output is up approximately 2 db at
50 cps and up approximately 4 db at 8000
cps, rolling off slightly at 10,000 cps. Minor
adjustment of the tone controls would permit practically flat reproduction from the
standard tape -and, consequently, from
recorded tapes.
The lower section of Fig. 1 shows the
-
-is
response from a "flat" signal fed into the
input, recorded on the tape, and then played
back. For both speeds the tone controls
were at the "10" position. Thus it may
be seen that the output is down only 3 db
at 10,000 cps at a speed of 71/ ips, and
down about the same at 5500 cps at a speed
of 3% ips. The frequency response curves
are essentially the same whether measured
at a high -impedance output (on the portable machine) or at the 15 -ohm speaker output. There are two inputs -one intended
for microphones, and requiring an input
of 3.8 my for peak recording level, and the
other intended for outputs from a tuner or
similar source and requiring a signal of
0.135 v. for peak level. The high -level input can also be used as an output to feed
other amplifiers in a system.
The Ferrograph, being British -made,
differs somewhat from conventional U. S.
recorders. It is available in a portable case
in which is mounted a loudspeaker, or it
may be had in a form intended for installation in a home system on a permanent
basis. It is also available with various speed
combinations, but the one most likely to be
used here has speeds of 71,E and 3% ips. It
is equipped with three motors -two of the
shaded -pole type for takeup and rewind,
and a synchronous hysteresis capstan motor
which provides a high degree of long -term
speed stability. A speed control knob is
mounted between the two reels, and a function control is just to the left of the head
assembly, which is covered for protection.
The machine is started by moving one
knob up to a stop, where it is held by a
magnet, being released by a push-button to
stop, or automatically when the end of
the tape passes through the head assembly.
The front section of the head cover may be
removed, without tools, to permit marking
the tape for editing. The portable model
is flexible in use, and will accommodate
inputs and outputs likely to be encountered in any application. On the ''permanent" model, switching is controlled by a
panel- mounted switch.
Flutter, wow, and hum level are all satisfactorily low, and the performance of the
Ferrograph is considered completely adequate for high -quality music system use.
Fig. 2 (left). The "permanent" model of the Ferrograph is intended for installation in a home system, and provides all control
from the panel. Fig. 3 (right). In portable form, there is greater flexibility but less ease of handling.
AUDIO
54
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APRIL, 1956
The Ampex
612-1Shruplosis Lue Phonograph ant
610
1
Amplifier-Swim
the last word in living room listening...
AMPEX
STEREOPHONIC
Once you've heard the Ampex 612
stereophonic tape phonograph system, you'll never be satisfied
with less. It's the latest and the finest in listening pleasure,
makes previous high fidelity seem old fashioned. The startling
realism and magnificent quality of the 612 system brings a
new panorama of sound into your living room new heights
in listening enjoyment that only a superb tape machine can
achieve.
Not only does the 612 system capture all the depth and clarity
of stereophonic sound, but its small size is really unique. Even
the most critical audiophile is astonished that such big, clean
-
AMPEX
CORPORATION
SOUND
sound can come from such compact equipment. Complete with
tape phonograph and two amplifier- speakers, it covers only
four square feet of wall space for convenient placement in any
living room.
With true Ampex quality, the Model 612 plays full- track, half track or two track stereophonic tapes. Both the tape phonograph and the amplifier- speakers are available in handsome
hardwood cabinets with either blonde or brunette finish. See
and hear them today. Special stereophonic demonstrations
are being featured this month at your Ampex Dealer's. Ask
about the Ampex Time Pay Plan.
Dealers in principal cities (see your local Telephone Directory under "Recording Equipment')
Canadian Distribution by Ampex American, 70 Grenville, Toronto, Ontario.
SIGNATURE OF PERFECTION IN SOUND
934 Charter Street, Redwood City, California.
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1I1I1N'I=
.e
L!!II
11 =II I
=1111 11111111111
1C1!
NMI
111
<
,
10
bridge" amplifier, a product of Rogers
C1IIBi.1.0ll1
,o.1l1
0
The two units comprising the "Cam-
l'1111
MIN
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.
ROGERS DEVELOPMENTS LTD.
"CAMBRIDGE" AMPLIFIER
Up
TONE
11
1111111
CONTROL
I_
N4H4r
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.
11111
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Fig. 4. Performance curves for the
"
Cam
bridge amplifier.
Developments Ltd., London, England, provide a small amplifier system suitable for
most home applications where the power
requirements are not so severe as to warrant
an amplifier of 25, 30, or more, watts. And
while it may be argued that any home system needs upwards of 20 watts, it must still
be remembered that the greatest majority
of hi-fi systems are started with 10- or 15watt amplifiers-as the user adds more
speakers or becomes more conscious of the
desirability of considerably higher power,
he may go to higher powers, but for the
average small home, 15 watts can be considered satisfactory.
The Cambridge amplifier consists of two
separate units -the control unit and the
power amplifier, shown in Figs. 5 and 6
respectively. Figure 7 is the schematic of
the power amplifier, while Fig. 4 represents
the performance of the combination.
The control unit provides for three inputs --a microphone input which requires
a signal of 2.8 mv for a 1 -watt output, a
radio input which requires a signal of approximately 32 mv for a 1 -watt output, and
a pickup input which requires a signal of
approximately 3 mv for a 1 -watt output.
In addition, there are two jacks on the
front panel which permit feeding a tape
recorder with a signal which is not affected
by the volume control, and another which
will accept the output from a tape recorder
(low -level, high -impedance). This makes it
posible to use the Cambridge with a portable tape recorder with a minimum of connection difficulty.
Four phonograph positions are provided
-with conventional curves being offered.
All fall within ±2 db of those specified by
the manufacturers, and are for HMV LP,
Decca LP, Ortho (RIAA), and 78. The input selector switch also selects the phono
curve. The equalization is obtained by feedback around the first section of the dual
triode, with a "flat" feedback being applied for the radio and microphone positions. Plugging a tape recorder into the
TAPE REPLAY jack eliminates the first stage.
The tone controls are associated with the
second stage-the bass control being a
six- position switch while the treble control
is a potentiometer. In addition, there is a
filter control which is continuously variable
from a cutoff at 9000 cps down to a cutoff
at 5000 cps. A switch on the counterclockwise end of the control's rotation cuts out
the filter altogether, leaving the response
essentially flat up to 20,000 cps. The effect
of the filter is shown in the upper section
of Fig. 4, while the range of the tone controls is shown in the center section. The
control unit employs only one tube -an
ECC-83, which is a high -mu twin triode.
The volume control follows the filter and
tone-control network, and the
TAPE RECORD
jack is connected at the high side of the
volume control. The control unit is con-
nected to the power amplifier by a single
cable which includes the a.c. pair leading
to the power switch which is integral with
the volume control.
The control unit is quite small, being
only 1% in. deep behind the panel, which
is 81 x 5% in. A feature unique to this
amplifier is its availability in four panel
colors -red, ivory, black, or bronze -and
with pointer knobs in red, ivory, black, or
gray or with round fluted knobs (as shown
in Fig. 5) in ivory, black, or brown. This
permits the user to select the colors most
suitable for use with his particular decor
and cabinet style.
In case the control unit were to be used
with any power amplifier other than the
10 -watt unit in the Cambridge combination, the connection could be made through
a single octal socket mounted on the power
amplifier chassis, and a plate supply of 8
ma at 270 volte is required. The heater
drain is 0.4 a. at 6.3 v.
The Power
Amplifier
The 15 -watt main amplifier of the Cambridge employs an ECC -83 as the voltage
amplifier and phase splitter, a pair of
EL-84's in the push -pull output stage, and
an EZ -81 rectifier. It is a relatively small
unit, yet sufficiently large to permit neat
and careful workmanship and to accommodate an improved C -core Partridge output transformer. A semi -fixed presence control (the 220 -ohm resistor and the 0.5 -µf
capacitor shown below the rectifier tube on
Fig. 5. The Cambridge control unit, which
is
compact enough for even the smallest
installation.
amplifier of the Cambridge combination.
Fig. 6. The power
Fig. 7. Schematic of the power
amplifier.
AUDIO
56
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APRIL, 1956
44.
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A m perex
TUBES
are Making Music in the
World's Finest Amplifiers
VOLTAGE AMPLIFIER TYPES
-
86
High -gain pentode with exceptionally low
hum, noise and microphonics.' Particularly suitable
for preamplifier and input stages.
ECC 81
Medium -gain dual triode with low hum,
noise and microphonics. Replaces the 12AT7 without circuit changes.
ECC 82
Low -gain dual triode with low burn, noise
and microphonics. Replaces the 12AU7 without
circuit changes.
ECC 83
High -gain dual triode with low hum,
noise and microphonics. Replaces the 12AX7 without circc t changes.
EF
offers the unbeatable combination of ultra- advanced design by
-
-
RECTIFIER TYPES
80 - Indirectly heated, full -wave rectifier with
6.3 v., 0.6 amp. heater, 90 ma. output capacity and
miniature construction.
Indirectly heated, full -wove rectifier with
amp. heater, 150 ma. output capacity and
EZ 81
6.3 v.,
-
GZ 34
Philips of the Netherlands plus
AMPEREX
engineering research for
American applications. Leading manufacturers of high -fidelity
equipment are now designing and building complete audio amplifier
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AMPEREX
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Detailed data, circuits, application information, as well as
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Unique AF power pentode combining high
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Exceptionally linear high -power output
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230 DUFFY AVENUE, HICKSVILLE, LONG ISLAND, N. Y.
APRIL, 1956
5:
57
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An integral transformer provides an output impedance of 50 ohms, and a built-in
switch permits adjustment of response so
as to allow the use of the microphone in a
close -talking position-the response being
18 db down at 50 cps. In the normal position- indicated by an M on the switch
(T indicates close talking and there is also
an off position) -the response is within
± 2.5 db over the range from 30 to 15,000
cps. The polar pattern indicates that response at 1000 cps is down 10 db at an
angle of approximately 50 degrees either
side of the front or back faces. Sensitivity
is rated at 55 db below 1 volt per microbar,
which means that normal speech would give
an output of the vicinity 2 my at a distance
the schematic, Fig. 7), provides a boost of
approximately 5 db maximum, commencing
at around 500 cps, for the frequency range
above 1000 cps. This improves intelligibility
with certain types of speaker systems, and
"brightens" up the response with practically any speaker. The output stage is of
the Ultra-Linear type and employs a transformer designed to a 25 -watt rating. It ha,
a response of ± 1 db from 20 to 50,000 cps.
and the leakage inductance is said to b.
extremely low, thus permitting the appli
cation of a relatively- high amount of feed
back.
The amplifier is mounted on a 6 x 11 in.
chassis, and is 5% in. high. The presence
network is introduced into the circuit by
inserting a shorting plug into a tip jack
on the top of the chassis, thus indicating
that it is to be set up on a semi- permanent
basis, since it is not a panel control.
The output circuit is arranged so as to
accommodate three ranges of loudspeaker
impedance -from 12 to 16 ohms, from G
to 8 ohms, and from 2 to 3 ohms. The
method of changing impedances permits the
optimum use of the interleaved secondary
of the output transformer, and at the same
time changes the feedback resistor and
phase- correcting shunt capacitor. This impedance selection is accomplished by the
use of loudspeaker matching plugs, as
shown on the schematic.
Study of the circuit will show that it is
fairly conventional in some respects, although the characteristics of the output
transformer are not apparent from the
schematic. However, with the increasing
use of the EL -84, even in U. S.-built equipment, the values employed may be of some
interest to the serious experimenter. The
signal input to the power amplifier for an
output of 1 watt is approximately 0.19
volts, which indicates the sensitivity of
the circuit used. Large coupling capacitors
and adequate bypassing of input and power
stage cathodes result in an exceptionally
stable amplifier.
It will be noted that the power amplifier
provides for plugging in a tuner or other
device which can draw as much as 40 nu
at 270 volts and 2 a. at 6.3 volts. This is
hardly sufficient filament current for an
FM tuner, for example, but would be sufficient for an average AM tuner. Most U. S.
tuners provide their own power supply,
however, although in England it is common to obtain the power for the tuner from
the amplifier. Since the plate supply is
adequate, it would suffice to place a filament
transformer on the tuner chassis if more
than 2 a. were to be drawn by the tuner
circuit.
On subjective listening tests, the Cambridge gave a good account of itself. Its
controls give a satisfactory degree of range
for both bass and treble, and the availability of a filter is a desirable feature, although perhaps less necessary with LP
records than it was with shellac 78's. We
believe that if the Cambridge is to be a
regular item on the U. S. market it should
be equipped with standard U. S. pin jacks
for the inputs so as to be readily interchangeable with other U. S. equipment. On
the whole, it is a well built amplifier and
performs most satisfactorily.
B &O -50 studio -type
velocity microphone.
Fig. 8. The Fentone
FENTONE B &O STUDIO -TYPE
VELOCITY MICROPHONE
It is difficult to evaluate a microphone
without entering into the realm of subjective judgement, yet after all this is the
crucial test of any equipment that is to be
used for reproduction of sound rather than
for making measurements. Velocity microphones have certain advantages that are
not duplicated by any other type, although
the unidirectional models can approach the
velocity in many applications and in some
situations they may be even more effective.
For interview purposes, for example, the
velocity microphone is desirable because it
offers maximum sensitivity on two opposite
sides, with relative freedom from interfering sounds coming at right angles.
The B &O -50 follows the modern trend
for small mircrophones, being only 1 3/16
in. in diameter and 7% in. long. The external projections on the chrome case indicate the directivity of the microphone, and
the ribbon itself is screened by two layers
of nylon screening, suitably separated for
maximum protection. When mounted on a
stand, the microphone can be tilted by
means of a ball swivel.
of 24 inches.
The microphone is extremely attractively
iu appearance, is small enough to be useful
in a TV studio for audience participation,
for example, and is particularly convenient
for person to person interviews. Because of
the close -talking provision, the B&O -50
does not have the boominess that is associated with certain types of velocity
microphones, but produces crisp, clear
speech. It would appear that this is a suitable microphone for the tape recording
enthusiast, for instance, when he wants
something better than the usual inexpensive
model furnished with the average recorder.
The low impedance would necessitate an
input transformer, however, but even this
might be well worth while because of the
improvement in quality.
The Fenton Company has recently announced an acoustic separator for B &O
microphones which permits using two of
them for stereophonic recording. This separator consists of a rectangular sheet of
damping material about 8 x 12 inches in
size and about 1 inch thick. It is mounted
in metal channels with one end about one
and a half inches forward of the axis of
the two microphones and extends between
them and back for some distance. The microphones are mounted on a bracket with
their two faces turned outward some 30 to
40 deg. from the plane of the separator.
Thus the back portion of the figure -eight
sensitivity pattern is effectively blocked by
the separator, and the whole device serves,
approximately, as the equivalent of a listener 's head. The microphones are about 8'F2
inches apart.
While there are two schools of thought
as to the placement of microphones so as to
make realistic recordings, it must be ail
mitted that the placement for binaural
recording -that intended for listening by
two headphones, one on each channel
practically demands that the microphones
be located in positions relative to the two
ears of the normal human listener. It is
possible that suitable quality and the
proper effect can be obtained for stereophonic recording-that intended for listening by means of two loudspeakers, both of
which are heard by both ears of the listener
-hut that is likely to depend on the acoustics of the studio as well as on many other
conditions.
In any case, for those who are interested
in making experimental recordings on a
two -channel basis-whether binaural or
stereophonic-the availability of the acoustic separator and the ease and convenience
with which it may be used with the B&O
microphones may come as a possible solution of the placement problem.
-
-
AUDIO
58
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APRIL, 1956
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UD'
Pdward Lâtna1I Canby
The Home -Grown Tape Program
Editing for the Home Experimenter
of this series,
which you will find in the September
1955, January 1956 issues of AUDIO,
have traced the informal history of my informal radio program produced more or
less regularly on tape right in my home.
In January I got as far as describing some
of the psychological aspects of tape editing
in such a program, some of the tricks that
can be used both for good effect and to
minimize the inevitable disadvantages of
home -style recording. This month I'm steering away from my own show, as an aside,
to bring you some accumulated observations on how anybody can best go about the
job of tape editing in the home.
By anybody, I mean anybody, amateur
or professional, who is gadget -minded, or
artistic -minded enough to want not only to
produce tapes of his own but to fix them
up, afterwards, for optimum effect. My
thesis is that You Too can be a Tape Editor. right in your living room. In other
words. I'm suggesting that there are many
things that can be done on a less-than -pro
fessional basis which can well rival the sort
of expert fixing -up that is produced by the
high- powered editing of the professionals
-probably a lot more can be done than
you have any idea. And your basic equipment. aside from tape and tape recorder,
need be no more than the simplest splicer
and a roll of white editing tape.
Professionals who read this please be
tolerant
old stuff to you. Amateurs,
or professionals in audio who are technically amateurs in this particular area, be
encouraged, and if I seem to say the ohvious, just remember that for some other
reader it ain't obvious at all. Depends on
how far you 've got in your own experimenting.
pRECEDING INSTALLMENTS
-it's
Scissors -Ugh
In this installment I'll confine myself
mainly to non- audible aspects of home tape
editing, and I don 't intend to be comprehensive and super- organized about it, either.
This isn't an instruction manual -yet.
Let's begin with a picture, that familiar
drawing found on innumerable boxes of
home tape which shows a large pair of
sissors slicing diagonally through two very
loose ends of tape that have obviously been
unwound from their respective reels. This
picture never fails to give me the plain
willies.
Sure, you can "edit" tape that way, if
you have to. Just dismantle the entire
machine, remove both reels, unwind the
tape, put the whole business in the middle
of a large table, get out your scissors,
bottom and shaped edges. You push it in,
snap it out. The less expensive blocks with
clamps to hold the tape down are slightly
clumsier to use but reasonably effective.
The first principle of tape editing, as I
see it, is to avoid dismantling your entire
set -up for each splice, as with OPERATION
SCISSORS, just described. That is, don't
take any more tape off the machine than
you can possibly manage. Leave the reels
in place. Do the work right on the machine.
It 's surprising how seldom this occurs to
those who do only occasional tape patching.
I've watched many a professional operator unroll tape from reels removed from
the tape machine, risking all sorts of dreadful accidents, preventing any sort of audible checking and, worst of all, losing time
courting confusion. We once lost a couple
of feet of tape, in this fashion, that put a
professional recording back a couple of
years
was a performance -made tape
and we had no satisfactory replacement on
hand for that second or so of missing
music.
The procedure for non -dismantle tape
editing, right on the machine, varies from
machine to machine but the principle is the
same in all cases. You pull out a loop of
tape, after you have marked the spots
where it is to be cut and excision made.
The tape splicer is mounted, or simply
placed, on any convenient flat part of the
recorder and you pull your loop out just
enough to reach to
without removing
reels. On the big professional Ampex your
loop is simple enough; just lift the tape
out of the channel that goes past the recording and playback heads. So, too, with
other recorders where this is easily accomplished, and that includes many newer
home -type tape recorders. You can place
your splicer directly above the tape slot,
for easy access.
But a useful trick, which I learned with
my Magnecorder, is to pick up the tape,
not at the heads but off to the left, between
the supply reel of tape and the first roller,
leaving the section directly over the heads
untouched. This is particularly useful in
the ease of those Magnecorders which have
the "lid" type of shielding over the head,
which must be lifted up on its little hinge
before tape can be removed. But it undoubtedly will work well with other recorders. Why to the left'? Because if you
make your splice to the left of the playing
head, it will be in position to play directly,
without rewinding, when you reel it back.
Saves a tiny fraction of a second on each
splice. Always do the reeling up of the
loop with the left reel, the supply reel,
after finishing your splice. That puts your
patch in position for listening-and of
course you should listen to every splice you
make before going on to another, no matter
how good you think you are.
You'll find that with experiment and
practice this non -dismantle system for
splicing can become very efficient on just
about any recorder, from the cheapest home
model on up. The thing to do is to study
your motions, find out how to reel off just
as little tape as you possibly can when you
lift it out to put on the splicing block.
You'll get so that not more than a few
incites are involved. Then things move fast.
Marking the spot on your tape is a
major problem, because the only proper
way is to do it directly at the playing head,
with a soft china -marking pencil. (Yellow
is a professional favorite; I find that jet
black shows up even better in most lights.)
Unfortunately, it is not always possible to
get at the playing heads with your pencil,
especially in those recordera that have a
slot into which the tape is dropped. The
difficulty is present in all price ranges;
-it
I
superimpose a foot or two of the free ends
two feet -and slice neatly decisively across. Then take your roll of
patching tape in hand, strip off six or
seven inches of the white stuff ; take the
two tape ends and lay them down on the
table next to a full -size yard- stick, to be
certain that your forthcoming joint will be
straight. In fact, you'd better get out a
batch of paper weights or maybe a dozen
empty milkbottles, to hold the tape down
fiat and taut in a straight line. When all
is rigidly under control, the tape straight
along the yardstick, the two butt-ends
nicely lined up next to each other (this
should take you a good half hour to accomplish), take your piece of patching tape
in hand, take a deep breath, hold it for
five seconds, then lunge towards the splicing- point, hitting both tapes simultaneously
and in a perfectly flat plane.
If your aim is right, you'll now have
a straight joint that doesn't overlap, nor
is it separated by a "crack " between the
tapes, and you may in due course of time
proceed to the final step. But the chances
are that your lunge missed fire, or the tape
slipped or curled up. If your new joint
turns a corner or has a crease down the
middle-throw the whole thing out, cut off
a foot of tape from each end and start
all over again. (Be sure there's enough
tape on each reel for four or five tries of
-make it
this sort.)
When you get your splicing tape on, pick
up the new joint in one hand, tape and all.
and hold before a 500 -watt lamp for proper
illumination; trim carefully and slowly
along each edge of the tape, leaving no
white margin of patching tape but, on the
other hand, avoiding any cuts into the tape
itself. This requires a steady nerve and a
practiced scissor- technique and you'll probably spoil your splice, in which case start
all over again... .
*
In other words, go out and buy a tape
splicer! It's just silly to edit tape without
the aid of one of these gadgets. You'll
seldom get a good splice without one, and
you'll save vast quantities of time with
even the simplest splicer as compared with
the deadly scissors technique.
My own preference, along with most
professional editors, is for the simple splicing block, on which you can align the two
tape -ends, cut your diagonal and even
splice the splicing tape to fit. But there are
many fancier gadgets if you feel like trying them. I'll stick with the EdiTall, a
plain block with groove into which the tape
fits without clamps thanks to a curved
it-
AUDIO
60
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APRIL, 1956
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APRIL, 1956
www.americanradiohistory.com
AmericanRadioHistory.Com
witness the Ampex 600, where in order to
mark tape at the playing head itself you
must (and can) remove the outer and inner
metal shields that cover the three heads.
One way to get around this problem,
though it will likely reduce your accuracy
somewhat, is to mark the position of the
playing head's center on the outside cover
or shield. Once you have determined this,
you can audibly spot the place where a
splice is to be made by moving the tape
back and forth, then lift it straight up and
out of the slot and cut it at the point
where the playing head should be. But as
I say, this is likely to be inaccurate if
you're not careful -and be very sure
you've marked the playing head and not
one of the others (record or erase, on a
three head machine; just erase on two
head models) which are some distance
away.
Whatever marking system you find is
best for you, stick strictly to the nondismantle technique. Don't take the reels
off the machine for splicing. Don 't unreel
great lengths of tape. Keep the splicer
block as close to the actual playing heads
as you can manage.
Perhaps I should point out, for those
who are likely to make the biggest boner
of all in tape editing, that one does not
edit dual -track tape! You can, of course,
edit tape on a dual -track machine provided
you use only one of the two tracks in your
recording. And (while I'm at it), a dual
track recorder will play a singletrack professional tape fairly well, though,
since the head is running along the edge
of the centrally -placed single track, there
may be some uneven fading or change of
quality. Usually not bad. But a single -track
machine plays a (single) recording made
on a dual -track machine perfectly, since
the single -track head works all the way
across the tape and will pick up anything
on it, wherever it is recorded.
Note also that a few recorders are dual track reversible, that is, the tape motion is
reversed when the second track is recorded
and the reels need not be interchanged. In
my remarks, above, simply delete the word
"left" and do your editing on the supply
reel side, whichever direction that happens
to be. DeJur, Webcor, and Twin -Trax
(ACA) recorders operate in this way,
among others. Note further that there are
two recording heads in these models and
you must be sure you're working at the
right one when it comes to marking your
tape for splicing.
-
-
The Tape You Remove
.
.
.
for the preliminary mechanics
of editing in the home, applying to any
recorder from the cheapest to the fanciest
professional model. Before I get to the
actual sound, let me consider more of the
mechanical aspect -for this is a vital part
of the whole operation. Without the proper
mechanics your ear will not help you a bit.
I suppose you may lump numerous kinds
of splicing together in this mechanical
sense under the general title of editing.
Repairing accidental breakage, joining odd
pieces of tape purely mechanically, these
things are not really editing in the higher
sense, since sound isn't important. Much
more interesting is true editing, whereby
you splice not so much tape as sound itself,
whereby you remove sounds, add sounds,
play tricks with sounds, all via the purely
mechanical operation known as tape splicSu much
ing.
The odd thing is-and this strikes me
every time I do it -that the entire subtle
art of tape editing, which can involve some
marvelously ingenious tricks with music
and with speech, which covers an enormously wide range of intellectual activity,
from, shall I say, Bach to Boogie, soap
opera to Shakespeare, boils down physically
to one, single, mechanical operation. Mark,
cut and splice, mark, cut and splice, go
through exactly the same motions again
and again, and the entire vast range of
artistic and intellectual interest, from one
splice to the next and the next, is in the
vastly different audible problems being
solved in the splicing. Mechanically it's
the same, routine finger process, and not a
very exciting one at that. Without sound,
splicing is no more than a minor menial
task, dull and repetitive. But the ideas,
the intellectual qualities of the operation,
fascinating and endlessly varied, are in the
ear and the mind, and there's no limit to
their interest, professionally or in the
home.
How do you make a splice? There are
always two points at issue -that is, places
on the tape upon which you'll operate.
You make two marks, you slice the tape
first at one (with the loop technique as of
above) and then the other, preferably cut-
ting the "earliest" first, then running the
tape through the player in the normal
direction (either by power at playing speed
or by hand until you reach the second mark,
which you then cut, too. Whereupon you
bring the severed ends together, lay the
excerpted piece aside carefully -never junk
it until the work is done on the splice -and
apply your patching tape to finish the job.
(More of this in a moment.)
If you slice the "early" mark first, the
spot which comes first in the playing of
the tape, you can often allow the following
tape, (to be excised) simply to play freely,
right out of the machine and into your lap
or on the floor, until you get to the second
mark. (But don't step on it.) You must,
of course, hold onto the take -up reel during this operation so it won't spin forward
wildly. A good idea ; for you can in this
way actually hear the tape which you are
going to remove and so be doubly sure
that you are doing what you want to do.
This playing- onto -the -floor is more or less
standard procedure professionally when
long pieces of tape are to be removed.
If your splice isn't right, you can reinsert the removed tape as needed, and
begin over again without prejudice, as the
legal phrase goes. You won't begin to
throw away the removed tape immediately
until you are a very old hand and extremely
sure of perfect results every time ; anybody
with any sense always puts aside the removed section until the all -clear is sounded,
the patch is played and it is OK.
And remember that all tape looks alike.
If you once lose a fragment among other
similar scraps, you're not likely to find it
again -and if you do, you'll probably
patch it in upsidedown and backwards. It
looks just the same that way, but it sounds
funny.
When you begin fancy tape juggling and
find yourself with three or four pieces of
tape from various rolls, waiting to be used
or tried out, it's a very good idea to attach
labels to them. Have a roll of sticky cloth
tape handy, tear off a piece, write on it,
and attach to the end of the tape -the
beginning end. (Or if the other end, be
sure you are clear as to which end is which,
or you'll have your sound patched in backwards before you know it.)
It is often a good idea, in such situations,
to stick the tape fragments onto a nearby
wall so they dangle down like clothes on a
clothesline. Then you can pick off the one
you want at your convenience. Don't rely
on memory as to which slice of tape is
which, unless you are extremely sure. And
look out for stray breezes. The breeze
62
caused by your own arm moving about
may easily blow two or three precious bits
of tape up in the air, on the floor, or upsidedown, reducing your delicate operation
to chaos in an instant. You can 't play a
tape fragment without splicing it onto the
longer tape on the supply roll, unless it is
long enough to pull over the heads. And
even then, it may merely produce unrecognizeable grunts and squeaks, unless you can
manage to get it to run through the capstan drive for long enough to recognize
the contents. But avoid this sort of trouble
by keeping track of your fragments, even
if it is a nuisance. Do all your audible
work before you slice, if you possibly can.
By the time you've done quite a bit of
splicing your work -space will begin to look
really professional -i.e. the floor, table,
waste basket, window sills and every other
open spot will be covered with snippings
and tangles and whorls and slivers of red
tape, a terrible mess and only a vacuum
cleaner will pick up the little pieces, though
it will choke itself on the long ones which,
moreover, have an annoying way of wrapping themselves around and in and out of
telephone wires, power cords, and the like.
The more you yank, the more hopeless the
snarl.
I suppose something of the sort is inevitable, and I watched a cleaning lady at
Columbia Records, with amusement, doing
a quickie brush -off of the editing room last
week in the time -honored way ; she didn't
brush the tape bits under the rug-there
wasn't any rug. But she deftly swished it
all behind several amplifier racks, where
not even a vacuum cleaner could get at it,
and her dustpan had only a token handful
in it, just for the record, so to speak.
In another ten years Columbia will be
knee -deep in the stuff, if I know anything,
and so will you. Wives beware.
Which leads me to a final thought on
tape fragments: don't try to save them,
and so economize on tape costs.
Economizing
Yes, tape costs money, even with price
reductions. When I started out, I saved all
the pieces I could, and spent much time
patching then together for re -use. But then
I discovered that a good proportion of tape
splices cause a noticeable thump or flutter
when a new recording is made over them.
Not all, and the effect varies according to
the machine, but you may count on an
annoying or even a disastrous bad spot
every so often even with the best professional machines. So-don't record over
splices, except for experiment or in work
where perfection is unimportant.
My first glimpse at a professional tape
recording session had me horrified at the
enormous quanitites of tape that are
"wasted" The big machines, running at
15 inches (or even 30), roll on and on and
are seldom reeled back; mistakes, aimless
conversations, long interludes, all go merrily onto the tape and are eventually
thrown out, by the mile, into the waste
basket. But on reflection I realize, and you
will too, that in such operations on a commercial scale tape is decidedly expendable.
Better a mile of lost tape than a few inches
of lost music or speech, paid for at fabulous overhead expense.
The record and radio people know that
their best policy is to take down everything, useable and unuseable, during every
recording, and they are very willing to
waste tape in vast quantities, if the tape
that is left after editing is what they want.
And, remember, bulk for professionals is
(Continued on page 68)
AUDIO
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63
APRIL, 1956
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EDWARD TATNALL CANBY,
The Fabulous Eighteenth Century
1. WESTMINSTER: CORELLI TO
CLEMENT!.
Organ Works cf Bach, Vol. 1: Orgelbuch lein (Little Organ Book). Carl Weinrich,
organ of the Varfrukyraka, at Skanninge,
discs. Ile is not a profound interpreter, not as
serious and as probing as Kirkpatrick nor as
electrically dramatic as Landowska, but this
is small criticism, in view of the urbane inclusiveness of the Valenti performance-the
longer he plays, tue more charming he sounds,
and these are getting better and better.
Sweden.
Westminster WN 2203 (2)
Here's the start of n new complete series, the
entire organ works of Bach, which will com-
plement the similar series released by Deceit
from Deutsche Grammophon with the German
organist Helmut WitchIa. (Comment in later
issues.)
Weinrich is a first rate authority, his playing brilliant, brightly registered, modern, a
bit on the cool side with strict and fairly
rapid tempi. He represents very well the continuing reaction against the old heavyweight
and soulful kind of Bach playing. The many
short chorale settings are here played In a
businesslike but colorful way, setting forth
their inner elaborations with clarity.
In the sumptuous accompanying
booklet
Westminster describes impressively the difficulties of "hi -fi" recording of the many sound sources spread out in such an organ as this
across the width of a church. In fact, the
company hung dozens of mikes, in order to
find a combination for each of the hundreds
of works, as registered on various sets of
pipes by Mr. Weinrich. (Not all mikes were
used at once!) The result is a hi -fi sound remarkably consistent with that in other recent
Westminster recordings, clear, brillant, close
up, the inner details standing out startlingly
like the white trees and clouds in an infrared photograph. My own preference would be
for a simpler and more distant talking, if perhaps more blurred, but this type surely affords
interesting inside views of the music and a
fine hi -fl effect via the phonograph.
The organ has a fine sound and splendid
variety and seems to have been an excellent
choice for the fort h cons ing series.
The Valenti records should be treated as Absolute recordings. I mean simply that in them
there Is virtually no recorded room sound, no
reverberation ; the mike is close and you hear
virtually "pure" harpsichord, without echo.
Thus you listen to the instrument without
being conscious, as in other recordings, of the
space in which the recording was made. That
means that, as you play the record, it takes on
the sound of your space. In effect, the instrument is playing inside your listening room.
In all such Absolute recordings (and there
are a good many on the market) realism is
impossible unless you set the volume at the
absolute volume of the original sound. No
more, no less. That sound is often less loud
than you tend to play your records. At any
louder volume the absolute recording is ugly
and mechanical, distorting the music and the
instrument. Hence some criticisms of this type
of miking.
But If you will turn Mr. Valenti down very
soft, you will hear him as he actually plays,
with unexampled fidelity, right in your room.
Remember, the harpsichord has a very small
literal sound, a tiny fraction of the piano's
volume, though its musical effect, oddly, can
be very massive, as we all know.
-
Scarlatti: Sonatas for Harpsichord, vols.
11, 12. Fernando Valenti.
Westminister WN 18094,18192
It's an accomplishment to have carried this
series on so lustily into its twelfth volume,
with more announced. At a dozen or so short
sonatas per disc, the net so for must be about
out of a projected grand total of something like 500. Many a project of th's sort
1-14
has foundered before it was on its feet.
I tried Vol. 6, for comparison, and found
no great tonal difference, though the new ones
seem a trifle heavier in the bass, perhaps due
to an intervening change of recording curve,
to the present RIAA for which I did not
change compensation. Valenti continues the
polished, fluent performer, a bit more easygoing and relaxed now than in the earlier
780 Greenwich Si., New York 14, N. Y.
Clementi: Sonatas for Piano (with
"Didone Abbandonata"). Vera Frances chi
Westminster WN 18091
Itere are more Clementi sonatas, supplementing those recently issued by Horowitz on
RCA Victor (see AUDIO, Feb.) -he is the great
pianist and composer of the turn of the last
century whose bigger works are now being
rediscovered. "Didone" (Dido Abandoned) is
his last sonata, composed in the full early
Romantic period and a touching attempt of
an essentially classic master to write in the
new idiom; the expression is Romantic enough,
but the harmonic language isn't ripe enough.
The earlier works, pioneer piano sonatas closet
to Haydn than to Mozart and remarkably foreshadowing Beethoven. are the best.
And the three earlier works here are more
congenial for Franceschi, who plays them in
a crisply expressive way, lacking only a certain
larger sense of line and phrasing that keep.
her performance out of the "extraordinary'
category. She is a sweet. .sincere. and under
BE
YOUR OWN
RECORD CRITIC
See page 77
64
standing player and does the piano literature
a good turn here- setting an example for other
pianists. ltig. handsome piano sound.
Corelli:
12 Concerti Grossi, Opus
English Baroque Orch., Quadri.
Westminster WN 3301(3)
This album continues the documentation of
the solid core of Italian 1811* century music
with another dozen concerti of the sort that
in pre-LI' days were often praised but seldom
heard. (The Corelli "Christmas Concerto" was
the standard example, out of many.) See also
similar collections of Vivaldi, Torelli, Albinoni.
etc. on various labels.
Nobody expects you to play these a dozen at
a time but since for convenience they were
published in dozen lots, they are now so
recorded. Take your time and you'll enjoy
them for many a month to come. Corelli was
the "father" of this now -familiar style, a
somewhat earlier composer than others who
write similar music-Vivaldi, Bach, Handel
et al. Ile has not Vivaldi's dramatic flair nor
his sometimes strange harmonies, but his
music is immensely solid, brilliant, strong
rhythmed, and makes fine fiddling.
The Italian conductor Quadri makes these
English players hop a bit more energetically
than, I suspect, they might do on their own;
the music is intensely vigorous, somewhat
choppy in the fast movements and not too
well phrased la very un- British fault), but
even so it makes a rather pleasant contrast
to the ultra- serious German playing of similar music in other recent recordings. Most
listeners will like this, and the fi is hi.
Mozart: Early Quartets, K. 155, 156, 157,
158. New Music Quartet.
Columbia ML 5003
Mozart: Early Quartets, K. 159, 160, 168,
169. Barylli Quartet.
Westminster WN 18092
Ait interesting collaboration-Columbia's
and 1Vestminster's releases, as you can see,
supplement each other nicely. These make a
fascinating dynamic study of the young composer learning his trade
astronomical
speed. The quartets K. 155 -160 were composed
during his trip to Milan, age 16, and are the
first in which he began truly to sense the possibilities of four strings. The first two or three
are already finished and competent, but not too
interesting; the interest rapidly deepens as we
move front quartet to quartet. The last two,
K. 168 and 169, are from a year later when
-at
Mozart visited Vienna.
Both quartets play exquisitely, the New
Music in a more classic way with physically a
smoother, less highly colored tone, the Barylli
quartet almost passionately, with a good deal
of vibrato and a real Viennese earnestness,
In the recording Westminster wins honors
with a brilliant, stringy close -up sound. bringing out the individual instrumental colors most
effectively in a good liveness. The Columbia
AUDIO
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6.
APRIL, 1956
recording is at a greater distance, the sound a
bit wooden and the sense of presence less conhieing. Not musically at all serious, this difterence.
Mozart: The Last Quartets, K. 499, 575,
589, 590. Budapest Quartet.
Columbia SL 228 (2)
here's the other
Nell, while we're at it
end of the line, some twenty odd quartets and
a dozen -plus years later. At first hearing you
won't notice much outward difference in style
-- -still the saine lyric, intimate transparent
Mozart. But, of course, there are vast differences when the quartets make their mark on
your memory. Outward lightheartedness, as
ue now realize, often covered the most pro found and intense expression on Mozart's part.
Takes awhile to feel it, but when you do ..
This is not a good album. First, the Buda pest, still at the top, are beginning to lose
their marvellous electric rigor now, after a
e,.uple of million performances and a quarter
century or so of constant work. There are
superb things here, as always, spots where no
usher quartet can match this group in perfection of ensemble and phrasing and in the
understanding of the musical implications. But
then, granted this ultra-high standard, there
is a slight but creeping sense of tiredness that
is just barely -yet persistently- noticeable.
In a word, this is getting to be an old quartet,
...
.
which is no reflection on it whatsoever. We
all get old. Yet it begins to show in the sound.
Secondly, Columbia has done poorly by the
Budapest. The sound is good, sharper than
that of the New Music Quartet, above, and
more live, but it is occasionally strident and
blurred in the reproduction, with pre-echo even
in softer spots. (Columbia's pre-echo has been
bad, lately.)
tVorse are technical faults of pitch that are
hardly to be excused. Not only an off- center
waver. in one of my discs, but in the last
movement of the B Flat Quartet K. 589 the
music begins, incredibly, almost a half step
Hat and so continues to the end. The pitch
seems to sag a bit even earlier, towards the
end of the Minuet movement preceding. I
haven't heard a faux pas like this since the
early days of LP and I'm amazed that, somehow. Columbia allowed it to get out at all,
even if (perhaps) it was corrected in later
production than nine.
18TH CENTURY WITH
L'OISEAU -LYRE ET AL.
2. THE
Mozart: Litaniae Lauretanae, K. 195.
Jennifer Vyvyan, Nancy Evans, W. Herbert, George James; St. Anthony Singers,
Bo id Neel Orch., Lewis.
L'Oiseau -Lyre OL 50085
This French record company, recording
often in England and sponsored in the U.S.
by London, has an extraordinarily enterprising group here, which has been turning out
unusual Items faster than I can keep up with
them-ranging from Monteverdi to Purcell
and Mozart.
The Mozart Litany is one of those astonishing works that most of us (musicians) had
not the faintest Idea existed -yet here it is,
one of the loveliest, freshest, warmest, most
expressive works of Its kind In all the Mozart
literature, and the performance is absolutely
lovely. no less.
Five movements. a medium -sized work,
plenty big enough to "rate" with the Masses,
The Requiem, but on a less formal basis.
Several lovely soprano arias, a generous mixture of solo quartet and chorus, with some
solo work for the tenor as well, a great deal
of wonderfully joyous expressiveness and a
few unearthly touches of more seriously expressive genius. What a piece! Double -A -Plus,
for all Mozart collectors and even higher for
lovers of classic choral works. Superbly recorded with a beautiful balance.
Ana when you've absorbed this, there's another waiting, the Litaniae de Venerabili
Altana Sacramento, K. 243, in album OL
5008.1. No review yet because I haven't played
it yet. One at a time, and I haven't got over
my excitement about the above work.
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APRIL, 1956
Y.
65
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Handel: Sosarme (complete opera). Alfred Deller, countertenor, Wm. Herbert,
Nancy Evans, Margaret Ritchie, et al.,
St. Anthony Singers, St. Ceceilia Orch.,
Lewis.
L'Oiseau -Lyre OL 50091, 2,'3 (3)
For a good part of my
life I've been waiting, just waiting. for a
chance to hear one of the dozens of Handel
operas, never staged and, so far, never recorded either, though numerous arias from
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Rameau: Hippolyte et Aricie (1733).
Claudine Verneuil, Geneviève Moizan,
Raymond Amade, Flora Wend, Cho.,
Orch. Désormières.
L'Oiseau -Lyre OL 50034
Another "first," a famous French opera
that also has seldom been heard, and done
here with all- French personnel. But these are
merely excerpts though the cover doesn't say
so, and the performance is less well shaped
than the English ones and, granted a tough
musical proposition here, a bit hurried in
many spots. The recording, too, is OK but a
bit on the dull- sounding side.
"Hippolyte," Ramenu's first opera, was one
of those revolutionary works that threw the
French into a tizzy of critical warfare, for
and against-the Ramists and the Lullists
(for the older master, whose monopoly of influence Rameau broke).
There is much colorful and boisterous popular -style music here, sailors' dances. mob
choruses, etc., and the choral background of
commentary is lovely. The solos are typically
French, with thin, bright, wiry voices, ultra accurate, and there is lots of accompanied recitative, a much freer dramatic style than in
Handel's music of the sante time. Marvellous
orchestral accompanying music, also numerous
suites of instrumental ballet music. A record
to get to know, but at the beginning its style
won't be easy and familiar as that of the
Handel operas.
Couperin: Messe Solennelle (for organ).
Gaston Litaize, organ of Saint -Merri.
London -Ducretet- Thomson DTL 93039
SOUND REPUTATION SECOND TO NONE
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them are known to every singer.
And so-Isere are three whole discs of the
finest solo Handel you've ever heard, an opera
complete, beautifully performed and styled.
The entire work is a series of recitatives, carrying on the drama, followed by big solo arias
and an occasional duet, plus a short chorus or
two. The format is rigid, but the music is all
plasticity. What the old man could do ! Every
aria is a gem, and there are dozens. Wonderful tunes, in the broad ilandelian manner,
memorable obligato accompaniments, like a
broader and more gracious Bach, and not one
will fail to stick in your memory after a few
playings. Priceless material.
Even the plot, highly classic, turns out to
be quite interesting, though you'll have to totlow the Italian -English parallel columns
closely to untangle it. No synopsis provided.
Battle between King- father and Prince -son,
abetted by wicked villain.
good, long
And when you finish all this
evening's worth for a single playing -there's
another waiting : the complete work "Semele,"
three more LP's, done in English by the same
group ! Haven't played it yet, either. (It's Oh
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This is a gentle and most memorabic organ
recording, mild and not impressive at first but
building up extraordinarily well as you play
it again. It is a whole Mass, for organ only,
numerous Gregorian chants set with florid
counterpoint forming the great pillars of the
work, interspersed with wonderfully ornamented quiet sections for the more colorful
registrations on the organ, full of the highly
expressive elaborate ornamentation of Couperin's time.
This is an interesting piece, since Couperin
has been known mainly for his harpsichord
music. If you have heard one of the several
recording of his "Leçons de Tenèbres," the
Tenebrae, or Lamentations of Jeremiah, you'll
jump to try this music, with its similarly
lovely dignity, a bit stiff and starched but
AUDIO
66
www.americanradiohistory.com
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APRIL, 1956
the more expressive for it. Fine organ recording and the French organ makes an interesting
comparison with the numerous early German,
Danish, Swedish organs we now hear on records.
Masters of Early English Keyboard Music.
(Four centuries of music for Organ,
Harps., Clavichord). Thurston Dart.
L'Oiseau -Lyre OL 50075/6 (2)
A two -record, one -man survey on three instruments, beginning with some raw and wild
Mediaeval tidbits on the organ that will make
you sit up. The organ, a 1760 "bureau" model
or the English type, without pedals, is unusually colorful and alive.
The harpsichord is less interesting. Coming
right after the organ, it is too loud and so
rather unpleasantly heavy In tone. Mainly an
engineering problem, since though the organ
should by rights be louder, both are necessarily
cut at the same standard level on the disc.
The clavichord on the second side of the first
disc is, again, at the same loudness as the
harpsichord on the same side, whereas it
should be much less loud.
Knowing this, you can treat the record as
three Absolute recordings (see Scarlatti,
above), setting each at a different and appropriate volume level for your own playback.
The organ music, all too brief, is the most
appealing part for general listening. The harpsichord items, heavy in sound, center on side
1
around the Elizabethan period, with Byrd.
ribbons, Farnaby; the music on side 2, of
the English "Bach- Handel" (18th c.) time.
is aurally more endearing, especially the
lively, Scarlatti -like Thomas Arne sonata. The
clavichord music (again, too loud) is quite interesting
comes over better than the harpsichord.
The second record (not mentioned on the
album cover, by a printing mistake) covers but
two composers and major ones, Byrd and
Tomklns, the latter well known for his madrigals. This disc, being more consistent and less
diffuse, makes for more purposeful listening.
Byrd is all harpsichord, Tomkins has two organ pieces along with the harpsichord.
-it
Johann Christian Bach: Three Quintets
and Two Sonatas. Collegium Pro Arte.
L'Oiseau -Lyre OL 50046
lie youngest Bach son, he of the Moza rtlike style, is given an excellent work-ont and
survey in this German performance. The interesting items are the quintets with flute and
oboe, highly colorful and airy works with
plenty of life, if lacking in inner harmonic ten
sion. The sonatas are for flute and harle-i
chord. This is a revealing display of the sort
of music that led from "old" Bach and Handel
on to Haydn, Mozart and Beethoven.
Four Concertos of the Neapolitan School
(Paisiello, Durante, Auletta, Mancini).
Ruggiero Gerlin, hps., Ens. Orch. de
L'Oiseau -Lyre, Froment.
L'Oiseau -Lyre OL 5009
From the same in- between period, these
lively works also illustrate the dynamic
changes of style that led from the Bach -Handel- Vivaldi concerto grosso to the light and
airy style of early Mozart and Haydn. These
range front the Ilandelian music of Auletta
(you'd swear it was Handel), to the Bach like Mancini, the lighter style of Durante and
the "Mannheim" fritters and furbelows of
Paisiello. A very nice study in style.
Haydn: Three Trios, Piano, Flute and
Cello. R. Veyron -Lacroix, pf., Jean -Pierre
Rampal, fl., J. Huchot, cello.
L'Oiseau -Lyre OL 50036
here's another nice item front the same
period -these (early) Haydns are actually no
more than keyboard sonatas, with extra baggage. The flute is virtually optional (as is the
violin in the slightly later early violin sonatas of Mozart) ; its part is doubled In the
piano and can be omitted entirely. The cello
merely plays along to reinforce the bottom. in
the old figured -bass style of Bach's time. It is
(Continued on page 78)
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APRIL, 1956
Zone_State
--1
67
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AUDIO
ETC
(from page 62)
far cheaper than tape for amateurs can
ever be.
What is a sensible home policy for tape
and tape editing in this respects
For all recording that is important to
you, use either (a) fresh tape or (b) old
tape in good condition that is not full of
splices-preferably without any splices.
One splice in a whole roll may ruin a
crucial bit of your recording.
Don 't save little bits. For that matter,
don't save long pieces, even up to 25 or 30
feet, unless you want to go to the trouble
of splicing a number of such pieces to-
gether for an extra experimenting reel, not
to be used for permanent work. (But it
takes a lot of tape fragments to make up
even a short reel of this reclaimed scrap,
at 1200 feet on a 7 -inch reel.) It just isn't
worth it, even for the most penny-pinching,
poverty- stricken beginner.
Buy tape in larger lots, a dozen rolls if
you can, and so get a discount that will
make up for all the salvaged bits you can
splice together in a dozen years.
There is only one exception to this
healthy but difficult admonition, that you
throw out all your tape fragments, even
the long ones. The exception covers two
possible uses for odd pieces of tape that
belong in a forthcoming installment, but
should be mentioned here. First, you will
need short lengths of extra tape to splice
into the middle of a reel on some occasions
when you plan to re- record a section of
material and are afraid that you may run
on accidentally into the following part and
so erase vital material that you can't afford to lose. If you will splice in a few feet
of loose tape at the point where you plan
to end your re- recording job, then in case
you run over the original distance a bit
you'll have that much emergency leeway
waiting for you.
You run the risk of a "thump" across
the splice, but better that risk than an accidental erasing of valuable material. I use
this method again and again in my radio
program when I am touching up work that
isn't entirely satisfactory.
The second use for extra tape bits is as
what I call background tape. Tape on
which the background sound of your recording is heard, but without recorded content. You can always find bits of this in
add around your recorded material and it 's
wise deliberately to record some of it at
every recording session. Just let the machine run freely for a couple of moments
at a point where no "program" material
is happening -just silence, or rather, background noise.
If you will keep a dozen or so feet of
this background-noise tape handy, you can
insert very useful pauses and breaks into
your recording in a completely natural and
undetectible way, during the editing. Not
only are breaks between musical numbers
and the like possible, as short or as long
as you may feel desirable, but you may
even re- phrase your speech recording to a
remarkable extent. Perhaps I should say
re -pace; for you can add pauses for dramatic emphasis, for audible "punctuation"
(to give the effect of a paragraph or a
change of subject), or to slow down a delivery that sounds too hurried and breathless. You can improve a speech recording
surprisingly in this fashion if you work at
it.
Note that your background -noise tape
should best be made at the same recording
session as the material- proper, since different sessions, different occasions, produce varying types and degrees of background which won't mix. You can convert
a liability- audience sound, coughs, autos,
etc.-into an advantage by using it in
your editing for a really "on-the-spot"
realism.
Note finally that you cannot patch blank
tape into your show for these purposes.
The sudden "dead" sound is instantly
noticeable, as is the equally sudden return
of the otherwise unnoticed background feeling. (See the discussion of this in the
January installment). Professional editing
makes far too much use of blank tape and
hardly adequate to reproduce modern
High Fidelity records.
Now you can hear in your own home, the living presence
of the world's finest music faithfully reproduced by a
Gray High Fidelity Record Player.
See your local Gray Dealer for a convincing demon-
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Descriptive literature on request.
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DEVELOPMENT CO., INC.
Manchester, Connecticut
even in the most professionally "dead"
studio recordings it shows up for the ear
as that effect of soundless "ionosphere"
that I spoke of ; it isn't any better because
you happen to hear it (between LP bands,
for example) on a highly professional commercial hi -fi recording, than it is in your
own home -grown production.
So far so good -and I haven't come any
nearer to actual recorded sound than the
faint hiss and rustle of background noise.
This account is, more or less deliberately,
hindside foremost, beginning with the
purely mechanical aspects of home -grown
tape operations. True, the very first thing
you do in tape editing is to listen -but as
far as technique is concerned, that comes
last. You must get the mechanical aspects
under control before your listening will do
you any good.
Next installment will take up the listening aspects of home editing.
AUDIO
68
www.americanradiohistory.com
AmericanRadioHistory.Com
APRIL, 1956
LONDON LETTER
(from page 16)
ehich lifts up discloses transcription turntable and pickup.
Finished in bird's -eye maple and walnut,
three drawers are provided for storing 40
tapes each whilst other cupboards provide
accommodation for about 100 records and
a further 25 tapes. This equipment is connected to one pair of a four -pair circuit
which runs around the house, out into the
garden, garage, etc. The other three pairs
are used for a main relay system somewhat
similar to those provided in hotels. Three
FM tuners, operating through 10 -watt amplifiers, are kept permanently tuned to the
three B.B.C. programmes. These tuners and
amplifiers are controlled by a time switch
so that they are switched on automatically
in the morning and off in the evening. In
each room there is either a built -in loudspeaker or a separate one each fitted with a
4 -way station selector switch and a volume
control. No other radio sets are used in the
11mae.
AUDIO PATENTS
(from page 2)
1P312
The inventor gives a sample arrangement
consisting of an amplifier rated at 10 watts
output using a pair of 6V6's connected in
class AB, with a plate -to -plate load of 10,000 ohms and a transformer ratio of 26 to
L The loop to which the secondary is connected has an impedance of 15 ohms and
uses a single wire composed of three
strands each .029 inch in diameter. This arrangement covers an area of 1,000 square
feet. Re points out, by the way, that the
amplifier should have plenty of negative
feedback to minimize the effect of the inductive impedance of the loop on frequency
response, and should be accurately matched
to the loop, a series resistor being inserted if neeessary.
Anti -Feedback System
One of the latest approaches to the cure
of acoustical feedback in public -address
systems is contributed to by John D. Goodell, a name not unknown in the audio industry, and Tenny Lode, and assigned to The
Minnesota Electronics Corp. One of the
methods disclosed is simple enough in principle not to require a drawing. The patent
number is 2,723,316.
Sound from the input of the system
which is probably a microphone and pre amplifier of some kind -is fed into a tape recording head. This, plus a playback head
and an erase head, is operated with a continuous loop of tape. The recorded sound
is picked up by the playback head and sent
t11 the rest of the system and the speaker,
the speed of the tape and relative positions
of the heads being such that the delay in
time is negligible.
The gimmick is that the tape -loop speed
is not kept constant. Instead it is constantly
varied -whether in a random or periodic
manner probably doesn't matter -so that
what is picked up by the playback head is
not at the same frequency as what goes
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AmericanRadioHistory.Com
into the microphone. And since feedback
requires a continuous loop for a given
signal, this breaks the loop at a point between the two heads. The limits and ampli-
TESTED IN THE HOME BY HIGH FIDELITY MAGAZINE
Rated BETTER Because...
tude of the frequency change are not specified and I suppose if .John Goodell says
it's practical, it is. But I can just imagine
the thing used in Madison Square Garden.
adding additional mechanical vibrato to the
already throbbing tones of some politico.
The idea reminds me a little of the phase shift vibrato system used in the Schober
Electronic Organ kits. Not only does it
make the music sound nice, but if you put
your finger on a preamplifier grid it puts a
lovely vibrato on the resulting hum!
The Goodell-Lode patent, by the way,
also contains some details of another
method, this one changing the frequency of
all signals by a fixed number of cycles. It
is all- electronic and rather interesting, but
the explanation is a little more involved
than we have space for.
"Such performance is excellent; exceeded only
by a very few units, all of which are much higher in price."
"The cantilever -stylus-armature construction is inherently capable
of more rough treatment than most moving -coil mechanisms."
"Will fit just about any American -made arm."
"Listening quality is very good, smooth and free of strain
even on heavily recorded passages."
"In
terms of what you receive per dollar spent,
the '500' is a noteworthy bargain."
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AUDIO CLINIC
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At leading hi -li distributors; write for descriptive literature to
RECOTON CORPORATION, 52 -35 Barnett Ave., Long Island City 4, N. Y.
Nassior[wu,
of World -famous Phonograph Styli.
Circle 70
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rest, the mollecular motion within the crystal causes some current drift or flow. The
crystal, having a high resistance, will therefore have a voltage developed across it
although there is no external stress applied. When such a crystal is stressed, its
resistance or impedance is changed, causing a change in the current. This causes a
change in the output voltage. This stress,
or bending motion, also produces great
acceleration of the mollecular motion, causing even larger voltages to be generated
which, again, vary because of the constantly changing resistance of the crystal
under stress. In some commercially available phonograph pickups using this principle, voltages as high as three or more volts
can be obtained at their output terminals.
Cabinet Finish
Q. I've heard that the finish used on the
sound box of a violin has some effect on
the sound of the instrument. Does this
relation to speaker
cabinets? Olive Torpe, Utica, N. Y.
A. The wood of which both the backs and
bellies of violins are constructed is made
same situation exist in
the 3rd
Reprints of articles which appeared in AUDIO
from July 1952 to June 1955. 124 pages of articles of greatest interest to the serious hobbyist.
The AUDIO ANTHOLOGY and 2nd AUDIO ANTHOLOGY
are no longer in print.
CUT OUT
-
MAIL TODAY!
Book Division, Dept. 10
Radio Magazines, Inc.,
P. 0. Box 629, Mineola, N. Y.
check
money order for $
Please send me
copies of the 3rd audio anthology (paper cover) @ $2.50 each
copies of the 3rd audio anthology (board cover) @ $3.50 each
Gentlemen: Enclosed is
.
Name (please print)
Address
City
i
m uu
i i
i i i i
Zone
i i i i
i i
i
i
li
m
i
i i i
i i i
i
.
i i i
State
inui11umu11 nunn1111uu11uumuumn11uu11u m11111111111111u11uuu11unu11u11nnuu n11 umnm1.tn.1111uuu nunu1111nnn1111unu11mG
very thin, since it is intended to vibrate
in accordance with the motion of the
strings. The finish on the instrument must,
obviously, be one that will not diminish the
ability of the wood to vibrate. Bridges and
posts are used to convey as much energy
as possible from the strings to the backs
and bellies. Holes in the bellies allow the
energy of the vibrating air columns inside
the instruments to be transmitted into the
surrounding atmosphere. The output from
the strings, without this added reinforcement, could scarcely be heard. Even with
all these precautions, the tone of a violin
is fragile and easily masked; a string section of perhaps forty violins can easily be
matched in acoustical power by the output
front two oboes.
Speaker cabinets, on the other hand, are
constructed of heavy wood -the heavier
the better. Sand, or even concrete, is often
used in an effort to minimize cabinet vibration; in some types of enclosure, sound absorbing material is placed inside the
cabinet to absorb the backwaves. Thus it
is apparent that the type of finish used
will not affect the performance of the
speaker cabinet, for the cabinet should
not be permitted to vibrate anyway.
AUDIO
70
www.americanradiohistory.com
AmericanRadioHistory.Com
APRIL, 1956
BE THE
IN YOUR
NEIGHBORHOOD
TRANSISTOR PREAMPS
(from page 40)
a
diode.
Ï
If this diode has an impedance
of the order of 12 megohms and a back
current, at approximately 22 volts, equal
or nearly so) to the cutoff current of the
transistor the circuit will be temperature
compensated-provided also that the
temperature coefficients of the two currents are similar. The collector diode of
another transistor would appear to be
the only device capable of meeting these
r. quirements and while the purist is
ely to be disdainful of the notion of
ing a transistor for such a simple
t'uußioa -with an unused electrode at
t
it
nevertheless remains a possible
ntiou to the general problem. The
matching of cutoff currents would certainly be tiresome and vexatious- virtually impossible to the experimenter with
a limited number of units at his disposal
although, at the equipment design level,
it is not improbable that the stage could
be designed to an acceptable tolerance
on input impedance es. temperature
without resorting to an exeessively large
number of current brackets.
Figure 9 is a two stage amplifier with
a power gain of 49 db from a 500 -ohm
source to a 5600 -ohm load and a frequency response flat within 0.5 db from
20 to 20.000 cps. Although constructed
with a 5 -volt supply (four mercury
cells) at approximately 800 pa, a similar
design operating with one or two cells
at somewhat lower gain is not particularly difficult. As in the case of the phono
preamp the large emitter bypasses may
be eliminated by changing to the type
of regulation in which the base divider
feeds from the collector at some sacrifice
in stability and gain.
1
I
-it
Compensation Methods
l'he network fur high -frequency cor-
r
favorite VW
_n_.
WITH
o
}
311'
I
e
300 uu.
.02
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2só
N
-
a
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adiusted to 400
amplifier
power gain of 49 db between a
500 -ohm source and a 5600 -ohm load.
AUDIO
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strip and low impedance audio output
operates perfectly with any TV set
and good amplifier system.
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APRIL, 1956
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AmericanRadioHistory.Com
et
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V &tiler Leal
rection (to compensate for alpha cutoff
in both stages) is in the second stage
emitter in the form of an extra emitter
resistor with a small bypass capacitor.
Although there are severe practical limitations to this type of network as far as
frequency range is concerned, it is quite
adequate to the present purpose of pro t iding flat response to 20,000 cps. The
actual values will, of course, vary aceording to highest frequency of interest,
transistor and circuit parameters, alpha
cutoff, and so on, and are consequently
more difficult to compute than to deduce
experimentally. At the risk of appearing
obvious, we may outline the following
routine:
(1) Run a response curve of the uncorrected amplifier out to 1.25 or 1.5
fH (fH is the high end of the desired
band).
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Features are outstanding. Response:
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db, 20 to 20,000 cps. Sensitivity: FM,
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for 0.5 watt output. Harmonic distortion: Radio input, less than 2 %; Phono
input, less than 0.7 °%. Separate front
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on
(2) Insert an emitter resistor (without bypass) of such a value that the
1000 -cps gain of the amplifier is now
less by an amount 2 to 3 db greater than
the loss at 1.25 fH in the uncorrected
curve.
(3) Add the bypass, computed to
have the same impedance at 1.25 fH as
the resistor.
In the final curve, slight second-order
curvatures will be discernible with magnitude depending upon the required
bandwidth and the alpha cutoff of the
particular transistors used. This is associated with the usage limitation mentioned previously and is due to the fact
that, while alpha cutoff has essentially
the same characteristic as an RC network, merging rapidly into a 20 db/decade slope, the frequency characteristic
of a stage using a selective emitter network is a sigmoid with asymptotic limits
at both ends. Figure 10 is a plot of stage
gain as a function of external emitter
resistance for a stage of reasonably
average characteristics and loading. In
Fig. 11, the corresponding attenuation
from maximum gain has been plotted
against frequency for a network having
a crossover point of 25,000 cps. Since
the maximum slope at any part of this
curve is only 8 db per decade, a casual
inspection might lead one to suppose
that the device is not particularly suitable but (1) more slope may be obtained
by increasing the value of the emitter
resistor and (2) the actual corner of the
alpha /frequency characteristic is somewhat more rounded than its RC analogy
because of dispersion of charge carrier
transit time, non -planar geometry, and
so on. This effect mitigates the severity
of the original problem of correcting the
response to 20,000 cps although, for a
band appreciably wider than this, it
would be preferable to use r.f. transistor
types.
For considerable amounts of treble
boost, it may be more practicable to use
an emitter network in more than one
stage in order to avoid attenuating more
than 15 db in any single stage. For the
completely transistorized tape recorder
amplifier in which both bass boost and
treble boost may be required, a considerable excess of mid- frequency gain will
be necessary and, if the over -all gain
must be fairly high, a promising stage
line -up would be:
1st stage : Wide open to secure good
noise factor and controlled input impedance.
2nd stage: Collector to base network
for low- frequency boost.
3rd and 4th stages : Emitter networks
for treble boost.
In the event that the low -level stages
must be restricted to three, it may be
feasible to incorporate the treble boosting into the first and third stages -leaving the second free to handle the full
swing of the low boost. The deciding
factors are the relative amounts of mid-
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AUDIO
72
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AmericanRadioHistory.Com
APRIL. 1956
mikQappv
effect© tiarn
With no need for occult advice on selecting a pickup, her former clients
f
now consult The Audio League Report. This authoritative publication rates
of stage gain vs. external
R for a typical RC- coupled stage.
g. 10. Plot
the ESL Professional and Concert Series cartridges as "by far the finest
phonograph reproducing instruments."*
f equency gain and end -frequency boosting required.
You're missing plenty wail you switch to the sensational new ESL,
the world's most advanced cartridge. Your dealer has it now.
Conclusion
-
By way of conclusion, we may be permitted to make some general remarks
particularly with respect to the noise
factor.
The hallmark of a good transistor is
its ability to withstand moderate increases of collector voltage and /or temperature without showing a substantial
increase in the noise factor. These are
also the units having:
FOR
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I
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AT
I
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REST
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r,
Anther- ,i qusati' \e.
¡'lase to oil 1 o!.
So. eN. 1 -., for the complete technical and subjective report.
s
N.Y.
Professional Series arm and cartridge $106.50
i'I,u:i -1pn!
..
Long Island City 6,
s-
\'or. so;;)
of The Audio League Report. Pleasann
ilk.
Circle 73
(1) 1000 -cps noise factor below 10 db.
(2) A noise power spectrum better
than that of the average vacuum tube
having an oxide coated filament or
c. thode.
(3) The same (or slightly better) integrated noise factor over a band of 16
to 20,000 cps as the spot noise factor at
TAPE RECORDERS
pat
Gat!
AND
TAPE RECORDING
TAPE RECORDERS
AND
1.100 cps.
(4) Wider tolerance to input mismatching without a significant increase
in the noise factor.
TAPE RECORDING
By
However, for the purposes described
in this account, the potential transistor
user should not place an abnormal emphasis upon the desirability of securing
units having factors of 4 or 5 db as
against those having factors of 7 or 8
db. It is a demonstrable fact that a subjective listening test conducted to provide a direct comparison between systems differing in noise factor by as much
as 3 db must be set up with virtually no
time lag between the two-as by direct
switching -in order to hear the difference and if the lag is as great as one half minute, it is extremely difficult, if
not impossible, to distinguish between
Harold D. Weiler
Author of
"High Fidelity Simplified"
Harold D.
WEILER
The first complete book for the home recordist. Tells why, how,
and what in easily understood language -not too technical, yet
technically accurate. Covers sound, room acoustics, microphones, microphone techniques, editing and splicing, sound
effects and how to make them, maintenance, and adding sound
to slides and home movies.
Board Cover
..
$3.95
Use Book Order card on
Paper Cover
.. $2.95
insert at back of this issue
they.
AUDIO:
ow,
APRIWIT956
73
www.americanradiohistory.com
AmericanRadioHistory.Com
NEW PRODUCTS
drive and a built -in illuminated stroboscope. The motor is of the conventional
4 -pule type and is fully shielded to assure
minimum hunt when magnetic cartridges
are used. Adding to the silence of the
Starlight's operation Is the manner in
which the drive motor is fully encased
and cast in lead to eliminate vibration.
Wow and flutter are less than 0.2 Per cent
rms. The turntable is machined of aged
aluminum to close tolerances for excellent
balance. The entire unit is mounted on
heavy -gauge aluminum plate with the
ernier -type speed control conveniently
located and clearly marked. For complete
information write to Dept. I), Metzner Engineering Corporation, 1041 N. Sycamore
A -13
SL, Hollywood 38, Calif.
River Edge Corner Enclosure Kit. The
new Kit No. 900, recently un. ttneed by
River Edge Sales Corporation, 80 Shore
Road, Port Washington, N. Y., is a deluxe
do -it- yourself version of the popular corner speaker enclosure. Designed according
to sound acoustic principles the No. 900
kit is a true horn -loaded enclosure dimensioned for optimum reproduction. It will
handle all standard speakers, including
tweeters of any size and shape. It is a
completely self -contained cabinet making
use of a front, top, and two sides. Deluxe
a
Transistor Transformers. i)eci- Ouncer
dynamic halo nee. Recovery to overload is
instantaneous and transient stability is
claimed to approae It perfection. Manufactured by Bigg of 'alifornia, 2506 W. \vashington Blvd., Los %ngeles IS, Calif. A -11
t
transt'urnters, re,emI ly introduced by
l'nited Transformer t'ompany, 150 \'arick
St., New fork 13, N. Y., advance the concept of such units for use in transistor
:applications. Remarkably small in size
Knight Music Distribution System. Featuring a Knight 24- watt high-fidelity
am! -applied complete with
-m
ihanget' and two 12 -In.
micropit'; ,
speakers, this new system Is ideal for
making voice announcements and for
aunplifier
'
,
furniture features include a decorative
grill cloth covering the entire front. Full
description and illustrated literature will
be mailed on request to Dept. \' -Al at the
A -9
address shown above.
TruLine Reproducer Arm. Elimination
tracking error through linear travel of
the pickup carriage is accomplished in the
Tru Li ne reproducer arm. It is engineered
in such a manner that the reproducing
stylus travels the exact path established
by the recording stylus at the time the
record was made. The Trul.ine arm is
available in both binaural and monaural
models, differing only in the fart that the
former is equipped with two pickup carriages. Since h,.th carriages function independently, the binaural model may be
used for standard records when desired.
Each r:nria ge is provided with a simple
adjustment to balance the weight of the
cartridge to meet the manufacturer's
recommended tracking force. Both !models
are designed for automatic indexing. Rotating the index knob to the desired record
Of
(hilly 0.03 eu. in. volume), Deci- Outcers
weq'ate at very high efficiency. They Permit excellent frequency response considering their small size, being down only 1 dl,
at 200 cps at 100 mw. Fully cased. They
are hermetically sealed for long life. Eight
standard models cover most transistor requirements. Literature is available on reI
quest frog l'TC.
affording background music in restaurants,
lounges, factories, offices, waiting roetnis,
etc. l'he amplifier is equipped with separate tune controls for bass and treble, and
contains a loudness control which assures
full -range S'und even at very btu' volumes.
an important feature when the system is
ark gro and music.
used for low -level
Amplifier frequency response is 20 to
4(1,000 cps at full nut put. The changer is
equipped with a G. E. magnetic cartridge.
The liti rerophene is at Shure reluctance type Model 520 -SL. Speakers rove G. E.
Type S- 1201 -A mounted in Argos b:tss,.11ox corner enclosures. Allied nadir Chrp.,ratio0, 100 N. Western Ave., ('hir :ago SO,
A -14
Altec Lansing Speaker. The new Model
is an 8 -in. full -range industrial
speaker designed particularly to meet the
requirements of public-address installations and va ri,'ti s types of commercial
sound systems. The unit has a power ca-
olA
h
I
size, then raising and lowering the arm,
automatically positions the stylus in the
run -in groove. Roth arms are equipped
with precision jewelled bearings. All parts
are machined. Audio Specialties Company,
A -10
12167 Steel Ave., Detroit 27, Mich.
II
A -1a
Starlight Hi -Pi Turntable. [tubbed the
"Starlight" as a token of its quiet and
dependable performance, this new turntable is of the center -drive type and op2/3
erates at four speeds, including 16 perrpm, all of which may be adjusted to
fect pitch by means of a variable-speed
Pifty -Watt Ultra- Linear Amplifier. Intended for professionals and l'or high fidelity enthusiasts who are pan'tieulauly
demanding, the Gott Model G -50 -D studio
amplifier meets the highest standards of
audio development. A 50 -watt basic amplifier, it is stated to have a frequency response of 5 cps to 200 ke, distortion 0.1
per cent at 35 watts, and noise level down
99.7 db below maximum output. The circuit employs 22 db of negative feedback.
Features include ultra-linear output stage,
variable damping control, and variable a.c.
pacitY of 14 watts. Impedance is S ohms
coil
and cone resonance is 75 cps. Voice
of the
diameter is one inch. Installationthat
the
401A Is facilitated by the fact
entire assembly is only 3% in. deep.
A -15
Altec Lansing Corporation.
AUDIO
74
www.americanradiohistory.com
AmericanRadioHistory.Com
APRIL, 1956
"BUILD -IT- YOURSELF" AND ENJOY
IN KIT FORM
Q
Heathkit FM TUNER KIT
Features brand new circuit and physical design. Matches
WA-P2 Preamplifier. Modern tube line-up provides better than 10 uv. sensitivity for 20 db of quieting. Built -in
power supply.
Incorporates automatic gain control -highly stabilized
oscillator- illuminated tuning dial -pre- aligned IF and
ratio transformers and front end tuning unit. Uses MODEL FM -3
@ /l /l C O
6BQ7A Cascade RF stage, 6U8 oscillator- mixer, two
6C136 IF amplifiers, 6AI5 ratio detector, 6C4 audio
Shpg. Wt. 7 Lbs.
amplifier, and 6X4 rectifier.
Heathkits
$245'
Q
Heathkit 25 -Watt HIGH FIDELITY
,000
AMPLIFIER KIT
Features a new-design Peerless output transformer and KTti6 output tubes. Frequency
response within ±1 db from 5 cps to 160 Kc at 1 watt. Harmonic distortion only 1% at
25 watts, 20- 20,000 cps. IM distortion only l% at 20 watts. 4, 8, or 16 ohms output.
Hum and noise, 99 db below rated output. Uses 2- 12AU7's, 2- KT66's and 5R4GY.
Attractive physical appearance harmonizes with WA -P2 Preamplifier. Kit combinations:
W -5 COMBINATION AMPLIFIER
W -5M AMPLIFIER KIT:
KIT: Consists of W -5M emConsists of main amplifier and
plifier kit plus Heathkit Model
power supply, all on one chassis. Shpg. Wt. 31 Lbs. Express $5915
WA -P2 Preamplifier kit. Shpg. $7950
wt. 38 Lbs. Express only.
only.
r
I© Heathkit
HIGH FIDELITY PREAMPLIFIER KIT
Designed specifically for use with the Williamson Type Amplifiers, the WA -P2 features
5 separate switch- selected input channels, each with its own input control-full record
equalization with turnover and rolloff controls- separate bass and
treble tone controls -and many other desirable features. Frequency MODEL WA -P2
$ 975
response is within ±1 db from 25 to 30,000 cps. Beautiful satin -gold
P `J
finish. Power requirements from the Heathkit Williamson Type
Shpg. Wt. 7 Lbs.
Amplifier.
Heathkit Williamson Type HIGH FIDELITY AMPLIFIER KIT
This amplifier employs the famous Acrosound TO-300 "Ultra Linear" output transformer, and has a frequency response within 4-1 db from 6 cps to 150 Kc at 1 watt.
Harmonic distortion only 1' at 21 watts. IM distortion at 20-watts only 1.3 %. Power
output 20 watts. 4, 8, or 16 ohms output. Hum and noise, 88 db below 20 watts. Uses
2- 6SN7's, 2.5881's and 5V4G. Kit combinations:
W -3M AMPLIFIER KIT: Consists of
W -3 COMBINATION AMPLIFIER
KIT: Consists of W -3M ammain amplifier and power supply for separate chassis conplifier kit plus Heathkit Model
struction. Shpg. Wt. 29 lbs. $4975
WA -P2 Preamplifier kit. Shpg. $6950
Express only.
©
Wt. 37 lbs. Express only.
Heathkit Williamson Type HIGH FIDELITY AMPLIFIER KIT
This is the lowest price Williamson type amplifier ever offered in kit form, and yet it
retains all the usual Williamson features. Employs Chicago output transformer. Frequency response. within ±1 db from 10 cps to 100 Kc at 1 watt. Harmonic distortion
only 1.5% at 20 watts. IM distortion at rated output 2.7 %. Power output 20 watts.
4, 8, or 16 ohms output- Hum and noise, 95 db below 20 watts, uses 2- 6SN7's, 2- 5881's,
and 5V4G. An exceptional dollar value by any standard. Kit combinations:
W -4AM AMPLIFIER KIT: Consists of
W -4A COMBINATION AMPLIFIER
main amplifier and power supKIT: Consists of W -4AM amply for single chassis construe plifier kit plus Heathkit Model
WA -P2 Preamplifier kit. Shpg. $5950
tion. Shpg. Wt. 28 lbs. Express $3915
Wt. 35 lbs. Express only.
only-
Q
Heathkit 20 -Watt HIGH FIDELITY AMPLIFIER KIT
This model represents the least expensive route to high fidelity performance. Frequency
response is ±1 db from 20- 20.000 cps. Features full 20 watt output using push -pull
61.6's and has separate bass and treble tone controls. Preamplifier and
MODEL A -9B
main amplifier on same chassis. Four switch -selected inputs, and
separate bass and treble tone controls provided. Employs miniature
$3550
tube types for low hum and noise.
applications.
N
Shpg. Wt. 23 Lbs.
W
itGitt
Heathkit construction manuals are full of big. clear pictorial diagrams that show the
plaèement of each lead and part in the circuit. In addition, the step -by -step procedure
describes each phase of the construction very carefully. and supplies all the information
you need to assemble the kit properly. Includes information on resistor color-codes.
tips on soldering, and information on the tools you need. Even a beginner can build
?Nth quality Heathkits and enjoy their wonderful performance.
AUDIO
in
Excellent for home or PA
WIZ
lY/{A/
The World's
Finest
Electronic
Equipment
. .
Kit Form
HEATH COMPANY
A
Subsidiary of Daystrom Inc.
BENTON HARBOR 25,
MICHIGAN
APRIL, 1956
75
www.americanradiohistory.com
AmericanRadioHistory.Com
Hi...M
.aytheon Sidi- Femperatdre Transistors. Design engineers will find welcome
interest in the new Rayytheo PNP silicon
tr;nststors for hiyggh- tbmper
rawer ure apDlicsLgns. Irttlnd -pt'1m
¿y fo audio a7d
low
eryój
rs¡,,
790
R
,CK791Itì po e gAtss
;Fig *Weal audlpl'.t
amplifier of 3 , and 3d db, respectively.
Hi Fi
T
This is It
.
t
i- O -S:ut Turata
meeting professional '''.:....rd
respect, the new Re
pickup
a n destly priced
t intended prim
for
me music sy errs$a. The arm proper
L: tabular constreenton. The cartridge
UV. rkade of di, -cadi aluminum is stetted to the arm l means of a bayonet arrangement
gb permits instant
ca
idge interchan
bSlity. Silver plating and spring lo.sd14ng assure positive
contact. Arm resonnee its
rabl be,
low the usable and:,+
e
e sap
aluminum die- castil,g I
pKovitiion for
raising and lowerlyyg e an. toeeoinclde
with the height of `The
ntable. Dual ball,
Searing races are em
ed sor move ent
'10 the horizontal lape and vertical corn,
',fiance is
the use of special
1 -mm- diameter
c
e -steel balls 1p. a
t
1
BRADFORD
The
Mira:
Perfect BAFFLE*
1
achieve
rent gains are
14
and
24
times. The
is a low -noise transistor for low audio preamp circuits typical unite
- yytng a noise factor from 'below 10 db to
aximum of 15 db. Collector dissipation
át135 C. is 50 mw. Complete data is available from Technical Information Service,
Raytheon Manufacturing Company, 55
Chapel St., Newton 58, Mass.
A -18
CliiI17
Ie1Fel
Radically new idea in loudspeaker enclosures. Not a ban reflex or folded horn.
The primary purpose of a loudspeaker enclosure is to prevent destructive sound cancellation
that takes place at low frequencies, when the
front and rear waves, emanating from both sides
of the speaker cone, merge.
It is obvious that no rear waves can escape
through a totally enclosed cabinet, and it would
be the perfect baffle, except for one reason. The
air pressure within she cabinet acts as a cushion
upon, and therefore restricts, cone movement.
This causes loss of life and color.
The BRADFORD Perfect BAFFLE Is totally
enclosed, yet It relieves cone
by an
ingenious device that ope
in unison with
cone movement.
Since this action conforms to an ultimate
scientific principle Me BRADFORD Perfect
BAFFLE ss the only enclosure that can gins you
the utmost in sound reproduction.
Fairchild Turntable. Operation which is
exceptionally free of vibration, and rumble
content lower than that of most records,
are inherent in the new Fairchild Turromatie "400" home turntable. Typical
measurements of flutter and wow show
lese than 0.07 per cent rms at 78 rpm and
.
bearing which is virtually friction -free.
Precise stylus pressure adjustment is obtained by means of a counterweight which
is threaded to the rear end of the arm.
For further information, write to Rek -OKut Company, 38-01 Queens Blvd., Long
Island City I, N. Y.
A-19
Stephens Low-Boy Enclosure. Known as
the "Catalina," this handsome new speaker
enclosure features a fully -expanding rear horn- loaded acoustic chamber with all
front radiation. It is capable of handling
virtually any type of speaker system in
which the basic unit is a 15 -in. driver.
When used with a high-quality two -way
system, such as the Stephens Model 801
with 800 -cps crossover, the Catalina provides ample room for the addition of the
Model 214 super tweeter and its associated
5000-cps network, thus making a complete
three -way system available in a moder-
And that, specifically, is .
.
ALL THE BASS, full, rich, clean bass, clearly
distinguishing each contributing instrument,
down to the lowest speaker frequency.
NO BOOM. Absolutely no boom. Boom, or
"one note"
bass, is
not high fidelity.
NO FALSE PEAKS. Does not "augment" bass by
false peaks that are really distortions.
ANY SPEAKER. Accommodate any speaker
any size, weight, shape or make.
NO TUNING. No port tuning or speaker match-
...
ing.
ANY POSITION. Operates in any room position.
NO RESONANCES. No false cabinet or air resonances.
COMPACT. Four sizes for 8 ", 10 ", 12" It 15"
maskers. Baffles only 2" larger than speaker size.
Prices:
finished,
$39.50
respectively. Unfinished
S39 50, $59.50, $69.50,
irch, $34.50, $39.50,
$49.50, $59.50.
REAL HARDWOODS. In all popular finishes
mahogany, blond, ebony, walnut.
...
CONSTRUCTION. Hand
INCOMPARABLE
made, band finished
by master craftsmen.
All walls %" thick.
GUARANTEED. Unconditionally guaranteed to
out -perform any other enclosure now available
regardless of size, weight or price.
If you want the very best speaker enclosure and will not be misled as to real
performance by deceptive size or price,
see your audio dealer at once. A demon ion will Convince you. Or write for
...
.
leas than 0.1 per cent at 83 1/3 rpm. An
automatic pressure release prevents flats
from developing on the idler, as pressure
Is applied only when the motor current Is
on. Additional details can be obtained from
Fairchild Recording Equipment Company,
57,
N. Y.
A-17
Fisher FM Tuner. Superb performance,
engineering excellence and moderate cost
are combined in the new Fisher Model
FM -40 tuner. Among Its specifications are
many features normally found only in
tuners designed for professional use.
Sensitivity is 3 microvolts for 20 db
quieting. Frequency response Is within
+1 db from 20 to 20,000 cps. Circuitry in-
literature.
Prices slightly higher west of Rockies.
Patent pending.
pt
BRADFORD
BAFFLE
BRADFORD & COMPANY
27
E.
38th
St.
NEW YORK 16, N. Y.
a three -gang variable capacitor,
three i.f. stages, and a cascode r.f. stage.
The chassis is completely shielded and
shock-mounted. Tuning accuracy: is assured by a panel- mounted meter which
indicates center -of- channel reception. The
FM -40 is self- powered and may be used
With any high -quality audio amplifier.
Fis i
Radio Corporation, 21 -21 44th
A -18
DtivA Long Island City 1, N. T.
eludes
ately small enclosure. Dimensions are
36 "w x 30 "h x 20 "d. Finishes are blonde,
walnut, mahogany, with grill cloth in
beige, bronze, or random gold. Stephens
Manufacturing Corporation, 853S Warner
Drive, Culver City, Calif.
A-20
Ragland "Golden Ensemble" 81 -Fl System. Combining three units in a single
compact cabinet, the new Rauland Model
HF335 "Golden Ensemble" consists of an
AM-FM tuner, a preamplifier- control, and
a 12 -watt amplifier. Addition of a speaker
and a record player is all that is required
to complete a high -quality home music
system. The tuner has separate front ends
for AM and FM. The FM section has a
tuned r -f stage, discriminator with dual
limiters, AFC with defeat on function
switch, and incorporates drift- compensated circuitry throughout. FM sensitivity
3 microvolts for 20 db quieting. Amplifier frequency response is 20 to 20,000 cps
within ± 0.5 db. Separate tone controls
afford both boost and cut of 16 db at 4Q
and 10,000 cps. A ,panel -mounted .tomes
is
AUDIO
76
www.americanradiohistory.com
AmericanRadioHistory.Com
APRIIí,'r956
switch permits a choice of regular volume
control or loudness control. An exclusive
feature is a special TV control position intended for use with the Rauland TV55
television sound tuner which permits hi -11
reproduction of TV sound over the home
music system. The HF355 measures only
e
ing and playback amplifiers are self -contained. An advance ball is furnished for
microgroove recordings. The control panel
includes a VU meter, level controls, a
high- frequency equalizer, and a tone control. Choice of recording, playback, and
public-address operation is made by means
of push- button selectors. The K -11 will cut
any disc up to 13-14 in. diameter. High fidelity enthusiasts who have their own
amplifying systems may purchase the
K -11 without amplifiers. Presto Recording
t ',n'pnratinu, Paramus, N. J.
A -22
Hi -Fi Microphone. Of special interest
to hi -li enthusiasts and semi -professional
recordists, the new American D-300 Series
dynamic microphone is built to meet
broadcast standards for quality, yet is
7.511
Hi -Fi
RECORD CHANGER
%"h x 15% "w x 1114"d. It is housed in a
charcoal black cabinet with marbleized
gold finish. Complete details covering both
the HF355 "Golden Ensemble" and the
'í'V55 television sound tuner are available
from the Rauland -Borg Corporation, 3515
r.
W. Addison St., Chicago 18, I11.
quality "intermix'
changing at
economy prices
A -21
Presto Disc Recorder. Compactly built
ad housed in a portable carrying case, the
ew Presto Model K -11 is a disc recorder
ï ,tended primarily for home and semiprofessional use. It affords three -speed
recording and playback without any adapters, cuts both standard and microgroove
r cords, incorporates two separate speak c:stweeter and woofer-in the carrying
c.oie lid, and is furnished complete with a
quality crystal microphone. Both record-
equipped with a built -in transformer to
meet the high -impedance input requirements of modern high -fidelity amplifiers
and tape recorders. Frequency response is
90 to 15,000 cps. The microphone is
equipped with the new Cannon Type XLII
"quiet" connector, which eliminates annoying clicks and crackles when the unit
is carried. Weight of the D -300 is only six
ounces and length is 9% ins. A miniature
desk stand is available as an accessory.
American Microphone Company, Pasadena,
Calif.
A -23
$4495
audiophile net
Enjoy superior record performance and
unsurpassed listening pleasure with the OA
magnificent DEKAMIX automatic intermixing changer. Wow, flutter and rumble
áre things of the past because of the .
quality that expert craftsmanship has
built into this outstanding changer.
BE YOUR
Choice of LP records for three
best reviews sent in each month.
Simple as that! Just write your own
review on the record selected by Mr.
Canby for the "Problem of the Month,"
send it in, and perhaps yours will be one
of the fortunate three chosen by the
judges. If your review is first, you may
select any three records reviewed in this
issue; if yours is second, you may select
two; the third choice may select any one
,ecord. Your selections will be shipped
-o you postpaid at no cost to you.
Each month, Mr. Canby will name one
record as the "Problem of the Month."
Listen to it, study it both as to music
and as to recording quality. Then write
a brief review on a postcard -no other
entries will be considered-and send it
o AUDIO, Dept. RR, P. O. Box 629,
Mineola, N. Y. so that it arrives on or
before May 4, 1956. Winners will be
announced in the June issue, and the
eview chosen as first will be published,
long with Mr. Canbÿ s own review, in
he same issue.
,
AUDIO
DEKAMIX changes stacks of intermixed 7, 10 and 12 -inch records at
all 3 standard speeds, automatically,
OWN RECORD CRITIC
For this month's problem, Mr. Canby
without distortion
Kid Ory's Creole jazz Band
Good Time jazz 1-12008
dency towards rumble.
Balanced turntable is of rubber covered non -magnetic metal, with a
weighted top -plate to insure against
record damage.
it, borrow it, or just listen to it
somewhere -then tell us what you think
Buy
about it.
ire
RULES
I
2.
4
Ilerìsi,i, nr Ilm iodi. are anal :uul no for respoadenre wilt he entered
into I- g:rdiug
entries or choice+ of the judges.
Review' of the selected record nnl -I be submitred nn a government po.tcani. No others
ill be considered.
Only one entry will he considered from each
contestant.
entries are to become lire Property of
Slag' tines. Iur
and the one chosen
first will be published.
From the list of record+ reviewed by Mr.
rnaby in the issue in which the "problem
remnl" is announced, the writer of the review chosen as first will be given three reeords of his choice: the writer of the review
chosen as second will be given two cereals of
his
choice: the writer of the review chorea
n
r
All
ßndln
.
as
b.
acoustically -balanced
high- fidelity tone arm
has minimum low- frequency resonance and
negligible tracking error.
Supplied with 2 plug -in shells, cne of
which accepts the new GE Reluctance
cartridge, the other accommodating most
other standard hi -fi pickups.
An
.
u
3.
or interference.
Heavy -duty 4 -pole motor is so well
designed that it minimizes any ten-
selected:
has
as
third
will
be
gilen
one
record
of
his
Also available with
a high -performance
crystal cartridge with two sapphire stylii
shell
for the GE cartridge
and one spare
. .
. a
tremendous value at only $5.00
11w
additional.
AT LEADING HI -FI MUSIC CENTERS
WRITE TODAY FOR COMPLETE LITERATURE
choice.
6.
Entries will be judged on the basis of both
musical and technical accuracy. Neatness and
form will not moot, brit the reviews must, in
the opinion of the judges, be sulnclently
legible to be read easily.
APRIL, 1956
ERCONA CORPORATION
Elect'onie Division
I
551 Fifth Ave.,
Dept. New York,
N. Y.
77
www.americanradiohistory.com
AmericanRadioHistory.Com
Listening quality
is everything!
RECORDS
(frost page 6ï)
wholly unnecessary here, though it would add
bulk if a harpsichord were being used instead
of a piano. as originally envisioned by Haydn.
No solo cello work at all.
But the music is lovely of its sort. Those
who know the Haydn piano sonatas will find
these works very much Ilke them, on a slightly
larger scale. Rather dull recording, evidently
L'U,aeau-Lyre s own home -grown product
see the Bauman opera above.
Impartial Lab reports on the new
Audak Hi -Q7 magnetic cartridge:
A leading recording studio:
"Because readings showed an
amazing total lack of distortion, check tests were
repeated 3 times."
-
Consumer sheet:
"Good frequency and
transient response.
Practically no high
frequency distortion.
Low intermodulation
distortion."
Ideal
3. THE VOICE OF VOX
as these reports
are, they belong in the
-
Lab. Listening
quality is everything
and the new
Audaz Hi -Q7 has it to a degree not equalled
by any other pickup. But
HEAR it
yourself
.
.
.
-
there is no other way!
Sweelinck: Harpsichord Music (Fantasias
and Toccatas; Vars. on Secular Tunes and
Dances). Helms Elsner.
Vox PL 9270
.Cell, maybe you've never heard o1 old
Sweelinck. If not-then get introduced, even
if solely via his harpsichord music, to the jolliest, most solid old Dutchman you'll ever run
into, musically speaking. Ile was truly a first
rate master and a showman too, as well as ait
expert in all the tricks of counterpoint and
structure. Ife had a masterful sense for the
apt tune and the danceable rhythm. All this.
of course, back in the late luth and early 17th
centuries
bit before our official Century for
this article, but let that pass. This usan was
a musical Peter Breughel.
This record makes an Interesting contrast
to Thurston Dart's of Byrd and Tomkins, front
England of the same tinte (see above). This
one Is Itmneasurably easier in the listening.
Part of it is in the more dramatic playing of
Elsner. l'art, too, is in the modern sweep of
expression that showman Sweelinck cons
mandel. Byrd, in England, was a great composer but no showman and no extrovert. Ills
keyboard
lc has that peculiarly British
antique quality that persisted-beautifullyuntil the tine of Handel a century later.
Britain was an isolated islnd, remember.
Une side of this rccurd goes to the brilliant
and e pies Toc,itas and Fantasias for keyboard. full of chromatics, echo effects, high
harpsichord coloration. The other is given
over to some of the astonishingly bright variations on popular tunes to the Sweelinck repertory. It is interesting that these memorable
old tunes were also used for keyboard variations in England-Sweelitl/k's "Fortuna werd
ich gelrielseti" is in England "Fortune. 31y
Foe" and well known. the sturdy tune "past -ce
Mars" also appears in British music, as dews.
if I remember, the wo nderful melody .tria
Junges I.ebelt." "My Young Life is at an
End." Highly catchy tintes. and brilliant keyboard variations upon them. and Helton Elsner
does a most intelligent and alive job in she
playing. A tine harpsichord ilIsc.
-a
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copy of
reference
guide,
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"ELEC-
by
TRONIC PHONO FACTS"
at your
pioneer Maximilian Weil
dealer, or write M.
Bach: Harpsichord Concertos in D Minor,
E Major. Helmet Elsner; Pro Musica Orch.,
Stuttgart, Reinhardt
Vox
PL
9510
Bach: Concerto for Two Harpsichords in
Minor; Concerto for Oboe and Violin
in D Minor, Concerto for Two Harpsichords in C Major. Helms Elsner, Rolf
Reinhardt, harps., Will Beh, vl., F. Milde,
oboe, Pro Musica Orch., Stuttgart, Rein-
hardt.
Vox
AUDAK COMPANY
500 Fifth Av'., dept. A, New York 36
Poe audio- elert, de apparatus over 30 years
Bach.
Corelli: 12 Church Sonatas, Opus 3; 12
Chamber Sonatas, Opus 4. Musicoram
Aradia.
Vox DL 163 (3); Special Album
Itere are twenty font- sonatas, each with
four or so nw remenis, all for two violins, a
cello and keyboard accompaniment, harpsichord
in the "chamber" sonatas, organ in the church
sonatas. You won't possibly be able to play
they are
11111.111 all at once, but you nerve not
;
all sweetly melodic, making for easy, melodious listening, the two violins floating in a
silvery duet above the accompanying music.
Recording of both sets Is big and live, sounding larger- than -lite, almost orchestral. .'laying
is excellent. An enmmoss and profusely decorated booklet gives a long and interesting history of ('orelli's life, plus detailed study of
every work, and a plethora of comparative
charts and the like, the latter of so -so Interest
to non- umsicologists, 1Cf. The Westminster
, reviewed earlier in this column.)
Corelli alb
Note that in there two ('orelll albums alone
(here is recorded one half of that master's
entire published life output. The LI' revolu-
tion!
Lalonde: De Profundis. Soloists, Chorus
of Radio Stuttgart, Pro Musica Orch.,
Couraud.
Vox
C
$1.00, 22 -page, 1956
ing, smoothly pliriased and without bouncing
and jouncing, happily minus that nervous
tautness which so often spoils "b!g- name"
Bach recordings. The orchestra is positively
velvety here-good for the nas :c, which conies
through in its own vigorous terms if played
thus straightforwardly.
The recorded balance between harpsichord (s)
and orchestra is remarkably well managed.
The instruments are recorded rather faintly.
ist a distance and surrounded by orchestral
sound, which is precisely right for the music.
Too many recordings blow up the harpsichord
Into a grossly ugly musical bull-in-a-chinashop. Yet, faint as they are, not a note from
these harpsichords is Inaud,ble, and the slow
movements with their solo harpsichord melodies are particularly lovely.
You'll enjoy the concerto for oboe and violin
too, with an oboist whose vibrato is almost
human, like a singing voice. And after a
playing or two you'll discover, perhaps to your
amazement. tuat this concerto Is the same
music as the preceding concerto for two harpsichords. It is, in truth, sa reconstruction of
a lost hypothetical original. that from which
the two -keyboard work had been arranged, by
PL
9580
Two excellent concerto recordings, featuring the saule vigorous lady harpsichordist ses
above (aided by the conductor In the e ertos
for two itistru1151.111s). Titis is fine Bach play-
www.americanradiohistory.com
AmericanRadioHistory.Com
9040
have thought possible. Itanteali. ( 'ouls'ri n, In
Marc-Antoine
Frame. then the once -f
Charpentier.
restored, und on this record
another uni- fatuous e poser of Louis X1%',
ti eke no mistake, these were big aven
La IA
in their him, profound musical thinkers, enormously respected e posers of the highest
rank. But we sure so steeped in the German
ants Italian music of the time that the French
Is still a rather unfamiliar variant of the basic
style for our Tsars-and to the ears of the
French, too, who did not worship their musical ancestors as heartily as did the Teutonic
I
countries.
This is
is big piece with all the trimmings.
but in a clearly "pre- leach" style as of the
lute 17th century. .lost notably, it is cast in
t1'agunaltary form. many short and dramatic
sect i,ai> :nid few forma "pieces" uninh'rI
AUDIO
78
PL
U. the ua'u of the past in music emerge
again from the mists of tinte--as who would
1111
APRIL, 1956
the famous
-
rupted by dramatic change... That was th,
method of earlier
posers of the time
Monteverdi, Schütz, Purcell. But the harmonies are full 18th century "Bach -style," though
there is the characteristic French ornamentation.
The German performance (under an imported conductor) leaves a 1111x011 impression.
Rather too grandiose and over- Itunlaut le, I'd
say, with a consequent loss of rhythmic security and shape, in favor of much fervor. The
sound is immense: the solos, Germanic rather
than French, are good.
But I'd like to lour an :11l- French try at
this music, to get, su to spu k, a triangulation
"fix" on it. It's a kind of music that has un
increasing attraction for us today.
terfraSm4=1.7p
t HIGH FIDELITY
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Especially
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4. ANGEL, VANGUARD, PERIOD
space
P ?rgolesi: La
Serva Padrona. Rosanna
Carteri, Nicola Rossi -Lemeni; La Scala
1
Orch., Guilini.
Angel 35279
L
(1)
Ilere is the famous short comic opera. with
its two characters, In a rousing and effective
is
performance. Both singers are excellent, the
bass a hearty Don Giovanni type, wonderfully
masculine (and eternally frustrated -until the
end), the soprano exactly the right blend of
coquettish fury and feminine appeal ! Gorgeous
Italian enunciation. Big, solid string accompaniment -too big, but very nitr in the sound.
Note that this opera, too, sent the French in
Paris into a tizzy of critical warfare, French
rs, Italian, As we know, the French are always going into tizzies.)
limited
Pergolesi: String Concertinos #1 to #6;
Sonata in stile di concerto; Sinfonia per
Musici.
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I
The finned I \ fusici pruwnt .come stylish
problems in their playing which can make for
i n Ieresting listening. Only eleven players, they
perform much c
eras -like material in what
is perilously close to at
dern "chamber"
style, ts'ith an intimacy- and lightness that suggests, perhaps, the Mendelssohn Octet-true
chamber
sic, wholly non -orchestral. This is
in contras: to the familiar tendency- to build
up small-scale concerto
IC of I his period
into orchestral inn press iveness, as in so many
performances of Bach, I131 111lel, 111111 Vivaldi,
Its I .111/11 1.1's playing the contrast between
solos and "tut ti"-orchestra-tends to be
blurred, and the continuo for harpsichord, invariably present in t:erman and English performances (and indicated, too), is
stly absent or inaudible.
But Pergolesi's music itself titillates tantalizingly 01i the border between "chamber" and
" orchestral" and so I Slush-Fs viewpoint here
Is mare t 111111 usually valid. The playing is
bra nml Oc, light
1111
I rulspar11t
Wit Mama a
!rat.. of on- healliii ponderousness- -which some
will miss, rightly or wr.ngly. Whit kna ws'r
You'll Rod the 5111111' little string concertos
on Westminster, for an interesting caul pa rison.
as playevl by a Swiss orchestra In the more
usual non-chamber style.
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Pergolesi: Stabat Mater. Stich -Randall,
Hoengen; Vienna Akademie Kammerchor,
Vienna State Opera Orch., Rossi.
Vanguard (Bach Guild) BG 549
The faim..., wart:
n ,ble ..ices- sopruuo
and altos solos. plu, :ni ,,-asi nab ehnrus -is
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66
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ICONA(Electronic
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Canada: Astral Electric Co.. Ltd..
44 Danforth Rd., Toronto 13
CIRCLE 79A
Al
DIO
,
s
to the prestige of soloists Stich -Randall :nid
l:.wngeu A gorgeous sound throughout and n
very
sing performance.
ll
y- only reservation, mainly intellectual. is
"I Shashi argument above I : should this
music sound as big and "orchestral" as this?
I honestly doubt it, though the presence of a
choral fugue more or liss indicates a certain
bigness of concept.
Most of the nus ie is as thinly and sparingly
the
ROCKBAR CORPORATION, Dept. LD -1
215 East 37th St.. New York 16, N. Y.
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Please send complete description of the
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i
APRIL, 1956
My Dealer is
CIRCLE 798
79
www.americanradiohistory.com
AmericanRadioHistory.Com
as the "Serva Padrona"-it could be
played with a handful of fiddles and a keyboard plus supporting bass. Borderline music,
again, and as such quite fascinating.
written
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Vivaldi: Concertos for Two Trumpets in
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Solos; Concert Hall Symphony, Acker mann; Winterthur Symphony, Dahinden.
Concert Hall CHS 1242
What a master of sheer monumental bril
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Given two valve! ".-
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works. outbiasting our feeble radio "entrance
music" fanfares 100 to 1 with ease. Relatively
immoveable music, static, but realizing the full
majesty of the mighty brass sound. In those
days of horse and man power. minus machines,
what a gorgeous effect of strength this sort
of music must have made:
The oboe concerti are, relatively, more
routine, that being the only word when one
considers the hundreds of Vivaldi Works now
reappearing for our enlightenment. The first
of the two is the more striking, with an unusually forceful last- movement idea, many
times repeated. Big, live, clean recording, fully
"hi -fi" though- wonderful -the jacket doesn't
even mention that word.
(Note that Concert Hall is still very much
worth watching, though the company's bloated
offspring. Musical Masterpiece Society, not to
mention its Jazz and Opera relatives, has dis
tracted most of its attention and Concert Hall
records are now rather haphazardly distributed. Hard to get, but worth it.)
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Minor,
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PRICE SENSATION!
E
Minor;
Prelude and
Fugue in E Flat). Michel Podolski.
Period SPL 724
Bach for the Lute? Yes, and Period ha,
obligingly reproduced on the cover a manuscript in lunch's own hand, headed In his
handwriting, "Sucre I'orn Ls LEITH, PAIL J. S.
#r 3
in
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MODEL 215A
MAGNETIC CARTRIDGE
With DIAMOND Stylus
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The lute was antiquated and on the way
out, but as we well know, Bach had an extraordinary seine of instrumental color and a
curiosity as to the possible uses he could make
of many exotic instruments; he used the viola
d'nmo-e, the gamba, the oboe ('amore, the
recorder -and the lute, even in his largest
works. such as the St. Matthew Passion, and
always with a special and wonderful effect in
mind. It is an increasing Pleasure for us to
discover his prowess, as we restore these color-Instruments to his music in they way he intended.
Mote that the big lute, related to the present
guitar, has a wider tonal range with bass
notes fan- below those possible on the guitar.
Its tone is flutter and less juicy, but it gets
over its complex effects, one -handed, more
adroitly than the guitar.
This disc, then, is highly recommended to
ell guitarists who have a yen for "classical"
stuff on their instruments. It'll make you feel
much more important when you play Bach
:1
While
Vanguard (Bach Guild) BG 548.
Here's the classical guitar, for a good contrast to the lute, above. The record covers a
pile of music, ranging from the 16th century
through the 18111, the composers largely unfamiliar; most of it was written originally for
the lute and so is of course appropriate for
you aren't a lutenist.
the guitar
Mr. Scheit's playing is technically proficient
ana nicely colored, but after awhile It seetns
to plod. Musically he is sincere. earnest, con cientious, hard- working. I suspect that many
an amateur guitarist will not only thank him
for the wide display of interesting repertory
here, but also for the chance to play the same
music with more life and verve.
-if
-828 rPNltfermrr $37r50
ys
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Lost,
la Segovia.
Renaissance and Baroque Music for Lute
and Guitar. Karl Scheit, guitar.
=213A Carlelege
They
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trumpets, that could play the notes of Ili,
overtone series only -what could be done*!
Listen and you will hear. Both trumpet concerti are extraordinarily rich and ornamental
APRIL, 1956
ORGAN REPRODUCTION
(
from page 28)
monaural, or stereophonic sound.
Four brief selections were chosen to
illustrate various properties of the organ,
including its mellowness on soft passages, its full dynamic range, the purity
of its upper registers, and the directional
effects made possible by the locations of
its two groups of pipes. These were
recorded an hour before the performance.
Changeover from recorded to live
sound was done by visual signals between
the organist and the operators. Although
the organist was not wearing earphones
and was unable to monitor the outputs of
the recorders, his tempo was so accurate
that he was rarely more than a fraction
of a note away from the recorded music
when a switchover was made.
The Result
At most locations in the rear half of
the church, it was nearly impossible to
detect the switching from live to recorded
sound. Even monaural playback sounded
enough like the organ to confuse many
listeners. During the final selection, the
signal lights were switched off, and the
transition from live to monaural and
stereophonic playback, followed by several alternate periods of each method of
playback, was made without being detected by most members of the audience.
At certain places in the church, particularly near the front, some tape hiss and
hum were audible at times. This usually
was the only indication that a recording
was being played. Even where differences
were detectable at changeover, it was
usually not possible to determine which
sound was live and which was recorded,
without assistance from the signal lights.
Our conclusions, as a result of these
experiments, concurred with by virtually
all who heard them, are:
(1) True -fidelity or facsimile recording
and reproduction of the pipe organ
in its original environment has been
accomplished.
(2) The audio art has progressed to the
point where high quality amplifiers
and loudspeakers, designed for home
use, are capable of virtually undistorted, true -fidelity performance,
when supplied with input signals of
comparable quality.
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ELECTRONIC MUSICAL
INSTRUMENTS
By
Richard H. Dorf
In one big volume, you can now learn all
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organs, including the Allen, Baldwin, Conn sonata, Hammond, Minshall - Estey, Lowrey
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Thyratone show you how to build one of
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A compilation in book form of the author's
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(Foreign, $8.00) .
Customary discounts to dealen and distributors
Acknowledgments
In addition to the individuals and companies named earlier, this experiment
was made possible through the wholehearted cooperation of St. Mark's Episcopal Church, Mount Kisco, N. Y. Valuable assistance was also rendered by the
members of the Harmonic Hill Radio
League, James Wallace and Gladden B.,
Houck, Jr. Photographs by Ed. Dombert.
AUDIO
RADIO MAGAZINES, INC., Book Division
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Please send me
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copies of Dorf's ELECTRONIC MUSICAL INSTRUMENTS
enclose check
for $7.50 each
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(Foreign, $8.001.
I
Name
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City
APRIL, 1956
Zone
Stato
81
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NORELCO
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(from page 29)
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Gain
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Materials are selected and treated for
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A = amplification
without
feedback
= feedback factor.
ß is the Greek letter beta, and is the
symbol used to designate the feedback
factor-the fraction of the output voltage fed back. This value may also be expressed as a percentage. Let us now insert the foregoing data in the feedback
equation.
A equals the gain without feedback.
which is 39. ß equals the fraction or percentage of the output voltage fed back,
which is 1.17 divided by 9, or 0.13. Therefore, the gain with feedback is equal to,
A
1
Available in sizes from 12 to 5
inches. Prices of Twin -cone ""FRS"
speakers range from $59.98 to
1
ßA
'or1
(-
39
6.07'
rithm of this ratio from a log table, and
multiply the log of the ratio by 20. It
is worked out as follows,
39
0.13x39)' which
is
or 6.13.
To express the feedback voltage as a
percentage we multiply Ii by 100. or
0.13 x 100 equals 13 per cent. It can also
he given in decibels and the reader
familiar with logarithm tables will have
no difficulty with the expression, db =
20 log H:1 /F.',. Here we ascertain the
ratio of the ctdtii,r _:tins. find flit It _a-
39
6.-13
(v.g without feedback)
(v.g. with feedback)
and this ratio equals 6.07. The logarithm
of 6.07 is 0.7832, and 20 x 0.7832 equals
15.7 db. Thus it can be stated that we
have introduced 15.7 db of negative feedback. The feedback in decibels may also
be found by employing the ratio of the
voltages of the input signal from the
audio oscillator with and without feedback in the same manner. The above
figures are accurate for all practical applications; the answers were found on a
slide rule and the results rounded off
for simplification.
The foregoing study of feedback voltage has been made with resistance only
in the feedback circuit which permits
feedback voltage to be of about the same
magnitude throughout the audio -frequeney baud. Frequency-selective circuits may be used which will result in
variation in the amplitude of the feed hack voltage with frequency. It is beyond
the scope of this present article to
analyze these circuits. The Radiotron
Designer's Handbook2 is an excellent
reference for further study of feedback
voltage.
Tube Department, RCA, Harrison,
2
\..1.
VOICE COIL:
R27
Specially hand wound for each speaker
type -assuring, maximum overall
%
efficiency.
MAGNET:
Distinctive steel alloy with preferential
crystal orientation to provide highest
magnetic power. Each speaker magnet
is individually aligned-thus damping
distortion, increasing efficiency and extending the frequency response.
ose
... and improve any
sound system with/4h,'e/co®
and prices of these unique speakers.
North American Philips
100 E. 42nd Street
New York 17, N.Y.
Co.,
Inc.
liAtO
i
Ti
16.
16..
9.0u
LOAD
(A)
R27
...
NON
10,000
ose.
16.
LOAD
I,4v.
*FULL RESONANCE SPEAKERS
Write today to Dept.A -4for brochures
0,000
0.13 v.
In all "FRS" speakers, the high range
cone is of special design and makes it
possible to obtain a smooth response
curve, extending a full octave above
10,000 -up to 20,000 cycles. Speaker
designs provide energy transmission almost independent of frequency.
ADD To
1
(BI
Fig. 3 (A) Circuit arrangement for measurement of amplification without feedback.
(B) Same circuit with feedback loop connected for measurement of gain with feed-
back.
AUDIO
82
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APRIL, 1956
NEW LITERATURE
PER FECTCJN!
MIRACORD
XA-100
with PUSHBUTTON CONTROL
and the "MAGIC WANO"SPINDLE
TWO in ONE!
(1)
12)
Pushbutton Automatic Changer
Pushbutton Manual Player
Nothing compares with MIRACORD
the
ache of modern high fidelity record reproduction! Acknowledged the world overr for
performance -perfection and versatile con.
venience.
what you'v been missing
MIRACORD at your Dealer n w.
-
Hear the
$67.50
Shipped completely assembled with all plugs
and leads attached, ready for operation.
with
GE
RPI.050A Cartridge
$74.50
AUDIOGERSH CORPORATION
23 Park Place, New York 7, N. Y.
WOrth 4-8585
Couda Atlas Rodeo Corp lid. Toronto. Canada
Circle 83B
Electra-Voice, Inc., Buchanan, Mich.,
has just issued Bulletin 222, a comprehensive, colorful brochure on E -V Circlotron
high -fidelity power amplifiers, amplifiers
with controls, and music control centers
with preamplifiers. The publication gives
complete technical data, specifications, and
prices on 15 -, 20 -, 30- and 50 -watt power
amplifiers, 15- and 20 -watt enclosed lowboy amplifiers with external controls, and
enclosed modular music control centers
for use with E -V power amplifiers and
AM -FM tuners. The bulletin also includes
information on the new E -V 100 -watt
high -fidelity amplifier for multispeaker installations and professional applications.
Your copy will be mailed free on request.
A-1
University Loudspeakers, Inc., SO S.
Kensico Ave., White Plains, N. Y. announces the availability of a new guide to
Progressive Speaker Expansion. Known as
the PSE guide, it is complete in every detail. It contains detailed information for
expansion of speaker systems to their full
potential, illustrating step -by -step expansion with simple color -coded charts. Included in the guide are data on the use
of adjustable networks, dual -impedance
woofers,
woofers,
adjustable- response
midrange speakers, and tweeters of various types. In addition, the complete line of
University speakers and network components 1s illustrated with all important
specifications. Your copy may be obtained
without charge by writing to the attention
of Desk LA32 at the address shown above.
A -2
International Resistance Company, 401
N. Broad St., Philadelphia S, Penn., offers
Bulletin A -3 describing the new IBC Type
2\V variable wire -wound control, which Is
ideally suited for many electronic applications such as outdoor -movie speaker control, and control for test and measuring
instruments. The cover of the unit is so
styled that, for all practical purposes, it
may be considered dust- pis st sf. Bulletin A -3
A.3
will be mailed on request.
Fine Hardwoods Association, f,Bd Lake
Drive, l'hicago II, III., offers a
wealth of information to anyone who specifies, buys, or sells hardwoods in the
. F'i ne I fardwoods Select nra uta," a handy
reference guide which has just been published. More than 400 commercially available species of hardwoods are described,
giving geographical sources, ci l or, pattern, common uses, availability, and general price range. hi addition, 146 of the
most popular hardwood flgurs and species
types are handsomely illustrated, 38 in
full color, as an aid in specifying or identifying woods. An especially valuable feature of this 60 -page reference book is a
chart of the comparative physical properties of 65 of the most widely -used haudsvond species. Each wod's ratings are
given
for specific gravity, weight,
strength, stiffness, hit does, sleek- resistinK ability, bending strength, and shrinkage. This hook will lie of great value to
Shore
THE NEWEST!
41.1.4
K -3
CORNER
SPEAKER
CABINET KIT
kitform of the original
...one
corner speaker horn
of 39 new units!
slightly higher west and south
Write for Complete
36fopages
of radio
$54
t-
furniture
the si -h
fidelity home kits and speakers
music system.
anyone engaged in the design and construction of equipment and speaker en1<
closures. Copies of the "Fine Hard
IN
Selectorama" can be obtained dil
in,,r copy A -4
from the Association at 'I
.
s
COMING EVENTS
(Jorn pu pt 1't
Mai -3 -3 oint Electronic Components
l
1
Conference, I.R.E., National Bureau of
Standards, Washington, D. C.
\luny 21- 24- Eiectrouic Parts Distributors
Show. Conrad Milton Hotel, Chicago, III.
June 17-23-Second International Congress on Acoustics. Registration at Mass.
99 North 11th Street, Brooklyn II, N.Y.
largest manufacturer of cabinets and kits for hi fi
a
division of G d H Wood Products Co.. Inc.
Circle 83C
AUDIO
Inst. of Technology, l'aunbridge, 'Stags.
Aug. 21- 24- \VESCON, I.R.E. Convention
and West ('oast Electronic Manufacturers Association show, Pan Pacific Asltlitoriuu, Los Angeles, Calif.
September 27 -30 -Neto York High Fidlity Show, New York Trade Show Building, New York. Sponsored by Institute caf
High Fidelity \lauufacturcrs, Inc. and
the Audio Engineering Scscicty.
October -1 -7 -Neto York Audio Fair, Hotel
New Yorker, New York City.
IT'S NEW !
IT'S SUPREME !
IT'S HERE NOW !
The Ferrograph Tape Recorder
AT LEONARD RADIO
Once again LEONARD RADIO brings
you the newest and finest innovations in
Hi -Fi. It's the Ferrograph tape recording
and playback mechanism. European made,
the Ferrograph tape recorder has all the
quality workmanship and perfection of
creative design that European manufacture is famous for.
Just look at these features:
3 individual motors
"Octnqued" hysteresis capstan too tor
Dual track
Auto -stop switch
3% -71,4 ips. (or 7IA -15 ips.
slightly additional)
Freq. resp. 2 db bet. 50 and 10,000
cps at 7iÁ ips., and bet. 40 and
15,000 cps at 15 ips.
Separate bass and treble controls
379.50
Price
[EONAJPDS
You Can Hear
The All-New
KELLY
RIBBON
Hi -Fi Tweeter
The Kelly Ribbon unit represents a radical advance in the development of tweeters. The diaphrant consists of a special
.0003" duralumin foil, operating in an
intense magnetic field. Freq. resp. 3000
to 20,000 cps. Attenuates all frequencies
below 1000 cps. Power handling is Netter
than 10 watts, Imp. Ft ohms. Requires no
baffle isolation and i- supplied complete
with 3000 cps dividing network.
.flail, Idiom ord,,,
fi';
Price
d,
89.95
pr',il. bolanro C.O.U.
E O N A R CI RD1Oe INC.
COrA.e MOM
r.M1 r. N.Y
Circle 83A
83
APRIL, 1956
www.americanradiohistory.com
AmericanRadioHistory.Com
PROFESSIONAL
SAVE
..s
1
This
-s
Is oar
GROUP SUBSCRIPTION PLAN
Now you, your friends and co- workers
can save $1.00 on each subscription
to AUDIO. If you send 6 or more subscriptions for the U.S., Possessions end
Canada, they will cost each subscriber
$3.00 each, 1/4 less than the regular
one year subscription price. Present
subscriptions may be renewed or extended as part of a group. Remittance
to accompany onion.
is still the only publication
devoted entirely to
Audio
Broadcasting equipment
Acoustics
Home music systems
Recording
PA systems
Record Revues
i
Please prints
Name
Address
New
Renewal
Name
Address
New
MUSIC
SYSTEM
(from page 25)
25%
AUDIO
HOME
AUDIO_
Renewal
TV /FM tuner. When not in use, the
front panel of the drawer is flush with
the rest of the rack, which makes for
a neat appearance. Both the changer
and the transcription arm use plug-in
cartridges, so that only one stylus need
be replaced at a time, instead of having
to replace two when only one is worn
out. Diamond styli are used throughout;
which not only gives less record wear,
but provides a needle which actually
costs less in the long run than any other
type.
Both the tape recorder and transcription turntables are powered by
hysteresis- synchronous drive motors.
There has always been a great misunderstanding about this type of motor in
that the user feels that it is included to..
reduce or eliminate flutter or "wow."
Actually, exactly the reverse is true, for
a synchronous motor creates flutter. The
very principle upon which it is built requires that the motor make instantaneous
speed changes. This motor locks itself to
the a.c. power -line frequency rather
than to the voltage. Then, if the frequency changes. the motor will speed up
or slow down. This continual "hunting"
for the proper speed shows up as flutter.
The great advantage of this type of
motor is that over a period of time it
will average its rated rpm. This results
in superb timing in tape and disc recorders and players, sometimes as little
as one second timing error in 30 minutes.
The inherent flutter due to hunting is
minimized in tape equipment by a care-
fully designed flywheel, and in disc
equipment by the turntable itself.
At the top of the rack panel area, just
above the tape recorder, is the master
power panel. This contains a fuse, an a.e.
convenience outlet, the master power
switch which controls. all the equipment
in the rack as well as power to the turntable and cueing amplifier, a tally light,
and an electric clock accurate within onehalf second. It the master fuse should
blow, the tally light will glow, the clock
will stop at the time of failure, and
'
Fig. 5. Bass-reflex two -way speaker system incorporating 10 -inch accordion -cone
woofer and
a
high- frequency horn.
Name
Address
New
Renewal
Name
Address
New
Program
mixer- amplifier to drive tape
recorder at proper
level and impedance.
Volume
metering is also
Fig.
Renewal
Name
Address
New
Renewal
provided in addition to three mi-
Name
Address
New
6.
line
crophone inputs.
Renewal
U. S.. Possessions. and Canada only
RADIO MAGAZINES, INC.
P. O. Box
629, Mineola, N. Y.
AUDIO
84
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AmericanRadioHistory.Com
APRIL, 1956
power to the above named equipment
kill be cut off. The bulb
117 -volt
neon lamp across the fuse -continues to
glow until the fuse is replaced. Since the
small toggle switch cannot handle all of
the 117 -volt 60 -cps current drawn by the
rack and its associated equipment, the
power is actually controlled by a relay
located behind the panel, and operated
by the master switch.
The system described above was designed essentially for home use. However, since it incorporates professional
equipment-besides being extremely versatile-it may find many commercial applications, depending upon the user's requirements. This set -up has been in use
for a number of months, and no design
-a
faults have shown up; so it can be assumed to be virtually foolproof. In addition, although no preliminary hook-ups
of the equipment were made prior to the
actual installation, no hum, distortion, or
switching difficulties were encountered.
Doubtless, the reader will find variations
of the design that he will wish to incorporate into his advanced sound sys-
Brings Out The Best
In Your Hi Fi Set!
tem.
POWER AMPLIFIERS
(from page 52)
tr.
MIRATWIN
Cartridge
may be listed as follows:
1.
Adequate power capability for the
task at hand. For common home installations this may be anywhere from 5
to 50 watts, depending on the electroacoustic efficiency of the loudspeaker
system (the percentage of amplifier
electrical energy converted into
sound), the size and furnishings of
the room, and the sound levels that are
desired.
2. Low harmonic (and intermodulation)
distortion-preferably
below 0.5 per
cent harmonic at rated power.
3.
Uniform frequency response, within
± 1 db, from 20- 20,000 cps at rated
power. Almost any amplifier will show
a wonderful frequency response curve
at very low power.
4. Low hum and noise
-at
NEWEST ADVANCE
MAGNETIC
IN
CARTRIDGE DESIGN AND PERFORMANCE
Miratwin Variable Reluctance Magnetic Car-
tridge features unusual wide -range response
and sensitivity
sitivity
Faithfully and minutely
brings out the rich, full tones of today's
recordings!
.
..
LOADED WITH NI Fl FEATURES
-
AT YOUR DEALER
MST-2A
MST.2D
.
NOW!
MIRATWIN Turnover
Cartridge with two Sapphire Sty li
;si 50
1
MIRATWIN Turnover
Cartridge with Diamond Stylus
for Microgroove and Sapphire
Stylus for Standard
$45.00
AUDIOGERSH CORPORATION
23 Park Place, New York 7, N. Y.
WOrth 48585
In Conada Atlas Rodio Cory Ltd
Toronto Corroda
Circle 85A
least 60 db
below the rated power.
5.
Stability- absence of "ringing" or
tendency to self oscillation.
6.
Proper damping factor for the application, or a variable damping factor.
tAttenuators,
Equalizers and Filters"
by Dr. George K. Teffeau and Dr. Howard 7. Trentaine
J]
.rewrassr.v uvaenR
'Phis now book thoroughly describes the
design, application and theory of operaion of every type of Attenuator, Equalizer and Wave Filter. Covers all types of
equalization and attenuation used in
FORTHCOMING
BOOKS
This series on "SOUND" by E.
M. Villchur will be published in
book form, with the probable publication date around October 1,
1956. His earlier series, Handbook
of Sound Reproduction, which appeared serially in the magazine,
will be published approximately
May 1, 1956. Further announcements of the publication date and
price will be made in the May
issue.
audio recording and reproducing systems, both professional and home -type.
Includes chapter on hi -fi crossover networks. Provides time -saving charts
which permit the easy determination of
component values required in designing
equalizers and filters. Fact -packed, indispensable to technicians in radio
broadcasting, television, cinema work
and to audiophiles. 176 pages; 5%' x
!t '; fully illustrated. Deluxe
á4O0
hard binding, postpaid
Also available in paper-bound
edition, postpaid $2.75
ORDER
HOWARD W. SAMS CO.., INC;
Howard W. Sams A Co., Inc., Dept. 20 -D6
2201 East 46th St., Indianapolis 5, Ind.
Send me:
U
I
"Attenuators, Equalizers & Filters"
Hard Binding ($4.00)
Paper -Bound ($2.75)
I
Name
Address
(priced sliehtly hirher outside U. S. A.)
Fig. 7. Rear
AUDIO
I1la111ttt.1MIM
view of the equipment rack.
ret1111111111MtR?t==1R1
Circle 85B
APRIL, 1956
85
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M
O
BIGGEST
DOLLAR'S
WORTH IN
RECORD
CHANGERS!
N
R
C
H
9Ka,sbut
nom...
L.R.E. CONVENTION SCUTTLEBUTT:
Harold Ronne, one of the country's best
liked and most competent editors in the
field of electronics, receiving congratulations on his new position with Bell Telephone Laboratories, Inc. .
John W.
Lowery, who designed and developed the
remarkable new RCA tube tester which
was cane of the hits of the I. R. E. exhibition, has promised to write an early article for AUDIO on his "perfect" hence
music system. Really an audio man's audio
man.... Harold D. Weiler handling hundreds of queries with the sane answer,
"April 1." That was the scheduled publication date of his new hook, "Tape Recarrlers tend Tape Recordings."
Saul White of Racon Electric Company,
Inc., elated t,vet the interest shown in the
new
Itacou "pneumatic- damped"
hi -fi
speaker. A two -cycle Inne was used to
display the speaker's exceptionally long
cone travel.
E. J. (Manny) Marcus
and Howard Weinberger of Tetrad, Inc.,
world's largest elan of art urer of diamond
styli, spent endless hours in the Tetrad
display proving to visiting engineers the
economy of diamond over sapphire, not to
mention the farmer's superior perfurm.
a
.
lice.
Sandy
.
Cahn
formally announced
ced
as
Executive Secretary of the Institute of
Ifigh Fidelity Manufacturers and will direct the New York High Fidelity Show to
he conducted this Fall..
Elwood King
(Woody) Gannett doing his usual firstrate job of hosting the visiting press, at
the same tinte proving, contrary to cotnnu,n upin ion, that it is thoroughly possible
for a top -drawer engineer to be equally
talented in the contrasting field of public
Observation: Whitney Easrelations.
ton of NBC and Will Copp of I. R. E. look
so much alike that, on at least one occasion, Whitney was introduced to an old
friend as "Mr. Copp." ... Jim Pord, advertising manager of Ampex Corporation,
dividing his attention between I.R.E. activities and the impending arrival of a
new "Henry" or "Lizzie" in the Ford
household so et tme around April 13.
NEWS BITS PROM HERE AND
THERE. The hi -fi picture in New York has
been brightened beyond measure by the
presence of Mrs. Harvey E. Sampson behind a counter in the new "Auditorium"
of Harvey Radio Company, Inc. Pressed
into service because of increased business
.
AVAILABLE
AT
.
ALL LEADING DISTRIBUTORS
Circle 86A
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 ad-
ditional 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. O. Box 629, Mineola, N. Y.
experienced
needed
flNments.
d lueed.
fell.
[nest
and
per
word
tommertld
for
net, and
aye
Copy meet
for non eommerc la
per Insertion
wore
25e
;
Rates
dime
no
le accompanied
reach
Nov
the
by
d
U,r111
lttanw
An
York
Ant al the month preceding the date
nus
rem
by
M
In
the
Inge.
.
.
THE A l'DleI EXCHANGE has the larges
fully guaranteed used
equipment. tin lalug of Isere' equipment on re
quest. Audio Exchange, Dept. AE, 159`1911 ill
side Ave...Jauna ica 32, N. Y. (IL 8 -0415 und 367
\Lutt:tr eek Ave., While l'laius, N. Y. WH
select i,sn of mow and
I
8.33s1
.\I'Ultl Ext9IANi ;l.:
EXCHANGES AUDIO
lI N'P. h'netory -fresh guaranteed 1.1' record., t ine and tip; send 2Ot for
st t I -I'I INVEST RK('ORIh SALES,
ea l a Logue,
I,ISt't
;
Dept. A.
1
N" inhere,
I
Houston, Texas.
HIGH- FIDELITY SPEAKERS REPAIRED
Alti ,rile Speaker Service,
70 Yesey St., New York 7, N. Y.
R\
7-2580
6- ELEMENT BROAD-BAND ANTENNAS.
\II sennlless at lu m inum. $10.05 ppd.
Wholesale Supply ('o., Lauenburg 10, Mass.
SELL
\1'ebcor Meslel 210 tape recorder;
:
good Mechanical and electrical condition, factory null utcnantr, $50. AMPRO Model 756
Ili PI, like new, $160. Sell either one. Ray
K000111. 1.iuc1l11. 111i11ois.
TRADE:: i'i,-keriag 1)-240 cartridge, used
5
hours, exeelleat. for an Audax III -Q7. Charles
Leigh, 162 l'assoie St., Trenton 8, N. J.
HELP WANTED
EXECUTIVE TO HANDLE CONSUMER
TECH\ I('A L CORRESPONDENCE AND
ASSIST IN GENERAL SALES. MANUYORK SALES
NEW
FACTURER,
AREA. TECHNICAL BACKGROUND
AND EXPERIENCE IN HI -FI AND
PUBLIC ADDRESS COMPONENTS AND
INSTALLATIONS ESSENTIAL. SEND
RESUME. STATE SALARY REQUIRED.
BOX CA -I, AUDIO.
"SOUND RECORDING & REPRODUCTION"
The BBC's Training Manual for its own Engineering Staff. 272 pages. 176 illustrations
covering every phase of recording and playback: disc. tape, flit, wire, pressings. etc.
illustrated
Every point concisely explained
with examples of American and European
equipment: technical level definitely not above
the ambitious layman. Send check or money
order- for $6.25 to: Gotham, 2 West 46th St.,
New York 36. N. Y. We pay postage in U.S.A.
:
TRONICS RECORDING TECHNICIAN
-LOS ANGELES LOCATION. REPLY
BOX ('A -2, AUDIO.
fall which caused a serious arm injury.
.. ]ä. Roberts Rogers, president of Washington's Good Music Station WGMS, has
FM ANTENNAE
FM BROADBAND YAGI for fringe and long
distance reception, high -gain design for maximum sensitivity to 72 or 300-ohm tuner input.
Apparatus Development Co., Inc.. Wethersfield, Conn.
sity. (Unpaid Adv.)
Jim Pickett, well -known New York factory- representative, hack on the Job after
a
SPEAKER DEVELOPMENT
for high -fidelity, television, radio, and special
applications
for high -fidelity application requiring eery low
,,
for
ehartlueent
in the new sound room, Mrs. Sampson,
whose husband, Harvey, is the company's
president, is adding a note of grace and
charm to an industry whose esthetic nature makes such qualities a virtual neces-
CARTRIDGE DEVELOPMENT
audio
engineers
105 per
.
.
AUTOMATIC
RECORD
CHANGER
CLASSIFIED
B eta:
tracking
/orce.
economical mechanised manufacture of speakers
and cartridges
Send resume to:
ELECTRIC
ELECTRONICS PARK
SYRACUSE. N.
;
('ustom. made, 22 cu.ft. infinite baffle, sand filled [iront panel, 1 3/16" plywood, fully lined,
braced. cut for 15 -in. speaker. Unfinished. Sacrifice $65. J. Albert, 135 -33 230th St., New
York, N. Y.
ing $110. ST
*
541 cut terhead,
4 -0420.
perfect, ask-
New York City.
ALTEC 60IA speaker. used, but like -new
condition. $65 f.o.b. N. Y. Box CA -3, AUDIO.
BACK ISSUES OF AUDIO, 1947 through
per year. W. Connor, 5304 N. Mason
St., Chicago 30, III.
WINLUND
1955, $5.00
Tele; icion Receiver Dept
GENERAL
Fisher TORT tuner, $125: Fisher 50C Audio
Control with cabinet. $60: Pickering 19OB
arm, $20 Hartley 215 speaker. $40. All like
new. Norman Tetemnan, 2350 East 27th St.,
Brooklyn 29, N. Y.
FAIRCHILD
PRODUCTION DESIGN for
E. S.
WANTED: EXPERIENCED ELEC-
AM and FM tuner repaire and realignment.
12 years experience. AUDIO CUSTOM CRAFTERS, 19
l'ire St.. Woburn, Mass.
Write for further Information.
Y.
Circle 86B
WANTED: Vertical transcriptions; also address of Chicago party regarding same.
James Orlando. Dickerson Run, Penna.
AUDIO
86
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APRIL, 1956
PROFESSIONAL
DIRECTORY
life member of the
Philadelphia Orchestra Pension Foundation. The honor was accorded in recognition of the special "high -fidelity" concert
he produced for the Foundation on February 13. .. Lawrence (Larry) LeBashman, vice -president in charge of sales for
Electra -Voice, Inc., Buchanan, Mich., announces recent expansion of the p: -V salles
division. Apiaui ll t meurs include Jay Carver
been designated a
New ENGINEERING DESIGN!
New LUXURY STYLING!
.
-
eeeretruoualy Sisee 1944
-
HOLLYWOOD ELECTRONICS
1
DISTRIBUTORS OF HI -FI COMPONENTS
New MUSICAL ENJOYMENT!
will handle wood prod uet sales,
Prank Stroempl who has been named assistant manager itf the distributor sales
division, and Jim Johnson as assistant
as-ho
of the manufacturers' sales di\isian.
Having completed a. tour of
duty :IS tin,: lieutenant with the Army,
Arthur Z. Adelman has re- joined his father's hUFilleSS term, the Leon L. Adelman
Company, manufacturers' representatives
In the metropolitan New fork area. .
nue na ger
.
Mlr ere
ALo. Angele. 46, Calif
WEbs,er 3-8208
Circle 87D
HIGH -FIDELITY HOUSE
Most complete stock of Audio
components in the West
Phone: RYan 1 -8171
536 S. Fair Oaks, Pasadena 1, Calif.
the finest in
L Oy07CC
SOUND
feat irring
Ohio.
HIGH FIDELITY COMPONENTS
820
W.
Olympic Blvd.
-
L. A. 15,
Calif
I
0211
CANADA
High Fidelity Equipment
Complete Lines
Complete Service
-
Records
Components
and Accessories
SOUND
SYSTEMS
WEST. TORONTO,
DUNDAS ST.
CANADA.
.1
AI High Fidelity Dealen Everywhere
$37.50
Shipped completely assembled with all plugs
and leads attached, ready for operation.
with GE RPX050A Cartridge
$44.50
.
William Herrman, well -known in New
his coverage of
the field for Retailing Daily, has been advanced to the position of news bureau
manager for Hoffman Electronics, Los Angeles firm which Bill joined after movingto sunnier climes.
. Burton
Browne,
Gaslight Club president and head of Chicago ad agency bearing his name, named
by mayor to special All-Chicago Citizen's
committee which oints to promote Chicago
as an industrial, commercial, cultural, and
leereat i"n:1l center.
York audio circles fr
NEEDLE BRUSH
KLeeNeeDLE
KLeeNeeDLE automatically keeps
record changer needles clean.
It is designed to remove the
familiar "dust- bleb" from under
the needle point.
AI Your
ROBINS INDUSTRIES
RENOWNED MIRACORD XA -100.
AUDIOGERSH CORPORATION
23 Park Place, New York 7, N. Y.
WOrth 4-8585
In Conodo AIIO, Rodo Corp LIS.
Toronto. Canada
.
Circle 87A
RECORDS PRESSED
COMPLETE PACKAGE DEAL
Tapes Duplicated
Discs Converted to Tape
Tapes Transferred to Discs
company president.
Circle 87C
AUTOMATIC CHANGER
ALL THE PERFORMANCE -PROVED BASIC RECORD PLAYING FEATURES OF THE WORLD -
George J. Parker, formerly
.
&LECTRO-UO10E
111
.
TRANSCRIPTION -QUALITY FEATURES
Constant -speed 4 -pole motor
Rubber
matted, balanced turntable
Special Spring
mounts
Plug -in head
3 -speed drive
Boll- beeringmounled tone arm PLUS .
operated I,y Robert G. Zurheide.
H. C. (Bill) Hornickle, who de ve Io pert the
"Rchickelgruber" noise cancelling microphone during 'World War II, was named
as general manager of the Pacific Division
'of united Transformer Company, and will
head a sales staff which will be located at
C. It. St'assner Company, in Los Angeles.
R. E. Carlson, formerly manager of the
High Fidelity Di vi.'
of Fairchild Recording Rquipment Company, \Vhitestone,
L. I., recently appointed vice-president and
general manager of the cram pat ny: Ray F.
Crews resigned as exeoUt ive vice- Presidnt
effective March 3Ist, according to :u1 announcement by Sherman M. Fairchild,
N.
Circle 87F
HIPf
XM ..1110A
Manual Record Player
president of the fluty utront Instrument Division at Archbald, Iva., has been named
vice- president of Daystrom, Inc., In charge
of the corporation's Washington office.
the East's newest high -fidelity haven
is Audio Enterprises, Inc., in Ifaekensack,
O N
RI 7
MIRAPHON
.
Circle 87E
C O R P O R A T
Bruce Payne, William R. Swett, and
Damon Van VW have been elected to the
board of dim, lors of 3lagnecord, Inc. Mr.
Payne, who n:Is chosen chairman of the
Alagnecord b,,a rd, Is also president of
Jtruce Payne X Associates, management
consultants of Westport, Conn. Both Mr.
Swett :nul Mr. Van Utt are vive- presidents
of the l'a o,. crc:mizatton..
Bob Haret
and John Margolin have organized the rep.
first of K :u'et- Margolin, Inc., with offices
and warehouse at 13 R. Hubbard St., Chicago 10, Ill. The company Is opening shop
with many high- fidelity equipment accounts.... Prod Gluck, formerly chief engineer of Fada Radio and Electric Company, has liven a ppui s t ed chief engineer
of The Astatic Corporation of Conneaut,
Bayside
Dealer
61, N.
Top Quality Pressings in Small or Large
Quantities
Send for Descriptive Brochure and
Y.
Circle 87H
Rate
Schedules
Dept.
.
E
CREST RECORDS,
INC.
220 Broadway, Huntington Station, N. Y.
Circle 87C
Everythingin HI-FI Sound Equipment
AMPEX
FEATURING
WORLD'S FINEST
TAPE RECORDER
TEL
SANTA MONICA SOUND
12.36
INDISPUTABLY...
GRanite 8 -2834
Santa Monica Bird., West Les Angeles 25, Calif.
Circle 871
the world's best
GIBSON GIRL TAPE SPLICERS
splices in a
wink!
(,
Ask about the
new CM 51
shown here
NO SCISSORS'
NO RAZOR BLDESI
At
(only
microphones
Sole U.S. Impo
41/2'.
high), and the
AMERICAN
famous
TourDeoI.rs
ROBINS INDUSTRIES CORP.
e., ,.e..1
N
,
Write for complete details.
Eu-
Dept. A
L,INCI7
wYrkl
New York 10, N. Y.
Circle 87B
AUC 10
APRIL, 1956
87
www.americanradiohistory.com
AmericanRadioHistory.Com
ADVERTISING
INDEX
Acro Products Co.
Allied Radio Corp.
Altec Lansing Corporation
American Elite, Inc.
Amperex Electronic Corp.
Ampex Corporation
Arnhold Ceramics, Inc.
Audak Co.
Audiogersh Corporation
Capps HOT- STYLUS UNIT
80
67
9, 66
.
87
57
55
16
78
83, 85, 87
Bard Record Company, Inc.
Belden Mfg. Co.
Bell Telephone Laboratories
Bradford U Company
80
7
22
76
British Industries Corporation
facing p.
Cabinart
Capps & Co., Inc.
Collaro Record Changers
Precision stylus pressure
gauges available in 2 models
calibrated from 2 to 15 grams
or 3 to 30 grams each way from
The
extra indicator "hand" will remain at
the maximum reading of the device until
reset by a knob on the dial face.
CORRECT STYLUS PRESSURE NOT ONLY
GUARANTEES MINIMUM STYLUS AND
RECORD WEAR, BUT ASSURES SOUND
PICK -UP AT MINIMUM DISTORTION.
-
Dealers
Why not investigate ...
Send for Folder Code GIOJU
ó'
SCHERR CO., Inc.
[GEORGE
Circle 88A
NOW ULTIMATE
PERFECTION
IN TONE ARM PERFORMANCE
Ortho-sonic v/4
srnus
TRACKS COURSE
Of ORIGINAL INONWI G
VITAL ENGINEERING
PRINCIPLE SOLVED!
Discus Corporation
du Pont de Nemours, E.T., & Co.
Film Dept.
3, 4, 5
83
88
Cover 3
87
86
Crest Records, Inc.
Classified Ads
center position.
1,
86
'Inc.),
37
70
Electro -Sonic Laboratories, Inc.
Electro- Voice, Inc.
Cover 4, 20, 21
87
Electro -Voice Sound Systems
2
Elgin National Watch Company
77, 79
Ercona Corporation
Fisher Radio Corp.
10
86
General Electric Company
79
Goodmans Industries, Ltd.
Gray Research and Development Co., Inc. 68
Harman Kardon, Inc.
Harvey Radio Co., Inc
Heath Co.
High Fidelity House
Hollywood Electronics
Hudson Radio and Television Corp.
Hughes Research and Development
Laboratories
Hycor Co., Inc.
Jensen
53
41
-48
75
87
87
Manufacturing Company
80
87
Kingdom Products, Ltd.
69
Lafayette Radio
Lansing, James B., Sound, Inc.
Leonard Radio, Inc.
Lorenz
63
33
83
69
80
Pickering & Company, Inc.
Pilot Radio Corp.
Presto Recording Corporation
Professional Directory
19
DESIGN:
record life
.
plays all
no scratching possible
Increases
fits smallest cabinet
records
size
..
.
.
.
all popular cartridges fit.
NEVER BEFORE in the history of Hi -Fi deintroduction of a
velopment
has the
single component created such wide interest, laboratory and editorial endorse.
ment.
Get ORTHO -SONIC V/4 with its 10 incomONLY $44.50
parable features.
At Better
Hi -Fi Dealers Everywhere
WRITE FOR ILLUSTRATED LITERATURE
ORTHO -SONIC INSTRUMENTS, Inc.
66
B
Mechanic Street, New Rochelle, N. Y.
Circle 88B
88.10 net
LP or 78
CU -1C Supplied with custom made stylus
This complete unit may be obtained
at your nearest dealer
Capps & CO., INC.
Valley Stream, N. Y.
20 Addison Place
Circle 88C
A
GOOD
LAW
TO
61
I
1
87
Rauland -Borg Corporation
Recoton Corporation
Rek -O -Kut Company
Robins Industries Corp.
72
Sams, Howard W., Co.. Inc.
Santa Monica Sound
Scherr, George Co., Inc.
85
87
73
65
87
80
Sherwood Electronic Laboratories, Inc.
Shure Brothers, Inc.
Sonotone Corporation
39
Tannoy (Canada) Limited
Tapetone Incorporated
81
71
United Audio Products
United Transformer Co.
to
70.50 net
customer's specification
McIntosh Laboratory, Inc.
35
Metzner Engineering Corporation
59
Minnesota Mining and Mfg. Co..... 12, 13
17
Mullard Overseas Ltd.
Ortho -Sonic Instruments, Inc.
INSPIRED
Model No.
CU -1 Supplied without stylus .... $60.00 m t
CU -1R Supplied with regular duty stylus,
51
Keros Enterprises
Kieruiff Sound Corporation
REPRODUCTION
attained.
FLAWLESS
Stylus moves in straight line from edge to
center as
When ordering specify make
and model number of cutter
head and stylus requirements.
15
8
North American Philips Co., Inc. ..
original recording.
The CAPPS IIOT'STYLUS UNIT.' is
used for applying heat to disc recording styli,
softening the disc material at the point of
contact thereby producing smoother, more
accurate grooves. This results in a substantial
reduction in surface noise, especially at the
inner diameters and minimizes the mechanical load on the cutting head increasing its
efficiency and frequency response.
88
Tracking error completely eliminated
in
LONGER STYLUS LIFE
REDUCES LOADING ON CUTTING HEAD
IMPROVES FREQUENCY RESPONSE
IMPROVES SIGNAL TO NOISE RATIO
FACILITATES PROCESSING
EASILY INSTALLED AND OPERATED
1
6
14
Cover 2
BREAK
The law of averages says that
cancer will kill one out of every
six Americans. But the law does
not have to prevail. You can help
break it in two ways. By having a
thorough medical checkup every year
...and by sending a contribution to
your Unit of the AmericanCancerSociety
or to Cancer, c/o your town's Postmaster.
Fight cancer with
a
checkup and
www.americanradiohistory.com
AmericanRadioHistory.Com
check.
AMERICAN CANCER SOCIETY
AUDIO
88
a
APRIL, 1956
INSTALLATION
.
.eutei
AS-tol
gehrice
,
1 64
Automatic Intermix
RECORD CHANGER
Three Speeds:
330, 45
and 78 rpm
-'M'
More people can now enjoy the reliable
quality and performance of the Collaro RC54- because something has been done about
the installation problem.
The two new RC-54 series have power and
sound leads wired and soldered in position.
Both are supplied with Automatic 45 rpm
Spindle Adapters and both offer a choice of
pickup cartridges: either the G.E. dual -sapphire magnetic or Collaro Studio O dual sapphire crystal.
The 'C' Series are supplied with pre-cut, unfinished mounting boards, suitable for easy
installation into record cabinets and consoles
without the need for intricate carpentry.
The 'M' and 'B' Series are supplied with
hardwood bases instead of mounting boards
for mahogany and 'B' for blond. These
require no carpentry whatever. They can be
fitted into most cabinets, or placed on open
shelves, tables or any other convenient surface.
With woodworking, wiring and soldering
eliminated -it takes no time at all to install
an RC -54. And of this you can be sure .. .
there is no finer record changer than Collaro.
-
Priced from
$5600
Sold by Leading
Sound Dealers
Write for complete specifications to Dept.
ROCK BAR COR PORATION
CD -1
215 East 37tb Street, New
York
16,
N. Y.
www.americanradiohistory.com
AmericanRadioHistory.Com
Made in England
...STOP UNWANTED SOUNDS
Now... Broadcast Performance Designed for Public Address
COMPLETELY NEW ALL-PURPOSE CARDIOID DYNAMIC MICROPHONE
BRINGS NEW EFFICIENCY OVER WIDE FREQUENCY RANGE
All the advantages of the E-V Variable D* are now available in the new
high -fidelity "664"... for public address, recording, communications and similar
applications. Uniform cardioid polar pattern provides high front -to -back discrimination
against unwanted sounds, without close -talking boominess. Easily solves sound
pick -up and reproduction problems under a great variety of conditions. Gives distinct,
natural reproduction of voice and music. Increases working distance from
microphone. Gives greater protection against feedback. Especially useful where
ambient noise and severe reverberation exist. Pop -proof filter minimizes
wind and breath blasts. E -V Acoustalloy diaphragm guarantees
smooth wide -range reproduction. Can be used on a floor or desk stand
or carried in the hand. No finer microphone for performance
and value! Write for Technical Specification Sheet A64.
EV
Pet. Pend.
Model 664. Variable D. Super -Cardioid Dynamic Microphone.
Uniform response at all frequencies from 60 to 13,000 cps. Output
-55 db. 150 ohm and high impedance. Impedance changed by
moving one connection in connector. Line balanced to ground and
phased. Acoustalloy diaphragm, shielded from dust and magnetic
particles. Alnico V and Armco magnetic iron in non- welded circuit. Swivel permits aiming directly at sound source for most
effective pick -up. Pressure cast case.''--27 thread. Satin chrome
finish. 18 ft. cable with MC4M connector. On -Off switch. Size:
1% in. diam. 7'/w in. long not including stud. Net wt.: 1 lb. 10 oz.
List Price $79.50
Model 419 Desk Srond available for use with the "664" (extra).
level
gle.c.roke
ELECTRO- VOICE, INC.
Export:
HIGH- FIDELITY MICROPHONES
13 East 40th
SPEAKER SYSTEMS
BUCHANAN, MICH.
Street, New York 16, N.
PHONO -CARTRIDGES
www.americanradiohistory.com
AmericanRadioHistory.Com
Y.
U. S.A. Cab /es:
Arab
AND OTHER ELECTROACOUSTIC PRODUCTS
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