Audio December 1953
now available
on new
2500-foot reel with a number of improved
design features that will appeal to many tape recordists.
HERE's A NEW
SOLID, ONE-PIECE CONSTRUCTION
STANDARD N.A.B. HUB DIAMETER
25 % LIGHTER THAN ALUMINUM REEL
HAS SMOOTHER FLANGE EDGES
WILL NOT BEND
RESISTS WARPING AND DISTORTION
IP'RACTICALLY INDESTRUCTIBLE
AUDIO DEVICES, Inc.
444 MADISON AVE., NEW YORK 22, N. Y.
Offices in Hollywood - Chicago
Export Dept., 13 East 40th St., New York 16, N. Y., Cables "ARlAB"
Audiotape can now be supplied on this light-weight
Fiberglas reel at no increase in price. For a trial order,
get in touch with your nearest Audio distributor. If he
doesn't have the new reels in stock, have him contact
our New York, Chicago or Hollywood office and we'll
see that your requirements are promptly filled.
This is another example of how Audiotape gives you
extra value at no extra cost. Its performance speaks for
itself. Output, frequency response, noise level and
distortion are correctly proportioned for the most satis-"
factory end result-with no compromise on quality anywhere along the line.
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Engineering
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INCLUDING
WRITERS
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C. G. McProud, Editor and Publisher
Henry A. Schober, Business Manager
Harrie K. Richardson, Associate Editor Edgar M. Villchur, Contributing Editor
Robin Melton, Production Manager
S. L. Cahn, Advertising Director
H. N. Reizes, Advertising Manager
Edgar E. Newrnan,Circulation Director
Re presenta tives
H. Thorp Covington, Special Representative
753 0 Nort h Sheridan Road, Chicago 26, III.
Sanford R. Cowan, Mid-West Representative
67 W. 44th St .. New York 18, N. Y.
West Coast
James C. Ga lloway
J. W. Harbison
816 W. 5th St.. Los Angeles 17, Calif.
CONTENTS
DECEMBER, 1953
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Audio Patents-RichO-1'd H. Do'r f . ... . . ....... . .. . ..... .. .. . . ... . .... . .
Book Revi ew .. ...... . . ... . . .............. . . . . .. . .. .
. . . ...... . .. . .
Letters .. . ...... . .. ........ . ......... . ..... .. . . . . ... . . . ... . .. . . . ... .
Audiology- W. R. A:-yres .. . .. .. ............... . . .... . ... . . . . . .. . .... .
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COVER
Most Christmas trees throughout the nation will feature toys and dolls this month
-the former for little boys and the latter for little gi rls. However, lives there
an audio hobbyist with soul so dead who never to himself has admitted
inclinations toward both-"toys" in the form of amplifiers, speakers,
tape recorders, and other parapherna lia dear to the heart of
those who search for good music reproduction, and "dolls"
such as model Marta Roman. This photo, conceived
three years ago, awaited realization until the right
doll could be located. Studio and equipment
were supplied by Ai r Tone Sound & Recording Company, of Philadelphia.
AUDIO ENGINEERING (title registered U. S. Pat. Olr. ) Is publlsbed monthly at 10 MeGof.rn Avenue. Lancaster, Pa. by
Radio Magazines, Inc., Henry A. Schober, President; C. G. McProud, Secretary. Executive and Editorial Omces:
204 )'ront St., Mineola, N. Y. Subscription rates-United States, U. B. PossessloIlJ and Canada, $3.00 for 1 year,
$5.00 for 2 y,ara; elsewhere $4.00 per year. Single copies 35 •. Printed In U. S. A. All rights reserTed. Entire content.
eop1rigbl -1953 by Radio Magazines, Inc. Entered as Second Class Matter February 9, 1950, at tbe Post Omce, Laneaster. Pa. under the Act ot March 3, 1819.
AUDIO ENCINEE.RING
•
DECEMBER, 1953
GRADUATES, for preparation
of technical manuals . . •
HUGHES RESEARCH AND
DEVELOPMENT LABORATORIES'
expanding program for production of?'adar, elect?'onic
digital computers, guided
missiles and othe?' military
advanced electronic syste7I'LS
and devices requires the
following:
D ELECTRICAL ENGINEERING AND
~ ENG INEERS EXPERIENCED in the
writing and preparation of
maintenance manuals for
electronic equipment or guided
missiles. These specialists will
work step-by-step with the
people designing, developing
and manufacturing the products
involved. Experience in the
writing of engineering reports
is of value.
I
Write full details
of your qualifications to
IL
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HUGHES
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HOW TO APPLY
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RADIO MAGAZINES, INC., P. O. BOX 629, MINEOLA, N. Y.
ENGINEERS, E. E. or PHYSICS
PHYS ICS GRADUATES to prepare
operating, servicing and overhauling instructions for complex
electronic equipment. Those
with previous maintenance
experience on military equipment preferred. Writers will
participate in a three-month
program in our technical
training school to become
familiar with the latest Hughes
equipment prior to writing
assignments.
Vol. 37, No. 12
2
6
8
12
14
16
Magnetic Ti'ansfer of Stainless Steel Recording Wire-Samuel Storchhei1·n 19
An Automatic D isc Recorder-Cu.rtiss R. Schafer ... .................. . 21
A New Wide-Range Phonograph Cartridge-John F . Wood ........... . 22
Vibration Reduction in Loudspeaker Enclosures- G. B . Houclz ...... ...... . 24
Tired Business Man's Radio Cabinet and Speaker - C. C. Fraser . . . . .. . . . . 26
The Audio Fair Review-Harr·ie 1(. Richardson . ............... ', ...... . 28
Handbook of Sound Reproduction-Chap. 15, Part 1- Edgar M. Villchwr
34
Audio ETC-Edwal'd Tat-nall Canby , ... . .... , ....................... . 40
Record Revue -Edward Tatnall CO-1vby ...... . . .. .. .. ..... ........ . ... . 42
Technicana ............. . ... ........... .. .... . . ......... . .. . .. . . .. ,. 46
New Products ..... .. . . .. ..... . .. .. . . . . ....... . . . . . .... . .. . . . . .. .. .. . 48
New Literature ... . ............................... . .. ..: ..... . ....... . 50
Industry Notes and People ... . . . .... . .. . ...... .. . . .... . . .. . . . . .... . .. . 71
Annual Index . . ............. . . . ... . .. . ... . . . . .. . .. . .. .. . . .. . . .. .. . . . 73
Advertising Index ........... . . . . . . ............... . ............... . . . 76
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Research and Development
Laboratories
SCIENTIFIC AND ENGINEERING STAFF
Culv.,· City, Los Angeles County
Calij'o"nia
Assurance is required that reloca tion
of the applicant will not cau se disrup t ion
of an urgent milita ry proj ect.
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NEXT TIME
BE SURE!
RICHARD H. DORP
T
Foo!ears Peerless engineers have
designed transformers to meet
the most unusual and stringent
sp ec ificat io ns subm itte d by
c i vII ian man uf a u r er san d
government contractors, and have
manufactured these transformers
with tight quality cont rol. .The
small difference in price means
a BIG difference in performance.
.. ~.:
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cf
ODA v'S BEST AUDIO AMPLIFIERS are becoming better and better; in fact, it is
quite possible that they are-from the
performance standpoint-as good as they
ever need to be. Distortion is down to negligible values which cannot affect our ears;
frequency curves are flat as a pancake; and
output powers are more than enough. This
may sound a little like the statements that
were said to be made sometime in the late
eighties that all the inventions that could
be made were already made.
That is not the sense of the remark. A
good many more inventions and developments need to be made in the audio fieldnot to improve the possible quality of amplifiers, but to improve the normal individual's
chances of obtaini ng an amplifier with optimum characteristics for something less than
an arm and a leg. In other words, now
that we know we can have amplifiers with
fidelity better than the original music,' let's
simplify and cheapen the circuits and components so that everybody can have one.
One of the paradoxical reasons for high
cost in amplifiers is that· the band to be
transmitted must usually be very much
wider than the band anyone can hear. A
few amplifiers are flat up to the apparently
ridiculous frequen cy of 100,000 cps. and
more where even a bat would need a hearing aid. But this is required to provide for
the la rge percentage of negative feedback,
which is primarily responsible for high
audio quality. If there is attenuation of the
pass band anywhere near the ends of the
audible spectrum, there will also be phase
shift whi ch spells death by oscillation to
* 255
1
W. 84th St., New York 24 N. Y.
Joke. No indignant letters, ple'ase!
the feedback loops because of reversing
phase at certain points.
It seems to the writer that John M.
Mi ller has struck out along the right path
in his patent No. 2,652,458, which is assigned to Bendix. The patent covers an
"amplifier with positive and negative feedback," but there is as much horse sense
as engineering in the approach, and more
than immediately meets the eye.
The advantages of negative feedback are
well known-reduction of distortion of all
kinds, including frequency, and ioudspeaker
damping. In the last couple of years the
advantages of adding positive current feedback wi thin the amplifier have come into
the open; with it some of the offset in gain
caused by negative voltage feedback can
be reduced and the output impedance can
be brought right down to zero, or even
negative values, for almost perfect speaker
damping. The rub is that the usual method
of app lying optimally large amoun ts of
positive and negative feedback requires
highly expensive output transformers and
wideband coupli ng in all the stages.
Mr. Miller's amplifier has both negative
and positive feedback loops. His trick is
principally (a) to recognize that with a
transformer of good but not premium qual ity, th e negative feedback wilJ, after the
extremes of the audible band, turn positive :
and (0) to simply incorporate a very elementary network in the positive feedback
loop so that when the negative feedback
tends to become positive and the positive
feedback tends to become negative and keeps
the amplifier form oscil1ating.
Figure 1 shows the schematic diagram of
an amplifier designed acco rding to the invention. The amplifier proper (which be-
SELECT Cx FOR
MINIMUM VALUE AS
PARASITIC
.SUPPRESSORS
0 .3
Next time let us quote on your
transformer requirements.
1
_PEERLESS
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Electrical Products
,"'' ' ' "'~Uilt
o
'"
0
'" '"'"
·POSITIVE
FEEOBACK,--,:;~;=.3_-4----+--o+2B5V
NEGATIVE FEEDBACK ..
9356 .S!lnta Monica Blvd., Beverly Hills, Calif.
161 Sixth Avenue, New York 13, New York
Fig. 1.
2
AUDIO ENGINEERING
•
. DECEMBER, 1953
NO OTHER RECORD CHANGER CAN MATCH THESE FEATURES
Here's what they mean
to you
lit
ACCESSIBLE
Prolongs life of records
ADJUSTMENT
weight of stylus upon delicate
grooves.
====O....J STYLUS PRESSUR E enabling you to keep correct
=,....o..J. . BALANCE
.
MDUNTED
TONE ARM
AUTOMATIC STOP
GENTLE,
....."""-..- PRECISION
PUSHER
PLATfORM
PRECISION
GRDUND GEARS
.....:;::......_ PRDfESSIONAL·
TYPE fiNGER LIfT
INTERCHANGEABL E
PLUG·IN HEADS
WITH STYlUS
VISIBLE
MANUAL
PDSITION
SWITCH
fAST
CHANGING
CYCLE
FOR 18 RPM.
RPM RECO RDS
WITH NORMAL
CENT£R HOLES,
•• Exclusive "Single play"
spindle
c.Exclusive "automatic"
spindle
b. Exclusive "automatic"
d. 'Single play" adaptor
~~~~ ~;~~n~~rom. clip for handy storage in
GARRARD
The only device that insure.
gentle handling of records
with standard center holes. No
overhead bridge to damage or
dislodge records accidentally.
Perfectly meshed to inhure
constant, smooth action and
years of service.
Permits safe lifting and set·
tlng down of pick·up arm when
piaying records manually.
Accommodates your personal
choice of magnetic, ceramic
or crystal cartridges, and pro·
tects record grooves, since
stylus can be front·inspeeted
for correct vertical position.
Gives you versatility ••• manual
or automatic playing, as you
prefer.
The same, regardless of playing
speeds; means less waiting
between long playing records.
Cannot slip. Eliminates belts
and guarantees smoolh. even
turntable speed, which you
will enjoy as perfect musical
pilch.
fAST.SLOW
SPEED
ADJUSTMENT
All 3 speeds variable and IIIjustable. Guarantees pertect
pitch; accurate speed settln=.
qompensates for current
IIerfectlons.
WEIGHTED,
BALANCED
TURNTABLE
Means freedom from rumbled
and constant turning spee
through "flywheel" action.
WATCH·LlKE
CONSTRUCTIDN
All levers fully adjuslable • .•
easy, inexpensive to service.
Bronze bearings at all moving
points for longer life!
SHOCKPROOf
INSTALLATION
Unique spring suspension.
Mounting holes are identical
with former Garrard models,
so Ihat replacement is simple.
MUTING SWITCH
A complete stock of replacement
parts readily available at all
times to Garrard owners, in any
part of the United States.
for tour convenience, Insures
posi ive and unfailing aclion
at end of any type record.
NDWOWSI
STEPPED PULLEY
DRIVE ••• WITH
INTERMEDIATE
BALANCED DRIVE
WHEEL
RUMBLE·fREE!
ADVANCED HEAVY
DUTY 4·POLE
MDTOR
INTERCHANGEABLE SPINDLES
Fit all records, all sizes, as they
were designed to be ptayed . Most
important, Garrard spind les are
removable, so·that records need
not be ripped upwards over
metallic spindle projections afler
playing. as on ordinary changers •
Guarantees true tangent tllck·
ing, eliminating disturbing
resonances.
Makes your RC90 the smooth·
est. most powerful, most
silent record changer ever
built! Weighted. balanced ar·
mature. No appreciable speed
variation regardless of number
of records on turntable; "hot"
or "cold" operation, or varia·
tions in line voitage.
Continuity of your music un
disturbed by extraneous noises
between records. No sound
while arm is In changing cycle.
MAGNETIC EDDY
CURRENT SPEED
CDNTRDL
A great high·fidellty acble
me ntl Speed controlled b
varying the field of a ~alr
~ermanent magnets ... el mlnat
ng old-fashioned mechanic.
or electrical braking.
CDNDENSOR·
RESISTDR
NETWORK
Eliminates startling "plop"
noise when changer shuts off
at end of last record.
World's Finest Record Changers and Record Players
Model RC90-3 speed "Crown" Super Changer' Model RC80··3 ~peed "Triumph" Automatic Changer
Model T-3 speed "Crest" Manual Player' Model 301 Transcription Turntable
bent spindle
Garrard Sales corporation," 164 Duane Street, New York 13, N. Y.
r- - - - --- -- -------------- - -- - - - -- --WRITE FOR A COMPLIMENTARY
COPY OF "SOUND CRAFTSMANSHIP"
16 pages illustrating and describing Britain 's finest
music reproduci ng equipment ... the Garrard Crown
Model RC90 Record Changer and the other products of
the British Ind ustr ies Group. Here , in concise, useful
form are facts you' ll want for planning improvements
and additions to your own high fide lity set.
Garrard Sales Corp. , Dept. AE-12 , 164 Duane St., New York 13, N. Y.
Send rny copy of Sound Craftsmanship.
Name _______________________________
~--------
Addre ss _______________________________________
City'_________________--LZone ___ State'____________
----------------------------------<
Voyager
The first one-case professional
recorder for remotes -- rugged, light, reliable. Complete
with line level amplifier,
$499.50. Other units available
with 10 watts of audio from
$590.00.
Standard Magnecorder
PT63-AH recorder includes a
3-head assem!Jly for monitoring directly from the tape.
PT7-P amplifier provides high
level mixing of three channels.
$850 complete.
MagneCordette
A professional , Magnecorder
enclosed in smart blond, mahogany, or black lacquer cabinet, $425.00. Also offered as
the new Portable MagneCordette -- a complete record playback-P.A . system . in a
single carrying case, $499.50.
New 'M agnecord M-80
W atch for the brilliant new
'Magnecord M-BO at your deal er~ s -- the finest tape recorder
ever built for the price. Features push-button controls
slot loading, 15 kc respons~
at 7'h ips!
Look under "recorders" in the
1Pa~;~;"
225 WEST .oHIO ST., CHICAGO 10. ILL., DEPT. AE-l1
4
gins at the output of the conventional 6]5
voltage amplifier) includes the 6SN7-GT
phase splitter and a 6V6 output stage. According to the tube manual the output rating can be conservatively set at a little
over 10 watts, with home music system
high-quality standards in mind. The 6]5
plate signal, after passing through a network A (of which more later) is fed to
the "self-balancing" phase splitter . The
grid of the lower 6SN7 triode obtains its
signal from voltage divider R.R, across
the push-pull splitter output. The output
stage is conventional, the value of the
cathode resistor having been supplied. by
the writer. All other values are given by
the inventor.
The negative feedback loop is a standard
type, from the secondary of the output
transform er to the firs t cathode of the phase
splitter. R, and the tube's cathode impedance form a voltage divider which determines the negative feedback factor.
The positive feedback loop is an internal
one, from the grid of the lower output tube
back to the first phase-splitter grid. The
positive feedback is fixed, for mid-range
frequencies, by the voltage divider R,-R,
(and, of course, to some extent by the admittance of the 6SN7 triode and the plate
resistance of the 6]5 in parallel with R.
and R,). It is adj usted to a point where
ther e exists a condition of critical regeneration in the amplifier with the negative
feedback loop disconnected. When the negative loop is c01111ected the over-all gain is
reduced well below the point of amplifier
instability. However, the high positive feedback has created an amplifier of high gain
without incurring the penalty of steep
boundary-frequency phase shifts which
would come with the employment of several stages, and, of course, at a cheaper
price. The critical regeneration can easily
be maintained over the entire range of
useful-that is, audible-frequencies.
The low inherent phase ' shift of the amplifier permits the use of a low priced output transformer even though it ' is in the
negative feedback loop. The over-an . gain
is primarily an inverse function of the feedback factor of the negative loop. Ordinary
feedback theory shows that under this
circumstance harmonic distortion and intermodulation are negligible up to any
signal level at which there is sufficient overloading to disable one of the feedback
loops.
Oscillation Prevention
So far, the scheme is apparently not new,
at least in theory. But the theory has always been very difficult to realize practically because at frequencies outside the useful range the sense of the negative feedback changes and it becomes positive, causing oscillation. There are some common
solutions. One is to design an the coupling
elements in the amplifier so that frequency
slope is no greater than 10 db per octave
within the range for which negative-feedback loop gain is unity or greater. That
costs money, especially where the output
transformer is concerned. Another method
is to introduce compensatory networks in
the negative loop to apply reverse phase
shifts. That is expensive, too, and risky.
The inventor's solution is to leave the
negative loop alone and deal with the positive feedback loop. Change in positive feedback phase is not a danger, of course, since
it could on ly tend to reduce amplifier gain
and reduce chance of oscillation. In the
diagram the job is done by the nework A.
At mid-range frequencies, we have said
that loop transmission is controlled by R ,
and R •. At low audio frequencies transmission depends on the ratio of capacitors
AUDIO ENGINEERING
•
DECEMBER, 1953
J·umps .are for Horses
.. . NOT for magnetic tape
That 's why you need SOUNDCRAFT Micro-Polt'shed* Tape.
No Raised Spots! No Roughness! No Jumps!
It's S moo t h right from the start!
Under the microscope, magnetic tape
may look like a steeplechase - replete
with all the "jumps." As you record,
th ese jumps-minute raised spots characteristic of all coating processes - momentarily separate large enough areas
of the tape from the recording head to
appreciably interrupt high-frequency
response. On some eq uipment, they
may even cause signal dropouts.
subjecting the ferrous oxide coating to
high-precision polishing. It leaves the
surface mirror-smooth, and preconditioned for immediate, stable, highfrequency response.
Breaking in tape by running it
through the recorder, with accompanying head wear and waste of time, is a
thing of the past.
The Answer Is Micro-Polish
In addition, SOUNDCRAFT R ecord in g
Tapes- are pre-coated with a special formulation to give utmost oxide ad hes ion,
and prevent curling and cupping.
All tape is dry-lubricated to eliminate
squeals and carries a splice-free guarantee on all 1200- and 2500-foot reels.
But Reeves SOU N DCRAFT eliminates
the "jumps" with its exclusive MjcroPolish process, assuring the most complete head contact possible right from
the start. That's because Micro-Polish
smooths oft' the microscopic nodules by
Other SOUNDCRAFT Advantages
REEVES
SOUNDCRAFT
CORP.
10 East 52nd Street, Dept. B
New York 22, N. Y.
*Pat. Applied For.
C, and C, which then have appreciable re-
ELECTRONIC DOOR
(ONTROl BOX
DESIGNING ELECTRONIC EQUIPMENT
WITHOUT RELAYS
Overwhelming evidence is accumulating to the effect that
relays are the weak link in Electronic Equip1l}ent. They are
expensive, unreliable, unprocurable, and, worst of all, mechanical.
In short, fashionable designs no longer contain relays. *
It's really perfectly simple. Assuming the usual block diagram
to contain sensing, amplification, and power device, it shouldn't
be hard to get the power from amplification in a form to run
the power device directly. It's easy -
no relays needed.
Of course, just as a device gets into production it may
develop irritating idiosyncracies such as non-operation or some
such minor defect. It's probably only a case of the moving
actance. They are designed to have about
the same capacitance ratio as the resistance
ratio of R; and R •.
At the very low frequencies (where the
negative feedback begins to shift phase
and become dangerous) the reactance of
C, becomes high with respect to the resistance of R •. CrR. then becomes a phaseshift and high-pass-filter network, reducing the positive feedbacK in the very low
audio and the subaudio ranges and shifting its phase so that as fr equency gets
lower the feedback becomes negative. This
offsets the tendency in the low range of
the negative feedback in the other loop
to become positive due to the natural deficiencies of such circuits and the reasonable-quality transformer. The positive feedback begins to reverse at frequencies only
slightly lower than the lowest desired useful frequency so that even if the transformer has rather sharp cutoff characteristics at this point the gain of the amplifier
is reduced sufficiently to prevent oscillation. Increase of distortion due to loss of
feedback does not matter-nobody can
hear it.
At high frequencies, capacitor C. (and
the input capacitance of the 6SN7) acts
with R, as a phase-shift and low-pass-filter
network. Just slightly above the audible
range the positive feedback is reduced and
starts to become negative, reducing amplifier gain so that the cutoff of the transformer just above audibility cannot cause
oscillation due to phase shift in the negative feedback loop.
It is obvious, therefore, that extension of
the range of the amplifier and the transformer to the usual ultrasonic range is not
necessary with this cin:uit. At some frequencies well above and below audibility,
phase conditions in the feedback loops may
make them both positive, but at these frequencies the loop gains have been made
deliberately too small to permit oscillation.
Thus we have an amplifier which is
cheap because (a) it can give sufficient
gain with only two stages and (b) the
output transformer can be standard-no
$30-plus quality and no tertiary or split
windings. Yet it can (or so it seems) give
all the quality which the art makes possible
today. The writer would like to hear from
anyone who tries the circuit.
'
There is not much more detail in the
patent specification but you can get a copy
for 25¢ from The Commissioner of Patents,
Washington 25, D. C.
coil of the perfistron being melted by high-Mu splurges from
the totemotor.
It'll take a Sigma relay to protect the thing because that's
the only gadget that will fit into the unavailable space and
respond to the conspicuous absence of signal power. Besides,
you can console yourself with the fact that it's only just
barely a relay.
* 1n 1940 10' ask,d a proptll" ,"annfac"",r lObo
lVas trying our rtldys In bls
pltcb·con/rol ,""banls," wby b, dldn'I SCOllt around for so,""blng b,tI" Iban
proptllm. :HIs anslV" was classic; ':Ho." do you know
noll'
10""
Type "P. Cood for
!:dn, ·no .rd~y ·
pdgeu.
:so InW. It! - llO WIt" out. In brae
qu.&l1ulin, comlllCKW .pea.. priced as low u
Uhhh) $I.OQ.
'U or
,
SIGMA
SIGMA INSTRUMENTS, INC.
BOOK REVIEW
CIRCUIT THEORY OF ELECTRON DEVICES,
by E. Milton Boon. 483 pages, $8.50. New
York : John Wiley and Sons, Inc., 1953.
This is a book primarily intended for
electrical engineering students. It analyzes
basic circuit operation, deriving expressions
relating to gain, source impedance, the
effect of feedback, ete. The use of equivalent
circuits, and the mathematical derivations
are presented especially clearly, both in
concept and in format. (The latter is never
forbidding.) The treatment of an amplifier
as a four-terminal network makes the
analysis a general one, applicable to all
electron devices. Both tube and transistor
circuit theory are discussed.
The clarity of the presentation recommends this book to general technical readers
as well as to students.
-EM V
95 PEARL ST•• SO. BRAINTREE. BOSTON 85. MASS.
AUDIO ENGINEERING
•
DECEMBER, 1953
SILECTRON -CORES ...
BIC or LITTLE
.... an)/ uantity and any size
For users operating on government schedules, Arnold is now producin.g C-Cores wound from %, %, 1, 2, 4 and 12-mil Silectron strip.
The ultra-thin oriented silicon steel strip is rolled to exacting tolerances in our own plant on precision cold-reducing equipment of the
most modern type. Winding of cores, processing of butt joints, etc.
are cilrefully controlled, assuring the lowest possible core losses, and
freedom from short-circuiting of the laminations.
We can offer promp~ delivery in production quantities-and size is
no object, from a fraction of an ounce to C-Cores of 200 pOllnds or more.
Rigid standard tests-and special electrical tests where required-give
you assurance of the highest quality in all gauges . • YOllr inquiries
are invited.
waD <4363
AUDIO ENGINEERING
•
DECEMBER, 1953
7
LETTERS
Comments on "The Piano"
SIR:
dl1ySilper
~t d rece tube for
performa~
"
your-Williamson or
amplifier?
'Uhra-Unear"
Check these ratings
of the Tung-;;Sol 5881
CLASS All PUSH-PULL AMPLIFIER-TRIODE CONNECTION
Grid 12 connecled I. Plole Vo/ue. ore (or fwo 'ube.
Heater Voltage
Heater Current
Plote Voltage
Grid Voltage
Peak AF Grid to Grid Voltage
Zero-Signal Plate Current
Maximum Signal Plate Current
Load Resistance
Total Harmonic Distortion
Power Output
6.3
0.9
400
-45
90
65
130
4000
4.4
13.3
RATINGS (Interpreted According 10 RMA Standard M8.210)
Heater Voltage
6.3
Maximum Heater-Cathode Voltage
200
Maximum Plate Voltage
400
Maximum Grid #2 Voltage
400
Maximum Plate Voltage (Triode Connection)
Maximum Plate Dissipation
Maximum Grid J2 Dissipation
.
Maximum Plate Dissipation (Triode Connection)
Maximum Grid Resistance (Fixed Bios)
Maximum Grid Resistance (Self Bias)
400
23
3
26
0.1
0.5
Volts
Amp.
Volts
Volts
Volts
Mo.
Mo.
Ohms
Percent
Watts
Volt.
Volt.
Volts
Volts
Volts
Wotfs
Watt.
Watts
Megohm
Megohm
In creating the 5881, Tung-Sol engineers have made fullest use
of design and production techniques which have proved themselves over the past 15 years. Pure barium getter to effectively
absorb gas for the life of the tube-gold-plated wire to minimize
grid emission-are among the major design improvements in the
5881. This tube is directly interchangeable with the 6L6.
Tung-Sol produces the 5881 under laboratory conditions to insure peak efficiency and maximum uniformity. Order it from
your regular supplier.
TUNG-SOL ELECTRIC INC .• Newark 4, N. J.
Sales Offices: A tlanta, Chicago, Culver City (Los Angeles), Dallas,
Denver, Detroit, Newark, Seattle
TUNG·SOL makes: AIl·Glass Sealed Beam Lamps, Miniature Lamps,
Signal-Flashers, Picture Tubes, Radio, TV and Special Purpose Electron
Tubes and Semiconductor Products.
8
It is good to see in JE such interesting and instructive ar·
ticles as the two of Mr. Preisman's on "The Piano." Unfortunately the music trades magazines seldom carry a rticl es of
technical scope and merit on the science of musical tone production, and you are to be commended on these because weyour readers-are all interested in musical tone production as
well as reproduction.
Especially since 1930, when my own research activities were
transferred from reproduction to production of musical tones,
expecially through electronics, I have been much concerned with
piano-tone production. Except for some sixty patents in this
field, I have published very little on the results of these reo
searches, but Mr. Preisman's articles leave a few interesting
gaps which can be filled in.
For example, it does not appear to be generally known that
the bridge and the soundboard respond to modulations of string
tension, and since these are bicyclic, except at very high vibra·
tion amplitude, there is a strong frequency -doubling action.
This occurs for all of the orbital rotational planes of the string
vibration, and can be easily demonstrated with a smalf desktype postal scale and a yard length of cord. Stretch the cord
between fixed supports over the scale pan with the scale near
one end and with an angle or "bearing" of, say, 30 deg. between
this "string" and the "hitch pin" close by. If now the string's
long section by displaced up, down, :illd to either side, the scale
will in each case indicate a larger pressure and deflection. Since
the scale pan, representing a piano bridge and soundboard, moves
downward for a downward deflection of the string, and again
downward for an upward or sideward deflection, there are two
complete cycles of bridge motion for one cycle of string motion .
Force-displacement measurements of the bridge and soundboard show considerable non-linearity and this accounts for the
appearance of a fundamental vibration component of the string
in the sound board motion.
The frequency characteristic of the sound board varies from
bass to treble along the bridge from about 90 cps to about 500
cps and these values change in different pianos. Poor fundamental response of a 30- to 60-cps string through a 90- to 100cps sound board is therefore to be expected. Likewise, in the
treble end, a 3000- to 4000-cps string fundamental is beset by
a 400- to SOO·cps soundboard.
The high and low registers therefore suffer from poorly
matched impedances and only the middle register-particularl y
the low middle range--has proper impedance matching, and it
is here where the output tone is at its best.
The orientation of a grand piano soundboard is, of course,
extremely bad. Acting as its own baffle, both top and bottom
sides are about in the plane of a listener's ears, so there is
strong cancellation of the low-frequency components of the lower
tone registers. Upright pianos are much better in this respect,
. but the low-frequency performance of both types can be much
improved by absorption of the radiation of one side or, as in
some commercial loudspeaker enclosures, by reversing the phase
of the radiation of one side through a folded horn, for example.
The better tone resulting from multiple unison st rings is due
not to the increased sound output so much as to the chorus effects
among slightly detuned overtones. If these unisons are tuned to
one beat in three seconds, for example--a value which is about as
good on the average as a tuner can cia-the higher numbered
partials will have higher beating rates so that the 10th, say, will
be ten times as fast or three per second. The vibration planes and
orbits of the three unisons will also have random and changing phases so that the soundboarcl motion and output tones
undergo a continuous change in quality as the tone decays.
Another element of piano-tone quality, as Baldwin's Knoblaugh has pointed out, is due to longitudinal vibration of th e
string. This va ri es according to the piano string scale design.
I n my six-foot Steinway "A" it is generally about four octaves
above the fundamental frequ ency and only by rare chance is it
harmonically related. We hear this as the ringing tone of the
lower register strings. It has a full- Fourier series of partials,
all but the fundamental being well up into the high-frequency
encl of the au!tio spectrum.
AUDIO ENGINEERING
•
DECEMBER', 1953
PLUG-IN
5 and
PPLIES
MINIATURE PROGRAM
BOOSTER or MONITOR
AMPLIFIER TYPE 5117
A plug-in two stage, pushpull, fixed ga in audio amplifier. The most compact
amplifier available for this
service. Outstanding Quality
recommends type 5117 for
applications requiring outstanding performance and
maximum avai lability. Push
button metering facilities
and gold plated plugs are
standard at no extra cost.
-the name synonymous with quality in
audio equipment and components since 1923
NEW! File Catalog for broadcast engineers and
sound technicians available without obligation. Request your copy today-just call or write, on company
letterhead, to:
Designed for use with Langevin Miniature Amplifiers.
Provides AC for amplifier filaments and well filtered DC
for amplifier plate . One unit
provides adequate power to
operate up to 22 Type 5116
Amplifiers or lesser combinations of Types 5116 and 5117
with separately fused filament and plate supplies .
LANGEVIN MANUFACTURING CORPORATION
37
AUDIO 'ENGINEERING
•
WEST
65th
DECEMBER, 1.9.53
STREET,
NEW
YORK
23,
N. Y.
9
The piano-tone production system is
really very complex and much still remains
to be learned. My few remarks cover only
a small part of this generally unknown area.
Piano designing and building is hardly an
exact science, insofar as tone production is
concerned, and this is a challenging field of
research.
B. F. MIESSNER,
Van Beuren Road, RFD 2,
Morristown, N . J.
Precision
SIR:
Prints
YOUR PRODUCTIONS
BESI REPRESENIAIIYE
CLOSE CHECK ON
PROCESSING
Picture ana sound results are held
to the " closest limits by automatic
temperature regulation, spray development, electronically filtered and
humidity controlled air in the drying cabinets, circulating filtered
baths, Thymatrol motor drive, film
waxing and others. The exacting
requirements of sound track development are met in PRECISION'S
sPilcial developing machinery.
YOUR ASSURANCE OF
BETTER 16mm PRINTS
16 Years Research and Specialization in every phase of 16mm processing,
visual and aural. So or~anized and equipped that all Precision jobs are of the
highest quality.
Individual Attention is given each film, each reel, each scene, each framethrough every phase of the complex business of "processing - assuring you of
the very be"s t results.
Our Advanced Methods and our constant checking and adoption of up-to.
the-minute techniques, plus new engineering principles and special machinery
enable us to offer service unequalled anywhere!
Newest Facilities in the 16mm field are available to customers of Precision,
including the most modern applications of electronics, chemistry, physics, optics,
sensitometry and densitometry - including exclusive Maurer.designed equip.
ment - your guarantee that only the best is yours at Precision!
Precision Film Laboratories - a di·
vision of J. A. Mauret, Inc., has i6
years of specialization in the 16mm
field, consistently meets the latest demands for higher quality and speed.
Mr. Preisman's discussion of the practice of mistuning the octaves at the extreme ends of a piano in accordance with
the "inharmonicity" of its overtones was
read with great interest. In my opinion,
tl:is practice is ill-advised. Its theoretical
usage seems to be dictated by the Pythagorean comma, a disparity existing between the pitch of octave unisons produced
by a circle of perfect fifths, and those resulting from harmonics. However, the beats
between the octaves of a piano "stretched"
in this fashion are much more annoying to
me than the "dead and lifeless" sound of a
piano in which the octaves are precisely in
tune. I am sure that a piano with octaves
tuned to the interval 'of a diminished ninth
would sound quite brilliant, but not necessarily pleasant. After all, equal temperament
is in itself a radical distortion of natural
harmonic relationships, so why compound
the felony by further tampering? There is
a possible parallel here between people who
prefer "Stretched" pianos and people who
like their reproducing equipment to sound
spectacular rather than natural.
Aside from these small matters, I have
found Mr. Preisman's articles valuable and
informative especially with their ' emphasis
of the musical element which all too often
tends to lose itself in this business. Incidentally, the Conn tuning device is called a
Strobocon, and someone seems ' to have recatalogued Chopin's Etude Op. 25 as Op.
75 in the footnote on page 68.
D AVID
HANCOCK,
4 West 93rd St.,
New York 25, N. Y.
Missing Decimals
SIR:
The article titled "Three-Element Bass
Control" in the October issue appeared to be
the best one I have ever seen. It is too bad
that I can't build this control. You left
off the decimal points and I can't tell if
one resistor or another is required. for
example, what is 01 or 047 or 005? Just
where is the decimal point? And why does
such a little thing get me so riled up I
make all sorts of errors in typing this
letter to YOll ? (He did, too. ED.)
H. A.
ROLLI NS,
2328 Proctor,
Garland, Texas.
(We're trltly sorry for this cond·ition,
which has been reported by many readers.
It appears that the photoengraving for the
schematic was overetched, and the periods
were all eaten off. However, becaltse the
circuit 1IJaS of so mu.ch interest to readers,
we remade the Cttt and a m01'e legible schematic may be found on page 70. ED.)
10
AUDIO ENGINEERING
•
DECEMBER, 1953
Fidelity and Simplicity are synonymous in the
E
TURNOVER
CERAMIC CARTRIDGE
Only through the magic of the Titone ceramic principle
-an original development of the Sonotone Laooratories
-may record reproduction have the advantage of both
Fidelity and Simplicity.
Now your finest records may be flawlessly reproduced
without equalizers, preamplifiers, oscillators , polarizing voltages-or any of the other cumbersome, erratic
and costly accessories heretofore deemed necessary .
NO EQUALIZERS
The typical frequency response -with no equalization
- is flat within ± 3.db from 30 to 15,000 cycles on the
new RCA 12-5-51V test record . Similar flat outputs
are obtained from records cut to LP, NAB, AES, and
other modern characteristics.
NO SPECIAL COMPONENTS
NO PREAMPLIFIER
This tiny new Titone reproducer utilizes barium titanate in a high compliance design to provide one volt
output on modern microgroove records. For example,
CD
average measured output at 1000 cycles on the RCA
12-5-51 V test record is 0 .95 volt.
The high output voltage and the ceramic structure
provide the highest signal-to-hum ratio available ,
eliminating the need for special motors, turntables or
mu-metal shields .
+5
+5
w 0
0
Cl
~
III
TITONE TURNOVER
List Prices
Z
~ -5
-5
III
W
a:
20
FREQUENCY
IN
CYCLES
9980-5 (Dual-sapphire) $9.50
9980-5D (.001 Diamond)
(.003 Sapphire) 34.00
9980-D (Dual Diamond) 56.00
TITONE TURNOVER RESPONSE ON RCA 12-5 - 51V RECORD
Electronic Applications Division
SONOTONE CORPORATION
Elmsford, New York
AUDIO ENGINEERING - . '. DECEMBER, .,1953
13
l'
,r1'II~1'111~1~
HAVE YOUR OWN
COMPLETE HiFi
SYSTEM
Nf)"T!
tervals ranging from one to many weeks
depending upon the power output, circuit
design, and extent of use.
A modern hearing-'"aid tube suitable for
front-end amplifier use has a filament power
requirement of only 10 milliwatts; with
usage of 15· hours daily, this can be provided for almost a month by a tiny "A"
cell costing only 75 cents, or ten dollars
per year. Even so, total battery costs may
run fifty dollars or more per year with
instruments using tubes throughout.
T ra nsistors
AT MODERA TE COST
START NOW WITH THE
~400's
At right-Model 401
(Recorder-Preamplifier) $199.50*
Not shown-Model 402
(Power Amplifier-Speaker) $100.00*
*Taxes not included. Prices s lightly higher
in Mountain and West Coast States.
HERE'S HOW! The Crestwood 401 is an extremely stable tape recorder (wow and flutter
less than 0.3 %) with. a full fidelity preamplifier (frequency response 30-13,000 cycles ± 2db).
It has separate inputs for microphone, radio-TV and phonograph, which are connected
to a selector switch_
The Crestwood 402 is a high impedance input, 10 watt power amplifier (frequency response
20-20,000 cycles ±2db) with an 8" extended nnge dynamic speaker, specially housed to
produce exceptional frequency respo nse for a compact unit.
IT'S EASY! With Crestwood models 401 and 402, here's all you do to complete you r
RiFi system:
1. AM-FM-tuner (of your choosing)** is plugged into radio-TV input.
2. Record changer (of your choosing)** is plugged into phono input.
Both may be permanent installations because of the selector switch , which allows choice
of inputs or tape playback.
**Certain AM-FM tuners and magnetic pickups may require special hand ling. Information
supplied on request.
Battery costs may be materially r educed
through use of a transistor in the output
stage, and further power economy is possible if transistors are used throughout.
But replacement of tubes by transistors is
more than a simple substitution, particularly if widely variable tone control is to
be provided. Full use of transistor potentialities in hearing aids is contingent upon
the development of suitably reliable related
components at reasonable cost, as well as
iJnprovement in the transistors themselves.
Novelty value alone can be expected to
become ever less, but power economy and
miniaturization are permanent issues in
which transistors have inherent advantage.
Transistors have been at some disadvantage from standpoint of circuit noise.
and with present . costs of subminiature
capacitors or transformers suitable for tone
control and for interstage coupling of low
impedance circuits. Thus manufacturers
tend to have active interest both in transistors and in improved subminiature tubes.
One instrument maker fulfills opposing requirements with a transistor in the output
stage and tubes in two earlier stages. But
as a useful tool in hearing aid design, the
transistor is undoubtedly already here to
stay, and has changed the whole outlook
on instrument planning.
YOUR HI-FI SYSTEM IS READY TO USE! By use of the selector SW'itch yo u can
listen to either radio or records. And, by merely pressing the Reco rd button, whatever yo u're
listen-ing to will be instantl y recorded on tape- accurately, faithfully, just as yo u' re hearing
it! The same selector switch controls microphone input, allowing you r own program
arrangement.
CAN BE USED WITH PRESENT SYSTEM, TOO! The Crestwood 401 is an
excellent unit to fit into your present RiFi system. Full fidelity and complete dependability.
FEA lURES INCLUDE
Full Fidelity. Two Speeds' Two-Track Recording
• Separate Monitor and Record Volume Controls'
Exceptionally Sharp Magic Eye Record Volume Indicator • Simplicity of Operation' 10 Watt Power
Amplifier· Precision Engineering • Modern Styling
r-
.
I
SEE YOUR DEALER
FOR FULL INFORM AnON
February 4-6-Audio Fair-Los Angeles,
Alexandria Hotel, Los Angeles, Calif.
OR
March 22-25--National cO'nvention of The
Institute of Radio Engineers, Kingsbridge Armory and Waldorf-Astoria
Hotel, New York City.
SEND COUPON TODA Y
;,-...................................
It··,.
Crestwood Div. of Daystro"; Electric Corp.
Dept. AE-12, Poughkeepsie. N. Y.
I
Please send complete information on the new
Crest wood s.
I
TAPE RECO'RDERS
. Open a Brand New '
World of Recorded Sound
"
o
Am interested in setting-up my own HiFi
system.
o
Am interested in HiFi tape recorder only.
Name ..•.•.....•............................ .
May 23-29-NARTB Annual Convention,
Palmer House, Chicago, III.
June 15-17-RETMA Annual Convention,
Palmer House, Chicago, Ill.
AcJdress ••• ••• •• .•••••••• ••..• •• •.•.•••• .• •• • .
City . .•••......•...... Zone ...... Stote ..•..•..
I ....................................
Awarded MEDAL OF MERIT for: Excellence of Product, Quality of Engineering,
Beauty of Design-by International Sight and Sound Exposition, Chicago, 1953.
14
May 17-20-Electronic Parts Show, Conrad Hilton Hotel, Chicago, III.
September 30-0ctober 3-High Fidelity
Show, Palmer House, Chicago.
October 13-16-The Audio Fair, Hotel
New Yorker, New York City.
AUDIO ENGINEERING
•
DECEMBER, 1953
These are the tests of high fidelity ... not claims, not
boasts. That's why Collaro, confident of the results,
invites you to compare.
Collaro bas developed an entirely new turntable drive
mechanism. and thus has succeeded in acbieving performance considered impossible in earlier record
changer designs. Rumble, wow, and flutter are virtually eliminated. Mechanical operation is smooth
••. gentle to the record and to the delicate stylus.
And while you are comparing these, look at the construction. Note that there are no intermediate drive
wheels employed and no belts to slip or to replace.
Rotate the turntable and observe how freely it spins.
This is the combined result of dynamic balance and
ball-bearing suspension. Now lift the turntable. It's
heavy . .. intentionally weighted to give flywheel
action for constant, steady rotation. You'll notice that
the turntable is rubber covered. Important ... because
unlike other materials in use this surface does not
shed; and dust and grit particles cannot become
imbedded. On the underside is a 4-pole motor with
self-aligning oilite beat;ings for silent steady power.
ANY
WITH
RECO
CHANGERS IN THE F LD
REGARDLESS OF PRI E
You will also discover that the Collaro changers are
absolutely jam-proof; that they automatically shut off
at the end of the last record; that the tone arm is ball-'
bearing mounted, and tracks accurately with as little
as 3 gram stylus pressure.
Remember these features ... look for them, ,..~ .... "."......a;
them ... and you will agree that Collaro really u'a·... lf,~,.~'f
high fidelity record changers for high fidelity rpr·nr," •••
reproduction.
for RUMBLE
FLUTTER
and wow
--
•
LIST 'RICE
•
Model 3/532 Intermixes 10 and 12 inch records.....$65.00
•
•
•
•
•
•
Mode13/531 Non·intermix .......................................................... 54.50
Model 3/534 Single record player ......................................... 33.60
•
•
•
•
•
Write for complete details to:
• ROCKBAR CORPORATION
• 215 EAST 37th STREET, NEW YORK 16, N. Y.
•••••••••••••••••••••••
Available at Radio Parts Jobbers,
Distributors, and Hi-Fi Dealers.
AUDIO ENGINEERING
•
DECEMBER, 1953
15
EDITOR'S REPORT
WIDER COVERAGE
M
people are becoming interested in
high-quality sound reproduction in the homea fact which l11ustbe apparent to any of £'s
readers who also see other magazines and newspapers.
Some months ago, L ife acknowledged the existence of
the hi-fi fad with an article which seemed to explore
the ultra-fanatic type of hobbyist to the exclusion of the
serious music listener who has found in hi-fi the solution to his desire for music as it should be heard. Most
of the big home magazines are taking 'notice at least
once a year of the existence of equipment which would
provide better sound, and they have . dressed up their
presentations in a manner which would be expected
from the "slicks." They are to be congratulated for their
interest and the manner in which they present the mao
teriai.
Weare inclined to "view with alarm" the tende11(:y
exhibited by the New Yorll Times which recently carried a 14-page hi-fi section in a Sunday edition. In this
section appeared the advertising of manufacturers and '
distributors of audio equipment, with which we have no
quarrel, but in the same section there also appeared two
articles which ridiculed the hi-fi hobbyist and the entire
hi-fi idea as a whole. How The Times can take advertising for a certain type of product and then ridicule
the users of that product is beyond our comprehension.
Be that as it may, we are acutely aware that the newcomers to the hi-fi field are not all hobbyists ·in the sense
that they build some of their equipment and are constantly experimenting with it in the search for perfection. Most of the newcomers just want good equipment which will give them good reproduction, and they
want it with a minimum of bot1ler and effort. Then
there are others who want information on how to assemble the factory-built components into a workmanlike and attractive combination which give them the
desired results.
For some time £ has been widening its coverage in
that direction, yet without reducing the technical articles which the audio hobbyists have come to exp·ect.
ORE AND MORE
In the February issue, therefore, you may expect to
find still more material for the non-technical music
lover, and with that issue a new department-as suchwi ll be inaugurated. Just a word of caution-don't be
confused by the facelifting job on the Feburary issue,
for a change is coming. After all, we haven't changed
the appearance of the magazine appreciably since March,
1949. (We planned the change for the January Issue,
but time goes too fast and we didn't make it. )
AUDIO FAIR-LOS ANGELES
Heralded as the "Audio Fiesta-A Festival of
Sound," the second Audio Fair-Los Angeles opens on
February 4 at the A lexandria Hotel in the City of the
Angels. This is the big audio event of the year on the
VI/est Coast, and we wonder how big the attendance
will be. Last year, the figure was around 17,000, and
was topped only by the recent Audio Fair in New York,
which racked up an attendance of over 25,000. This
may be the new East-West contest of the year. In any
case, don't fail to be there if it is at all possible. If you've
never seen an Audio Fair, you've missed something;
if you ever have attended one, the chances are that you'll
be there again.
APOLOGY
Everyone makes a mistake occasionally, and we're no
better than the average, ·it seems. One of the .photos
used in the article " It Can be Attractive" was wrongly
. credited . Naturally when an organization does a good
job on putting in a musIc system, it likes to receive
credit for it-and particularly does it not want credit
given to someone who had nothing whatever to do with
the work. At the top of page 31 in the November issue
is shown an attractive installation which was actually
made by Shrader Manufacturing Company, Inc., of
Washington, D. c., and we take this opportunity of
apologizing to Bill Shrader-who has often contributed
to £'s pages, and who will be back again soon-and to
give the credit where it is due.
:!Itrry <t1qrtntman &jfappy NtUt Itar
frnm nIl nf 'us tn all nf ynu
16
AIJDIQ ;- 6NCINEERING : ~ _QECEM.BE~~: 1~53
glad 8 wailed ..."
Here's how I solved a prohlem that bothered me •.. and may be bothering you.
Many of my favorite recordings happen to be 78's. They mean as much to me as any of my
newer LP's or 45's. Changing pickups was often a rea l nuisance-and yet I wasn't wining to
give up rhe superior quality of my two Pickering cartridges.
Last fall my dealer offered a suggestion. " Wait a little 'longer," he said. "You'll be glad you did."
He was right. I now have Pickering's new turn-o~er cartridge. A simple Rip of the handy
lever and I'm ready to play any favorite that fits my mood-whether it's standard or microgroove.
Mo~e than that, I'd swear my recordings sound better than ever.
Ask your dealer to show you this convenienfnew turn-over cartridge. Have him' demonstrate it.
See if you, too , don't h ear the difference!
'PICKERING
New York'
and company incorporated.
PICKERING PROFESSIONAL AUDIO COMPONENTS
I
f'.' ~'\.
':E%daw~~lknzl~~ (
. •. D.m••", ••• d •• d ,.'d by L•• di'g ,.di. Po." Di",ib,/O" .,.'ywh",.
For the one nearest you and for detailed literature, write Dept, A-3
,
lill ~ I~ I~ L~ IX IJ IJ LI
:4'Ci
'AUDIO ENGINEERING
•
DECEMBER, 1953
)·
1
~ I
'W:l!~~"""".
_ __
17
p
•
Watching the serenity of Christmas skies, we
are conscious of deep silence. Yet the stars are talking to us all the while - talking in radio waves
that are full of m eaning to scientists probing the
depths of space.
The important discovery that some stars produce
radio waves was made by a Bell Laboratories scientist while exploring atmospheric disturbances which
might interfere with transoceanic telephone service.
His discovery marked the birth of the fastgrowing science of radio astronomy. It is telling
us of mysterious lightless stars that broadcast radio
waves, and it promises new and exciting revelations
about the vast regions of space concealed by clouds
of cosmic dust.
Directional n dio antenna used by Karl G. Jansky, in the discovery of
stellar radio signals at the Holmdel, New Jersey, branch of Bell Telephone Laboratories. In 1932 he detected waves of 14.6 meters coming
from the direction of Sagittarius in the Mil ky Way.
It is another example of how Bell T eleph one
Laboratories scientists make broad and important
discoveries as they seek ways to make your telephone
serve you better.
BELL TELEPHONE LABORATORIES
EXPLORING AND
INVENTING, DEVISING
AND
PERFECTING , FOR CONTINUED IMPROVEMENTS AND
ECONOMIES
IN TELEPHONE SERVICE.
Magnetic Transfer of Stainless
Steel Recording Wire
SAMUEL STORCH HE l M':'
Wi re reco rding is sti ll employe d in many useful applications, and th e effec t s of signal t ransfer
betwee n adjacent turn s ma y becom e troublesome. The author reports th e resul ts of a num ber
of tests made t o determi ne . th e optimum working cond iti ons for. vari ous recording w ires.
OF THE phenomena accompanying magnetic wire recording
is that of magnetic transfer. This
condition involves the mag netization of
unrecorded turns of w ire by adj acent
turns of recorded wire, the wire' usually
being made of 18/ 8 stainless steel.
T ransfer is popularly r eferred to as
"crosstalk" and is pa rticularly noted
when qui etly recorded passages of wire
:fiollow or precede heavily recorded portions of wire. A n illustra tion of what
this sounds like w ould be the hearing of
two radio stations on the same setting,
one station coming in normally, ' the
other annoyingly clear, thoug h at a
lower volume than the desired program.
In order to investigate transfer, a
stutly was made of the effect magnetic
properties such as r emanence, B,·, and
coersive force, H e, had upon transfer
when wires were magnetized with increasing r ecording currents.
O
NE
Procedu re
The mag netic parameters of r emanence and coersive force w er e measured
directly from hysteresis loops proj ected
upon a previously calibrated cathoderay oscilloscope screen . The hyster esis
loop tester used t o make these measurements was specially designed1 and constructed, and was capable of accepting
wires of a maximum of 7'8 in . diameter.
* Engineer-in-Char.qe. Atomic Ene·ygy
Division, Sylvania E lectric Products Corp.,
Bayside, L. I., N. Y .
1 W . W . W etzel, "Review of the present
status of magnetic recording theory. Part
1," A U DIO E N GINEERI NG, Nov. 1947.
.0 0 4
SlpE~'~~N II,I _
DIAM ETER WIRE
+ 16
,
+12
+4
~
SPECIM EN 2
e,
H,
260
!II..
/
-8
..;fII'
a:
- 12
-16
-2 0
- 24
~
.
,
./
Br
2500 -
l/
,
"-
SP ECIMEN 3
e,
H,
.....
"
440
108 0
0 .5 0 .7
1.0
2 .0
RECORDING
AUDIO ENGINE ERING
•
10 .0
CURRENT,
_
Fig. 1. Transfe r vs.
recording
c urrent
for t hree specime ns
of .004- in. wire .
....",.".
•
I""
5 .0
•
1 900
,/
- 4
VI
t-
......... I-- 320
""'" ~
He
",.
I
a
r%
...'"
.,z
.J1I'
/
+8
"
The accuracy obtained us ing this unit
was ± 2. 5 per cent for the H e values
and ± 5 per cent for the B .. values. Several strands, generally six, of fine w ire,
.004 in. or .0036 in., had to be tested in
order to obtain accurate B,· readings .
The larger the a rea of wire used, t he
more lines of flux were available fo r
measurement, i.e., the hysteresis loops
were longer and B ,· measurements were
more readily made. T he value of coersive
fe rce was dependent upon the applied
field. Once the fi eld was established, the
H e remained constant regardless of how
11'::any stra nds of wire were used.
The testing procedure followed was
tu take a s pool of 7500 ft. of fin e diam.
wire and record a 1000-cps signal fr om
an a udio oscillator through a 4.5-to- l
step down transformer upon the fi rst 100
ft. The sig nal was placed on the wi re
using a S hure r ecording and playback
head and a 50-kc bias at 75 mao T he recording currents used for thi s purpose
ranged f rom 0.47 to 85.0 mill iamperes.
Once the 100-ft length of w ire was
magn etized it was rewound upon its unr ecorded balance. A ft er this was done,
th e wire was played back through the
Shure head and an amplifying and filter
system so the output of the recorded and
unrecorded parts could be measured.
These determinations wer e made in db
using a Ballentine voltmeter with an
a rbitra rily chosen zero point. It was
fo und that the output of the wi r es dir ectly r ecorded upon ranged f rom + 30
to + 32 db at a noise level of - 26 db,
whil e the output of transfer sig nals
ranged fr om a high of + 16 db to a low
of - 25.5 db . ( T he negative values exist
30
50
mo
DECEMB ER, 1953
80
because of the a rbitra rily chosen zero
point on the indicating voltmeter.)
T he transfer of the wires was observed to occur immediately after the
original signal on the r ecorded portion
of wire dropped off as indicated by tl}e
voltmeter. Transfer was shown to be not ·
a uniformly r ecorded signal along the
length of wire but rather a series of
"bursts" of magnetized portiqns a~o ng
the wire. It was noted that the transfersignal g radually diminished in output
as the distance between the r ecorded and
unrecorded portions of wire increased.
A very effective visual demonstration
of the actual transfer phenomena was
cbserved by placing a cathode -.ray
oscilloscope in the system. T ransfer
could then be seen as a succession of
"flashing" sine waves cOlTesponding to
the orig inal signal but of lesser ampli.:;
tude. These flashes decreased in amplitude with increased distance between
the recorded and unrecorded passages
01 wire until eventually no trace of transfer could be observed.
Result s
The data bbtained during these studies
are tabulated in T able 1. Curves plotted
fr om these da ta, Figs. 1 to 6, indicate
the following :
Figure 1, plots of transfer vS. r ecording current for .004-in. diameter wires
of various H o and B ,· values, show that
transfer first increases to a maximum
value, levels off and then declines as the
recording current is increased. There
appears to be a trend as to the effect
tile actual values of H e and Br have on
the maximum transfer value of the
curve and where this maximum value
lies along the recording current abscissa.
Figure 2 is a plot of maximum transfer
value for l). particular wire versus the
r emanence of the wire. The curve shows
that as the remanence increases the
maximum transfer value also increases.
Figzwe 3 shows the curve obtained
when the r ecording current for maximum transfer value for a specimen is
g raphed vs. the coersive force of the
specimen . The trend is for increasing
r ecording current w ith increasing coersive force; i.e., the peak of the curves
in Fig. 1 move to the right as the coersive force increases. This means a lower
rate of i'n crease in transfer at the lower
r ecording currents, which would be of
p.ractical advantage. Thus, Figs. 2 and 3
19
+ 20
20
.004 DIAMETER WIRE
+16
/
+12
+4
~
v
~I
./
+8
0
---
......
~
·-4
.1-
-8
-12
1000
1,....00
1~
~~
./
W",
o:z
""
~~
,
~
0,"
0: -
OX
I--
V
/
10
0:«
=>0:
01-
-
.004 DIAMETER WIRE
'"
/
0«
w,"
0:
2000
1500
2500
0
2700
200
250
REMANENCE, GAUSS
300
350
FORCE,
COERSIVE
400
OERSTED
450
500
Fig. 2 (left). Transfer vs. remanence for one of the specimens of Fig.!. Fig. 3 (right l. Recording current for maximum transfer vs. coersive force
in oersteds, for one specimen of .004-in. wire.
'
indicate that transfer can be minimized
by decreasing the remanence and increasing the coersive force. Lowering
the remanence in turn lowers the output
of a recording wire and there is, therefore, a limit to how Iowa value of Br
can be tolerated. Too high an increase
in coersive force, which increases the
difficulty of erasure of a recorded wire
is, therefore, also limited.
. ·Fi gl.we 4 is a plot similar to that of
Fig. 1 The specimens used in this case
were .004-in. diameter wires obtained
from another source. H ere it is seen
that the same general trends occur ; i.e.,
the curves rise, level off and then decline. The maximum transfer values
also show up as incr.e asing as the remanences increase. The effect of coersive
force is not as clear as in Figs. 1 and 3 ;
however, both lie values are rather close
and the indication is that the currents
fo r maximum transfer for both curves
are about the same.
Figure 5 represents the transfer val ues
V~·. recording current for finer wire,
namely, .0036 in. rather than .004 in.
Again the curves repeat the now familiar pattern of rise, level, and decline.
Also, the higher remanence values cause
higher maximum transfer values. The
higher coersive force also moves the
peak transfer value toward higher l-eccrding currents. I n addition, as with
.004-in. wire, the higher coercive force
seems to cause the slope of the rising
part of the curve to be less steep.
Finally, Fig. 6 shows a comparison
between the effect the diameter of the
w.ires involved has upon the curves of
transfer vs. recording current. Here it is
seen that the general appearances of the
two curves are similar, however, the
peak value for transfer for the .004-in.
wire is higher than that of the .0036-in.
wire, both wires having almost the same
Br values. As with the curves representing .004-in. wire, the higher value
of the H e appeared to move the peak of
the curve representing .004-in. wire to
higher recording currents. Interestingly,
the slope of the lower H e curve, .0036in. wire, was steeper than that of the
higher H e curve. This seems to be a reversal of what was fo und regarding the
effect of H e on .004-in. and .0036-in.
wire when compared to other .004-in.
and .0036-in. wire, respectively.
Thus, a smaller diameter wire would
appear to minimize transfer and so a
finer wire is more desirable. There is a
limit to this however, for as the diameter
of the wire in fine sizes is decreased,
v
~z
«
0:
I-
0
I
-B
I
-12
"
""
He
2~0
8r
I I II"I
•
I I II I
2.0
5.0
1p.O
RECORDING CURRENT, m.
II
//
...
- BI-+-r+-l-H-I+-I1f-t--+-r+-l-H-+t~--r-++HId-t*---;
-4
~
r"
"'-
-12 ' -H_+ I-t-#I-iI1,- -i--j- I-t-+l- - - :--- I---+-H--H'H - I
SPECIMEN 4 1.' -161---+---+-H--I-I-~---I--i+-i+-H
He
Sr
-201---t--t-+-t--Hft-t---1---+--:-1--H 250 14BO
--j
t--~~-t-~HHH+----1
. "",-
J -
~
I
5.0
30
10.0
I
mo
50
BO
-·~~--+--r_H-H_~Ht----i
I
~
- 4
z
- 8 I-H_H_H+bl+- /"",,-
'-
'(
• ",,-
-I-
"-
~ -1 2 ~~~~~~~~--~~~~~-=~~~~~~~~--~
-161--I--I-+-14'''l+-I.III/~
- SPECIMEN
7 -H-H+~--I-H_+HId-t*--;
~
He:
Dr
- 241---1--11
CURRENT
III
~
ol----+---+-H--I-I--~j_-~-I_.~--
-2 BI-+++-+H-++~--I-H_-I-·I-t11·+I--~-H_H_+--+-+-+~--H
2.0
80
+4 ·~-H-t-+-+*I++~'rH~--+-rTHT~~
-24 ~+-tl~~~H---~-t-~+++H+---+-~~rrH+t--~
RECORDING
50
B,
- 20 1---+--hf-:tooi"f1i+-- 320
1.0
30
+ 121---+---+-H--I-I-+l---I---+-++ H,
~ ... ~ 280 _Hj_26-0-0 -t--Ir-I-t-+++H----t
+ 8 I---+--I-H--I++j--- .l~-I--I-N_-H
f---
2BOO
1""'-
+161---+---+-H--I++I--'---I--I--H- ~pIECIMEN ~+--t--t-t--+f++-h---I
- j_- I- I, + -H-!+I----J
/.fI' ....
-
.0036- DIAMETER WIR E
[4
0.5 07 1.0
o I-++-H-H-++-~f-+:=l--H-H-++--~~+
0 .5 0:1.
_.
SPECIMEN 6
H,
B,
2BO 2600
-20
-24
~.
II
-4
-16
•
""'IiII
Sp,ECIMEN
...ffe·, Dr '_~
320 2500
.004' DIAMETER WIRE
J
+4
~
Fig. 6. Comllorison of
transfer vs. recording
current for two wires
of differe nt diameters.
"'-
......
.0036 DIAMETER WIRE
/I
.
1/"
Ji.."..,o'
+B
+ 4 I-++-H-H-++--t-/"I-H+IH -+~,,~
+-I- SPECIMEN 5 f - - -
~
(C ontin'l/ed on page 56)
+12
•
io"'"
"'.....3
A possible explanation of why the
magnetic transfer phenomenon behaves
as it does has been considered and is
as follows:
Magnetic transfer is simply the physicalor very near physical contact of a
magnetized . permanent magnet, a turn
of wire, inducirtg.a contacted non-magnetizec;l permanent magnet to a partial
.'
+B~~1-t+++H----+--~~~±tr---t--t-ttiiitr---i
~-
Discussion
+16
.004 OIAMETER WIRE
+12 r- (FROM ANOTHER SOURCE) - jf- H-+I-I-I--I--
:
wire drawing- costs rise very rapidly.
Another limiting factor is that the wire
in finer sizes would snap if the recording
unit started or stopped too suddenly: i.e.,
the wire although having a greater tensile strength as measured in pounds per
square inch in the finer sizes would actually allow only for a lesser breaking
load as measured in pounds.
2300
-H-H-+-+----.,I-H_++-+--H'I+-~
~H
~ -H+t---![.LI-J·I-HH-+-+·/--/--I-+-H-H-+I--~
0 .5 0 .7
1 .0
2.0
RECORDING
5 .0
30
10 .0
CURRENT I
50
80
ma
Fig. 4 (left). Transfer vs. recording current ·for two specimens of .004-in. wire from a different source than those of Fig. 1. Fig. 5 (right).
Transfer vs. recording current for two samples of .0036-i n. wire .
20
AUDIO ENGINEERING
•
DECEMBER, 1953
An Automatic Disc Recorder
CURTISS R. SCHAFER ':'
Time-saving is money-saving-in recording studios as well as elsewhere. The
author describes a system whereby considerable tim e and attention is saved
by making an opera tion partially automatic instead of entirely manual.
HE EQUIPMENT to be described was
deve1'oped to meet the needs of the
recording studio with a great deal
of tape-to-disc dubbing work to do. Once
the tape playback machine has been
started, and the cutter head lowered
onto the disc, the operation is almost
completely automatic; that is, the program material will be dubbed to the
disc with the proper spacing between
selections, __and both the disc and tape
machines are stopped at the end of the
program. Control of the disc cutter from
the tape is accomplished through sman
pieces of Scotch tape which have aluminum foi l on the outer side. These are
stuck in place on the tape by the operator when he edits the tape, and act as
miniature shorting bars which operate
the appropriate relay on the recorder
panel.
The automatic di sc recorder is shown
in Fig. 1. It is built around a Fairchild
s39-G recorder which has been modified
as follows :
1. A spirall ing motor and overrunning
clutch have been added.
2. A dual Micro-switch has been
mounted on the left lead screw support
so that when the cutter has finished the
center spiral it strikes the switch actuator and a relay shuts off the turntable
motor, stylus heat, and spirall ing motor.
3. Other additions to the Fairchild
unit are a suction pump and tube, a
T
•
Fig. 1. Th e con trol
panel mounted a djacent to t he disc
record er
provides
~ onven i e n t
opera t ion.
•
microscope, and spiralling and l111cro- which is loaded with a 10-db isolation
pad, it comes back to the panel and into
groove attachments.
Figure 2 is a diagram of the audio the meter switch which sets the recordsection of the panel. The program ma- ing level at 20 dbm for microgroove
terial leaves the tape (on an Ampex and at 26 dbm for standard recordings
"400") via a sOO-ohm line, goes into when the meter indicates 0 VU. This
the T-pad, through the passive equal- switch also monitol's the voltage (apizer, t.o give the proper h igh-frequency proximately 6 volts at 0 VU) across
characteristic for microgroove (LP) or the heater coil in the thermostylus unit.
* Consultant to T he Dubbings Company standard (78-r.p.l11 .) recording, and out . From the switch and VU meter, the
41-10 45th St., Long Island City, New into a h igh-quality 30-watt power ampli- signal goes into the SOD-cps crossover
Y ork .
.
fier 1 . From the output of thi s amplifier, network (for bass equalization) and the
cutter head .
Fi[fl.£re 3 is a wiring diagram of the
automatic control section. The indicator
lights, PL, are numbered 1, 2, 3, and 4
~~__-t~_A_
MPtL_
'FI_ER__-;=S=
UC~TI_
OO-t~==
TU~RN_~_~_E____~======~-r --l
from right to left when looking at the
SW1
front of the panel, and are associated
117 VAC
6O'V
with the switches just below them on
,os
the panel and correspondingly numbered
on the diagram. Terminals AA lead to
the heater coil on the thermostylus unit
and terminals BB lead to the microscope light. The relays indicated are of
the latching type. The 3D-watt an~plifier,
suction pump, turntable motor, and
spirall ing motor are plugged into the
twist-lock receptacles mounted on the
rear of the chassis. SWs is a push-button switch for manual control of stylus
heat. Another push-button switch is used
for manual control of separating spiralling if desired. On the octal socket at
A
8
the left of the diagram, term inals 3 and 7
10
'
I
I
I
:
go to the section of the dual Micro1 Curtiss
R. Schafer, "30-watt highTIMING MOTOR
fidelity audio amplifier", AUDIO ENGINEERING, July 1948, p. 21.
Fig. 3. Comp lete schematic of the power and signal ci rcuits for operation of t he disc re(C ontinned on page 51)
corder and its accessories.
__
1_ _ _ _ 1
AUDJ,O ENGINEERING
•
DECEMBER, 1953
21
A New Wide-Range
Phonograph Cartridge
JOHN F.
WOOD:~
A description of the newest contender in the field of hi-fi reproduction. The principles of operation
of the ba rium-titanate cartridge are outlined, and the economies of such a device are discussed.
the magnetic phonograph cartridge has been accepted
as the standard of the industry and
used in practically all professional and
high quality reproducing systems. With
specialized associated equipment, excellent response can be obtained over the
major portion bf the audio spectrum.
While ideally suited for the constant
velocity recording characteristic, there
are definite disadvantages to the use of
a velocity type of pickup on modern
records. Until recently there has been
little else available and the use of the
magnetic cartridge has been accompanied
with equalizing circuits and preamplifiers of increasing complexity.
With the development of the barium
titanate piezoelectric element a new
medium was available to the cartridge
designer. Experience had been accumulated with the design and production of
various ceramic cartridges for conventional phonograph use where high output and low cost were primary considerations. Accordingly, it was logical
to pursue the development of a cartridge
in which the full potentialities of the
ceramic could be realized.
As the outgrowth of this program,
the E lectro-Voice Model 84 UltraLinear ceramic cartridge is presented to
the music listener and professional as a
cartridge eminently suited to the reproduction of modern records.
OR MANY YEARS
F
* Senior
Engineel', Electro-Voice, Inc.,
Buchanan, lJ!Iichigan.
-
fREQUENCY---+
FREQUENCY
The new Electro-Voice Ultra-Linear ceramic
pickup cartridge.
Amplitude and Velocity
Unfortunately, a number of misconceptions have existed regarding cartridges and recording methods. In view
of these misconceptions, a brief review
of recording characteristics is desirable
and follows in the paragraphs below.
Fig~wes 1 and 2 are shown to clarify
the relation between velocity and amplitude. The waveform is that of the
record groove with frequency increasing
toward the right. The frequency scale
has been reduced because of limited
space. According to the equation:
V=2JtfA
where V = velocity of a stylus moving
laterally with the longitudinal motion of the groove,
f = frequency
A = amplitude of groove excursion,
velocity will increase with frequency for
a given amplitude at the rate of 6 db
per octave. Conversely, [email protected] will
decrease with frequency for a g iven velocity at the rate of 6 db per octave.
The statement is often made that a cartridge or system is "fiat." To Be accurate
it is necessary to indicate the reference
to constant amplitude, constant velocity,
or some recording characteristic such as
the New Orthophonic or National Association of Radio and Television Broadcasters recommended curves. For example, a velocity-fiat cartridge would
not reproduce a modern music record
with an Orthophonic characteristic without considerable equalization.
Origin of Recording Characteristics
The origin of constant-velocity recording goes far back into the history
of sound recording. The old acoustic
recording method, Witll elaborate horns
and strong voiced artists, utilized essentially a velocity characteristic. The
first electric cutters were of the magnetic
type and recorded with a 6 db per octave
descending slope on an amplitude basis.
When played back willi a magnetic
pickup with the inherently inverse characteristic, the result was a fiat reproduction of the original sound. Since the
amplitude of the groove can become
quite large at the lower frequencies, a
reduction in level below some arbitrary
crossover point was necessary to prevent
the overcutting of one groove into the
FREQUENCY
FREQUENCY
In
i~ t:~~ I~
.
CONSTANT
, AMPLI TUDE
REGION
.
FREQUENCY
CONSTANT
VELOCITY
REGION
131
FREQUENCY
121
FREQUENCY
Iffi1l
-
FREOUENCY
NARTB - - AES -
NEW ORTHOPHONIC .•.•... _.
[~Ffi1+Mi]U>f81n
oCt
50 100
5001000
5000
50100
FREQUENCY
5001000
5000
FREQUENCY
~
141
Figs. J to 4. ( J ) Constant amplitude operation. (2) Constant velocity operation. (3 ) Standard frequency test record characteristic. (4) Modern
recordin g characteristics.
22
AUDIO ENGINEERING ' .
DECEMBER, 1953
(Left) Production testing of compliance, using a magnetically driven vib rating reed which is loaded by the stiffness of the cartridge. The change
in amplitude of vibration is read from the meter which is calibrated directly in compliance-the reciprocal of stiffness. A high value of compliance is necessary to prevent distortion and actual damage to the record groove. (Right) Production testing of output voltage and frequency
response. Voltage output at 1000 cps is indicated on the meter while playing a test record , and frequency response is checked within a 2.5 db
envelope on the face of the oscilloscope over the range from 50 to 10,000 cps. The source for this test is a sweep-frequency record .
next. At thi s crossover point the transition was made electrically from constant
velocity to constant amplitude. This
characteristic is shown in Fig. 3 and is
still used for a number of standard frequency test records.
When interest was aroused in the
more natural reproduction of sound, it
was fou nd that the signal-to-noise ratio
was very poor. This was true because
of the small groove amplitude at the
higher frequencies. Consequently, highfrequency equalization was provided for
the cutters in various degrees until, today, records are cut w ith very nearly a
I ClaractenstlC.
I
. . V alla·'
cons t an t -amp II't uce
tions from this characteristic exist for
several reasons. The first I'eason is to
f Tta t d '
f
r .
t
k
aCI Ii e. eSlgn o. equa IZ111g r~e wor s.
Anot ler I11volves Improvement 111 needle
tracking at the high frequencies. Variaf
ft
d b tl
d·
IOn.s are 0 en ma e y le r eco.r mg
en~me~r to compensate for a~oust!c defiCiencles and to produce speCial effects.
Th.e NARTB,. ~ES and New .Ortl:ophol11c characten shcs are shown 111 F~g.
4. The crossover . po~nts still exist but do
not have the 5lgl11ficance of the old
transition point: The lower point is
shown at 500 cps (f,) and the upper
point at 2 120 cps (f2)' Because of the
g radual transition, the crossover can be
defined as the intersection of the
asymptote or tangent of the curve with
the 1000 cps level.
Obviously, the correct reproduction of
these curves requires compensation of
any magnetic cartridge, whether it be
variable reluctance, moving coil dynamic, or other. The5e cartridges operate in accordance with Faraday'S Law:
d</>
e.m· f·
= dt
where e.1n.f. = the generated electromotive force,
N =the number of conductors
in the field,
AUDIO ENGINEERING
•
d</>
.
dt = th e tl1lle rate of change
of magnetic flux.
For this reason this class of cartridges
is referred to as the velocity type.
For the magnetic ca rtridges, equalization is uwally accompli shed by a
ri sing gain in the preamplifier of about
6 db per octave below the lower crossover point. As the magnetic cat·t!·idge
is inductive, high-frequency equali zation can be accomplished by shunting
with a load I'esistance of the proper
value, as is done in some preamplifiers.
In others this is done in other section5 of
the circuit.
The effects of this extensive reshapin g
of the response curve can no w be considered. As mentioned above, the cartridge is inductive and is therefore
susceptible to hum pickup from stray
magnetic fields. These fi elds a re produced
by phonograph motors, transformers, and
other electri cal equipment. At 3D-cps, the
output of this cartridge is 18 db below the
1000-cps level, or from 1.25 mv to 5 mv
in an ave rage cartridge. Amplification of
this low-level signal will increase the
hum along with the s ignal. Furthermore, there is the consideration of tube
and circuit noi se which is always a
problem in low level amplifier desig n.
The Barium Titanate Transducer
Bari um titanate i5 a true ceramic
material, simila r to the material used
in an ord ina ry tea cup. H owever,
barium titanilte possesses the unique
ability to generate an electric charge
when subj ected to mechan ical stress.
This phenomenon is known as the
piezoelectric effect. In such an element the generated e.m.f. is proportional to the mechanical strain in the
material. Because of this ph enomenon ,
pickUps utilizing the piezoelectric effect
are referred to as amplitude or di splacement devices.
A fypical element consists of two
DECEMBER, 1953
slabs of barium titanate separated by
an electrode surface which may be a
metal strip or a deposit of silver. (See
Fig. 5.) Electrodes are deposited on the
outside surfaces and the entire assembly
is charged by the application of a high
voltage, just under the breakdown pote~tial. .Th is "charge" accomplishes an
orientatIOn of tl:e molec1:1 lar str.u~t~re
and pr?duces ptezoe~ ectnc sensItivity.
A. bendmg force .app~led to .the element
Will stt;ess one sld~ 111 tensIOn and the
other 111 C0I11preSSlOn. The generated
voltage~ of t?e two slab.s are usually
added 111 senes to provide max imum
output.
Wh'l tl
.
I t ' ff t I b
'd I I e . lde plezoete~drtc e ~tCl Rlas he]eln
WI e y use 111 c.ar 1"1 !?es WI 1 oc e e
Salt or al11mOl1lum dl-hydrogen phosphate (ADP) generating elements, cert '
It ' f
r 't d tllelr. use
a m c larac e rt~ ICS 11111 e
fo r the conventIOnal home ph.onograph.
The hig her output voltage of the Rochelle Salt element is offset by its susceptibility to damage by excess humidity
and its dehydration by exposure to extreme dryness . Furthermore it dissolves
in its water of crystallizatioil at 130 0
F. A DP is better in these respects but
has a much lower dielectric constant.
On the other hand, the barium titanate
element is completely resistant to moisture, is unaffected by temperatures up
to and above 212 0 F ., is r elati vely
strong, and has a very high dielectric
(Contilmed on page 52)
ELECTRODE
--
SURFACES
BARIUM TITANATE SLABS
APPLIED FORCE
Fig. 5.
A barium-titanate element.
23
•
Vibration Reduction In
loudspeaker Enclosures
G. B. HOUCK ':'
Presenting the reasons for bracing a bass-reflex loudspeaker cabinet, and showing
how to do it with the assu rance of improved performance when the job is completed .
B
ENJ AMIN FRANKLI N once observed
tha t "Empty barrels make the loudest noise." In this case he w-as Teferring obliquely to the common phenomenon of uninformed vociferation, not
describing the performance of a loudspeaker enclosure. G. A. Briggs, in the
second chapter of "Sound Reproduction," was commenting on the latter
when he wrote: "The indications are
that the effect of cabinet resonance has
been wlderestimated in the past. " H e
observed tha t the 't one-quality of reproduced sound was g reatly improved when
the loudspeaker cabinet was constructed
of materials having a hig h density. In a
paper presentesJ before the IRE PGA \
Frank McIntosh pointed. out that
"boomy" sounds are caused by acoustic
radiation due to i:lecaying vibration of
the panels in a poorly braced cabinet .
Briggs offers one solution to this
problem- make the panels massive and
they won't vibrate. The principle involved is that of relative momenta. Consider the effect of a moving mass of air
striking a panel. Referring to Fig . 1, if a
unit volume of air having a massMl,
and an instantaneous maximum velocity
V, strikes a unit volume of panel having
a mass lVI" initially at r est, both masses
will have a resulting velocity V •. This
relationship may be written:
M¥l - M .O' = (Ml+M, )'JZ,.' . (1~
Note that for the optimum condi tion,
V. approaching zero (panel does not
move) it is necessary to have t he rat io
of M.j Jl1'1 as large as possible. Since Ml.
* Geneml Precision Laboratory, 63 Bed_
ford Road, Pleasantville, N. Y .
1 IRE
Professional Group on Audio,
No. 10. September, 1952.
TABLE
Physical Properties of Common Ccnstruction Mate rials
Materia l
Mass
Ibs./ ft."
Thic k.
In.
Dry packed sand
1
105
Bri ck
125
3
Concrete
150
3
Plaste r
1
W hite Pine
26
'V8
Wh ite Oak
46
'V8
2- 'V8 wood pane ls with 1" sand betwee n.
the mass of a ir is fixed at roug hly 1/ 13
lb./ cu. ft., M. remains the only variable.
By varying M ., it is poss ible to obtain
the ratios shown in T able I for several
different materials. It appears obvious
from a glance at this table that a small
improvement in V. (hence a reduction
in vibration) may be had only at t he
expense of a large increase in weight.
For example, a panel made of concrete
would tend to v ibrate (other things such
at the modulus of elasticity being equal )
1/ 4.5 times as much as one made of
wood, but would weigh 20 times as
much. Thus a typical bass reflex cabinet
weighing 50 pounds constructed of
wood, would weig h 1000 made of concret€-probably too much for the average living r00111 floor to support. Even
if this were permi ssible, such an enclosure would be vi rtually immovable
and would present the baffling (no pun
intended) problem mentioned in a recent
editoriaP
.
Fortunately for the cabin et designer
there is another solution to the problem
of reducing panel vibration. Instead of
relying on weight alone to accompli sh
the desired results, he can make the
panels sti ff, and join them rigidly together.
Mo
Ibs·/ ft ."
Mo/ Ml
VI/V.
8.75
3 1.2
37.5
8.0
1.9
3.36
12.5 5
11 4
406
488
104
24.7
43.8
163.5
10.7
20.2
22 . 1
10.2
4.9
6.6
12.8
thermore, it can be shown that a much
simpler method of analysis provides the
essential information necessary to make
very substantial improvements in cabinet construction.
For all practical purposes it is reasonably sufficient to consider a pa nel as
made up of an infinite number of small
beams a rranged side by side as shown in
Fig. 2. Notice that in this type of analysis, the beams are represented as extending across the shorter dimensi0n
of the panel. ASsu~lling the edges of the
panel are supported, it is logical to suppose that the beam exhibiting the most
severe deflection when subject to a load,
will be one near the center of the panel
such as beam A. Now, without attempting to determine an exact coefficient for
the stiffness factor, it can be shown that
the maximum ·deflection of beam A is
dependent on a few easily determined
va riables. Actually, since the beams are
integral parts of a homogeneous plate,
the deflection will be somewhat less than
that of a single unatta~hed beam.
The equation for the deflection of a
rig idly supported, uniformly loaded
beam may be written as
WU
Z=384EI
(2)
St iffness of Panels
BEFORE IMPACT
AFTER IMPACT
Fig. J. Kinetic energy effect of Unit Volume
of air M impinging on Unit Area of plnel, M•.
"
24
Several factors determ ine the stiffness
of a panel. The chief factor of course is
the geometry of the panel. In most cases
it is very difficu lt to analyze the behavior of a vibrating plate, especially
if one attempts to relate various design
pa rameters' to .~ resulting acous.tic output. I t is enti'r ely beyond the scope of
this discuss ion to examine these theoretical considerations in minute detail. F ur-
/ , - - - - - - - ; ' ? - UNIT BE AM
A -/'
,.>- .
2 ELlITOR's REPORT, AUDIO ENGINEERING,
March, 1953.
Fig. 2. Typical panel as used in the discussion.
AUDIO ENGINEERING
•
DECEMBER, 1953
of supporting the panels is highly im·portant. Since most panels are made of
plywood, it is necessary to insure that all
joints are constructed to achieve the
SUB-PANEL
maximum
possible rigidity. A simple
! 2 X4 BRACE
'"
but effective method for accomplishing
=:J!
suB - PANEL
this is to use corner posts to which the
21 2X4 BRACE
=:J+
panels are securely ancho red. A few
: 21 SUS-PANEL
typical joints of this type are illustrated
ZX4 BRACE
in Fig. 4. It will be found that such
1 21 SUB-PANEL
methods also contribute to the over-all
---..l.appearance of the finished structure.
IA)
I B)
IC)
At first glance, the prospective builder
may be somewhat dismayed by the sugFig_ 3. Typical bass-reflex enclosure, with dimensions as used in the sample problem. All
gestion that special tools are needed to
stiffening beams are mounted so that their maximum cross-section dimension is perpendicular
prepare the joints for assembly. This
to the plane of the panel.
type of work is best done using a joiner
/1,/ L-'
in which Z equals the maximum deflecor router, although the patient crafts(4)
tion, W equals the load on the beam
Z=8E I
man may use a plane with very good
(maximum instantaneous value), and I
results. In many instances the whole
For convenience, the terms ' in the problem can be greatly simplifi ed by
equals the moment of inertia of the
cross-section of the beam. If this equa- equations wh ich remain more-or-Iess having a local mill cut each piece to
tion is compared with that for a non- constant in anyone design, are Wand size and prepare the joining sudaces
rigidly supported beam, in which case E, and they may be lumped into one con-' from drawings furnished by the destant, K. T he equators are then re- signer. The task, then, is merely one of
5W V
wri tten as:
assembling the finished parts.
(3)
Z= 384 E I
Simple beam-no end supports
During this assembly operation it is
5KV
be;,t to screw and glue all joints together
it will be observed that the deflection is
Z= 384 I
(5)
so that the finished cabinet will be tight
five tiWes the magnitUde of the former.
and solid. The front panel of the enOf course in actual .practice these exSimple beam-fixed end supports
closure can also be permanently antremes are almost never encountered;
chored if the loudspeaker is mounted as
KV
no panel however loosely secured would
(6)
shown in Fig. 5. It is fairly well recogZ= 384 I
exhibit a vibration five times as severe
nized that speaker performance is greatly
as one firmly attached to an immovable Cantilever
improved by mounting the speaker in
support. Nevertheless, this simple comKV
(7)
this manner. As illustrated, an alternate
parison emphasizes the need for rigid
Z = 8T
method using two superimposed panels
support of the panels.
Figu,re 3 and the sample problem obviates the necessity for special routThe maximum deflection of such a
beam may also be reduced by decreasing show the suggested method of analysis ing. In either case captive nuts attached
to the back of the panel receive the
its length as far as is practicable. On the
s~aker mounting bolts from the fron t.
other hand, littl-e' benefit i$ derived from
Many loudspeaker manufacturers will,
attempting to vary the valu,e o'f 'B~; I-eferupon request, supply suitable gaskets
ence to approp riate tables reveals that
for this type of mounting.
the modulus of elasticity of commonly
used lumber varies from about 1.00 x
Conclusion
106 to 1.6 X 10 6 •
The moment of inertia of these beams
.It has been the purpose of this disequals bd 3J 12, where b is the width of
cussion to analyze the problem of spurithe beam and d is its thickness . (See
ous acoustic output caused by excessive
Table II) It is interesting to note here
panel vibrations in a loudspeaker enthat doubling the thickness of a panel
closure, and to suggest an approach
(and hence the thickness of a unit-width
which will result in a definite reduction
beam) reduces the deflection by a factor
in the effect and a vast improvement in
of eight ; tripling the thickness -reduces
the over-all performance. As might be
deflection by a factor of 27; and so on.
(C ontinued on page 54)
Before demonstrating a typical solution
to a cabinet design problem, it will be
121/8- OIA. (VARIES WITH
SPEAKER)
GASKET
found helpful to introduce one further
Fig. 4. Exa mples of cornerpost construction.
1/4" DEEP
beam equation into the discussion_ In
- - ./ /'", .- .. BREAK TO FIT SPEAKER
-. -. ....... AS REQUIRED
the case where a panel contains an open- as applied to a typical capinet. Cabinets
of
different
shapes
will
present
stiffness
ing (speaker mounting hole or reflex
I 101 /4- DIA. (VARIES WITH
toSPEAKER)
port), the beams which 'have one termi- problems somewhat different from the
ALT ERNATE METHOD
nation at an opening are Classified as sample illustrated. In this case, the
cantilevers. The deflection for this type analysis is used to determine the size,
shape, and number of braces required
of beam is written as :
to improve the performance of a cabinet
fuE WITH
USE SCREWS IF
originally constructed without full conTABLE 2
siderat ion of the factors just discussed.
Naturally the need for extensive bracing
Moment of Inertia about the Center of Gravity
for Comman Lumber Sizes (max. Value)
is reduced if the enclosure is properly
designed from the start.
Nominal
Dresse d or
Moment of
-----r
.
~-~I
P~ESSURE.
Size
In.
J x l
lx2
1X 3
2 x3
J x- 4
2x4
Finished Size
In .
"VS X
"VS
"VS X
1 5/s X
"VS X
J 5/s X
Inertia
In.4
.049
.3 J
1.32
2.45
3.44
6.45
"VS
x 15/s
25/s
25/s
35/s
35/s
AUDIO ENGINEERING
•
I~"" ""I
P~ACTI;AL
COi.~truction
There is more to the problem of designing a rigid speaker cabinet ~han
mere choice of adequate panel thickness
and arrangement of bracing, however.
As was observed from the disCl1SSiolJ- of
the beam equations, above, the method
DECEMBER, 1953
Fig. 5. Loudspeaker mounting details.
25
Tired Business Man's
Radio Cabinet and Speaker
C. G. Fraser*
Music-time means relaxation fo r many-but when there is no cabinet available which
provides the convenience demanded by the t.b.m. at the end of a hard day's work, the
solution is best arrived at by a cut-and-try building operation-as described here.
HE ACCOMPA NYI NG PHOTOGRAPHS r epresent the culmination of some seven or -eig ht yea rs of inte resting
a nd satisfy ing work in the hobby of sound reproduction. Figmoe 1 shows a rad io, turn table, a nd ampli fie r cabinet recently completed, the design of which incorporates
a few interesting feat ures. T he height of the cabi net has
been selected to stand even with the arm of a chair in such
a manner as to be of maximum conveni ence to the operation
of either the radio or the turntable. The chair whi ch normally stands beside the cabinet has been r emoved for photog raphic purposes. A considerable amount of thought has
gone into this des ign in an attempt to overcome what we
regard as disadvantages that appeal' in nearl y all other desig ns· of cabinets. Most cabinet designs fall in two general
categol-ies: ( 1), Controls positioned fo r operators who prefer to lie on the fl oor ; and (2), Controls positioned fo r
peopl e who prefer to stand facing a blank wall . The design
fin g~r tip reach whil e sitting comshown has all controls
fo rtably in a chair. The cover to the turntable rolls back at
fin ger tip touch. A detail of this operation is shown in Fig. 2.
The equipment used consists of a Meissner AM-F M
tuner, Rek-O-K ut turnta ble, Cla rkstan .to}le arm, Pickering
pickup and recol-d compensator, and preampli fie r.
T
af
* 7516
N. B oyd Way, Fo.t: P oint 11, W ise.
T he turntable is mounted partly beneath the tuner so as
to shorten the cabinet as much as possible from fron t to
back. S ince all cont rols a re still readily accessible, nothing
is lost by th is overlap. T he record compensator is offset by
means of flex ible couplings. T he purpose here is to be able
to cluster the control knobs wi thi n easy reach on t he f ront
panel. A neon glow lamp over the compensator dial indicates when the turntable is in operation. Small lamps placed
on the two f ront corner s of the turntable compa rtment turn
on when th e cover is rolled back. T he top of the tuner
compa rtment has a hinged cover to facilitate tube r eplacement.
T he IS-watt amplifier used in thi s equipment was built
hom a UTC desig n and )ncorporates a UTC tone control
whi ch has been permanently fixed to g ive 10 db of bass
boost and 5 db of t reble boost. This tone control as sold
has a low-fl'equency peak at 50 cps and a high-frequency
peak at 8,000 cps. This was unsatisfactory for best operation
of the speaker system so the unit was taken apart and capacitor values changed to g ive a low-fr equency peak of 27
cps and a hig h-f requency peak of 14,000 cps. A little work
on a Saturday aftern oon and a can of hot oil w ill do it.
THE LOUDSPEAKER
The development of the speaker system has taken place
in parallel with the oilier equipment which confirms the
sfa tements so fr equently heard that perfection of one component uncovers the fa ilings of another component. F ig%1o e
3 illustrates what was once a S tephens bass-reflex cab inet.
In this connecti on the number of a rticles which have been
written dealing with ways and means fo r imp roving the
operation of a bass r efl ex cabinet mig ht be taken as an indication tha t certain people a re dissatisfi ed w ith thi s type
of reproducer . T hat, at least, was th e writer's e..'Cper ience.
T he original speaker used in thi s cabinet was a n A ltec 603 .
As perfection of various components \vas achieved, it became incr eas ingly evident that the speaker-cab inet combination could stand some attenti on.
A t about thi s time an dpportuni ty occur red to w itness
the performance of a fo lded horn installati on. After studying vari ous literature which is available f r0111 the library
on sound in general and fo lded horns in particular, it
seemed that it was worth a try to r emodel a good bass refl ex
cabinet in hopes of improving the performance with a
homemade and rather poorly eng ineered exponential horn.
After a considerabl e a mount pf doodling on g raph paper, it
was possible to design a horn 56 in. long a nd w ith a 19-in.
fla re w ithin th e dimensions of the original cabinet. Next
came the problem of using the p resent speaker if poss ible,
Fig. 1. _Combining simplicity of construction and ease
of access, this " home-made" cabinet houses the turntable, phono preamp and controls, radio tuner, and the
power amplifier.
•
lar tweeter was selected fo r two reasons: The cross-section
of the horn is small enough that it can be placed within the
large r horn with a minimum of interference, and the driver
can be removed without the use of a screw driver. Obviously this driver is far inside the cabinet where no tools
can be used. The standard crossover frequency for the University tweeter is 600 cps. This was a matter of some concern because all literature on the subject indicates that a
cut-off of 400 or 500 cps is necessary for this type of cabinet. Probably it is again fortunate that no instruments have
been put on the cabinet or probably it is because of the
6 db of attenuation in the cross-over frequency, but any
missing notes in the 500-600 cps zone simply cannot be detected. As a further safeguard towards a break in response
the fo lded horn was constructed of ~ -in. Weldwood, which
is an all biJich plywood, then finished with hard enamel.
If there is any conclusion that can be drawn from this
type of progress, it is that the man without technical knowledge must be satislied to make hi s progress' slowly. He
must also anticipate a mistake now and then, and most of
all he must be satisfied to imitate the work of others. There
probably is not a good original idea in this entire paper-:Anything that might be classed as purely original would
probably be also classed by the technical boys as undesirable.
The performance of the unit, at least so far as the ear is
concerned, is good. It app~ars to reproduce 32-cps fu ndamental tones well, although the only available source of this
material is an FM broadcast of live pipe organ music.
(C ontinHed 0 '1 ' page 59)
With the controls for the radio tuner at arm level when the
user is seated, as indicated in Fig. 2 above, listening can be a pleasure
uninterrupted by the need for jumping up
and down to change stations or records. The loudspeaker, shown
in Fig. 3 below, is located across the room. The cabinet
was modified from a standard model.
and perhaps this illustrates to perfection the adage, "Fools
rush in where angels fear to tread." The high-frequency
horn of the 603 speaker was removed. It probably was fortunate at the same time that some damage occurred to the
voice coil, so for something like $13.00 a new copper voice
coil and cone to coiwert the speaker to a standard Altec
woofer was installed. The change was simple but it appeared as though the 57-cps resonant frequency of this
speaker should be lower ed if possible, After obtaining as
much advice as possible the periphery of the cone was sandpapered and a la rge portion of the voice-coi l diaphragm
was cut out. This was a step by step operation, each one
a littl e bolder than the one before, until it was possible to
get the resonant freq uency down to . 32 cps. It might be
added however, that the paper cone by this time had been
sanded so thin that it was transparent. An application of
rubber cement closed the pores and made it substantially
air tight. It was necessary also to close the center of the
cone and to open up relief ports in back of the diaphragm.
This enti re venture would make Mr. Hilliard feel bad but
there seem to be some advantages in not having test instru" ·
ments because if the quality of the tone of this speaker has
been adversly affected, it is not apparent to the ear.
The next problem was the selection of a high-frequency
unit. Note that thi s fo lded horn does not have the "Queen
Mary super structure" that is common with this type of
enclosure. The high-frequency unit is here but it is not in
sight. The actual installation was made by the selection of
a Un iversity cobra unit. The ho rn is mounted permanently
within the convolutions of the low-frequency cabinet. The
driver, however, can be reached from the back of the cabinet and l'emoved by unscrewi ng if necessary. This particu-
AUDIO ENGINEERING
•
DECEMBER, 1953
27
The 1953 Audio Fair
•
Review
HARRIE K. RICHARDSON '::
A
FTER PREMISING a number of these
annual observations on the growth
of Audio as an industry, it is some, what relieving to di scover. that the 'path
.of -this year's wordage leads directly to
evaluation of Audio as a m arket.
In Fairs gone by-even as recent as
last year-there has been present the
lagging indica tion of two disturbing
situations.
(1) Audio manufact ure rs, with few
notable exceptions, were not on a common ground of understanding with the
prospective buyers of their equipment.
Too often they placed themselves in the
_ position of selling 'scope traces and
printed specifications, overlooking the in_
ability of their audience to interpret technical demonstrations in terms of livingroom performance,
(2) Buyers of home music systems as
_ a whole had ' not equipped thems ~ lves with
the basic knowledge necessary for intelligent selectiofL,. of th e system's va rious
comporients. There was far too much of
"An audio engineer's dream" could welJ
be the title of the display presented by
Acro Products Company. Acrosound transform ers, Ultra-Li near amplifiers, and a
host of other precision audio devices made
up an exhibit which was easy to take and
hard to leave.
Featured in the exhibit of Alpha Wire
{::orporation was the release of the company's new catalog 153-S, which is concerned exclusively with wires and cables
for use in sound equipment. This catalog
dramatizes the extent to which Alpha has
gone in keeping pace with the audio industry. Also on hand was a complete display
of Alpha products.
th e "I-don't-know-from-nothing, technically-speaking" attitude.
On the one hand, you had the engineering brethren describing their a udio
progen'ies in a vocabulary which was.
v irtua lly meaningless to their listener s.
On the other ha nd the listeners, not to
be outdone, blossomed forth like a mass
mig r ation of Deems Taylors with a n
effect which was equally bewildering.
The 1953 F a ir w itnessed th e meeting
of the twain. One could take his choice
a nd use low-freqH ency boost or basso
fortissimo with reasonable assura nce of
conveying the desired connotation to
w homever he was speaking, be it music
lover or engineer.
In essence, the 1953 Fair marked the
moment in a udio history when tll e professional engineer an d the embryonic
hobby ist met each other half way. Engineers deserted their slipstick terminology and spoke in terms of musical values, w hile music lovers m et th e challenge
Genuine stereophonic sound-the kind
reproduced with three or more recording
channels-was the highlight of Ampex
Corporation's showing of th e Model 350-3
stereophonic recorder. Housed in three
portable cases, th e 350-3 is perfectly suited
for location recording in the production of
3D motion pictures with dimensional
sound. So realistic were the recordings used
The"m a-jor-_p.cl.l:tion of. the Altec Lansing
Corporation exhibit was devoted to stressing the purely home atmosphere of high
fid elity. Five tastefulJy arranged groupings
of typi cal living room furniture successfulJy
dispelJed the idea that .special cabinetry is
needed for a high-quality home music sys-
.tem. The remainder of the Altec d isplay
consisted of a miniature anechoic chamber
with transparent sides, in which an Altec
Duplex speaker was put through tests to
show the basis of its un conditional guarantee of frequ ency response from 30 to 22,000
cps_
* Associate
28
Editor, Audio Eng'ineel"ing
by tossing aro und such words as f1"eq'Mency response, disto1"tion, and eq!tabizat-ion w ith full knowledge of their meanings ,
Credit w ithoul limit is due both
groups. Because, wi thin the space of a
sing le year they have solidified a basis
of mutual understanding which has long
been needed.
Clearly evidenced by the scope of the
1953 Fair was the fact tha t the a udio industry has at last become a major commercial entity. No longer is it accord ed
the paterna l pat of condescension by maj o r manufacturers, nor is it accepted w ith
resignation as a necessary evil by the
la rger recording companies. If there be
clearer proof that a udio h as passed
twenty-one, tbis reporter remains to be
so enligbtened.
Herewith th e observations which
stand uppermost as r eli ef at the passing
of th e 1953 Fair g ives way to a nti c ipation of the one scheduled for 1954,
staple tool of their profession-the numature, portable tape recorder. Of the many
models of Amplifier Corp.'s M agnem ite recorder exhibited, interest was centered on
the new battery-opera ted-motor unit which
affords every recording facility within a
small case a nd weighs but eight pounds.
Known principaJly for the exceJlent motiOfr pichrre equipment the company has
manufactured for many years, Ampro Corporation has successfully transferred its
enviable reputation to the au dio field with
a new line of tape recorders. Available in
a number of models, the new Ampro recorders are exceptionaJly fine performers
within their various price ranges.
One would have to travel far aad wide
to discover more appealing exampl es of
audio cabinetry than that shown by Angle
Genesee Corporation. Custom-built, wel1constru cted, and acoustically-correct, th e
enclosures on display were the subject of
many complimentary observations.
to put the eq uipment through its paces,
that "only th e difference in acoustical surroundings prevented virtual dupli cati on of
the live performance. Of more realistic interes t to Fai r visitors were the new Ampex
Model 350 recorder console and the Model
450 continuous tape reproducer.
Newspaper and magazine correspondents,
as weI! as radio and TV commenta tors that
covered the Fair-and many they weremigrated quite naturally to the suite occupied by Amplifier Corp. of America. H ere
they were treated to an outstanding display
of a device which is rapidly becoming a
Imagi ne, if you can, a competent concert
pianist playi ng the wel1-known Chopin Polonaise; suddenly her fingers leave the keyboard, yet the music continues without
noticeable change. This was th e dramatic
means chosen by Audak Company to demonstrate the realistic performance of the
Audak Polyphase Chromatic reproducer.
Unchallenged was the opinion of audio engineers and fans alike that the Audak pickup pass-ed this most trying of tes ts with
flying colors.
The dominant theme of the Audio &
Video Products Corporation exhib it was
based on the completeness of the products
handled-by the company for radio stations
and professional recording studios, with
primary emphasis being placed on tape recording equipment and accessories. Among
the wel1-known trade names in evid ence
were: Ampex, Altec, Electro-Voice, McIntosh, Cinema, T apak, and Telefunken .
Also of great interes t was the display of
AUDIO ENGfNEERING
•
DECEMBER, 1953
~Beam
W/B STENTDRIAN
HIGH FIDELITY DIRECT
RADIATDR SERIES
6/1, 8", gn. 10", 12/1,
Extended bass and
smooth highs. Bala nced
response without color·
ation, from 35·14 ,000
cps. Incorporates the
exclusive new cambric "Fibre·tone"
cone. Voice coil impedance, 15 ohms.
Die·cast Chassis. Crackle gold finish .
Priced from $6.95(6") to $39.50 (12"),
W/B STENTORIAN
HF TWEETERS
T12 Specifications
Ideal with any cone
speaker. Respon se,
2,000 to 20,000 cps.
Coil impedance, 15
ohms. Power handling, 15 watts . Rigid
construction. Prices : T 10 (5 watts),
$17.95 ; T 12, $45.00
Crossover unit, 15 ohms, matches
all Stentorian tweeters, H.F. spea kers
and woofers, $7.25.
Specifications, 12" Duplex Model
W/8
10" Full·Range Duplex,
illustrated
12" Full·Range Dupiex,
$99.50
Frequency Response, 20-20,000 cps •• Bass Resonance, 35 cps •• Built-In Crossover Network. Graduated "Fibre-tone" L.F. Cone • Pha~ .. Matched H.F. Drive.
Power Capacity Conservatively Rated 15 Watts. "Alcomax 3" Magnets. Die-Cast
Chassis· Crackle Gold Finish. Weight, 16 Ibs., 4 oz •• Both Duplex models have
twin concentric voice coil driv es.
Here is a new spea ker line which will become one of the great names in the
American hi-fi field. Built on a revo lutionary new principle, th ese speakers are
priced remarkably low for instruments of such ou tsta ndi ng quality.
Beam W / B Stentorian speakers, British-made by the world-famous Whiteley
Electrical Radio Company, complement to the fullest ex tent the most modern
achievemen ts in hi-fi recordin g and in amplifier design-provide vivid realism,
high sensitivity, and a degree of musically satisfying balance never before attained
in a speaker.
The wonderfully smooth performance of Stentorians over an exte nded range is
made possible by W/ B Beam's new " Fibre-tone" diaphragm and cone process ...
and by the patented, brilliantly-designed twin concentric drives (duplex ). And
Stentorians are made entirely by one organization; every component, without exception, is manufactured under one roof, to strict quality specifications. Compare
price and pe1joniwnce, and you' ll wan t to own one of these remarkable speakers.
Also 18 /1 woofer••• and the revolutionary
18 " I1 Quaclrup/ex" lull-range unit having
lour independent drives on a single axis.
BEAM
Audition These Beam Stentorian Speakers at Your
Audio Dealer's. Descriptive literature on request.
STENTORIN .
W/B
BEAM
'NSrRUMENrS (ORPORAlION
350 FIFTH AVENUE
NEW YORK, N. Y.
*Leaders in Loudspeaker Manufacture for over 30 years.
AUDIO ENGINEERING
•
DECEMBER; 1953
29
pre-recorded music-on-tape shown by the
A-V T ape Libraries division . No doubt
about it this rapidly growing library of
recorded tape offers a challenge to the disc
companies which now occupy the major
portion of the home mus ic market.
The thoroughness with which Audio J?evices, Inc., penetrates the field of recordmg
materials was well evidenced by an attractive exhibit which included the entire line
of Audiodiscs and Audiotape. Stressed in
the display was a large wall board devoted
to the theme -"Of the 30 best selling records of 1952 29 used Audiodiscs for the
master recording." The black sheep, incide ntally, was a Lond on record made
abroad.
Packaged high-fidelity equipment of unsurpassed a ppeal to both eye and ear was
shown by the Appliance and Elec tronics
Divis ion of Avco Manufacturing Corporation. Spotlighted was the Crosley "Enrico
Caruso" FM-AM radio-phonograph. This
unit is housed in two matching cabinets,
one for record changer, tuner, and amplifier · the other is an acoustically-engineered
spe~ker enclosure. Although the Avco display was essentially high fidelity in character a small portion was devoted to the
compiete line of Crosley Coloradios, portables, am! a new portable clock-radio-phonograph.
A relative newcomer to the high-quality
audio industry is Beam Instruments Company, American distributor for England's
famous Acoustical QUAD amplifier, first
shown in this country at the 1951 Audio
Fair, and the Stentorian line of high-fidel-
ity speakers, also manufactured in England.
Especially interesting was the Stentorian
"Quadruplex," an l8-in multispeaker
which has four ind ependent voice coils and
diaphragms matched to a built-in crossover
input; power rating is 30 watts. All Stentorian speakers are constructed with a cambric cone and surround, and as a result
have remarkablv low fundamental cone resonance. Also shown was a group of striking enclosures manufactured by Beam for
housing the various types of speakers.
The Fair offered no more complete showing of high-fidelity amplifiers than tha t of
Bell Sound Systems. Beginning with the
low-powe.r Model 2l22B and continuing
through the higher powered remote-control
Model 2145A, Bell presented an amplifier
for every home music requirement. Sharing honors with conventional amplifiers was
the new Bell binaural amplifier which was
demonstrated with remarkable effectiveness. Also displayed were tape and disc recorders, a nd two high-fidelity transcription-playing units.
You can always count on Berlant Associates for equipment d isplays which are
both entertaining and informative. This
year's showing was no exception, featuring
as it did four Concertone higa-quality t ape
recorders which cover the needs of both
professional recordists and advanced audio
hobbyists. As in previous years, gracious
Bert Berlant, company president, was on
hand to eJo..--plain the whys and wherefores
of the fine recorders his firm manufactures.
30
There's no better , example of g rowth in
the field of high fidelity than David Bogen
Company, whose exhibit was one of t he
F air's more pretentious. So complete is the
Bogen line of tuners and amplifiers that it
satsifies everyone from the budget-minded
to the connoisseur whose only criterion is
perfection. The highlight of the Bogan exhibit, at least to this observer's way of
thinking, was the "decorators' corner"-an
assembly of tasteful furnishings which
proved beyond doubt that a home music
system must not necessarily be an eyesor e.
The expanding diversity of the comp any's line of high quality speakers was
emphasized in the display of R. T. Bozak
Company. In addition to speakers themselves, Bozak is now merchandising an assortment of enclosures which are impressive in p erformance a nd stunning in appearance. O utstanding is the mod el which
houses two matching speaker systems, and
which may be used with eq ual effectiveness
for either stereophonic or monaural reproduction.
P ersonalities were the order of the day
in the exhibit of British Industries Corporation, with G . A. Briggs and Harold
L eak, both noted audio authorities from
across the water, on hand to demonstrate
and discuss the equipment with which they
are most closely identifi ed. Mr. Briggs who,
in addition to having written many books
on sound reproduction, des ig ns Wharfedale
Model 7 preamp and is but little larger. Attractively finished in gold and brown, the
22A is the first completely enclosed amplifier Brook has built. Output power is 10
watts and controls include input-selector
switch, variable record equalization, bass
boost, treble cut, and compensated volume
control.
Along with exceptional tuners, there was
displ ayed a high-quality amplifier in the
exhibit of Browning Laboratories. Featured
was the new RT-42 AM-FM tunc r, a ncw
precision-built unit whi ch offers widc-ran~c
reception a nd is virtually free of an:J.oi-::! :~
drift. Although precision-buil t, the RJ-42
is designed for opera tion by the non-teclmically-incl ined music lover, having only two
control knobs-one for tuning both bands,
the other for channel selection, AFC control, a nd switching on and off. A screwdriver adjustment on the rear of the ch assis
is used for setting the tuner's output level
to match that of other input devices.
The Columbia "360", first of the twospeaker hig h-fidelity table-mod el phonographs, together with the matching XD
speaker for stereophonic effect, was featured in the exhibit of Columbia Records,
Inc. CRI deserves a special pat for the
cou rtesy a nd attention which were accorded visitors by genial Bill O'Boyle, n ational sales manager of the phonograph division.
speakers, thrilled visitors with a three-way
sp-eaker system mounted in a corner cabinet
whose hollow walls were filled with sand.
Mr. Leak, as might be supposed, had paternal interest in the amplifier which was
used in the demonstration. Mr. Briggs, in
his first appearance at an Audio Fair,
found a deep spot of affection in the hearts
of his American contemporaries-while
Mr. L eak, an Audi o Fair veteran, was received with the welcome of an old a nd respected friend.
One of the real pioneers in the audio industry, Victor Brociner, president of Braciner Electronics Labora.tory, presided over
his company's display of a magnificentsounding new -speaker system, a new power
amplifier, a nd the well-known Brociner
audio cont rol system. Of particula r interest
was the Model 4W wall horn, designed for
use in rooms where a corner speaker is not
feasib le. Powered by a twin-cone driver
unit, the 4W has in effect a "built-i n"
corner, and provid-es performance eq ual to
that of the original Brociner Model 4 corn er horn, without requiring corner placement. Styling of the enclosure is both conservative and graceful.
Sticking to a tradition which was established with the first Brook amplifier, Brook
Electronics features the use of low-mu triodes throughout in th e new Model 22A,
which r esembles in appearance the Brook
Indicative of the tremendous expansion
which is taking p lace in the tape-recorder
fi eld were the new Crestwood recorders displayed by D aystrom Electric Corporation.
D esigned essentially for home use, the
Crestwood 401 approaches professional
standards in many respects. It is a lowlevel-output recorder for which Crestwood
manufactures a companion power ampli fi er. The two units are supplied in ha ndsome luggage-type carrying cases for portability.
Officials of Conrac, Inc., travelled all the
way from California to presen t the Fleetwood li ne of television receivers which are
specially designed with high-quality a udio
output for fe eding high-fidelity music systems. Parti cul ar attention was accorded
Models 600 and 700, both of which are
equ ipped with a remote-control unit which
may be located as much as 100 fee t from
the p icture chassis.
AUDIO ENGINEERING
•
DECEMBER, 1953
. vou
don'
buy
one of
these
every
tAr!
Purchase of a tape recorder is a major investment. And, with so many unproven
brands on the market, it simply does not pay to select anything but a recognized,
precision built and proven recorder.
Compare these RC·7 features:
• Instantaneous speed accuracy
• Dynamic range better than 50 d b.
at 3 % distortion
• Three-motor drive
The PRESTO Re-7 is just such a unit. Designed and manufactured by the world's
foremost producer of precision recording equipment, the RC-7 with RA·l reel
adapter is today's No.1 bu y in fine tape recorders. Here is a unit that is fully
portable for field recording, yet with the rugged construction and precision
operation characteristic of th e finest studio equipment.
If you're planning to rep lace an existin g unit or add an additional tape recorder,
your selection of a PRESTO Re·7 wi ll pay long term dividends in faultless
service, ease of operation and the genuin e sati sfaction of owning the best.
• No friction clutch or frictionJ
brakes
• Heavy duty construction
throughout
• Separate-erase-recording. playback heads
Do you own a Presto Re-7? The RA-l adapter
• Twin speed: 7 V2" /sec. or .
15" /sec.
diameter. Write for full details and price.
will allow you to use reels up to 10'12"
• Frequency response to
15,000 cps.
@U®
• Reel size: to 10 V2 " (with RA-l
adapter)
RECORDING CORPORATION
PARAMUS, NEW JERSEY
Export Pivision :
Canadian Division :
WORLD'S
LARGEST
MANUFACTURER
OF
25 Warren Street, New York 7, N. Y.
Walter P. Downs, ltd., 'Dom inion Square Bldg., Montreal
RECORDING
EQUIPMENT
AND
DISCS
It seems to be a pleasa nt habit of Cook
Laboratories, Inc., to present each Audio
Fair with a fabulous example of r ecorded
sound. This year was no exception. Using
a ba ttery of 20 specially-desig ned speakers
fed from one of his compan y' s binaural r ecordings of a la r ge pipe org'i!on, Emory
Cook, president, thrilled thomands of visitors with sta rtling r eproduction of a 16cycle note-fundam ental, tha t is. Those
who could remove their a ttention from the
rema rka ble demonstration of sound were
treated to a preview of the first working
mod el of a new-changer a rm which mounts
two pickups for bina ural records .
DuKane Corporation rigged up a 'scope
to illustra te the recording a nd playback
frequ ency response of the new Tru-Fid elity ta p e recorder. Clearly shown was the
new Fairchild developments- a plug-in
tone a rm which accepts all sta nda rd cartridges, a nd a preamplifier-equalizer whi ch
is exceptional both in appeara nce a nd p erform a nce. Both of th ese items a re certa in
to crea te a stir when they strike the a udio
m a rket place; first deliveri es to dealers a re
scheduled for a round December 30.
A new ribbon-type pickup, desig ned by
D . T. N. Williamson of Willi amson a mplifi er fame, was given its fi rst Ameri can
showing by Ferranti Electric, Inc. Known
as the Ferranti pickup, the new un it features a n integra ted d esign of arm a nd h ead,
with a n extremely low m ass movement, a nd
exceptional compliance. The unit was demonstra ted tr acking perfectly a 20-kc cut o n
lacq uer a t I-inch conce ntricity a t 78 rpm.
R esponse is uniform from 20 to 20,000 cps.
Avery Fish er a nd J ames Parks, president
a nd sales manager, r espectively, of Fisher
Radio Corporation were on ha nd to g ive
offi cial san ction to th e 'fi rs t public introdu ction of several new Fisher entries in th e
high-fidelity market place. Pa rt icula rly out-
Strictly profess ional in ch ar acter, th e
Gates Radio Company displa y presented
the firm's new CC I master control console
which r epresents many innovations in techni cal des ign. Flexibility of contr ol afforded
by the CC 1 is creating wid e accepta nce for
the unit throug hout the b road cast and recording industries.
D icta tin g equipment shared honors with
tra nscription a rms, equ alizers, a nd a h ost
of other a udio components in the exhibit
of Gray R esearch & Development Compa ny. Althoug h the bulk of its a ctivity
these days is devoted to the m a nufactu re
of studi o equipment for TV sta tions, G ray
is still deeply involved in a udi o as was evidenced by a display which was thorou ghl y
entertaining.
Among the m ore impressive complete
hig h-fid el ity m usic systems shown a t the
Fair was th e Model 162 1 console introdu ced by The Hallicrafters Company. Enclosed in a ha nd som ely-styled cabin et, the
unit' s ability to ha ndle 20 to 12,000 cp s a t
7 Y2 ips. Availa ble in both p a nel-mounting
and portable models, th e Tru-Fidelity r ecorder operates a t 3 % a nd 7 Y2 ips, a nd is
a mas terpiece of industrial desig n.
L ong known principally for the excellence of the jewelled styli m a nufactured by
the compa ny, Duotone chose its Fa ir exhibit to a nnounce tha t it is now ha ndling
American distribution for the Hollandmade Philips lin e of loudsp eakers. As in
previous Fairs, the focal point of the Duotone suite was an excellent display which
dra ma tized the supe riority of the di a mond
over other stylus m a t erials for hi-fi music
systems.
Espey Manufacturing Co., Inc., a firsttime p a rticipa nt in the Audio F a ir, displayed a g reatly expa nded line of tuners
and amplifiers, including a new bina ural
unit which was featured in demonstra tion .
Of particula r inter est to dealers who w ere
present was an Espey-designed demonstration stand, which contains one each of the
various Espey models a nd incorporates a
switching a rrangem ent for playing a n y desired tuner and/ or a mplifie r.
As in yea rs gone by, Electro-Voice, Inc.,
came throug h with one of the F air's truly
outstanding exhibits of fin e a udio equipment. Sha ring honors with the h a ndsome
Georgian 4-way speaker system w ere' E-V's
new ultra-linear cerami c cart ridge and
Model 15-TRX triaxial reprodu cer. R epeating another aspect of former E-V exhibits, program m a teri al used for demonstration was exceedingly well ch osen.
Fairchild Recording Equipment Corporation, which h as long been among the
leaders in the m anufacture of p r ofess ional
disc a nd tape r ecorders, used its Fair exhibit to emphasize its p enetrat ion into the
consumer market for high-qu ality a udio
equipment. Along with the Model 215 m agnetic pickup which was first shown publicly
at the 1952 Fair, the exhibit featured two
32
sta ndin g was the new M odel 70-RT AM FM tuner, which includes bu ilt-in preampequalizer, with tone controls. Beyond all
qu estion, the 70-RT satisfi es the n eed for
a precision tuner whi ch includes within a
single chass is all the control facilities requred for a high qUfllity music sys t~m.
A delu xe addition to the well-known
Garra rd line of record cha ngers a nd single
players was given its first public showing
by Garrard Sales Corp·oration. The new
RC-90 cha nger p ermits va riable speed control at all opera ting speeds, along with a
number of other features including a
m a nual play position and easy adjustment
of tone a rm pressure. A noise suppressor
across the a.c. switch elimina tes th e
" clunk" which is usually heard in th e
sp eaker when a cha nger is shut off. Shown
with the new RC-90 was the sta nd a rd
RC-80 change r upon whi ch Ga rra rd has
bu ilt its envia ble reputa tion.
Visitors to the exhibit of Gately D evelopment Laboratory Were treated to the first
publi c showing of the " Pures t," a newlydeveloped fold ed-horn enclosure whi ch
does not r equire cornel' location. Perform a nce of the Pu rest, also of the orig inal
Gately Super-Horn co rner-typ e enclosure,
was enti rely satisfying.
General E lectric Company, whose development of th e GE magnetic cartridge
played no small pa rt in bri nging the country's musi c love rs face -to-face with t he
wonders of high fid elity, has broadened its
coverage of the industry t o in clud e a new
remot e-control amplifier, a wid e-ra nge coax ial speaker, and a record compensator.
The la tter item, for connection between
p ickup a nd amplifi'e r input, is designed to
bring up-to-da te existing music sys tems
whi ch a re not equipped with record equ alization.
unit comprises a H allicrafters AM-FM
tuner a nd m at ching amplifier, Ga rra rd
three-speed r ecord changer, two J ensen
speakers, a nd the H allicrafte rs studio r ecord adjuster. Especially noticeable was the
fact tha t a mple cabinet space has been allowed for sp eak er housing.
H. A. Hartley, president of the English
compa n y bearing his name, in his third
Audio Fair a ppear a nce found his time
equally divided between acknowledging 'the
welcom e of his m an y Amer ican friends, a nd
demonstra ting his firm' s new 20-wa tt amplifie r, together with a new t ap e recorder
produ ced by his com pa ny in collaboration
with an oth er English firm , Wright and
Weaire, Ltd. It goes without saying, however, tha t the H artley Model 2 15 sp eaker
a nd Boffl e were his primary interest . According to Mr. H a rtl ey, "The pa rticula r
object of our exhibit this year was to show
tha t in pinning our fa ith to the single-unit
speaker to cover all frequencies we could
-s till p rovide really impressive bass in large
rooms ."
Harvey-Wells Electronics, Inc., long
known for the m anufacture of communications equipment, m ade a n a uspi cious
(C ontim{,ed on page 63 )
AUDIO ENGINEERING
•
DECEMBER, 1953
Dimensions:
high
33W' wide
19/1 deep
REGENCY ENCLOSURE ONLY
Mahogany. List $200.00; Aud iophile Net, $120.00
Blonde.
List $215.00; Audiophile Net. $129.00
COMPLETE REPRODUCER SYSTEMS
REGENCY n. Includes E·Y Model 114·A
2·way system in Regency enclosure.
Mahogany. List $517.00; Audiophile Net, $310.20
Blonde.
List $532.00; Audiophile Net, $319.20
REGENCY m. Includes E·Y Model 114·8·
3.way system in Regency enclosure
Mahogany. List $592.00; Audioph ile Net, $355.20
Blonde .
List $607.00; Audiophile Net, $364.20
Handbook of
Sound Reproduction
EDGAR M. VILLCHUR ':'
Chapter 15, Part 1. Power Supplies, Hum and Noise
must control ~n
mdependent source of energy 111
order to amplify, and for its operative needs must also use up power that
does not get passed on. The a.c. power
receptacle is the most common source
of this energy, but the electric power
supplied commercial1y must be changed
in form before it can be used. The circuit that performs the necessary conversions is cal1ed the power suppl y.
The alternations of the a.c. line make
power transmiss ion and distribution
more convenient, and make it possible
to employ step-up and step-down transformers in the amplifier. The common
value of 117 volts (in the U.S.) is, simila rly, a convenient one. However the
alternations have no direct use in the
vacuum-tube circuit itself, and the voltages required by the amplifi er stages
differ in value from 117 volts. The
power supply must therefore step the
voltage .down fo r tube heaters, and perform the operations of voltage step-up,
rectification, and filtering for the plates
and screen grids.
Unfortunately the alternations always
get into the signal channel to a g reater
or lesser degree, creating hum output
at the fundamental and harmonic line
frequencies. In addition the power supply intrudes its own characteri stics into
the picture, limiting the amount of
power that can be drawn by the load,
disturbing the essentially constant-voltage n.ature of the line source, or serving
as an inadvertent path for low-frequency
A
N. AUDI9 AMPLIFIER
* Contributin g
ING.
Editor,
AUDIO ENGI NEER-
positive feedback between stages. A
properly designed power suppl y reduces
all of these effects to such proportions
that there is no significant effect on amplifi er operati on.
Power Supply Design
A typical audio amplifi er power supply is illustrated in Fig. 15-1, labelled
with voltages common to such application. The dual diode tube acts as a fullwave r ectifier, conducting during both
halves of the power cycle. S ince each
plate is alternately positive for each
half-cycle, electrons can flow from the
cathode to one or the other of the plates
during both cycl e halves, as illustrated
in Fig. 15-2.
The resultant recti fied voltage has a
fu ndamental frequency double that of
the input-a 60-cps a,c. line procluces a
rectified output of 120-cps pulsating d.c.
- and this fact works to our advantage
by making the task of smoothing out the
pulsations easier. The shunt capacitive
reactances of the filter capacitors are
halved, and the series inductive r eactance of the choke is doubled for the
same values of capaci tance and inductance, which g ives us a more effective
filter or, fo r the same effectiveness, a
small er one. Where the size' and weight
of the power suppl y components are
critical, as in aircraft equipment, a primary supply fr equency of 400 cps or
higher is used in order to reduce the
requirements imposed on the filter.
The power amplifier stage uses the
major part of the total B current, and
is relatively insensiti ve to ripple. It is
fed from the suppl y point indicated in
TO
10 HENRIES
HIGH CLARENT
OUTPUT
STAGE
TO HIGH LEVEL
TO LOW LEVEL
VOLTAGE AMPLIFIERS VOLTAGE AMPUFIERS
20 HENRES
BLEEDER
1 WATT
r" r'
+
8~1
+
8~f
RESISTOR
Fig. 15-1. Typical power supply for an audio amplifier. The high voltage winding of the
transformer is rated as 700 v c.t., or as 350,0-350. The bleeder resistor is not required if the
output stage is in Class A.
34
Fig. 15-2. Operation of a full-wave rectifier.
Each half of the tube conducts alternately.
Fig. 15-1, because the low d.c. resista nce of the choke enables thi s component to cari'y a la rge amount of current
without introducing too great a voltage
drop, and because the power. amplifier
does not need the added filtenng of the
R-C sections. (In some cases the screen
grids may require added filtering .) A
comparable number of milliamperes
flowin g in the filter series res istors, besides requiring r esistors of high wattage, would i"ntroduce a totally unreasonable voltage drop. It is thus desirable
to use a choke with the lowest possible
d.c. resistance ; any changes in load current associated with signal var iations
will not then involve a significant
change of d.c. voltage drop across the
choke, a nd hence wi ll have little effect
on the B+ voltage.
Voltage Regulation
10 ,000
lOW CURRENT
(A)
The voltage regulation of the B power
supply refers to its constancy of voltage
under changing load. A straight Class A
amplifier draws the same amount of current at all times, but class AB amplifiers
draw more current at large signal amplitudes. If the B supply voltage goes
down significantly on signal peaks the
amplifying characteristics of the tubes
will be instantaneously changed and di stortion introduced. This is particularly
true of Class B amplifiers, and in some
cases gas-filled voltage regulator tubes
have been employed to keep the voltage
constant despite changes of either load
current or line voltage. It is possible to
AUDIO ENGINEERING
•
DECEMBER, 1953
SRECIALIZATION
MAKES THE DI F FERENCE
Specialization may be defined as the concentration of
all effort to a special or specific course of action
Even a mechanical device concerned with the function of record
reproduction should possess all the advantages of such specialization.
Most units undertake to do much more. They change records,
mix records, llip records, reject records, and assume a multitude of other
functions. This is 'generalization' as distinguished from ·specialization'.
The REK-O-KUT turntable, on the other hand, is devoted
entirely to playing records. And every design feature, every fragment
of engineering know-how has been devoted and restricted
to the all-important job of playing records . .. to provide the
constant, steady, unwavering record motion necessary for
the faithful reproduction of records free of mechanical distortion.
Specialization makes that difference. And all of the
efforts and facilities of the manufacturer shall continue
to be 'intensively devoted to that one objective ...
that one aim: To make the finest turntables in the world.
There is a REK·Q·KUT Turntable for your specific discriminating
requirement. Seven models are available at prices ranging from $59.50.
At Leading Radio Parts Distributors and at Sound and Music Dealers.
Write for Descriptive Literature
TURNTABLES
REK-o-KUT COMPANY, 38-03M Queens Boulevard, Long Island
City I, New York
Export Division: 458 Broadway. New York 13, U. S. A. Cables-Morhanex
In Canada: Atlas Radio Corp" Ltd., 560 King Street, W., Toronto 2B
AUDIO ENGINEERING
•
DECEMBER, 1953
35
tional voltage in ser ies with the choke,1 \ sections necessary in any case. This is
causing the total voltage output of the
the danger of regenerative interstage
filter to increase. A power supply serv- coupling through the power supply.
ing a varjable load usually has a bleeder
resistor connected as shown, of a value
TABLE 15--1
equal to about 1100 ohms per henry of
VOLTAGE
REGULATION
CHARACTERISTICS
choke inductance.
O~~~----------------------(A)
::i
"'
~
O ~1-T-IM-E----~~.~--------~~··~.~'~
INTERVALS ,OF NO CURRENT FLOW
(s)
Fig. 15-3. (A) Full-wave rectifier output curre nt. (B) Rectifier current with insufficient load.
The discontinuities create an increase in output
voltage. This can be avoided by the use of a
bleeder resistor, which increases the minimum
value of the curren t.
secure sufficiently good regulation without going to such lengths, however, and
voltage regulators are in general reserved for other, more critical applications. The use of a well-regulated power
transformer conservatively rated as to
current capability, of a rectifier tube
with good regulation, and of a low-resistance choke is normally sufficient.
Rectifier tubes present a resistance in
series with the line which causes the
output voltage to vary inversely with
the amou nt of current drawn. Where
regulation is important because of anticipated changes of current flow, the
regulation characteristics of the rectifier tube, as described by tube manuals,
should be taken into consideration. The
voltage vs. load characteristics of several r ectifier tubes are li sted in Table
15-1.
The filter shown in F ig. 15-1 is of the
capacitor-input type. When the first
capacitor is eliminated the circuit becomes a choke-input filter. The latter
has lower output voltage (the voltage
of the capacitor input fi lter is usually
at some value between the r.m.s. and
peak values of the input a.c. voltage to
the rectifier) and greatly reduced effectiveness as a filter, but better voltage
regulation . It is not usually considered
necessary to accept the first two results
as payment for the last.
The "bleeder" resistor across the B
supply line is for the purpose of improving regulation when there is a danger of load current dropping to low
values. It has only a minor effect on the
total percentage of current change, but
it prevents the current from dropping
below a certain minimum point. This
minimum is that value of d.c. load current which falls below the negative peak
of the variable component. If the d.c.
flow did fall below this point discontinuities would be introduced into the
wave form, as illustrated in Fig. 15-3.
Such a discontinuity represents a sudden
break in the rate of change of the current, and is like introducing an addi-
36
OF COMMON RECTIFIER TUBES
Ratings of Power Supply Components
Components of power supplies are
rated for given voltages and specified
maximum load currents. If these ratings
do not meet the requirements of the
amplifier the results may be improper
operation, failu re in service, or both.
Filter capacitors must have a working
voltage rating with a comfortable margin of safety over the voltage at the
rectifier cathode. Current is not drawn
from the rectifier until the cathodes of
the working tubes have warmed up.
Since the latter are usually indiiectly
heated they are only beginning to draw
current when the directly-heated rectifi er has already become operative. The
voltage across the filter capacitors (and
especially across the first one) is thus
reduced very little by voltage drops in
the power transformer or the rectifier
tube, and may be significantly higher
than normal during the warm-up period.
Transformers and chokes that are
made to carry more current than they
are designed for exhibit several effects:
they overheat and in time may fail, and
they cause the available voltage to vary
unduly with change of load. F urthermO!'e the inductance rating of a choke is
in terms of a maximum current flow,
and if t his maximum current is exceeded
the eledrical il1ductance is correspondingly reduced due to core saturation .
Power Supply Filtering and De-coupling
As the amount of amplification ahead
of a stage is increased the percentage of
ripple that can be tolerated in the B
supply is reduced. It is a lot simpler and
cheaper to improve the filtering for such
low-level stages separately, rather than
to filter the entire B supply so well that
the point from which the output stage
derives its power is also suitable for the
rest of the amplifier. But there is another factor, over and above considerations of hum, that makes separate filter
1 L. B. Arguimbau, "Vawutn-Tube Cirwits." New York: John Wiley and Sons,
Inc., 1948, p. 40.
Approximate change in output voltage associated wit.h
change from half- load t o
full-load current*
Tube
Type
IMPEDANCE OF
I
:- -POWER
- - - °rSUPPLY
_____
~
'-------~
50 v
BO v
15 v
20 v
40 v
40 v
10 v
25 v
5Y3
.' At specified input voltage
Consider the three cascaded amplifier
stages in (A) of Fig. 15-4. The output
signal voltage coupled from one stage
to the next is that between plate and
ground. While this voltage is almost
equal to the voltage across the plate
resistor at signal frequencies (B+ being
considered as signal ground due to the
effective short of the high capacitance
filters), the reactance of the fi lter capacitors becomes large enough to be significant at very low frequencies, and the
above is no longer true. The impedance
between B+ and B- then forms part of
the load impedance of each of the stages,
and this added element of load impedance is common to all three. Part of the
output voltage of the second and thil'd
stages is thus coupled back to previous
points in the signal channel.
For any two adjacent stages the feedback is negative-a fraction of the output signal of the higher level stage is
effectively fed back to its own input,
where the signal, ignoring phase shift,
is exactly opposite in phase. But the
feedback between the first and third
stages is positive. The input signal to the
first stage has suffered two phase reversals, and the output of the third stage
has the same phase as the output of the
first stage. When the amount of feedback
is great enough, which is to say when
the frequency is low enough for the
filter reactance to have become sufficiently high, regeneration and self-sustaining oscillation occur. The subs'onic
frequency of this type of oscillation has
given it the name of motor boating, and
[Continned on page 57J
+
I
-
J
Choke-input
filter
5T4
5U4
5V4
s+ ~------~~------~
.. ----_... _----,
i
Capacitor -input
f ilter
..
+
DECOUPUNG
NETWOOK
I
II. -
s(A)
,------.1.--__ ..'
IMPEDANCE OF .
,I POWER
SUPPLY:
(s)
-
---r-----,
-1:-
Fig. 15-4. (A) Feedback between stages due to common power supply impedance. (B) Avoid- .
ance of regenerative feedback t hrough the power supply, by the insertion of a de -coupling
network.
AUDIO ENGINEERING
•
DECEMBER, 1953
learn the inside story of ...
tk~fFined
coaxial speaker
1£ you were a highly skilled combination of toolmaker, machinist and jeweler,
you could build yourself no finer coaxial speaker than this IS-inch masterpiece.
Built to jewel-like tolerances, it is, at the same time, so rugged that
extreme overload conditions and even mishandling are all in the day's work.
Do see it and hdar it, at any Stromberg-Carlson Hi-Fi dealer's. Until you do,
here's an audiophile's eye view of the features which make it superb_
Complete specifications-in bulletin SED 3.40-will be sent on request.
SOUND DIVISION. 1219 CLIFFORD AVE.
ROCHESTER 21, NEW YORK
AUDIO ENGINEERING
•
DECEMBER, 1953
37
~
o IT WASN'T directly my idea, the new
title of this newly severed section of
what fo r all these years (since May,
1947) has been part of the REcORD REVUE ;
but I'll admit that I've long had a secret
yen to make use of those initials of mine
in some "practical" way! Best idea previ<Jus to this-a license plate for my car.
(Connecticut, where initials may be used.)
Haven't been able to swing that one yet
a nd I'm still an anonymous YV-493. So
the editor 's brilliant brainstorm, quite independent of me, is welcomed and you can
send in all th e cat-calls you want, we don't
care. That "ETC" is going to have to cover
a lot as has the old title in the past. But
no n;ore, perhaps, than our o:vn favorite
HI-F I, which is pretty soon gOlllg to cover
everything as fa r as I can see.
N
*
j
*
•
H erewith a n experimental report on a
fine collection of gadget equipment for
phonophiles th at has been sitting about
my place, waiting to b ~ noticed. I'd better
say quick-like that thiS new department,
while it will surely comment now and
then on equipm ent of one sort or anoth ~r ,
is not and ca nn ot set itself up as an offiCial
Equipment R eport. That sort of thing will
be handled elsewhere and in a wholly different manner. W hat I can contribute here,
occas ionallv, is th e A mateur' s R eactionth e sort of thing that happens to a nonengineer phonophile when the gadge.ts d<;signed for him actually tum up m hiS
home and a re put hopefully to work. I
haven't got a reputation as A udio's Number One A mateur for nothing. When I
get going, I have a heavy han~ . If an y machi ne is subject to breakage, mIs-use, wrong
connections and th e like, I fin d it rema rk.a bly easy to oblige with ~he man power.
If instructions are, as LI'1 A bner says,
'Confoos in', I'm ready to get confused .to
t he point of utter confoundedn ess. I Qualify
very nicely, 1 think, a s A udio's Road T est.
or as an audiomatic Genera l Motors P roving Ground.
'T he difference between me and a million other lethally equipped amateurs, how'ever, is that I have a strange way of stop'ping aften va rds and analyz in~. Now.why
·did tha t happen ? Also, I wnte my Ideas
-down and publish 'em, which I am, fortul1ately in a position to do. And so, I venture
to suggest. my reactions t<:> th~ stuff may
iust possibl y be constructive 111 the end,
'if destructi ve at th e beginning!
* 780 Greenwich St., New York 14, N.
40
Y.
EDWARD TATNALL CANBY '
Gadget Collection
It's with that spirit in mind that I tackle
today's batch of home gadgets. A nd I'll
add this. Most new gadgets that get tc? ~he
market a re designed, by some e!lterpn s.mg
person, to F ill a N e~d, to Rectify a S lt~­
ation to Do Somethmg Better that hasn t
been ' done very wel l. There's al ways a
minus va lue in the background, somewhere.
Mos t gadgets are thus brave attempts
to solve bas ically insoluble problems.-ofthe-moment. Few of them are perfection.;
there wouldn't be any need for them Ii
perfection we re possible. A nd so very few
gadgets go all the way ; al~ost all of t.hem
have di sadvantages. Don t be surpn sed,
tl1en if I mention the di sadvantages.
They're inherent in the breed, .and let's
praise those who defy the drawbacks and
go right ahead with their gadgets anyhow
for what they're honestly worth, the plus
with the minus-the following included.
*
*
*
My collection is a s follows-and the
batch of tl1em a re COUSil.1S, inter-related.
Discs : T he Dubbings company's two test
LP's, D-IOO and D-101; Audax's StylusD isc for testing stylus wear. M eaS1lrrmmts : A neat little SO-power Japanese
"Vista" microscope, to complement the
Audax di sc ; the Weath er s Stylus P ressure
Gauge ; th e Dubbings D-SOO Test Level
Indicator. Rec01'd Treatm ent: Duotone
E lect ro-Wipe Magic Record Cloth ; the
Walco F oam-D isc turntable covers. Let' s
take a look at th ese latter first.
Record Savers
The Foam-Disc, distributed by Wale?
of VV-aleo stylus and Stati-Clean fame, IS
a turntable mat made of poured foa~
rubber ( not ordina ry foam ) , dressed up 111
ni ce colors in manual table models covered
with smooth suede. About an eighth of an
inch thick and ver y go.od looking, especially in bright red and ··green.
To tell th e truth I was a bit baffled by
these, since normally I don't go for brig-ht
decoration. for its own sake. But W~co
claims utility-a soft base fo r droopmg
records and fo r accidental pickup fal ls, a
firm adhesion with minimum grittiness
(much better than grit-collecting flock, J
agree) and in particular a magnetic sep~­
rati on between steel tumables and magnetic
ca rtridaes that reduces obj ectionable magnetic "pul1." Sounds reasonabl e and I like
tl1e squishy feeling of the stu ff. The suede
model incidentally, is excellent fo r di,(jockey style slipping (allowing tabl e to
spit:! while holding ~ r~col'd <:> n cue), a
maj or interest of m111e 111 radIO program
making. DJ's note, if you've had troubl e
with rubber covered tables.
I'd expect a changer's capacity record
load to be reduced by two or three discs
by the foam mat. Not overly importa nt, in
view of the above advantages.
The Duotone Magic R eco rd Clotb is as
magic as most gadgets using th.at overworked term- i.e. not at all ; but It works.
Don't know what th e impregnation is in
th e soft folds of felt-like cloth, but it'~
somew hat sti cky and greasy to th e feel and
comes off rather too much, if your wipin!1
away of th e static is vi gorous. The stat.; c
goes, defi ni tely, and so does dust and g-nt.
But I wonder what happens ( a ) when the
cloth becomes grit enfouled, even a bit and
(b ) when it is left out of the plasti c casing.
to dry? I haven't had it long enough to
know-but I do find myself using it, and
the job is simpler than with the assorted
spray techniques for record treatment.
The Not-50-Eternal Stylus
Needl es, needles! Now that our diamOl.ldbea rin g friends have done such a fin e Job
in publicizing the quick wear 0f. metal and
sapphire points, people are gettmg a lmost
neurotic about their styli , and I among
them. It's not so easy to tel l just when a
point is shot, especiall y when you get to
listening for distortion so hard th at YOll
fo rget to hea r th e musi c.
.
I've t ried a number of pocket magl11fiers
of one sort or another on stylus POill tS with
ve ry little satisfacti on, as far as judgi ng
the condition of a I-mil point is concerned.
It's ei th er not magn ified enough, or wit.h
a higher blow-up, the focusing problem I ~
hopeless; nobody has steady enough ha,nds .
Only a real mi cr oscope, an d that speCIall y
adapted, will ordina rily give th<?se fin e.
jagged images of wOf11rdown tips that
we've all seen in th e ads of late.
T he "Vista" SO-power pocket glass from
J apan, is the size of a .sawed-?ff pen Ii g~t
and as convenient. but Its speCial feature IS
a brilliantly simple solution to tl1 e probler:n
of focus. The business enQ @f the tube IS
sliced off diagonally: th e slanted ellipse.
with a hole in the middle for the o.bj ective,
~s sHa htly G011CaVe and chromed so that it
is a ;efl ecto r to spot light on tl1e point of
focus. Neat. In order to find that focus yotl
mer ely rest th e lower end on the surface to
AUDIO ENCINEERINC
[C otr>tinued on pa·g e 591
•
D.ECfMBER, 1953
small Garner)
.
f..
ACTUAL
AUDIO ENGINEERING
•
DECEMBER, 1953
41
EDWARD TATNALL CANBY':'
MORE SPOKEN WORDS
Shakespeare: Romeo and Juliet. Old V ic
Company. (Cla ire Bloo m , Alan Bade l ).
RCA Victor LM 611 0 (3 )
Com plementing the recent Macbeth fro m the
Old Vic is this more imposing album, a further
s tep in th e modernization of Shakespeare and
(st rangely enough) the return, v ia records, to the
dependence on imagination for scenery that actu·
ally characterized the origina l Shakespeare pro·
ductions. The plain theatres of Shakespeare's day,
the modern·dress . (as of then) costumes, the ele·
mentary stage and so und effects, left virtu a lly
everything to the playwright and to his words,
written for h is speaking characters. The amazing
versat ilit'y of the Elizabethan playwright in the
straight use 0 1 words unadorned to build up a
drama never came t h rough more nicely than here,
in Romeo and Juliet!
T rue, one must cope with and get used to the
special and exaggerated Shakespearian way 01
acting, as it now exists in a trad it ion t h at is as
rigid, outward ly, as that of our own fine soap
dramas on the radio. For awh ile, the unfamil iar
gram m ar, the strange words, the mouthfilling
phrases, wi ll get you down. But the Old Vic
knows its stuff. A fter awhile the conventions of
th is special and very grea t k ind of drama begin
to adjust themselves to yo u , so to speak , a nd the
sen se comes th rough. Conventions, mi nd you,
that are now less rigid, no less artificial than
th ose of soap opera, where every vo ice is a type,
every sentence, every inflection is done jus t so,
by act ors wh o study and m imic un t il a hundred
radio voices sound e..x:actly like one a nother.
Shakespeare has the same conventions-but of
different sorts, and hi s, one begins to rea lize,
a llow for a lo t bigger scope in the drama t h an
the soap drama. Both (never forget) , being dram a
are essentia lly artificia l and utterly unlike na·
ture-though the more dramatic for it.
And so Shakespeare's extraordinary preoccupation with death and d ying is the m ore vividly
and absorb ingly clear he re because of such unlikely and improbable monologues as those of
Rom eo and of Juliet, dying or about to die--and
the p lain fact that the O ld Vic actors kn ow this
convention for what it is, and exploit it with th e
utmos t finesse. Drama on r ecords has never quite
equalled thi album before.
Hi-Fi, definitel y, with the simples t 01 sound·
effects, unobtrusive musica l curtains, s light
changes in Iiveness to ind icate s m all or large
places, the us ual formaliz ed "mob so unds H for
parties, crowd scenes, d iscovery-of-the-dead- Iovers,
etc. It's extraordinary how little is n eeded to back
Shakespeare up-as he intend ed it sh o ul d be. Not
even the slightest direct ind ication of who is
whom or where is where-it all comes Qut, expertly devised by Shakespeare, in the course of
the actual words. Better grab this a lbum fa st,
and play it often.
Columbia
Masterworks
Literary
Series.
Prose readings by famou s authors. Columbia SL-190 (12) . (Special album , bu t
probably availabl e soon sepa rate ly.)
_
:H ere is another revolution from Columbianot so much in the mere mechanics of recording
*780 Gremwich S t., N ew York 14, N. Y.
42
a batch of voices, which is hardl y revolutiona r y
now with five years 01 tape a lready behind u s,
but r ather in the new a nd excit ing understanding of the LP m edium itself that this shows.
The series is not yet focu ssed in intent. There
seem to be two aims here, one, to r ecord "documentaryIJ read ings of works by the ir OW11 authors, to a length and continuity never before attempted, a nd , second, to record s poken stor iesas stories. My impression is that the firs t aim
is' uppermost, t h e documentary; I am convinced
that the second-wonderfully exploited in a few
of the records-is by far the more important.
At this point I'm only halfway through the
batch, hav ing covered readings b y Somerset
Maugham, Steinbeck, Saroyan , Sir O sbert Sit·
we ll and Edna Ferber. I still have Edith Sitwell
(of the famous "Facade" recordings where she
r eads her OW11 texts t'o V\'alton's music) , Truman
Capote, A ldo us Huxley, Joh n Collier, Sacheverell
Sitwell (third s ibling of the lamous fam il y)
Katharine An ne Porter and Cbris toph er Isher·
wooq-phew! Each of th em has an entire 12- inch
LP, approachin g a solid hour of read ing. Enough
to keep me and anyone else busy for a good
month , without a s ingle musical record. The n onstory discs are interest ing, no doubt, and ins truct ive and docume ntary. But what gets me are t h e
s tories. For stories, jus t keep in mind, were originall y and timeless ly meant to be to ld-out loud.
It's only us moderns who have the new-fangled
idea that a story shou ld be read.
And so-out of tbe batch, so far , I recommend
as a grea t experience two discs, Edna Ferber
reading and acting her long short s tory, "The
Gay Dog," 'about a pathetic hen-pecked Chica go
bachelor, and Somerset ~Iaugham's two stori es,
" T h e Fat Women of A n tibes"-which is -"'a bsolutel y superb entertainment-and a somewhat
lesser value on the obverse, concerning a circusact lady who dives into a six-foot tank of wate r
flaming with gasoline, two shows every evening.
(Nope, she doesn't m iss-not in the story.
Maugham's too clever for that_) John Steinbeck 's
two stories are both crackerjack ones, but h e's
no read er and you can follow them in suspense
thanks to their own sheer power, not to h is ant ic limactic reading. Saroyan is unintelligible as he
Utt-ies" (so says the label) to read his own work.
He in s isted on us ing h is own tape recorder and
I'd hate to have to mention tbe brand ; luck ily
I tlon't know. It st... .........ks.
I' ll report on the others when I get 'em played
over. I've beard good things abo ut the Truman
Capote "Children on Their Birthdays"-two entire sides long. Might try it too. I ' m all for more
s tories on records-complete and long-by rea l
stor y tellers, of every sort. How about folk
s tori es? They're always t o ld out loud, except
when people "collect" them for books.
Stravinsky: Oedipus Rex . T ext w ritte n a nd
spoken by Jean Cocteau. Co logne Radio
Symphony and Cho rus. Columbia ML 4644
Le Petit Monde de Don Camillo. (Sound
trac k) Fe rnand el and othe rs.
Decca DL 7024
Here ar e two records indicating among other
things what vast new areas LP has been entering. A large number of musical works which in
their original form included some species of
speech-narr ator, operatic dialogue, even s traight
drama to which J,ad b een added incidental music
- now sudden ly can appear in unexpected w'holeness via the new medium of LP; \Vher~ for m erly
the s peech parts were un iversa ll y scrilPped in
record ing as quite impractical, now we've dis covered that speech adds m ightily to the effectiveness of an LP, as we ll as allowing for a more
complete presentation. Especiall y h i-fi speech, undis torted, with "presence" and life, and with lots
of sibilants.
Oedipus Rex is an odd piece, composed t o a
synthetic Latin text that was t ranslated-into
Latin, not out of it-from a Cocteau original out
of Sophocles. The narrator's role in the score is
supposed to be spoken in tbe langu age 01 the
audience, wherever the piece is done. I n th is case,
howeer, Stravi nsky has got the autho r himself
of the original, and so the narration is done in
Cocteau's own F r ench, though the Latin part s are
trans lations from Cocteau I
French, you' ll fin d , is a rem arkab ly effective
language on records, u ndoubted ly because it is
liq uid, re latively unper cussive, d epending on q uanti ties-syllable length s-instead of accent, which
is ver y nea rl y equal in every syllable. I deal for
the mike, which objects to percussions a nd all
sudden ch anges of dynamic level, as every radio
speaker mus t learn.
Techn ical note : the performance o f Oed ipu
was taped in Cologne, Germa n y, but Cocteau's
voice was taped at a F rench performance som e
eight months later.
*
*
•
Le Petit Monde (The Little World of Don
Camillo) is nothing more than the straight sound
track (or excerpts 1) of th e fi lm itself, in French ,
and the remarkable thing is its mere existence in
th is fo r m-for Decca has released it witho u t an y
adornment whatsoever, not even notes on t he
album cover, nor any transla t ion, synopsis, b lu rb ,
or what have you. Even the labe ls, m ade in
U.S.A ., are in French. Obviously Decca must
take for granted that any buyer 01 this record
knows his French by heart, which only goes t o
show h ow "esoteric" an LP can be these clays
and s till sport a big, popular label like Decca.
The original seems 01 high qua lity-could it
have been taped, rather than made on so ulld fi lm 1
Beethoven: Music from Coethe' s Egmont,
op_ 84. Wurttemburg State Orch ., State
Theatre Chorus (?) soloists, F. Le itner.
Decca DL 7540
I-fere's another- with words in German. Not, it
is true, the entire drama, which would be somewhat impractical even with LP to put it mildly,
but instead of th e usual overture, so very fami liar,
we now have a g roup of eight musical numbers,
in trumental and for t enor and contralto o losand, at the end , a long and impass ioned dramatic
mono logue by the hero hi m self who at its can·
clusion rushes forth to "die for freedom" against
tyranny, in t y pical Beethoven (if not Goethe)
s ty le. The German is excellent and well recorded
for this last band; again it gives a sense of rea lis m
an d a liveness to th e who le work.
Odd note: Tbe Chorils, as mentioned i n the
labe l and also in the cover annotations, is not t o
be found; I haven ' t spotted it yet after a couple
of p lay in gs. Maybe it got edited out by Decca's
(right hand ) engineers, without te ll ing th e producti on (left hand) department.
AUDIO ENGINEERING
•
DECEMBER, 1953
the
question
When to change stylus -
finally answered by
Audax
features
III
STYLUS-DISK
Gives visual indication (before yOul' valuable
l·ecol·ds are ruined) of whethCl' 0.' not the stylus
is in playable condition.
2.
Will test ANY type of stylus, in any type of pickup-in a jiffy.
3.
Neithel' the stylus no.' the eal·tridge need be
removed f01' the test. Nothing need be disturbed.
4.
The g.·ooves may be used over and ovel' again,
until finally a worn 01' defective stylus scrapes
the delicate gl·oove-walls.
5.
Should last for yem's-ONLY costs $3.90 net,
at yOul' dealers. (Add 25¢ if shipped from New
YOl·k City.)
STYLUS·DISK is a MUST for any music sys·
tem, for just as a fuse protects an electric ciJrcuit,
the STYLUS·DISK protects your records against
ruination by a worn stylus. You need no longer
worry about the stylus. This remarkable device,
the STYLUS.DISK, will give you the needed
warning.
a
-.
I.
Listening quality in music is eve.·ything. Only
tlte Audax CHROMATIC magnetic pickup, satisfies this all imp01·tant requh·ement.
2.
Replaceability of stylus at home. Highly imPOl·tant because a jewel point, be it diamond 0.'
sapphh'e, has only a limited playing life.
3.
Compliance nem'-infinite, both lateral and vel·tical.
4.
Needle-talk pmctically nil.
5.
Musical l'ange, smooth, f01' full audible spec·
U·um.
6.
Stylus must be in full view for the all impOl·tant
stylus-g.·oove alignment.
The Audax CHROMATIC has everyone of these
MUSTS to a degree not equalled by any other pickup. To
those who asked about it, the Audax is the highest quality
magnetic pickup ..• it is neither a rochelle salt nor a
ceram.ic crystal. It. has no hangover or phase-lag, "the
worst type of distortion."
Now, as in the past, pickups come and pickups go,
but the Audax CHROMATIC is still by far, the finest
per/ortning instrumel1t yet devised.
BUT, only YOU can tell what sou11lIs best
therefore, see amI HEAR the CHROMATIC, and YOU
be the judge.
Write for FREE literature
AUDAK COMPANY
500 Fifth Avenue
III
high quality pickup
PAT'S PEND.
I.
•
42nd Floor
New York 36, N. Y.
Creators of Fiile Audio-Electronic Apparatus for over 25 years
FI
(Since al l Fi is Hi these days, we might as
we ll save a coupl e of pi eces of type now
and then .)
Full Dimensional Sound-A Study in High
Fidelity. Notes by Charl es Fowl er.
Capitol SAL 9020
Those who have attended recent Audio Fairs
will know a ll about this albu m , which was distributed to practically every exhibitor and immediately put to usc. (There was a lso a "trade"
hi·fi record with announce r, but that one is not on
public sale.) An excellent job and to my knowledge the first of its type from a major record company's catalogue. The material is predominantly
classical mus ic on one side, popu lar On the other,
but t he range is greater than this im plies-and
on ly goes to show, as a matter of fact, how Hi-Fi
has levelled out the old differences between those
arbitrary categories. From G lazounoff to Stan
Kenlon, Bloch to Foghorn Boogie, this disc illu stt'ates most of the major points of Hi-Fi sound
and its interest for addicts will be as great as it is
t ransient-what with isolated single-movement f..."(cerpts-to the music lover, popular or classical.
Try the Studies in Percussion, parts 1 and 2, first.
Cowbells, gongs, drums, etc.
The surfaces are exceptionally Quiet (and other
Capitols have been relatively noisy at times). A
significant innovation is the soft plastic envelope
for the record, which has enough overlap to allow
a fold that is dustproof. Not practical for standard
r ecords probably (it won't fit into an ordinary
record s leeve), but a step in advance nevertheless.
Enthusiastic notes, at length, by Charles Fowler.
No vocal explanation s on the d isc itself.
Scriabin: Poem of Fire; Poem of Ecstasy.
M itropou los, N. Y. Philharmonic.
Columbia ML 4731
Scriabin: Poem of Ecstasy. Loeffler: Pagan
Poem . Pari s Ph ilharmonic, Rosenthal.
Capitol P-8188
An easily described comparison between th ese
two ve rs ions of the Scriabin piece (which, musically, is a work that makes my insides crawl,
so twisted and over-wronght a nd out of sty le and
taste is its post- \~T agnerianism)-the two rate as
I-Ti-Fi, one of them Columbia's by now fairly
un iform high standard, the other Capitol's Full
Dimensional Sound, but they represent, to my ear,
two. opposing mike ph ilo ophies. The Capitol may
or may not be a one-mike job but it s t011al color
is of that type, the complex of Ol-chestral sounds,
the hundreds of submerged solo in strumen tal passages typica l of this music blended at a considerable distance. A mellow, good sound, but not too
sharply highlighted in the monaural reproduction _
Columbia 's, on the other hand, is less literal, less
"faithful," more artificial, but in the )-ecorded
medium seems to me to bring out lTIore of the
score, to ac hi eve more presence and aliveness. In
t his version, presumab ly with nlore than one
mike, the solos, notably the so lo violin and trumpet, are shar p, steely, etched against the tota l
sound ; not the original concert h a ll intention in
litera l t erms but a good equivalent of the bi naural on·the-spot impression.
Note the markedly different equalization required. Columbia has considerably more pre·emphasis that Capitol, in the highs. Be sure to adjust when making comparisons.
Th e pleasu re you derive f rom th e
magn if icent fidelity of an A ltec home
music system is eq ualed only by the prid e
that comes with knowing you possess
the finest. Alte<; fidelity is truly t he
highest fidelity assuring you
unsurpassed performance .
Visit you r Altec d ealer soon and plan
now to install in your home an Altec hom e
music system for a lifetime of
listening pleasure. Altec home music
equipment is well wort h waiting for
because A ltec f ideli ty is highest
fide li ty withou t comprom ise.
Borodin: Polovetsian Dances. Moussorgsky,
Night on Bald Mt. R.-Korsakoff: Cap.
Espano/. Austrian Symphony, vario us conductors.
Remington R-199-130
REPUTATION
SECOND
TO NONE
9356 SANTA MONICA BLVD., BEVERLY HILLS, CALIF.
161 SIXTH AVENUE, NEW YORK 13, N.Y.
44
One of those discs of pot-pourri usually unreviewable because the title is too long (hence abbreviations) or the content is too conventional. As
representative of Remington's current Musirama
Three-Dimensional sound it warrants notice. With
this sort of opportunistic publicity (please, I ask,
show me some two-dimen sional sound) I have
no sympathy whatsoever. Will we ever get 'Past
the -rarna craze? B ut the record remains to be
judged for itself. This one, I hasten to add, is a
good one for the price though I do not know wh at
the Austrian Symphony ma y be, nor whether, as
is possible, it exists on other labels under more
familiar but already-contracted names. The playing is good, in the final part of the Borodin unusually warm and musical. No complaints!
AUDIO ENGINEERING
•
DECEMBER, 1953
The sound, wha te ver the dimens ions, is good
too~ though not technically up to top I-li-Fi, nor
entIrely ideal aco ust ically. The mike setting is
strangely Hollywoodish, a close-to, rather dry
effect, the strings on ly feet away. Austria? Perfectly listenab le, nevertheless. Pre-emphasis is
moderate, less than Columbia, there are no ap preciable highs over abou t 8000 or so but th ere ar e
enough for a n y musical purpose-specifically,
enough to bring through faint triangles and the
breath of a flute. Plenty for anyone who is interested in the music.
Surfaces, in this low-priced line, are of course
substandard and may be sh ort-wearing. The hiss
of earlier Remingtons is gone, the background
crackle is not ob jectionable. But on the Borodin
side there is an interes ting effect that is sig ni ficant
• as to ~lusirama three-dimensional merchandizing.
A n odd extraneous sound, like a faint tambourine
being shaken, goes a ll the way through and on
wide range eq uipment is distinctl y d isturb ing_ It
disappea rs entirely, h owever , w ith a cut-off of
about 7000 cps. It will not be heard on most
machines on wh ich this record w ill be played_
A calculated risk, a shrewd appraisal of the pres ent situation? Possible, but it might also have
been an unavoidab le accident.
Wagner: Preludes to Lohengrin , Meistersinger; Overtures to Tannhaiiser; Ride of
the Valkyries. Detroit Symphony, Paul
Mercury MG 50021
Paray .
A sample from the recent new branching out a t
Detroit of the "Living P I-esence" technique chez
M ercury . Eviden tl y this kind of presence is not
the fai rl y fixed sound·style that we've found con·
s istent in London' s ffrr, in Columbia's (nameless)
t echnique, in the New Orthophonic. This Detroit
~i c has a sharp, very close and dea~ sound , brillian tl y recorded, tremendously effective but ver y
un like some of the earlier Liv ing Presence onemike jobs at Ch icago and Minneapolis. Not un·
like the Remington disc a bove, strangely enough,
as far as acoustics go. Interesting. Very low distortion, good surfaces. Real Hi·Fi, no doubt.
Paray (he's 70 yea rs old ) is a strange conductor
and ra ther intriguing to hea r. I-l is Wagner tends
to be on the sprightly s ide, French·style, in con·
t ras t to the familiar heavy German manner, al)d
the really flighty parts -mid ·section of the Tannhaiiser overture (Venusb erg) for instan ce-are ::LS
electric as cat's fur. Excellent! The Valky ries'
violini stic flames crack le as you's never heard
them. On the other hand, Paray h as the strangest
way of bouncing a nything that is tnarch -like, as
though he were hoping up an down witl; excitem ent on the podium ! The Meist ersinger Pre lude
is unforgivably bouncy and staccato-missi ng the
ma jesty of it altogether; the Valkyrie ladies
bounce up and down too, though to bette1 advan tage. A highl y individual conduct or and, a ll in
a ll , an attractive and unaffec(ted musical persona li t y. I' ll look forward to more of his quirks.
Franck: Symphony in 0 Minor. St. Louis
Symphony, Gol schmann .
Capitol P-8221
Khachaturian: ' Gayne Ballet. Indianapol is
Symphony, Sevitsky
C.a pitol P-8223
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R ate d output, 10 watts. Response, + 0.5 to -0.2 db from
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at 3 watts. Input imp., 100,000
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+ 0 .3 to -0 .2 db from 2020,000 cps. H armonic distortion less th an 0.5 % from 3015 ,000 cps a t 20 watts; less
than 0.5 % from 20-20,000 cps
at 6 watts. Input imp., 100,000
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Capitol, too, is busy in the middle West; here
are samples from recent additions t o the FDS
catalogue. The somewhat close and dead sound
of these records is evidently not at all a coin cidence, for the two records (and the French , '· ·
Scriabin disc, above) are remarkably consistent .
in their tonal effect. This, I'd · venture t o guess,"
is an extension of a very honorable tradition often ·
referred t o as West Coast Sound, stemming b oth
from the big fi lm studio sound stages and from ·
popular recording, in which area Capitol is of ~_
course a leader. ~eciall y built stages are--or . J
were-morc or less· inevitab ly ver y dead. Film
m usic is scarcely in need of concert h a ll reverberation, for music or the speaking voice. The dead,
close-up technique of popular music is enormo~sly
effective with brass, percllssion, and piano; but
wh en applied to the symphony orchestra it gets
h old not of t hese powerful elements- which are
at the rear-bu t the strings, which are in front.
Hence the over-stringy --sGund of m any a modern
classica l record using close-to techniques.
I'm not extra enthused over Capitol's som ew h ~t padded sound, but then I don' t like the
ultra li ve one-mike sensatioJls any better. In the
recorded m edium, it seems to me, concert h a ll or
no, the ideal is always between the two, with a
good, round, big Jiveness, but also with strong,
sharp highlights for the individual sounds. Can
be done with many mikes and a lso, given the
right set·up, with one.
AUDIO ENGINEERING
•
AUTHORIZED
INTERMATCHED
DECEMBER, 1953
SL-·12 Extended-Range 12" Speaker SL-8 Extended-Range 8" Speaker
Olson-engineered. Usable ra nge from
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6Ifs". Shpg. wI., 4 Ibs.
Usable ra nge from 65-10,000 cps;
wide dispersion angle throughout
range. N atural treb le and full bass
reproducti on. Will hand le 10 watts.
Imp., 8 ohms. M agnet wt. , 6.8 oz.
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980671. Net .. .............. ' .' .$18.95
..
_
-------.••
ALLIED RADIO CORP., Dept. 17-M-3
100 N. Weslern Ave., Chicago 80, III .
o
Send FREE 1954 Catalog
Ship the following '... .. . . . •• . . •• . . . . •• .•.•. . .• • •
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.;Y~'~ .~. ~o~ . ~t~. iiiii _ ~
45
inside this package on your Jobber's shelf ...
JL
~=====II
-L-JI_
D on't let the Capitols go by, then, without
ma king yo ur own decision. A lot d epends, r em ember, on the acoustics in your listening room.
It is a safe bet that Capitol records will sound
terrifi c in a big, live list ening room . For a sm all,
padded living room, t ry L ondon or the earlier and
very live M ercur y Living Presence di scs.
Albeni:r;-Arbos: Iberia. Orch . des Conce rts
Colonne, Sebastian .
Urania URLP 7085
Faure: Pelleas et Melisande; Dukas: La
Peri. Orch . des Concerts Colonne, Sebastian.
Urania URLP 7097
U ra nia in t he pas t has been reissuin g assorted
German r adio tapes-m y impress ion being that •
the dates have progressed a bit fas t er tha n time
has and a re now almost caught up in the m ai n,
b aving begun wi t h earl y German tapes probably
from before we knew there was s uch a th ing. I
take it tha t Uran ia's " 50-15,000-----" trade mark
n ow indicat es its brand new records; the a bove
are two o f the k in d. A sharp, g littering t echnique
but with a g ood backgro und liveness m ake these
excellent as to Hi·Fi acoustics. The st r ing t one
is bright, well blended and not t oo steely, which
i3 m or e th an can be said of m ost o f the discs
a bove, a ll o f which these s urpass. Clean record·
in g, too, and fine surfaces.
The Dukas- F aure disc is musica lly unusual, t he
Faure piece-a mild and a ttractive item , t he
Dukas a novelty o f stun ning unimportance- it
h as a superb array of orchestral brillian ce, u p t o
the famous Apprent ice Sorcerer , but pract ~cally
n o content at all. Sheer, brilliantly contrived
n oise and as such it m akes splendid Hi· Fi!
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46
High Fidelity
A n editoria l on the meaning and use of
the term high fidelity ( "Ia haute fidelite")
appears in the June, 1953 R evue du Son,
signed by M. ]. de Cadenet. It is defin ed as
" . .. th e quality possessed by an electroacoustic chain that would give the listener
the same a udi tory impression as if his ears
had replaced the r ecording mi crophone".
But M . de Cadenet concludes that technical
exactitude (which would necessari ly involve binaural processes ) is not the complete answer. The results are judged
aestheticall y, and it is felt that musical
standa rds must be involved: We have too
much of a tendency to consider the quality
of an electro-acoustic installation on a
purely technical plan. Compa ri son with the
original, it is concluded, must be on an
"aesthetic plane," which may not yield the
same results as pu rely physical fidelity.
This r evi ewer might add that if the
electro-acoustic chain that is being discussed does not go beyond the recording
microphone or th e reproducing loudspeaker,
and if such factors as the relative acousti cal
conditions between the concert hall and
the living room, th e balance of sound f rom
the di ffe rent instruments, and so on a re
not taken into account, there can be li ttle
to di sagree with in this editoria l.
Record Surface Noise
T he July, 1953, iss ue of W in!less W orld
reports on a lechlre delivered by D . T . N.
Williamson on "Suppressing Gramophone
Sll1iace N oise." P a rti cula r reference was
made to the "impulsive" type of noise associated with dust pa rticles attracted to
plastic long-playing di scs.
A nalysis of a typical pulse shows th at it
can b~ di stinguished from r ecorded program
tranSIents by the fact that its energy content
above 20,000 cps or so is hig her. The use
of a high-pass filter with this cut-off can
therefore furni sh a segregated pulse-actuated signal. Such a signa l is used to operate
AUDIO ENGINEERING
•
DECEMBER, 1953
15
10
0
.0
"
,
. ...
......
-5
\
...
-10
,
'.
-15
b y L. H . Bogen
Member. Audio Eng inee rin g Society
Vice Preside nt. David Boge n Co .• Inc,
~.
-20
,I
;i1
-25
1000
5000
10000
20000
FREQUENCY IN CYCLES PER SECOND '
Fig. 1
a gate circuit that squelches the program
- music and noise pulse both-momentarily.
Mr. W illiamson stated that experience has
shown the ear to be tolerant of individual
pulse deletions of up to 250 microsecond
duration. T he cumulative time taken up by
the cut-off periods, however, could be as
high as one tenth of the total program
time.
"Clicks" were successfully removed from
a specially mar ked record, but if is stated
that some fu rther work is required to perfect
t he gating circuit
LP Record Pickups
The July, 1953, issue of Wi'reless W Q1'ld
also carried an article by G. H . R ussell,
discussing "Inexpensive P ickups on LongP laying Records." Mr. R ussell points out
that the increased compliance of the longplaying record material reduces the frequency of the high-frequency pickup r esonances. Tests conducted with a moderately
priced pickup, using an LP t est record,
showed a very annoying peak of about 12
db at 9,000 cps. ( See Fig , 1) Such a peak
results in a buzzing string tone ("reminiscent of a cloud of mosquitoes in flight"),
in rapid cut-off as the frequency of the
recorded signal is raised, and in an amplification of distortion in the recording.
A pickup whose upper resonance is above
14,000 cps is expensive, and also involves
added amplificati on due to r elatively low
output, The solution to the resonance problem proposed here is the use of an antiresonant electrical circuit, shown in (A)
of Fig, 2. The improvement in pickup performance from the original response is
evident from .th e graph in (B) ,
['!'It'. ;..
f
1
1
0
§ II~
PICKUP
h
'"
AMPLIFIER
J
25OO
MAX., '
(A)
5
The Satu?'day R eview Home Book
of R ecO?'ded Music and So,!md Reproduction wr ites of the Bogen DBI0:
The Bogen DBIOA now features
Record Compensation (and the
cost is still only $54.45)
For several years now, the Bogen
DBI0 amplifier h a s been supplying
a very happy solution to the problem
of how to assemble a good system at
a r ealistic price.
By selecting the DBI0 (and the
later DBI0-l), thousands of purcha sers have saved enough money on
the amplifier to be able to afford a
r eally good speaker set-up. (I think
this mak es for a more sensibly balanced system, since it is generally
acknowledged that amplifiers have
been brought to a higher stage of
perfection today than speakers. )
To this field-pro ved amplitier, our
Engineering Dept. has added a new
refinement for 1954: recQ?'d equalization con t7·ol. T.hrough the use of
3 additional positions on the circuit
selector switch, the listener will now
be able to compensat e for the varying characteristics of the different
ma.kes of r ecords in his collection:
"LP " position - Approximately equal
to the AES curve ; for optimum response from American microgroove
records.
"78" position - For shellac classical
records (in good condition) .
"Pop" position - Simila r to the "78",
with a sharp cut-off (about 2000
cycles) for a more mellow tone, and
for reducing surface noise of worn
r ecords.
In addition, we , provide calibrated
tone con trois to correct modifications
for other r ecords, such ;;tS FFRR
and orthophonic.
0
-5
- 10
.0
"
ANOTHERSURPruSEFROM
A SURPRISING AMPLIFIER:
- 15
~
- 20
f L
- 25
l
-30
10000 20000
5000
1000
FREQUENCY IN CYCLES PER SECONO
(S)
fM
!!.~~!wm.
of fine electronic equipment
Companion FM-AM Tuner
is the Bogen R604
This unit fills a real need in the
m a rket for a n FM-AM tuner with a
solid circuitr y, excellent performance and m inimum controls, to sell
for und er $100. Sensitivity is 5
micro-volts for 30 db quieting. FM
Frequency Response is 50-15,000 cps
± 1 db. Stability is exceptionally
go od, with Automatic Frequency
Control and temperature-stabilized
oscillator effecti vely preventing drift
a nd eliminating warm-up period.
Send for your copy of
"Unders tanding High Fidelity"
Thi s b oo k, we think,
s t r ik es a n i ce ba lanc e
between t he01'y and the
pmctical as pec t s of hi-ji.
lt cove1'S such subj ec t s as :
H ow to evalu ate and
se le ct th e bes t comp onent s f or your loca tion,
li s t enin g 1'e qui1'em en t s
an d bu dg et. For a copy,
mail the coup on with 25¢.
MAIL COUPON NOW
.-------------------------------J David Bogen Co. , Inc., Dept. VL
29 Ninth Ave., New York 14, N. Y •
Send " Unde rst anding High Fidelity" (for
w hich I en close 25¢ ). and free ca t a log.
n
a~e
_________________________
addre s a ________________________
city_
o
_
_
_
--"zone_state _ __
S end f ree catalog only.
--------------------------------
Fig. 2.
AUDIO ENGINEERING
"This is a compact little marvel of
tone and versatility for the price. It
was resourceful enough to compete
over most of its range with several
amplifiers costing three times as
much ... "
Now you get record equalization too,
and the price is still only $54.45.
•
DECEMBER, 1953
47
NEW PRODUCTS
• Magne,t ic Amplifier s . Remarkably high
powe r h andling ca pa bility for t-heir s ize
and weight c h a rac t e riz es a n ew line of
miniaturize d m ag neti c amp lfi e r s jn ow
being manufactured by D & R, Ltd., 402
E. Gutierrez S t., Santa Barbara, Calif.
Special co r e materials, winding techniques, an d mou ntin gs, co up le d with t h e
u se of hig h-freq uen cy a.c. p owe r, p ermits
triode r-f amplifier affords sensitivity of
1 !LV for 20 db q u ieting. Low regeneration
a nd easily aligned transitionally- coup led
i-f stages result in l ess tha n .05 p er cent
inte rm odula tion thro ughout the en tire c irc uit. Amplifie d AFC reduces drif t 100
times. Tubes m ay be r eplace d without
n eed for realignmen t. AFC ac tio n i s con tinuou s ly variab le. D escriptive s h eet availa b le on req u est.
• " Write-On" L a b eling T a pe. Ide n t ifi cation of tape r ecordings is made easier
wi t h "Scotch" write-on tape No. 48, r ecently introd u ced by Minnesota Minin g
a nd Manufacturing Co., St. P a ul 6, Minn.
Pressure sensative, the ta pe is s upplied
in a continuous r oll of 40 labels which
are a ppli ed clirectly to the s ides of t h e
r eels. Printed o n t h e white tape is "Reel
sw itch whic h provides eq ua lization for a ll
types of r ecords, as well as inputs for TV,
t a p e, a nd tun e r . Speaker outp u ts h ave im pedances of 4, 8, a nd 16 o hm s. Th ere is
a lso a high- impedance ou t put jacl, for
fee d ing recorders. Vo l um e contl'ol is com p e n sated . Sepa r a te b ass and treble controls
pl'ov ide b ot h boost a nd droop. Removable
brus h ed-bronze esc u tsch eon and l %,-in.
ext ension shafts s impl ify mo u nting in any
cab inet. Bell Sound Systems, In c., Columb u s, Ohio .
• E-V 4- W a y Speaker System. H a ndsome
cabinetry is co mbin e d with advan ced e ngineering d esig n in th e Georgian, a new
attainment of rapid respon se time a nd
hig h p ower-han dlin g capacity in units
extremely small and light. The Model
MA-4 8 illustrated weighs on l y three
ounces, yet delivers a power output con servatively r ated 25 watts .
• High-Gain Audio Input Tube. Amplifi er manufacturers primarily will find
inte r est in the Gen e lex Typ e Z729 pen tode, a low -hu l11 , lO\V-110ise, lo\v-microphonic vo ltage-amplifying tube manufactured by Ge n eral E lectric Com pany, Ltd.,
of Engla nd, a nd m a r kete d in this co untry
b y British Indu stries Corporati on, 1 64
Dua n e St., New York 13, N. Y . Th e Z729
fits a standard 9-p in miniature sock et,
and has been express ly d esigned for u se
in high -gain preamplifier and e9 ua lizer
stages. An intern a l s hi eld completel y
No. Data S u b j ect" , together with
blanks for filling in the desired 111formation. The tape is s uppli ed with a specia l
matte finish which can be written on wit h
pen or pen cil.
• Scot t T ranscrip t ion Amplifier. Resembling in appear a n ce the "front en d" of a
conventional remote-control amplifier and
but little larger in s ize, t h e new Scott
Model 99-A i s in r eality a comp lete 10watt a mplifi er a nd power supp ly, inc l ud ing '
preamp-eq ualizer a nd fu ll- range control s .
Trebl e a nd bass controls afford both boost
an d c u t, and are con tinu ou s ly variable.
An a u tomatic lo udness control is pro-
.
C). .() () •cj~
A.
. \..)p.
._- -.
s u rro u nding the elements i s one of the
tub e's feat u res. D a t a sheets giving full
technical informati on a nd performance
curves are availab le f r om British Indus tries Corporation.
• Craftsmen FM Tuner. Remarkab le performance characteristics are e mbodie d in
~he n ew M od e l C900 FM Tun e r , r ecently
mtroduce d by 'l' h e Radi o Craftsmen, In c.,
4401 N. Ravenswood, Chi cago 40, Ill. D e-
'~..)
IJ
•..1,
vided with means fo r a d j u s ting compensatIOn from zero to fu l L Selector switch
permits r ead y c:hoice of four inputs. Freq u ency r esponse is flat from 20 to 30,000
cps. Harmonic distortion is less than 0.8
per cen t and intermodulation under 0.3 per
cent at 10 watts. Output t u b es are ba la nced a u toma tically by a self-bala ncing
phase-inverter system. Dim e n sion s a r e
13'4. x 3
x 9
in s. D escipti ve bulletin
will be mailed on request to Hermon Hosmer Scott, Inc., 385 P u tnam Ave., Cambridge 39, Mass .
• Low-Priced T a pe Recorder. Introduced
as the lowest priced tape -r ecorde r with
comparab le c h aracteris ti cs, the new T e lectrotape is a d ua l-track unit with operating
speed of 3%, ips. F eatures inclu d e fas t
~ol'war d a nd r ew ind, t hree hig h - imp ed ance
mputs, a nd r ecording leve l indicator. A
* *
e Bell High-Fidelity Amplifier. Although
moderate in price, the new Bell Model 219 9
---:p::~
,
•
•
s!gned for u n u l!ua l sensitivity, low distortIon, a nd maxrrnu m s tabi li ty, the t u n er
i n cluaes a n u mb e r of a dvancem e nts i n
ci r c uitry and components. Cascode do u b le -
48
()
Electro-Voice
m u ltispeaker
r ep r o du cer
which utilizes a Klipsch "K" h orn w ith
spec ia l 15-in. drive l' for exceptional bass
r esponse. An e lectrical crossover feeds
f r eq u e n cies above 300 cps to a compressi~n - ty p " h orn~loa de d mid-low freq u ency
drIver WIth 58 -111 . path l ength. An aco u stic
C~'o ssove r confines frequencies f r om 1000
tv 35 00 c p s to a s p ecia l diffrac tion horn .
Above 3500 cps, a n E -V Super Sonax veryhigh-f r eq u ency driver takes over to ext en d response beyond the upper limit of
a udib ility. The unit is eq u ipped with two
contro ls, one to govern "presen ce", the
other to control br ill a nce . Dimensions are
52" h x 34" w x 26 " d. For complete d e script ion a n d technica l spec ifications write
to E lectro-Voice, In c., Buchanan, Mi ch .
a mplifi er represents no com prom ise in
audio c ha r acteristics or operating fl exibility. Output is 12 watts at less than one
per cent distortion, a nd f req u ency res pon se is 20 to 20,000 cps ± 0.5 db . Six con trols inclu de a seven-position selector
Singl e control p el'lnits switchi ng from
r ecord to p lay to id le. 'l'h e u ni,t h a ndles
s pools up to 5-in. diameter, a nd m ay be
operated with the cover closed. It is
h O)l sed in an attractrive l uggage- type carrymg case an d meas u r es 7 x 10 x 11 ins
W eight i s 14 l bs. Manufactured by Te lec:
tI'o so ni c Corporation, 35- 18 37th St. L ong
I s la nd City I, N. Y.
'
AUDIO ENGINEERING
•
DECEMBER, 1953
EDGE
LOWBOY Model P-1260
For TV and Hi-Fi
sturdily constructed, handsomely
finished 60·inch cabinet designed
to house TV chassis and Hi -fi com·
tubes up to 21-inches :with IS-inch
with 12-inch speaker. When IS-inch
speaker is used, record storage compartment, shown in illustration, is
eliminated. Mode with perma-bonded heavy plywood and lumber, treoted with protective lacquer, and hond-rubbed. Styling i,s modern and
matches any decor.
Model P-1260 in Cherry or Cordovan Mahogany ......................
$195.00
MAGNECORD
PROFESSIONAL
TAPE RECORDER
REK·O·KUT
12-inch, 3-Speed TURNTABLES
Model L-743
A broadcost quality turntable designed for
discriminating users . . • professionals and
audiophiles. Driven by 4·pole motor. Turntable
itself is made of cast aluminum, and exerts no pull
on magnetic cartridges. It is precision machined with
dynamically balanced flywheel action.
A single knob permits instantaneous selection of any record speed : 33 113.
45, or 78 rpm. Record slippage is eliminated through use of new mat
material. There is virtually no rumble, wow or flutter. Complete with 45
rpm record ada~ter
........................
$59.50
Model T-12H
A Deluxe version of the above for the ultimate in turn·
table design for 33113 and 78 rpm only. Driven by constant speed
hysteresis synchronous motor...
·············································· .. ·· ..
$119 .50
M80 Series
Provides full range response: 30 to
15.000 cycles at 7th inches/sec .• and 30
to 20 1 000 cycles . at 15 inches/ sec . Has
new, slot-loading feature, and automatic
tope lifter. After loading, all operations
are pushbutton control. Storts and stops
within 1/ 10 second . Accommodates 10 111
inch reels. Flutter and wow are less than .1 % at 15 inches/ sec . Employs high quality, low noise amplifiers with direct-coupled cascade input
stages. Can be adapted for remote operation.
$1240.00
MBO-A chassis only for rack mounting ...............................................
MBO-AC portable. with cases ................. .............. .......................
.. ....... 1295.00
M80 .. ACC console complete with cabinet.
..... 1345.00
GARRARD
CROWN
RECORD CHANGER
Model RC-90
An entirely new chonger with outstanding innovations . A new type of A-pole. motor provides absolutely silent
operation, and freedom from wow. waver, and rumble . Gives instant
selection of speeds with all three speeds adiustable ± 3 rpm . Other
features include : gentle pusher platform, weighted turntable , manual
positio" for single records, finger- lift for manual use of tone arm, muting
switch, automatic shutoff, and interchangeble plug -in cartridge heads.
............... Less cartridge
. Model RC-90 Record Changer
$66.00
The NEW
TRAVIS TAPAK
Portable
TAPE RECORDER
A dry · cell battery-operated tope
recorder which closes up to
smaJl ..s.uitcase. size: 10x14x 5 111
inch e s. The Tapak is ideally
suited for on - location recording anywhere : at sea, in the air , aboard
train s, in cars, or on foot . It erases, records, mon itors , and has built· in
editing device . Provides for fast power-rewind and instantaneous playback
through single earphone headset. Drive mechanism is spring -powe red .
Runs 5·6 minutes on one winding . Indicates when spring has run down,
and permits rewinding witnout interrupting recording operation. Records
at 7';''' Isec.
Complete with microphone, earphone, two flash cell A
batteries , and 67%. v. B battery ....
$329.45
The
RE L
Precedent
FM TUNER
Unquestionably the finest FM tuner
ever made . This successor to the famous 6468 incorporates every important advance developed in the art of FM reception. Sensitivity is 2
microvolts for better than 40db quieting. Frequency response is 30 to
40,000 cycles ± 1db. Waveform distortion is less than .5 0/ 0 for 100 0/ 0
modulation . Provides 2 -volt output to high impedance, and . 2 volts to
600 ohms. Front panel includes slide-rule dial, tuning meter, signal
strength meter, tuning control, radio frequency and audio gain controls,
and power switch. Power supply is self-contained . Supplied complete
with tubes.
Chassis only (for custom installations) .................................................
Relay Rack Madel...
Cabinet Model (Mahogany, Walnut or Blonde} ...
FERRANTI
The
RIBBON
PICKUP
$325.00·
............... 335.00
.. . ......... 360.00
•
~~.~ Q
~..,.iii
..;
~!~.r.
ro.r.r_·_-p. .~~~
~.. ,.,
..
~
Designed by O. T. N. Williamson , this new pickup represents years of
stud y on'd de velopment . It is a complete unit of pickup head and arm
with the head interchangeable for either standard or microgroove
records .
Frequency response is uniform to 20,000 cycles with output provided to
100 kc. Only 3 grams stylus pressure. Mechanical resonance has been
kept to 3 cycles. well below the recording range . Greater than normal
compliance promotes uniform response and minimizes record wear. 80th
heads employ diamond styl i with an elliptical stylus used for standard
groove records. When used with appropriate transformer, output is 20
mv into 100,000 ohms .
Ferranti Pickup with arm and
transformer ~... .
..
Specify standard or microgroove.
$76.95
Extra Head (standard or microgroove) ....... 37.50
R. C. A. MICROPHONES
Broadcast qua li ty un its of tested and pro ven performance
ideal for on-fhe-air and record ing studio applications.
Known to, and pre ferred by leading sound engineers .
Model 44-BX (Ribbon) ...
Model BK-l-A (Pressure) ...
Model 77-D (Poly-Directional) ...
.. . ......$129.00
79.50
175.00
If you want to See and Hear the
flnest • • • the widest selection of
high ' fldelity equipment ••• be sure
to visit the HARVEY AUDIOtorium,
It will thrill you.
NOTE: Prices Net, F.O.B., N.Y.C.
Subject to change without notice.
AUDIO ENGINEERING
•
DECEMBER, 1953
49
NEW LITERATURE
let
• Vaco Products Company, 317 E. Ontario
St., Chicago 11, Ill., illustrates and describes screw drivers of almost every
type, including all of the recessed head
models, in a new pocl<et piece now being
distributed to dealers. Of particular interest to a udi o engin eer s is a non-mag-
netic unit made of beryllium copper
which should be an excellent tool for
servicing tape r ecorders.
you the sin1ple, accurate way to .
PLOT YOUR OWN FREQUENCY CURVES
with our new, inexpensive test instrument:
0-500 TEST LEVEL INDICATOR
• S. O. S. Cinema Supply Corp., 602 W.
52nd St., New York 19, N. Y ., does an
excellent job of living up to its reputation as "The D epartment Store of the
Motion Picture Industry" with a new SOpage catalog commemorating the firm's
2Sth anniversary. Virtually every mechanical and el ectronic device req uired for
motion picture film production is li sted
and priced. A handy cross-reference index
assists in finding any item desired.
and two new, and different test records:
0-100 AN 0 0-101 FOR PH 0N0 PERFO RMANCE
"THE MEASURE OF YOUR
PHONOGRAPH'S PERF'ORMANCE"
Check frequency response (30- 12,000 cps
flat response). Check for Rumble, Hum,
Flutter and Wow . Check stylus compliance
and tone arm tracking ability.
recording characteristic curves for Columbia
LP, AES, NARTB, RCA's "New Orthophonic".
with the TEST LEVEL INDICATOR
Calibrate your equalizer for flat response
on all recordin g characteristic curves.
Calibrate yo ur amplifier tone co ntrols
to double for an equalizer.
• CBS-Xytron, Danvers, Mass., has prepared a series of d esign r ating c ha rts an d
curves defining the performance of the
firm's new Type 5AW4 h igh-vac uum rectifier under a wide variety of operating
conditions. A CTS-rated t u be, the 5AW4
is d esigned to r eplace the 5U4. It has
el ectrical c h a racteristics sim ilar to those
of the older tube, but it incorporates
many of the feat ures of tran smitting
tubes which afford much longer life.
WITH PRECISION ... WITHOUT
EXPENSIVE VOLTMETERS ...
DUBBINGS CO., INC .
DEPT. AE-3
41-10 45 ST., L.I.C.4, N.Y
STillwell 4-7370
50
• Sun Radio and Electronics Co., Inc., 650
Sixth Avenue, New York 11, N. Y. , in its
new High Fidelity A udio Equipment
Catalog, feat u res an absorbing five-thousand-word article ' on the subject of planning and insta lli ng a home music system .
Hundreds of illustrations and descriptive
text cover the many high fidelity items
on the market today.
• Cannon Eleotrio Company, 3209 Humbo ldt St., Los Angeles 31, Calif., r ecently
issued a r evise d bulletin on its XL series
of lOW-l evel sound connectors. ' Coded
XLS-1953, the 4-page 2-color p amph let
contains deta iled technical inform ation
and is fully illustrated with dimen s iona l
s]{etches, sectional dra wings , and exploded
views of p lu g and receptacle. Copy wi ll be
m a ile d u pon request.
"THE MEASURE OF YOUR PHONOGRAPH'S
EQUALIZATION" ... Plot your own
order from
your local
dealer or
mail this
coupon to:
• Minnesota Mining and Manufacturing
Co., 900 Fauquier St., St. Paul 6, Minn.,
will mail u pon written request two recent
issues of "Sound T a lk" bulletins titled
respectively "Low Frequency Problems
in Magnetic Recording" and "Splicing
Techniques for Magnetic Tape." Both of
these publications are worthy additions
to any collection of magnetic recording
data.
EnClosed is
o
o
o
0 Check
0 Money Order
for $............. .
0-100 .TEST RECORD @ $3.50 .................................. $.......:.... ..
0-101 . TEST RECORD @ $4.95..................................$ ............ ..
0·500 TEST LEVEL INDICATOR @ $3.9·5.................. $............. .
Postage and Handling................ $
.50
TOTAL.. .. $.,.......... ..
fREE!
o
HI·FI CATALOGU§.
0 RECORDI NG SERVICE BULLETIN " B"
!Vame ......... ..
Address ...•.
CitY.,............................. .
.......... Zone .......... S,alt' ... ............................. ,...
• General Cement Manufacturing Co., 904
Taylor St., Rockford, Ill., h as just announced a new 64 -page catalog which
gives detailed descriptions, specifications,
and prices of the complete line of G-C
products for use in the manufacture and
repair of electronic equipment. Requests
shou l d specify Catalog 156.
• Engineering Products Department, RCA
Victor Division, Camden 2, N. J., applies
the self-explanatory title "Power Plant
Communications Systems" to a new 16page booklet in which are graphically
shown many methods of using s u c h systems to improve operati ng efficiency. This
publication shoul d be in the hands of a ll
concerne d with power plant management.
Requests sho uld specify Form P-S31.
• Terminal Radio Corporation, 85 Cortlandt St., New York 7, N . Y., is now distributing the new 1954 edition of the
T erminal Audio Guide. One of the more
complete catalogs of its kind, it contains
130 pages devoted solely to audio equipment for both professional an d c u stom
hi-fi installations. Classifications include:
Radio a nd TV t un ers; r ecord c h a ngers;
recorders and recording equ ipm ent; amplifiers; speakers; cab inets; pa rts alld accessories. Copy will be mailed free on request.
AUDIO ENGINEERING
•
DECEMBER, 1953
A new concept
of recorded music
DISC RECORD
THE HEATHKIT
(from page 21)
t)uai
switch that is closed at the start of a
recording; terminals 1 and 3 to the
Micro-switch that is closed at the end
of the recording; terminals Sand 6 go
to a toggle switch on the r ecorder base
for manual control of the turntable
motor.
The ollerating sequence is as follows ;'
1. P ut on blank disc and screw down
conical aluminum clamping nut.
2. COlU1ect tape r ecorder to AUTOMATIC SPIRALLING CONTROLS plug.
3. Turn on a .c. power to both r ecorders .
4. Put edited tape on Ampex; set
controls fo r playback.
S. Turn on suction pump .
6. Vvith meter switch on HEAT, press
,stylus switch and. set heat ad justing
rheostat so that meter ·indicates 0 VU,
Then set meter switch at microgroove
or standard, as required, Set equalization and gain controls a lso,
1. Turn turntable switch ON .
8, Turn microscope lamp switch ON .
9. Lower cutter head to r ecord and
check g roove with microscope.
11. Cut a run-in spiral by depressing
MANUAL push-button (to get a lead-in
groove for record changer operation.
10. Set sp iralling selector at SEPA~A­
TION .
12. Start tape.
The recording is now being dubbed.
This continues until a foi l strip closes
the contacts on the automatic spiralling
control. When this occurs, a sp iral
groove is cut fo r about 3/ 32 in, (measured radially) and then the recording
of the next selection on the tape starts.
At the end of this selection, another
foil marker again starts the spiralling
motor, and the cycle is repeated until
the last selection is being cut.
The operator may now r emove th e
finished record, put on another blank,
and start the cycle once more. The equipment described enables the average good
operator t.o take care of about twelve
recording set-ups simultaneously, instead
of the usual two or th ree.
RECORD
PLAYER KIT
•
•
•
•
•
Plays all record sizes, all speeds
Newly developed ceramic cartridge
Dual Matched speakers
Acoustically correct cabinet enclosure
Automatic shut off for changer
and amplifier
Here is a new introduction to
qu ality record reproduc t ion. A
simple to operate compact table
top model wi th none of the specialized custom installati on problems usually associated with high
.fidelity systems. T wo match ed
speakers mounted in an acoustically correct enclosure reproduce
all of the. music on the record, re.
production wi th the unique sen.. sation of being in a halo of glorious sound. This
spectacular characteristic is possible only because
of the diffused non-directional properties of the
matched speakers. The performance.level of the H eathkit Dual is easily superior to that of the ordinary
console selling for many, many times the price of the Dual.
record changer plays all three sizes at all three speeds wi th automatic
for both changer and amplifier after the last record is played. A wide
. cartridge 'features an ingenious "turn-under" twin sapphire stylus
or 78 records without turning the cartridge, Simplified easy to assemble
tube amplifier featuring compensated volume control and separate tone conProxylin impregnated fabric covered cabinet supplied completely assembled.
build only the amplifier from 'simple detailed step-by-step instructions. No
ized tools or knowledge required.
kit project has ever tempted you here is the perfect introduction to an
n"'''''''',r,o and exciting pastime. The Heathkit Dual Kit includes cabinet, record
6" speakers, tubes and all circuit components required for amplifier
con§1:ru.c[!()n. Build the H eathkit Dual and enjoy unusually realistic room fi lling
of fine recorded music.
7aHt0«4
o HER
H ATHKIT AMPLIFIERS
T'1~IE HEAT,HKIT 6
WATT
,
"'i-.
HEATHKIT
'71~
FIDELITY'
AMPLIFIER KIT
$35 5.°
AMP L IF I E R K IT
Model A-7B
Model A-9A
$1~5.o
Ship. Wt. 17 lb ••
A 20 watt hJgh fideliamplifier especially
designed for custom in·
stallarinns. Lqw hum and noise Jeve1
!Jp{n miniature dual rrlodes in pre·
amplifier and tOne c.o otrol circuit!,
Four switch. selected inputs. Frequen·
cy respoose ± 1 db 20 to 20.000
cycles, Outpu,t impedaoces of 4, 8.
and 16 ohms.
ty
INPUT
FROM
AMPLFIER
OUTPUT
Write For Free
TO
CUTTER
CATALOG
New 32 page 1953
Cata log lists all kits,
specifications, schematics and latest
price information .
Fig. 2. The audio section of the control panel,
In schematic form .
AUDIO ENGINEERING
•
YOU
SAVE
BY
ORDERING
DIRECT
FROM
FACTORY
51
DECEMBER, 1953
.
.
PHONOGRAPH CARTRIDGE
·Now At Leonard •••
ANew Peak
In Listening Pleasure!
(from page 23)
Mi
M2
Cl
lR
BEAM QUAD AMPLIFIER
& CO'VTROL UNIT
complete
unit
amplifier . .. ...
control unit . . . .
$120 n e t
$130 net
Here is one of the finest amplifiers
made today . . . brought to even
greater perfection by the amazing
new Beam Control Unit. Technically perfect . .. almost audibly
perfect . . . The Beam Quad gives
you a new ease of operation!
Gl:less work and effort are eliminated ... Replaced by pushbutton
controls, automatic circuit correction, harmonic filtering and many
other brand new, built-in devices.
Full range fidelity-IO to 60,000
cps; Built in pre-amp. 1.5-40 ~v.
inputs; Less than 0.03 % distortion. Automatic circuit correction.
Mail & Phone Ord\l'& filled . . .
25 % Deposit, Balance COD. Send
for Free Hi-Fi Catalogue, "L"!
• IMPEDANCE OF RECORD GROOVE
M1
• MASS OF NEEDLE TIP
M2
C1
M3
M4C3
•
•
•
•
a
COrtlandt 7-0315
... ,R1
C4R2
• MASS a RESISTANCE OF VISCOUS DAMPING
• COMPLIANCE
RESISTANCE OF CERAMIC
C3
T
R
•
•
•
con~tant. The sensitivity of this element,
while somewhat lower than Rochelle
Salt at 72° F., is of the same order of
magnitude~. ltgd does not ordinarily require changes in assoqj,ated equipment.
In all piezoelectric materials, sensitivity and dielectrie · constant are dependent upon temperature. In a practical Rochelle Salt pickup, maximum
output occurs at 72° F., and may temporarily drop to 60 per cent of this value
at 90° F. The temperature output curve
of barium titanate is relatively flat and
the loss of sensitivity is negligible
throughout temperature ranges encountered by any phono cartridge. Because of a dielectric constant four and
one-half times greater than Rochelle
Salt and an ultimate strength approximately five and one-half times greater,
a practical titanate element can be much
smaller in all dimensions. Accordingly,
the effective mass of the element and
associated drive mechanism is much
less. Mass must be held to an absolute
minimum to prevent excessive mechanical impedance from appealring ·at ..the
needle with resulting distortion and increased wear on record and stylus.
Development of the Ultra-Linear Cartridge
In the last few years, ceramic cartridges have been available for use in
commercia] home phonographs. A ceramic of this type has sufficient output
voltage to replace the majority of Rochelle Salt units. However, response..
has been restricted to 4000 to 5000 cps.
This limitation has usually been considered desirable. In fact, some manufacturers have required a 2500-cps "roll off" to minimize surface noise and
distortion.
In contrast to this performance, basic
requirements for the Ultra-Linear ce-
Fig. 8. Frequency response of E- V model
84 cartridge
COMPLIANCE OF CERAMIC ELEMENT
.
ELECTRO-MECHANICAL TRANSDUCER COUPLING
LOAD RESISTANCE
ramic cartridge were set up as follows:
1. Frequency response was to fall
within 20 db of the New Orthophonic curve throughout the range
of 30 to 15,000 cps without re--quiring equalization in associated
equipment.
2. Output voltage was to be adequate
to drive standard amplifiers without preamplification.
3. Lateral compliance should be 3.0 x
10- 6 cm/dyne or higher, with maximum allowable damped vertical
compliance consistant with mechanical stability in all arms and
changers. These values are important factors in reducing record
and stylus wear.
4. The stylus should be replaceable
and of a standard type.
Reinforcing the high-frequency response above the constant amplitude
level a required amount is one of the
most important problems of adapting an
amplitude device to a complex curve
such as the Orthophonic characteristic.
·Thi~ is often accomplished by allowing
the system [email protected] resonate in this range and
dampihg b.;> the desired leve1. The result
is a somewhat peaked response falling
off rapidly above resonance. Needle
impedance can become quite high in
such cases producing mis-tracking, distortion and actual ' damage to the r ecord
groove.
Damping Methods
Damping is necessary in any cartridge
and can be applied in a number of ways.
Common practice is to rely on materials
such as viscoloid, audioid, and various
rubber compounds. While they are usually necessary for mounting and restraining the element, undesirable stiff-
':11111111 fll~1 tllll1l
30
50
500
100
FREQUENCY
52
a
MOUNTING PAD
Fig. 6. Electro-mechanical equivalent circuit of a ceramic pickup cartridge.
LEONARD RADIO
69 Cortlandt St.
New York City
a
MASS OF NEEDLE CHUCK
ELEMENT CLAMP
COMPLIANCE OF NEEDLE SHANK
MASS OF TONE ARM
MASS
COMPLIANCE OF CERAMIC ELEMENT
M3
IN
CYCLES
1000
PER
AUDIO ENGINEERING
5000
1OOOO1SOOO
SECOND
•
DECEMBER, 1953
ness and temperature instability result
if these materials are used entirely., The
propel ty of a viscous material (a true
mechanical resistance) can be expressed
as:
F=kv
where F = force developed upon an Immersed body,
k = a constant dependent upon the
viscosity of the material,
v = velocity of motion.
If [email protected] material were uti lized as
a fulcrum or restraining medium on
the element, the applied fo rce or "drive"
would be greater at the higher frequencies where the velocity is increasing,
Thus it is poss ible to incorporate a resistance for damping purposes and, at
the same time, to reinforce the high-frequency re",ponse, A very low "Q" can be
obtained, which is essential for a smooth
response.
Viscous loading of the element is
used in this cartridge by surrounding
the ceramic with a viscous material.
Coupling to the viscous material is adjusted to the correct value by means of a
small metal vane attached to the midpoint of the ceramic. The material 'itself
is a silicone prepared for this application in which values of viscosity, plasticity, mass, and stiffness have been
established for optimum results, Silicone
has excellent chemical and physical stability, particularly with respect to temperature.
BEAM
x,
C
,,
X<:s
::~::
,,,
I
Fig. 7. Equ ivalent of pickup havin g a capaci tive impeda nce working into a resistance load
shun t ed by stray and circuit capacitance. ' ,
Equiva lent Circuit
Equivalent circuits using electro-mechanical analogies are often useful in
underst,lb1ding the operation of a mechanical system, The equivalent circuit
of the Ultra-Linear ceramic cartridge
is ShOW11 in Fig, --6. The conversion' of
rnechanical energy to electrical energy
is represented by the transformer T.
R, is the actual load resistance on the
cartriege.
Input Circuits
The electrical circuit of any piezoelectric device can be represented by a capacitance in series with a generator, as
in Fig. 7. It should be recognized that
the shunt capacitance of a lead and input
circuit directly across the cartridge will
not affect the frequency response to a
noticeable extent. A voltage divider is
set up consisting of the reactances of the
ceramic capacitance (Xc) and the shunt
capacitance (Xcs)' T he rat io of these
reactances is constant at all frequencies.
The net result is a g iven reduction in
signal voltage at all frequencies.
T he low-frequency response of a ceramic cartridge,l1owever, is directly dependent upon the value of load r esistance
AUDIO ENGINEERING
•
• Full Range Fidelity
10 to 60,000 cps(Attenuated 20 to
20,000 cps)
• Buill-In Pre· Amp.,
1.5-40 mY. Input~
• Push-Button Recording
Equalization and
Program Selection
• Plug-In Matchingto
Pick-Up Type
• Automatic Circuit
Correction
• Unique Stability, with
Less Than 0.03%
Distortion
• Beautiful Styling to
Match Any Decor
The finest in contemporary amplifiers, bro ught
to an even finer point by t he most versati le control
instrumen t ever des igned-this is the new
Beam QUAD Amplifier and Con trol Unit.
Every care has been taken to assure completeoperating facilities and fau ltless reproduction
in this superb amplifica tion system. Relat ively
perfect technicalIy, the Beam QUAD is also
relatively perfect audibly. And your thrill at its
sound is enhanced by the ease of its operationby the fact that guesswork and elfo~t on yo ur
part are eliminated. Push-button controls,
automatic circuit corr ection, harmonic fi ltering
and other built-in devices make your listening
enjoyment absolute. Audition the QUAD Amplifier
and Control Unit at your audio dealer's today.
Prove to yourself that th is is the world's finest
amplification system, that here truly is a new
standard in listening pe~fection. Complete
data sheet on reques t. Also send fo r f ree
brochure on revolutionary new Beam
"Stentorian" f ull-range loudspeakers.
QIIAD " Amplilier ancl QC " Conlrol IInit
System Complete, $ 237.50 net
QC " Control Unit Only •
$120.00 net
QUAD " Amplilier Only • • • • • • $ 130.00 net
_ _ _ _ _ _ _ _ _ _ _ _ _ BE AM - - - - - - - - - - - - - -
DECEMBER, 1953
BEAM INSTRUME NTS CORPORATION
u. S. Agents
350 FIFTH AVEN UE. NEW YORK, N. Y.
53
HYCOR
T YP E 4201
~ P R OGRAM ' EQUALIZ_- ~R
•
•
•
•
•
•
LOW HUM PICKUP t hrough the use of to ro id coils.
__.
Switch contact noises are inaudible even 0 1 mic.ro p ho ne leve ls;:::_
Low .jf,:equency equalization pe a ked '-al 40 cy'cle,s :"<:T!'~.~' -00 ' cycles in 2 db sleps up to 12 db .
High ·.frequencY equalization peake d a t 3 kC;f- 5'1<c~~and 10 kc in 2 db sle ps up 10 12 d b.
Low "!~~.9uency attenuation in 2 db steps a t 10~ ~~~a n d~has a maximum a tte nuation of 16 db .
Higl1'" fre9 uency attenuation in 2 d b ste ps at .._Q:'.~f.::and has a ma ximu m a ttenuatio n of 16 db .
~_.
"G!Hl!!ral S pe.cificatwns . . .
Standard ra ck-::'p a nel, slotted, 3W' high . Ma xim um de pt h 7W '.
BridgefL:I~':~ nsta n t impedance.
5001~600 ohms, in ·aut.
14 i:lb"'constant.
),,~w~~and high frequency se lector switches. Low and high frequency
trois in 2 db steps, in·out key.
_=; ~ ,,,raved panel, medium g ray ba ked enamel. (Special colors a nd
hes upon request.)
Send for Bulletin E
.DIMENSIONS:
~_. - CIRCUIT:
-::::: IMPEDANCE :
-:==:;lflISERTIIOIII' LOSS :
..
Representatives :
~..
~.
,
~ ",
.... ,'
of California
1 1 423 VA N":'0
NORTH HOLLYwt),
- STREET
ALI F.
BEEBE ASSOCIATES
5707 W . Lake St., Chicago, Illinois
BURLINCAME ASSOCIATES
103 Lafayette St.. New York Cit y
HARRISON J. BLIND
1516 Cord St .• Indianapolis 24. Ind.
-Solid. %~. thick. d im ension ally stable d ie
stock-cork latex cov e rinq
-non-b ell-like-neve r n eed s
lifting from w ell.
· CONSTANT SPEEDS
33.33. 45. 78.26 " Floating Idler" decouples
motor v ib ration from chassis sturd y, m icro·
balanced 4·pole induction motor on isolatioD
m o untings , care fully positione d for minimum hum.
Complex mechanisms a re eliminated in
th e NEW DO. R DR-1 2, the mos t s ignificant advance in turn table d e sign in 17
y e ars!
A n e w mag nit ude in low n oise le vel
a n d 1M dis tor tion due to m in imu m flutter
and vibration . _ . all p'arts eas ily
THE D & R
DR-12, a completely
new
design, allowing
improvements in
basic enqineerinq
never b efore possible!
Turntable only, with
standard panel mountin g • • .
$78.50
m ahogany box mountinq, e xtra
accessible, ma chine d to p rofession a l tole rance . . . especially de signed for the
m ore e xact regu irements of LP record
reproduction.
Acclaime d o y HI-FI e xperts and broadcaste rs a s the ide al combination of laboratory quality and moderate cost.
See the NEW DR-12 at le ading HI-FI dealers. or write fo r
des crip tive lite rature to . . . Audio Equipme nt DivisioD,
D & It. Ltd •• 402. E. Gutierrez St.. Santa Barbara. California
(R I) ' A t low fr equencies, Xc becomes
appreciable and a smaller portion of the
signal is available across R I . F or this
reason, a minimum load resistance of 3
megs is reco mmended fo r flat LabS down
to the lowest freq uency permitted by
tone are resonance.
Output at 1000 cps is 0.6 volt as
measured on th e R CA 12-5-49 V frequency test record. This r ecord r epresents the normal reference level fo r
microg roove recording. Fig'ltre 8 illustrates an actual response curve taken on
th e R CA reco rd.
Di stortion tests, using the Cook "N-A
Beam" test record indicate inter-modulation well below 2 per cent throughout
the entire recorded range. This method
is specified as it is easily duplicated and
evaluated by anyone without spec ial
equi pment.
E xtensive "A-B" listening tests have
corroborated all laboratory data and
demonstrated the improved performance
of the Model 84 U ltra L inear ceramic
cartridge.
VIBRAliON REDUCT-ION
(from page 25 )
ex pected, the vibrations dealt with are
those which occur at low frequencies.
The various equations do not take resonance into account but explain the phenomenon below resonance where dynamic and static deflections are nearly
the same. If one remembers that the
natural r esonant frequency of a solid
varies inversely with its weight and
directly with its stiffness, it is obvious
to conclude tl1at constructing panels as
rig idly as possible helps to r aise the
resonant fr equency to a region where
damping is more eas ily accomplished
by the use of padding and sound absorbing mater ials. This is easily demonstrated with the test set up illustrated
in Fig . 6. Connected in this manner, the
oscilloscope indicates the power factor
of , the load. A t resonance, the power
factor is unity and a straight line appears on tl1e scope. P ower factors at
non-resonant frequencies show up as
• loops of various widths. If the oscillator
is adjusted until a panel resonance is detected, it may be observed that the application of hand pressure to the vibrating panel will cause the stra ight- line to
open up into a loop, and by returning the
osciIlator it will be found that the r esonant f requency occurs at a higher fre-
@
VUO
lO
OSCILLATOR
~
j-ov
'j' G
-
H
G'j'
1 1
g~
~?
T O TEST S:E AKER
Fig. 6. Test ci rcuit used fo r ch eckin g imped ance and reson ant frequency of speaker in
e nclosure.
54
AUDIO ENGINEERING
•
DECEMBER, 1953
quency. During this test, of course, one
must not pick an oscillator frequency
which corresponds with the natural
acoustical resonance of the cabinet. In
this case applying pressure to the panels
will have little effect.
HI-FI POWER SUPPLY
"TAB"
THATS A Buy
SAMPLE PROBLEM
DIAMON DS AN " LP'S"
BEST FRIEND
Consider the bass r eflex cabinet shown
at (A) in Figure 3. Assume that it is
constructed of I-in. plywood (VR -in.
dressed), and that all corners are joi ned
in such a manner that the panels a re rigidly
supported.
The top panel will exhibit the smallest
maximum deflections because it is the
smallest panel. The defl ection of unit beam
1 is given by equation (6).
s upply . C hol{c & caJ)3citor fil-
tered, 3 % - -reg ulated, -outout
420 V / 250 MA. D. C . . 6 1nmon t; A,e. 12.6 vet/6 amp
or two 6 . 3 V comlllon at 6
amp eac h . Filame nt- A.C . 5
V / 6 amp. Size
H / 5" W.
"TAB"
Protect your records that's "sound" advice . Mail
your cartridge, we r eplace sty li at cost of
QUALITY RECORD
CABINET
diamond on ly .
A. Diamond single styli for Ast atic, Philco,
Magn avox, RCA, Shure & W ebst er cartridges
$12. 00
B. Diamond LOOll LP & sapphire (003) 78
for G.E. RPX047 , 050, 051 cartr idge
$14.00
Sam e except diamonds (,00 1 ) &
LP' s play best when
ve rt ical at r est. Com pact, smartly sl.yled,
selected mahogany veneer . Made by master
furniture
craftsman.
Divided in four scc-
(003 )
$24. 00
tions. Holds 120 r ecords . H 25" x W 20"
D I S ", W gt. 25
Ibs .
C . Diamond single (, 001) or (.003) for G.E.
RPX040, 041, 042, 046 .. ... . $ 12. 00
Prices are prepaid to your door*
KV
X
ARE YOU A PILE-IT?
Zmax = 384 J
Record Collectors
In this case I , the moment of inertia, from
Table II is .049 and
K 13'
Zmaa; 384 x .049 = 117 K
=
Since unit beams chosen from the bottom
or sides would have identical dimensions,
the maximum deflection of th ese panels
would be the same as the top panel.
The maximum deflection of the front
panel is determined by considering unit
be<!m 2. In this case
K 26'
Zmax = 384 x .049 = 936 K
The deflection of the back panel ·is similar.
Because of its shape, the area of the front
panel below the port (6 x 26 in.) exhibits
a deflection which is characteristic of unit
beam 3, which is a cantilever. The deflection is given by
K V
K 6'
Zmax= 8 i = 8x .049 =551 K
I,n determining the bradng required to
reduce front and back panel vibration to a
value consistent with the top panel, consider the load as the area defined by panel
"P" in (B). Its width is roughly 10 inches.
Since a unit beam has a width of 1 inch,
and the deflection is 936/117 or roughly
8 times as severe as for unit beam 1, th e
required stiffness of the brace beam is
8 x 10 or 80 times that of unit beam 2. From
T able II it may be seen that the best brace
would be a 1 x 4. The stiffness factor eq uals
3.49/.049, or 71, which is close enough to
the desired value. Actually it may be more
desirable to use a 2 x 3 as shown at (B)
with a stiffness factor of 245/.049, or 50, in
some instances where a brace 1 x 4 would
adver sely affect the acoustics of the cabinet. Since such effects are generally not
serious near the back of the cabinet, it is
recommended that 2 x 4's be used. H ere the
stiffness fac tor is 6.45;'049, or 132. If three
braces are used as shown at (C) , each will
support approximately one fourth of the
total load. This makes the stiffness facto r
33K
equal to 8 x -4- or 66 K. If the above calculations are applied successively to the
braced panel shown at (C), two defl ections
are obtained.
Since both sub-panels and braces vibrate
in unison, the final deflection is obtained by
adding the two and the sum will be found
to equal 117 K.
Because of th e short length of unit beam
3, sub-panel Q (A of Fig. 3) requires less
bracing than sub-panel P. Just to be on the
safe side however, a 2 x 3 should be installed as shown.
The reader will note that all the braces
used add up to a total volume of 0 cu. ft.
which is about 1/12 of the cabinet volume.
AUDIO ENGINEERING
Top s rOT hi -fi sou nd, Wi lli am-
so n or similar amplifiers. New
"sola" cOI1stant volt.age power
•
Yo ur Pile of LP's
Need Not Be
Sensational R ecord Cabinet.
" Grow As Yo u Go"
DC ON FILAMENTS
A mu st for " super hi -fi" .
No hum level wi th DC in
the filament supply. Bridge
se lenium r ectifier 600 0 mfd
brute filt er 6.3 or 12. 6
volts DC / 2 amp fo r preamp
or ampUfier.
" TAB" model 2DCF
$12.98
8ame 6.3 or 12.6 V / 4 amp
supply "TAB" mode l 4DCF
$20.98
Each section h olds 150 rec~
ords W 251/4" X D 141/2 " X
H 17 1/2" in Quality fini sh
ma hogany, walnut or blonde .
Model 700 Base .. $25.45
Mod e l 701 F i ller .. $24.45
Model 7B Top . . . . $ 4.75
NEW UNIVERSAL
FM TUNER
"TAB" WILL BUY, SELL
AND SWAP AS WELL
WE SELL NEW & USED EQUIPMENTALL ITEMS ARE SOLD ON MONEY
BACK GUARANTEE. WE BUILD TO
YOUR SPECIFICATIONS AND RECONDITION YOUR PRESENT EQUIPMENT.
ALL EQUIPMENT "TAB" ADVERTISES
ON THIS PAGE IS BRAND NEW. ·
Automatic thermal drift compensation . B uilt in power supply . Higain plus selectivity. Out performs
higher priced 10 or 12 tube sets .
Handsome
mahoga ny
cabinet,
L 11 1/2" X W 7 " x D 7 "
711C
Model
711
. . ... .. . $44.75
less
cabinet $39.95
ENJOY RECORDS & FM. THE
MODEL 3AB SUPERIOR PORTABLE WITH ADDED OUTLET TO
WORK WITH 711C HI-FI TUNER
PREPAID " . . .. .. .. .. $130.00
71lC TUNER WITH COLUMBIA
MODEL 205M. PREPAID" "TAB"
SPECIAL .. . . . . .
$180. 00
PORTABLE AUTOMA TIC PHONOGRAPH
Excellent reproduction, hi-fi conso le Quality, two heavy
duty 6" speakers, 8 watt , 4 tube, amplifier, separate ba~e
& treble controls, VM-9S1 chan ger & 80noto no flll)
cartridge, plays 7, 10, 12" & interm ixes 10 & 12" r ec ords . B eautiful suntan lea there tte fini sh .
181/4" D / 161/ 2" W / 8 3/4" H Shp . wt. 30 Jbs.
R eg. $109.95"TAB" specia l prepaid to yo ur doorMod e l 3A6 hi-fi portable phonograph prepaid . $ 89.95
COLUMBIA 360
A ROOMFUL OF SOUND IN A COMPACT HI-FI
PACKAGE. 3 SPEED AUTOMATIC CHANGER, 2
SPEAKERS , TONE CONTROL , COMPENSATED VOLUME C ONTROL & L ATEST DES I GN FEATURES.
SET IN BEAUTIFUL MAHOGANY CABINET.
PREPAID '10 YOUR DOOR"
Model 205M table mode l .. . . . . . . . .. ... $139.50
Mode l 207M consolcltc . . . . . . . . . . . . . . . . $169.50
Mode l 107M HXD" extra speaker & clock .. $ 24.95
BUY RICHT WITH " TAB "
THAT'S SOUND HI-FI ADVICE
" LYNNE " 800
HI-FI AMPLIFIER AND
PREAMP WITH EQUALIZATION
20-20,000 cps within 1 db at
3 watts & 11/2 % harmonic distortion at 8 watts. Six cont rols,
and all the featu res of $65.00
amplifiers, plus added "Lynnc"
cxtras. 11" Vv' x 5" H X 91/2" D, 6 1/ 2 Ibs.
Mode l 800 "TAB" 81)ecial . . . . . . . . . . . . . . $37 . 50
"TAB" HIGH FIDELITY PACKAGE
EXECUTIVE SPEED-
"T A B
------
IHAT'S
BUY
Dept. A-E
DECEM~ER,
BUY RIGHT! " TAB" WRITE ! PRICED RiGHT
WE SHIP THROUGHOUT THE WORLD.
WAY KIT
Gromm es SOPG3
$ 53.90 A must for hi-fi's who roll
their own . Combo holster,
Garra rd . Re80
$ 45. 08 asst .
chrom e
vanadium
speed (lrill bits, 1/4" elecG.E . RPXOSO
$
8 . 20 t ric dr Ill w / Jacobs chuck
G. E. A1400
& attachments for po lish$ 39.95 ing, sanding, buffing, U L
31)pvd., polis h ed chromium
Universa l 711
FM .. $ 39.95 fi nish. In heavy vinyl
T ot l l
. $ 187 .08 pla stic hol ster . prepai d ·
Mode l Al000 executivo
" Tl\B" Spec ial
$162.00 kit •• ..• . . . . $24.00
•
H eadquarters lea d ing hi-fi manufacturers. Before buying
cons ult "TAB" for your audio needs. Ou tli ne your problems and we will hclp in se lect ing, trading, exchangi ng,
or buying hi-fi eq uipm ent. Write und be convinced. We
se ll all the loading a udio ma nufacturers. From styll, pickuP's, tu ner s, t urntables , preamp, ~mp1ificr s, speakers,
cabinets, co mb inations & record furmturc .
1953
.
/I
lHAT'S
BUY
•
11 1 LIBERTY STREET, NEW YORK 6. N. Y_, U.S.A.
" PREPAID
WITHIN
CONTINENTAL LIMITS
OF THE 48 STATES.
CHECK WITH ORDER
OR 25 % DEPOSIT.
PH . : RECTOR 2-6245
55
cE?~ ;~-:-
MAGNETIC TRANSFER
(from page 20)
you can hfjJr
permanently magnetic condition. Increasing the number of lines of flux per
unit area of the magnetized turn allows
more lines of fiuJC to be induced into the
unmagnetized turns for the same contacting areas. Thus the initially unmagnetized turns now have more lines of
flux to be cut by the coil of the playback head. This in turn subsequently
allows for a greater playback or transfer
output. The fact that the signal on the
originally unrecorded turns of wire appears as a series of bursts when viewed
on an oscilliscope screen probably is depE.ndent upon the manner in which the
turns of wire lie against each other.
That is, this is probably an effect of
geometry.
The decrease in amplitude of the trans-
~ /iff/rimoro_.
ThQ
Sample
No.
ClARf<§A.N RV201
17
magnetic pickup with sapphire
stylus: net price ..... $15.00
.004 in .
Discover for yourself the truly exciting
difference a Clarks tan Magnetic Pickup
gives to your music enjoyment~a difference you can hear. If' your ear is tun ed
to the fines t in sound, you'll want the
vivid, life-like reproduction obtainable
only with the Clarkstan RV 201 Variable
Reluctance Pickup-over 15,000 cycles
of low distortion, flat response is yours.
Ask your hi-fi sound jobber to let you
hear this difference. Then you, too, will
join the growing thousands of discriminatillg music lovers who buy only the
best in pickups-the Clarks tan RV 201.
2
.004 in .
3
Type- Magnetic, variable reluctance
w ith removable stylus.
Armature-Stylus is armature; weight
31 mg (.031 g)
Response - Flat to over 15,000 cps.
Stylus - Sapphire wi th standard .003"
radius ball point or .0012" as desired.
Styli are interchangeable and replaceable. Other sizes available.
Needle Force-5 to 7 g for LP microgroove; as low as 9 g for standard records.
Output - 60 mv at 1000 cps with lateral
displacement of .001".
Recommended Termination - High
imp e dance.
Electrical Characteristics - Inductance
350 milihenries at 1000 cps; 'Q~ 1.05;
DC Resistance 1450 ohms.
Mounting -Standard holes Jr' b etween
centers, 3-48 screws.
Weight- 30 grams.
.004 in .
4
.004 in.
5
.004 in .
(Another
source)
6
.0036 in .
SEE YOUR HI·FI SOUND JOBBER OR WRITE FACTORY
r-----------------,
56
22
31
32
32.5
32
31.5
31
20.5
30
3 1.5
32
31
30
28.5
27
12-17
17
a sound investment •••
I Pacific Transducer Corp., Dept, E 123
I 11921 West Pica Blvd . • los Angeles 64, California
S,end me free literature on the
I o Clarkstan
RY 201 Magnetic Pickup.
I
I NAME
I
i ADDRESS
L
________________
I_
CITY
Transfer
1000-cps
output
I
I
I
I
I
I
I
I
7
.0036 in .
31.5
32
32
31
31.5
18
24
31.5
32
31
26
23
18
25
32
32
31.5
31.5
30
24
30.5
32
32
31.5
30
30
22
28
31.5 .
32
31.5
30.5
29.5
fer signal as the distance between the
magnetized and unmagnetized porJions
of wire increased probably came about
from the fact that the actual magnetiz<J.tion of one turn of wire by the next
was an inefficient process. That is, there
was always a magnetic loss and consequently the actual transfer of magnetism became less and less the further
along the unrecorded wire one went.
This continued until no signal was left
on the wire.
The ri se of the curves of transfer vs.
increasing recording current was believed based on the fact that as the current was raised, more lines of flux were
induced in the wire and consequently
into the unmagnetized turns and therefore, was the cause of increased trans-
TABLE
Transfer
- 25
- 25
- 4
+ 12
+ 16
+ 8
+ 9
+ 3
-21
-16
- 4
0
- 4
.,. 15
- 16
- 20
-2 1
-25
-15
- 10
- 6.5
-12
- 18
- 25
-22
- 3
- 2
- 6
- 21
- 22
- 25 .5
- 24
+ 1
+ 8
0
- 7
- 11
- 23
- 12
+ 8
+ 10
- 8
- 10
- 12
- 22
-20
- 6
+ 6
0
- 13
-20
Recording
Current- rna
.47
.70
1.30
2.00
10.00
30.00
50.00
80.00
.47
.70
,.1.30
5.00
10.00
30.00
50.00
85.00
.47
.70
2.0
5 .0
10.00
50.00
85.00
.47
.70
2.0
5.0
10.00
50.00
85 .00
.47
.70
2.0
5 .0
10.0
20 .0
85.0
.47
.70
2 .0
5.0
10.0
50 .0
85.0
.47
.70
2.0
5 .0
10.0
50
8 5.0
He = 320
B, = 2500
He = 260
B,.= 1900
(max)
He = 440
B,. = 1080
(max)
AUDIO ENGINEERING
He = 250
B,. = 1480
He = 230
B, = 2800
He = 280
B,. = 2600
He = 320
B,. = 2300
•
DECEMBER, 1953
fer. The fact that the curve lev.el.ed off
and decreased was probably a sclf-d~­
magnetization effect of the tiny magnetized magnets making up the wire. As
the recording current increased, the
magnetic fields- of . th~se small magnets
affected each other, i.e., demagnetized
each other, to a greater anQ greater extent. This could account for the transfer
decrease observed.
The reason for the higher maximum
transfer value for .004-in. wire as compared to .0036-in. wire of the same
remanence is believed to be based upon
the following explanation : The number
of lines of flux for a larger sized wire
is greater than for a wire of finer diameter, both wires having the same B" .
That is, transfer appears to be dependent not on the number of flux lines per
unit area but rather on the total number
of lines for the area involved. These
would inct:ease as the:- area increased
eyen though the B .. remained the same.
Conclusion
It was learned -that the remanence
,and coersive force of a stainless steel
recording wire had a definite influence
upon the transfer. characteristics of the
wire. Increasing remanence c a use d
higher transfer values for a given recording current. Increasing coersive
force necessitated higher recording currents in order to attain the maximum
transfer value of the wire. In addition,
it was noted that the maximum transfer
value attained was lower with wires of
finer diameter, indicating the direction
to be followed to reduce transfer.
The author wishes to thank the Wilbur B. Driver Co. for their kind permission to publish this article.
SOUND HANDBOOK
(from poage 28)
Probably the most common "bug" in
individually built or design model audio
amplifiers of high gain is hum. Modern
low-output pickups and tape reproducing
heads require amplifiers of such gain
tHat several potential sources of hum,
which might not have had any significant effect in an amplifier of lower gain,
must be carefully eliminated.
occasionally the oscillation is at so low
a frequency that it can be observed as
a very slow oscillatory motion of the
speaker cone, sometimes referred to as
"breathing."
The standard cure for such regeneration is the use of added R-C sections
of filtering, called de~coupling networks,
as illustrated in (B) of Fig . 15-4. Decoupling Retworks improve the anti-hum
effectiveness of the filter, but their primary purpose is to prevent alternate
stages from having a common load
impedance. No more than two successive
stages of amplification can be fed from
the same B supply point without danger
of regeneration. Phase-splitters that use
two tubes must be considered as two
stages, and the preceding amplifier
should be fed from a de-coupled point.
Hum Level
Hu m and Noise
We may now turn to a more detailed
consideration of the way in which noise
is introduced into the signal channel,
and of ways to combat it. Although the
additional components may be periodic
rather than composed of random frequencies, they are classified as noise because of their irritating nature, in accordance with the definition of noise
of the American Standards Association.
Noise can be readily generated by defective tubes, resistors, capacitors, lead
connections, and so on. We will confine
ourselves here to discussing noise inherent in original design rather than
that resulting from defective parts.
Three types of noise will be considered:
hum, "microphonic" disturbances, and
thermal noise. Two other typeS of noise
which the signal may pick up are record
surface scratch and turntable rumble.
These are associated with mechanical
activities of the pickup and of the phonograph motor rather than with electronic
flow in the amplifier, and are referred
to in appropriate chapters.
AUDIO ENGINEERING
•
o
The amount of hum at the output of
an audio amplifier, or at some point
within the amplifier, is most often desoribed in terms of the decibel relationship between the hum 'v pltage or power
and the maximum signal at that point.
This procedure is followed in recognition o'f the fact that the tolerable amount
of hum depends upon its relative level
in the total range of amplitudes being
'reproduced. The absolute amount of
hum produced by a public address system in a large hall, for example, may be
considerably greater than the hum produced by a low-power living room amplifier, but the amount of noticeable hum
of the two may be the same.
A relative rating of this type, however, must be used with care. There is
a certain amount of amplifier hum output which is introduced above the volume control and which therefore remains constant regardless of the volume
control setting and the level of reproduction . This hum will have a higher ratio
to the signal when soft passages are being reproduced. It may leap into prominence if the loudspeaker system is especially efficient and if the maximum
power capacity of the amplifier, upon
which the hum rating is based, is far in
excess of the power used. In the latter
case i't is important to know the relationship of the hum level to the maximum electrical output actually in use
rather than to the output capabilities of
the amplifier. The absolute minimum
DECEM BER, 1953
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57
value of the output hum of an amplifier,
in microwatts, may therefore be a useful
rating to have in addition to the relative rating in db below maximum output.
The Federal Communications Commission regulations permit a total hum
and noise level for AM broadcast stations, exclusive of microphone and studio noises, of SO db below 100 per cent
modulation (representing maximum
audio level) at frequencies between 150
and 5,000 cps, and 40 db down from the
maximum signal outside of this frequency range. FM stations are required
to keep their hum noise level 60 db below the maximum amplitude of passages
being broadcast. Modern amplifiers
should, and commercial amplifiers usually do meet or exceed the FM requirements.
EW
~
DC·AC CONVERTER
by
(~ma~l]
If a lO-watt amplifier has 10 micro-
watts of hum output the signal-to-hum
ratio is 10/ 00001, or a million to one.
Converting to db by the power form ula:
Delivers MORE Power
for PROFESSIONAL Use
db
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log 1,00~,000
=60
we find the hum level to be 60 db below
10 watts.
It would be extremely difficult to
measure 10 microwatts in the low-impedance secondary of an output transformer, as the voltage involved is minute.
The voltage across the relatively highimpedance primary ' winding of the output
transformer is much greater, and may
be measured with a low-scale a.c. voltmeter or calibrated oscilloscope of known
volts/ inch sensitivity. (If the latter is
used, peak-to-peak indications are employed directly; sensitivity is normally
rated in sine-wave r.m.s volts. )
The ' secondary is connected to the
proper value of resistive load rather than
to the loudspeaker, in order that the impedance rating of the primary, which
is a reflected value, be accurate. The
square of the voltage across the primary,
divided by the primary impedance, will
then give the power of the hum output.
For example, 0.2 volts across a 4,000' ohm secondary indicates a power of 10
microwatts.
•
The hum level of voltage amplifiers is
calculated in the same way, except that
the dblvoltage formula [db = 20 log
(E,/E.) 1 is used.
1'hese latest-of-all Carter DC to AC . Converters are specially engineered for professional and commercial applications requiring a high capacity source of 60 cycles
AC from a DC power supply. Operates
from storage batteries or from DC line
voltage. Three "Custom" models, delivering 300, 400, or 500 watts 115 or 220 V. A C.
Wide range of input voltage, 12, 24, 32, 64,
110 or 230 .'v. bc. Unequalled capacit y f or
oper ating professional record ing, sound
movie equipment and large screen TV receivers. Avai
with or without manual
I
=10 log ~~ =10
I
Examination 'of the Fletcher-Munson
curve will reveal the fact that 60-cps
hum, at the usual order of intensity
that might be expected of such a disturbance, requires an intensity level at
least 10 db higher than that of 120-cps
hum to be heard with the same loudness .
Suppression of hum at harmonic frequencies of the line is therefore especially important. One of the best meth ods (and certainly the simplest) for
checking final noise level in a complete
home reproducing system is a listening
test, which automatically takes into consideration speaker efficien~y, hum frequency, and acoustical conditions under
which the reproducing system will perform. W ith the volume contl"Ol set for
high but usable volume and no program
material present, an exceedingly low
hum level would be represented by little
or no audible sound in a quiet room
at a distance of two or three feet from
the loudspeaker.
B+
------------ -,,
{:. -i:.
,
~
POWE R SUPPLY
RIPPLE VOLTAG E
Fig . 15-5. Applicat ion of power supply ri pple
vol t ag e to t he voltage divide r consist ing of
plate resistor a s an uppe r a rm, and t he pa rallel
combina t ion of tube and grid ~esisto r as
lower a rm.
Sources of Hum
The sources of hum in an audio amplifier may be divided into four main
categories :
1. Insufficiently filtered B supply, the
common garden variety of hum.
2. Inductive or capacitive p ick-up, by
some point along the signal channel,
from components or leads carrying a.c.
or pulsating d.c.
3. Coupling from a.c. heaters.
4. Differences of a.c. potential along
the chassis or between differ ent chassis.
Hum is also introduced into the signal
in d. circu its, in which case it is cililed
"modulation" or "tunable" hum.
B+ Filtering
.r,..
Alternating ripple in the plate supply
of a resistance-coupled stage is applied
to the voltage divider formed by the
load resistor and tube impedance and is
coupled to the grid of the f01l0wing
stage, as illustrated in Fig. 15- 5. It is
sometimes thought that B+ hum is int roduced by plate modulation of the electron stream in the tube being supplied,
but vacuum tubes are relatively insensitive to plate voltage changes, and the
fractional r ipple voltages involved cannot have an appreciable effect on current
flow. Thus the tube does not have to be
in its socket for ripple in its plate
supply to be introduced into the signal.
As a matter of fact less plate supply
hum will be introduced with the tube in
place than without it.
The voltage division of plate-supply
ripple will be most favorable to a low
hum level when the tube bas low plate
resistance, when the circuit uses a high
value of plate resistor, and when t he
grid resistor fo llowing, which is effectively in parallel with the plate resistance of the tube, is low in value. Pentodes are more susceptible to B+ ripple
than triodes because of the fact that their
plate resistance is higher, and because
electron flow in the tube may be screen
modulated by the ripple voltage. The
screen requires a more highly filtered
supply than the plate.
When there is doubt as to whether
hum is due to inadequate filtering an
ext ra res istance-capacitance section may
be temporarily connected in series between the suspected stage and the B+
line. For the output stage the test circuit would have to be an inductancecapacitance section.
AUDIO ENGINEERING
•
DECEMBER, 1953
TIRED MAN'S CABINET
(f1'OIII
gieettUtt
page 27)
I t goes without saying th a t the work
has been a great deal of enjoyment. At
present the biggest r emaining problem is the elimina tion of a small amount
of hum which seems to ori g ina te in th e
output stages of the tuner. It has recently been written that no tuner on th e
market possesses all th e desira ble qualities of quietness and freedom of hum
that could be found in a good high fidelity amplifi er. Some day perhaps
someone else may be confronted with
this problem and will wri te a story on
ways a nd means fo r substituting the two
6J5 Ohltput tubes with something more
quiet. This again fa lls into the t echnical
fi eld and the writer must wait until
someone else more quali fied is s ufficiently annoyed with this problem that
he publishes something about it.
AMPLIFIER KIT'
FE
A'TU RES
• Practically distD~tionless. Harmonic and liJlermodulation dlslortion
both 16$s Ihan Dno hall 011 % at 5 watts.
• Frequency response ± I db Irom 10 cycles to 100 kilocycles.
• Allee lansing PEERLESS or ACROSOUND Iranslormers available.
• el'lrslWllllomson Iype AmpDDer supplied witH .malcbing' preampfi fier.
When selecting an amplifier for the heart of a fine high.4 fidelity audio syslem. invesli~ate the outstandin~advantages
offered by the Heathkit Wilhamson type Amphfier. ·Here is
an amplifier that meets every high-fideli.ty audio requiremeJ1t .and makes listening to recorded music a thrillin~ ne",
experience through naturally clear. lifelike reproduchon qf
sound at all lonal levels. Wide acceptance of the Heathkit
Williamson type Amplifier by the most critical purchasers
clearly demonstrates that high-'fidelity can be coupled wi\h',
low cost. For factual 'informalion regarding the tleat~kit
Williamson type Amplifier. consult "CONSUMERS RE- ·
SEARCH ANNUAL CUMULATIVE BULLETIN 1952~53. "
This outstanding amplifier is offered with the optional
CROSOUND output transformer or the PEER,
ansformer, ACROSOUND features ULTRA, which is tlie exclusive development of the
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choice of· eit her lIte extended power circuitry, now enjoying
cur relit popularity. or all of Ihe advantages of Ihe original
Williamson type circuit.
. ,
manual has been simplified to the point
• The.cons
lete novice can successfully construct
dlffh;ulty. Write for a free catalogue, ~ •
specificallo-ns and schematics 01 the
type Amplifier.
RECORDS
W-2 Amplifier Kit (Inci . Matn Amplifier
with Peerless Output Transform-
(69 50
(49 75
e r, Power Supply and \VA-P I
Preamplifi er Kit) Shipping of
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only.
W·3 Amplifier Kit UncI. Main Amplifier
(69 50
(49
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$19 75
with A crosound Output Transfonner, Power Supply and WAPl Preamplifier Kit) Shipping .,
Weight 39 lhs. Shipped express
•
only,
W-3M Amplifier Kit UncI. Main Amplifier
with A crosound Output Trans press only_
(from page 40)
WA-Pl
Pre-amplifier'
Weig ht 7
l hs.
or parcel post,
be magnified, and a slight rocking back and
forth gives an extremely accurate "geared
down" adjustment to exactitude. It took a
brain to think that one up.
The gadget wasn't designed directly for
stylus examining, of course, and there is a
bi t of trouble sometimes in operating on
your needles, since styli are not ordinarily
mounted on flat planes. But I've managed
usually to rest the device on some handy
pa rt of the cartridge and so locate the j ewe!
in reasonably steady focus. It is definitely
possible with this "mike" to see stylus
damage, though . the magnification is about
the minimum one 'can get away with.
My "Vista" came direct from Japan (at
an absurdly low price there) but I've seen
it advertised in the U.S. and you'll probably
find it in the ads' that feature such imports.
Sold under various trade names.
Maximilian Weil's Stylus-Disc is a somewhat controversial offering, it seems, that
can easily involve one in the kind of mathematics that we used to fight about in the
first days of the microgroove-remember?
(Who has the most distortion at what
diameter?) I'll steer clear of it-I've given
the disc a good trial on all the styli I could
find hanging around, checked against both
the sound and the sight, via the "Vista,"
previously described.
The Stylus-Disc, from Audax, is of a
soft material, cut with bands of eccentric
grooves that swing the pickup from side
to side heavily. In order to approximate
th e friction of a musical groove, they are
modulated with a fixed high pitched tone,
of about 3000 cps. You're supposed to play
the bands with your pickup, ex tra-weighted
with a quarter dollar on the end, and observe what happens. "Gray" eff ects indicate stylus troubl e. The company warns
that the disc is sensitive and detects incipent damage before it actually is risky.
Well, I began with incipent guilt, expecting to find most of my much-used points
in unmentionable condition. No such thing!
AUDIO ENGINEERING
_
W-2M Amplifier Kit (Jnel. M a in Amplifier
with P eerl ess Outpu t Transformer
and Power Supp l y), Shipping .J
Weight 29 lbs . ShiPPed express
_
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•
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·
OF FULL FREQUENCY RECORDING.
The
Ii'RCHILO
SERIES 215
.HIGH-COMPLIANCE
Diamond Cartridge
This amazing new cartridge, a radical dep·arture from
cartridge design, achieves near-zero mass of stylus assembly. The
result is HIGH COMPLIANCE - accurate, distortion-free tracking which reproduces without listening fatigue the full, rich tonal
qualities of th e most sensitive recordings.
"Amazed at new purity of sound . .. darity .. ,distinctness of
orchestral texture.,. which all add up to something fabulously
beautiful!" says B.. H. Haggin, noted Record Reviewer.
~
rl/P/
~f.!I!l'l'U RECORDINO:
InfU,"/~ /I. EqUIPMENT:
RDER
FROM YOUR
,tt§
~ :. :
AUDI7 DEAL~R
or mat coupon or
==n
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DECEMBER, 1953
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Manufacturers of the World's Finest Professional Sound Equipment
1 Without oblIgation, please mail FREE folder. "HI-FI FACTS •
I
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59
3 OUTstanding
DYNAMIC
MICROPHONES
D-20
Models D-12 and D-20 are cardioid t ype un idirectional moving
coi l dynamic m icrophones with s ingle diap hragm and a phaseshifting network . Its f requency range is extended by new
patented principles. The cardioid pick-up patte rn provides an
easy solution to the feedback problem and eliminates aud ience
and background noise . Both models are provided with a wind
screen to permit quiet outdoor operation. The units are springsuspended in si ~ .the m icrophone case.
D-12 SP ECIFICATIONS
Frequency range . . .. . ... 40 to 12.000 cps
Frequency response ........ ± 4 db max.
Discrimination between f ront
D- 12
and rear at
a ll frequencies ...... Approx imately 15 db
D-20 SPECIFICATIONS
St udio Mode l
Freq uency raAge ...... 30 to 15 ,000 cps
Frequency response ... . .... ± 3 db max.
Discrimination between front and rear at a ll
freq uencies .. 15 db min. to app rox . 25 db
BOTH MODELS
Effective output level ........ - 50 dbm
( referred to a sound pressure of 10
dynEs/ cm')
Sensit ivity-60-ohm open circuit
0.14 mv / ~b
CONTROLLABLE-PATTERN MODEL
D- 36
Moder D-36 is a dyna mic stud io m icrophone
with remotely controlled directiona l characteristics. A selector unit is provided to
adjust a number of characteristics by turning the k nob on the sca le. A schematic
Point Pressure
rep resentation is given by ei ght different
patte rns. A new e ra in pick-up technique
starts. T he sound engineer can , from the
control room, se lect between two ca rdioid
Cont rol k nob
patterns in oppos ite d irection, or s ix other
indicates pattern
characteristics includ ing the omni- and bid ire ctly o n sc ale
directiona l patterns. Changes may be made
during program pick-Up so as to adjust the mic rophone to the reverberation of the individual studio, o r for such effects as varying t he
apparent dista nce of the art ist from the microphone.
D-36 SPECIFICATIONS
Frequency range 30- 15,000 cps. Frequency response ± 3 db max.
Effective output level .. - 50 dbm ( referred to a sound pressure
of 10 dynes/ cm') . Sensitivity-60-ohm open circuit, 0.14 mv/ ~b .
Out put level and sensitivity equiva le nt to D-12 and D- 20 so that
both models may be used together with operating ease.
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BRITISH TECHNICAL PUBLICATIONS
ANNOUNCI NG a r e\' ised (1953) edition of
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60
I didn't get any "gray" effect or any effect
at all for the first five or six tries. including an Audak diamond that I was sure
must be poohed out. By golly. I looked at
It with " Vista" and it looked OK too.
Check-negative. But I had to find at least
one bad needle. and couldn't, A n old GE
78 sapphire-nope. OK. 1\ still oldel' fixedstylus early GE cartridge? OK. A CAC.
much used .. OK. And "Vista" said yes. too.
This was too good to be true.
Enfin-I found a CQ Astatic with a di amond shaped sapphire point; that is, a
sharp triangle where the r ound ball should
have been. That should do it, and it did.
Not g ray, but shiny, however; it seemed to
polish the A udax grooves. Didn't matterI could see the change in their looks. Bad
point, by every test. (I broke it off. just to
end that experiment. An old Pfansti eh l
sapphire cartridge with a lop-sided flat
(via "Vist a" ) made a fine gray trace on
the Stylus-Disc. Check again. Mathematics
or no. the prognosis seemed fairly good.
thoug h by this time I'd just about used up
the available test grooves. both microgr oove and 78.
Aha! A diabolical idea. I pulled forth a
brand new. untouched crystal cartridge
with an ALL-GROOVE sapphire. What
would the Stylus-Disc do about that? ·1
am happy to report that the r es ults were
emphatic. The all-groove point, brand new.
produced a lovely. healthy band of dark
damage on the microgrooves. fully as bad
as the worst used point I'd tried! On the
78 side of the disc the same all-groove point
seemed to do OK. M oral : K eep away from
all all-grooves for your LP's and 45·s.
How about measuring stylus pressure?
That's another toug h problem fo r the home
user, thoug h the professional engineer and
the advanced amateur may well have the '
requisite tools. Most changer and arm and
cartridge makers blithely talk about adjusting stylus pressure with never a thought
as to how the poor dope at home is supposed to go about doing it. Baby's bath
scales won't help and not even a T)ostage
letter weigher is any good-not with our
present gram pressures.
Again. I've tried this and that home
point pressure device without much luck
so far. Note well that an excelfent new
solution for the home is the GE arm with
the 'built-in scale balance, a type of gadget
until now quite unavailable for ordinary
home u se. at lowish cost. But what to do
,,.ith some other arm-any oth er among
millions?
I've tried the Clarkstan pressure gauge
and must r eport a fundamental trouble
with all spring scales that operate from
underneath the pickup point. resting on the
turntable or on the hand. The spring is in
itself accurate enough; but its end, the
tiny cup into which you place the stylus
point. moves up and down in a cu.r ved
track, an arc. That m eans that either the
pickup or the supporting base must move
forwards and back as the stylus moves
up and down. If not. things tend to jam
and th e reading-at such tiny pressures as
a few g rams-can go way off. Of course
if you can nl ace the scale sidew ise to th e
pickup so that the arch is in li ne with the
a rm's swing. the trouble is gr eatly decr eased (though not r emoved since the
a rm's travel is also an a rc ) but in most
machines there isn't r oom for thi s so rt of
trial.
Weathers. the FM pickup firm. has a
new stylus pressure gauge that hangs from
above, and r emoves this trouble neatly. allowing fo r considerably more accurate
r eadings, as far as I've been able to observe. No springs-a system of simple
AUDIO ENGINEERING
•
DECEMBER, 1953
levers and a circular turning weight gives
readings from I to 10 grams with hir
exactitude. You hook the bottom under the
pickup and lift the whole works, by a ring,
slipped over your finger; take the reading
when the music stops playing or as the
point loses contact. Basically a sound idea
and I recommend it, or similar devices of
the sort, when and if. But , I've a few annoyances to air, of the minor-irritation
sort, in the hopes that Weathers will make
changes.
First, the two little levers slip over pins
to assemble the gadget. Fine-but every
time you put it down, and every other instant in between, the things fall off again.
E xtremely exasperating, and the levers
will be lost behind the radiator or inside
your amplifier in a day or so if I know
most people's habits. The levers should be
fixed, or at least shouldn't fall off in every
breeze! Secondly, the thing is right-handed.
HEAR the difference, SEE the difference I'm lefty. Got to break your neck or c1iJ'11b
out the window and look in, to read it.
in the
model 1826 Why not print both sides. (One side reads
more exactly, but even so . . . . ) I'm also
a bit suspicious of the friction at the top
u'ltra-fidelity ensemble
of the little indicator arc; it's at a crucial
The proof of unprecedented
point.
All in the spirit of better Audio, etc.,
'"P~;""Y
0 ' ,h, "'W "U~ND
•
0 0 @ o
Ultra-Fidelity Ensemble is in
and I recommend the gadget for those
its unmatched performance.
That proof awaits you now at • who would Know the Worst as to their
J'
your Hi-Fi dealer. The Master own pickups' pressure. Final note: Be
sure to hook the Weathers gauge directly
,
Amplifier is of matchless
at the stylus point spot on the arm, not
quality. The unique self-powered
"Libretto" Remote Control-Preamp,
ahead or behind. A short distance either
with its amazing flexibility"
way reflects a false reading by several
is an ingenious innovation. The
grams . ..
laboratory tests are a revelation, but the ultimate proof of
superiority is in the thrilling
Dubbings' Tests
listening and operating experience.
And now, finally, to the trickiest a nd
The specifications summarized
most complex set of gadgets of the month,
below can only hint of the quality
the Dubbings Co. test records and the T es t
of this new dimension in sound.
Level Indica tor.
As for the first Dubbings disc, D-IOO,
the master amplifier
there's not much to say and all of it good.
A truly superb instrument A straight frequency run in the usual bands
with frequency response of heads things off, and will tell a lot of pearle
±0.3 db, 20 to 40,000 cps at rated 20 whether their phonographs produce highs
watts output. Harmonic d~stortion less than and lows, or merely middles. 30 to 12,000.
(High enough-a IS,OOO-cps band isn't go0.5 % at rated output, less than 0.3 % at 10 ing
to stand 'up and many people can't hear
watts. Intermodulation distortion less than it anyhow.)
A 4S-second unmodulated band
0.4 % at I watt (home level), 0.7% at rated rather neatly-if you follow the excellent
output (measured at 60 and 7,000 cycles 4 to I and simple directions-sorts out audible
ratio). Output imp., 8 and 16 ohms. 4-posi- hum and rumble. A 3000-cps . steady tone
tion input selector-for magnetic pickup, crys- uses your ear in its best range to check
tal pickup and 2 auxiliary. Dimen'sions : 14" wow. A set of 400-cycle bands each up 3
x 9" x 8" high.
db over the last is for tracking and compliance; Dubbings says a home machine is
the LIBRETTO
OK if it plays the first three without fuzziremote (ontrol
ness. My system played 'em all very nicely.
A true remote control, com- (Seems like I need some really good punk
pletely self-powered and capa- equipment around. I can't get anything to
ble of operation several hundred feet from go wrong.) Sides A and Bare identicalamplifier. Uniquely fashioned in the form of two reco rds for the price of one, or somea luxuriously bound book (only 8% x II x 2" thing. (But a good idea.)
D-101 gets ' more complicated. It's called
thick). Backbone lifts to provide easy access
to tuning controls. Operates flexibly in either The Measure of Your Phonograph's Equalization and includes complete frequency
horizontal or vertical positions .
band runs according to the four main reCONTROL FU NCTIONS
cording curves. labelled Columbia LP,
NARTB, AES, and RCA New Orth1. 6-position crossover control (flat, 150, 300,
aphonic. Again, both sides are identical.
450, 700, 1000 cycles). 2. 6-position roll-off conLevel-setting bands at 1000 cps occur at
trol (flat, -5, -8, -12, -16, -24 db at 10,000
both the beginning and the mid-point of
cps). 3.Volume Control-instant choice of conventioneach range and are easily picked out ,by
al control or loudness control. 4. Bass Tone, +24 db
'
sight. Good.
10 -20 db·at 20 cps (db calibrated}.5. Treble Tone,
H ere we are at the ragged edge of the
+18 db to -...: 30 db at 10,000 cps (db calibrated).
whole amateur-professional schism-and I
Custom-Engineered, Custom-Styled
tmich admire Dubbings' enterprising and
For Audio Connoisseurs
reasonable fling at that old dragon, equalization, a monster that has slain many of
See the RAULAND
_ _
1826 Ultra-Fidelity
~
th~ best of us, on both sides of the profesensemble at your Hi.Fi ,
:
.
•
'
" .
sional fence. It's sorta hopeless-not even
dealer, or write for
Dubbings can .untangle the mess; and there
full details.
are complica'tions' for the amateur here tho.t
RAULANJ)-BORGCORPORATION . .
are almost overwhelming. Thanks to some3515 W. Addison St., Dept. AD, Chicago 18; 111.
body, the simple explanations of the earlier
~
fXI
)~
AUDIO' ENGINEERING : '. ;. D.ECEMQ:ER,
1~53
WITH THE
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FOR LOW RESONANCE
This exclusive PermoAllx fealure,
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:rhe spectally designed single
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",both high and low frequencies
with exceplional clearness,
.and avoids the inherent
distortion of coaxial
61
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• Absolute listenableness-for the super-critical
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• Acoustic damping down to unity, with perfect
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"THE BAROQUE" 15 cu. ft.
• Three-way speaker system of the finest units operating
in an adequately supplementary circuit; special damping
process, solid construction preclude spurious hang-over,
ringing, or distracting resonances. The ISOTONE definitely sets the limit to the approach to tonal perfection,
brushes the borderland of realism.
• Patrician cabinetry, hand-rubbed. Blonde Oak or polished
mahogany 20 watts and 30 watts.
On demonstration at our showroom, 247 Fourth Ave.,
New York 3, N. Y.• or write for information to
ISOTONE
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If you are novice, hobbyist,.experimenter, or engineer ... if you
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•.. Audio Engineering will be your faithful, reliable companion all the way. You will find no more pleasureable and
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''What to Do" and "How to Do" will guide your every move
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MA.lL this
Coupon
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AUDIO ENGINEERING
P. O. Box ,629, Mineola, N. Y.
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.end a copy of each new
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62
D-lOO are continued Ull this disc, to make
the best of the trouble. Moreover, a lot is
left to the listener's good ear, which is an
immeasurably wise thing to do.
With this disc alone, you can quickly
get a good idea of equalization settings on
these four familia r curves either through
the usual bass and treble tone controls
minus separate equalizer system, or via
the fixed equalization positions now so
popular, the record acting as a check on
their performance. But you must of course
have a voltmeter. No other way, ordinarily,
to measure the signal strength. Cheap ones
aren't accurate. Good ones cost. And that
is that. Cuts out 99 per cent of phonograph users.
-But not quite. Dubbings, having got
this far, has found itself bound to push on,
and the Test Level Indicat0r is the result,
a gadget strictly for home use that is designed to take the place of a fancy and
complex voltmeter at a low cost, about $3 .
With it, you can use the Dubbings records
to measure your phonograph's exact output to the speaker on any of the test
LP bands, and thus you call check its fr equency response and equalization quite
simply.
The gadget mounts three small light
bulbs (radio dia l type) in a small plastic
box; when the thing is hooked onto your
speaker leads via alligator clips, the bulbs
light up progressively at 3 db differences
in level. You set it at "neutral" via the
level-set bands at 1000 cps on the test
records; then you may check deviation as
accurately as a couple of db (3 db is as
small a difference in sound intensity as
you can hear) in your machine's response
from the recorded frequencies, for each of
the recording curves. (Le.-for those who
may be unfamiliar with this sort of jargon
-if your set plays the AES-curve bands
"flat" all the way up and down when it is
set for AES response, it is operating correctly, and will reproduce an AES-curve
musical record in correct tonal balance,
correctly equalized.)
A neat and intriguing little device and
it performs admirably in every way-except
for one most unfortunate weakness; the
bulbs burn out, with too much volume. Do
they burn out!
Dubbings pessimistically gives buyers a
couple of spares; I killed nine of them, in
my diabolic way, in a half hour of dickering. As I say, I have a heavy hand on light
equipment, and use it deliberately in such
cases. But I fear, nevertheless, that others
may have the troubles I had and I'm
wondering whether something couldn't be
done about it, to make this extrem ely useful gadget a bit more shock-resistant.
Specifically, I burnt out bulbs in these
easy ways. (1) Though I carefully kept the
volum e down low, as instructed, I got imP'ltient with the tone signal test bands and
. moved the pickup onward a few times.
Mostly, all was well; but one slightly
firmer drop of the stylus produced a mild
plOD in the speaker-and burnt out two
bulbs. (2) - I turned on my phonograph
motor. The "pop" of the switch (my muting
condenser was loose) burnt out the whole
set of bulbs instantly. That could happen
with any old switch in the nearby electrical
neighborhood. (3) I clipped the test leads
onto a speaker plug, loosening it slightly.
The speaker line was jostled loose for an
infinitesimal fraction of a second a bit later.
Bulbs blew. (4) In rearranging my equipment I happened to pull out a phono input
plug in the back of my ampli fier, forgetting
that the Test Indicator was still connected.
When the ground connection broke for a
tiny instant, with the usual loud humthe bulbs blew, all of them. Took me quite
a while to figure what had done it that
time.
AUDIO ENGINEERING
•
DECEMBER, 1953
Enough said? and yet this is an excellent
device, on a sound and reasonable principle.
All that is needed is some sort of satety
factor. Neon bulbs-two would be enough
-might do it, but with a transformer tne
price would be up. Perhaps an overload
circuit of some sort ahead of the bulbs
would do it. I'm going to try 4-volt bulbs
instead of the 2-volters (#40 instead of
#48) to see what may happen then. What
say Dubbings? Let's not lose such a good
idea.
You can use the ~ubbings records with
a "real" voltmeter and I highly recommend
them to all readers who rank between the
utter amateur and the man who already
owns his own oscilloscope and signal
generator.
P.S. One question, largely curiosity on
my part. When volt readings are taken
with the speaker in parallel in the out1)ut
circuit-as Dubbings suggests-is not the
response affected directly by the speaker's
operation, including the effects of the enclosure and even of the room-standing
waves, ' for instance ? My own readings
suggested that this was the case. An ideal
speaker enclosure in an ideal acoustical
situation (not for listening but for speaker
performance) would reflect pretty much the
electrical output of the system; but few
home owners have such conditions.
I doubt if the deviations thus occasioned
are important enough to spoil the readings
from these test discs, yet some users may
be unduly disturbed at what seem to be
peaks and valleys in over-aU response,
even when the average is set to equalize a
given curve. Not - vital because, as I well
know, many a home system, including a
vast number of mis-used hi-fi outfits, are
so drastically and horribly off on equalization that even an accuracy of 6 or g db in
these records would be plenty to d0 a good
corrective job. How many times have I
seen-and heard-a system exuding highs
at roughly 20 db boost from the flat or
correctly equalized position! Let's not
worry about details.
THE AUDIO FAIR IN REVIEW
(from page 32)
entry into the audio industry with its first
Fair appearance. High-fidelity equipment
on display was easily recognized as coming
from a firm thoroughly versed in building
electronic devices to a high standard of
precision.
pearing cabinet which utilizes the exponential slot principle, held the spotlight
in the exhibit of Karlson Associates, Inc.
"High-fidelity speaker performance in
a small package" was the introductory
theme of Jensen Manufacturing Company's new "Duette" two-way speaker system. Comprising a special 8-inch woofer
plus a multi cell horn-loaded _compression-
type tweeter, the Duette is housed in a
compact enclosure- which may be mounted
in a bookshelf or used on a table where
space is restricted. Sharing interest with
the Duette were Jensen's new H-S30 and
H-S20 coaxial speakers, both of which
offer ' an exceptionalIy high standard of
performance within their respective price
ranges.
Klipsch and Associates, along with demonstrating the original Klipschorn, introduced the Rebel III, a smalIer ·back-Ioading enclosure designed to improve the performance of direct-radiator speakers. Moderately priced, the Rebel III is an impressive performer.
The popularity of the Baruch-Lang
miniature corner speaker system was well
evidenced by the crowds which attended
the exhibit of Kloss Industries. Stressed in
the display, as in the firm's current advertising, was the fact that Kloss was the
original manufacturer of the .Baruch-Lang
unit, and that the company sells direct to
consumers at considerable savings.
An improved version of the Karlson
Ultra-Fidelity enclosure, a handsome-ap-
AUDIO ENGINEERING
•
For the ultimate in
HIGH FIDELITY TUNERS
the
AF-824 FM-AM
PILOTUNER
10 tubes, with two stage pre-amplifier
equalized according to lP NAB, AES and
foreign recording standards selected by
Switch. Three magnetic phono and crys'tal
and AUX. inputs. Two stage audio ampli.
fier with cathode follower output. Sensi·
tlvity on FM·AM 10 MV. Audio frequency
response ± Y:.OB, 20 to 20,000 cps. Hum
level 800B below one volt with hum bal·
ancing adjustment provided. Controls:
Volume, Equalizer, Treble, AM-FMPHONO·AUX, Bass, Tuning and AFC on·
. off. Built·in antennas for FM and AM.
THE AA-901 AMPLIFIER
John Karlson, company president, gave
frequent lectures in order to ·familiarize
acoustic engineers and audio hobbyists
with the unique approach to speaker
matching which allows a relatively smaU
enclosure to "surpass the bass response of
a 31-foot horn."
I
In its second Fair appearance, The Kelton Company displayed an entire line of
economicalIy-priced high-fidelity music systems, also a number of individual components. Here, incidentally, is excellent
evidence of how rapidly the audio industry
is expanding; last year the company's display was devoted almost entirely to the
first public showing of the Kelton speaker.
A new line of miniaturized professional
preamplifiers, line amplifiers, and power
supplies were featured in the exhibit of
Langevin Manufacturing Corporation. Of
equal interest were the standard audio
devices for sound service organizations and
those for wired-music services, for which
Langevin has long been noted.
In an initial Fair appearance, K ingdom
Products, Ltd., introduced the Lorenz
woofer-and-tweeter combination which,
when used with the Kingdom high-pass
DECEMJER,1953
New improved Williamson type Amplifier
using famous KT·66 tubes. Power Output: 10 waHs - less than 0.1 % distortion, 25 watts - less than 0.3%
distortion, maximull'l output - 30
waHs. Frequency Response ± 1DB 15 to
50,000 cycles. Hum level 90 DB below
10 walts. Speaker output impedance 8
and 16 ohms. Tube complement 6SN7GT.
6SN7GT (2), KT-66 (2) Push·Pull Power
Amplifier, 5U4G Rectifier.
FREE •I
NEW 1954
AUDIO GUIDE
You'll want this up·to·the·mlnute TERMINAL
AUDIO GUIDE. The most ~omplete catalog of its
kind. • • Information·packed ••• A Ready
Reference to the world's finest Audio equipment
In all price ranges to suit your taste and budget
Amplifiers, Speakers, RadiO Tuners, TV, Record
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Sound Equipment tor professional and home
Installation.
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63
"
•
.
filter and specially designed enclosure, provides an economical means of achieving
excellent audio performance. Also intro-
Broadcast
. EQUALIZER PANEL
~
FACILITIES
Provides equalization for two
lines
OPERATION
FI'Ollt-pallel adjmttne1Zt in steps
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Equalizes short lines up to
15 KC. . .long lines up to 10 KC
MOUNTING
Simple clamp-type mountingfits any 19" rack. Requires just
3 ~" height clearance
FOI" c01Jzplete inforlllatioll write: Gelle1'al Electt'ic Co.,
Section 44123, Electrqllics Pat'k, Syracuse, New Yotk
duced was the English-made Emitron Type
KT-66 tube, known the world over as an
excellent output tube for audio amplifiers.
Other G-E Audio Equalization & Filter Accessories Include:
FA-18-A
FA-14-B
Sound Effects Filter Panel
Equalizer Unit
True, it was a little on the bulk y sidebut Brother how did it sound. Thus is interpreted this observer's reaction to the
new Model D-55060M speaker system
shown by James B. Lansing Sound, Inc.
In reality a scaled-up version of the company's well-known M odel 3400 1, the new
unit makes use of two woofers a nd a
theatre-type tweeter to give forth with
music which is plenty cool, son, plenty
coo!.
IN ORDER TO FIND ITWHY NOT BIND IT?
Your reference library of AUDIO ENGINEERING can be up -to-the-minute
by keeping your copies in an AUDIO Binder.
APPEARANCE ••• Your den, workshop . . . or wherever you do your experimentation can be kept in "apple-pie" order when all your copies of
AUDIO ENGINEERING are within easy reach. The deep, blue cover
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will be gold-stamped with AUDIO ENGINEERING and any year you
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CONVENIENCE ••• No more wondering what happ~ned to last month's issue
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COST ••. For only $2.75 you can have this handsome binder for your ready
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Audio Engineering
P. 0; Box 629, Mineola, N. Y.
Enclosed find $ . . . . . . . . . . . . . . . . . . . . .. for '"
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Year Wanted 01951 0195201953 01954.
6'4
The Fair was chosen by Livingston Electronics Corporation as the propituous occasion for announcing its entry into the commercial record field. Both binaural and
standard microgroove records will be distributed under the Livingston label, with
a catalog of recordings currently available
now on the press. Equipment spotlighted
in the Livingston exhibit included the
company's binaural reproducer arm and
a new twin-channel stereophonic amplifier.
Stereophonic sou nd from a single input
source was the center of attraction in the
exhibit of Madison Radio Sound, p a rticipating in the Audio Fair for the first time.
The firm's Multichannel amplifier is designed for either single or binaural input,
and is startling in the dim ensional effect
it gives to the former-at times approaching the qualities of a dual-input system.
The long-awaited introduction of the
Modcl MaO professional t ape recorder
brought literally thousands of visitors into
the exhibif of Magnecord, Inc. And, it may
be said with full truthfulness, their enthusiasm was without limit. In addition to
occupying display space at the F a ir itself,
Magnecord engaged a large parlor on the
N ew Yorker's mezzanin'e to conduct a press
exhibition of the MaO, as well as the newest Magnecord binaural equipment. R esponse of those who attended was more
than gratifying.
The keynote of the display of Jeff
Markell Associates is well defined in a
statement by Jeff Markell, company .presid ent-"We are designing all our units to
make audio cabinetry look like furniture
you would want in your living room rather
than like equipment. enclosures." How well
A.UDIO"ENC1NEERING
•
DECEMBER" , 1~53
M r. M arkell's compa ny is carrying out this
premise was dramati.zed by a stunning enclosure which successfully solves the problem of vibration transmitted mechanically
from speaker to equipment housing. Known
as Model RC-1 30, the unit employs shock
mounting in its construction to achi eve the
desired isolation of the two basic sections.
eq uipment in -th e entire show. Along with
the compa ny's complete li,ne of high-quality amplifiers a nd t ranscription players
there was featu red a n excellent demonstrati on of two-channel dimensional sound.
Bin a ural or stereophonic-call it wha t you
will- when played the Newcomb way it
is a n unforge ttable experience.
Appearing as a Fa ir p a rti cipant for the
first tim e, H. S. Martin & Company introd uced its new Model 153-T AM-FM tuner
A number of uni q ue electronic developments were unveiled in the showing of the
new 1954 r adios a nd radio-phonographs
introdu ced by M otorola, Inc. Among them
with built-in control amplifier. Sensitivity
of the tuner is one mi crovolt for 20 db of
qui eting. Both tuner a nd p reamp a re designed to be p owered by the Martin 352-B
power amplifier. The 153-T is notable for
its inviting app ear an ce as well as fo r its
exceptional performa n ce.
Highli ghted in the exh ibit of the Mark
Simpson Manufacturing Company were the
new M asco " C ustom T en" la-wa tt highfidelity amplifier, the " Concert M aster"
20-wa tt a mplifier, a nd the n ew Model 5 3
tape r ecorder. Althoug h low in price, the
" Custom T en" provides five equalization
curves for all m odern r ecor ds, sepa rat e
bass a nd treble t one controls, a nd a bassand treble-compensa ted volume control.
Th e new M asco tap e recorder incorporat es
a two-m otor m echa nism a nd is a vailable
with or without built-in AM tuner.
Along with the highly-regarded Model
SOW -2 50-wa tt a mplifier, McIntosh Laboratory, Inc., displayed a new 30-wa tt a mplifier, also a n ew p reamp-equalizer unit
which is r ema rkable in the flex ibility .of
control it p rovides. D esig na t ed Model
C -IOa, the n ew McIntosh " front end" features push-botton swit ches which p ermit
accura te logging of tone control se ttings
fo r various recordings. In appearan ce t oo,
th e C-IOa is a distinct innovation.
Precision with a capital P was the order
of the day in the exhibit of Measurements
Corporation. As a t previous Fairs, this was
the spot t o go fo r m eeting m any of the
country's leading desi gn a nd d evelopment
engineers . J erry B. Minter, M easurements
vice-president, was on ha nd a gr eat p art
of the time r eceiving cong ra tula tions on
his election as president of the Audio
Engineeri ng Society .
It would be a little redunda nt to review
the M innesota Mining & Manufacturing
Company exhibit on the basis of th e various types of Scotch bra nd magne tic t ap e
which were shown ; every conceivable t yp e
of tape was there, p eriod . On the other
hand, the 3M display must be singled out
as hi ghly exceptional beca use of the excellent literature whi ch was distributed .
The writers of these pieces are to b e com mended fo r thei r ability to d escribe the
techni cal side of m agnetic r ecording in a
vocabula ry which m a kes it entirely und erstand able t o the layman.
Assembled in the exhibit of N ewcomb
Audio Products Compa ny was one of the
more inclusive showings of fin e audio
AUDIO ENGINEERING
•
was a new oval-type inve rted speaker
whi ch offers imp roved t on e a nd _g reat er
speaker area tha n conventional units for
simila r a pplication. Am ong cpmpleted instruments, the bulk of a ttention was
fo cussed on the M otorola Sona ta r adiophono, a low-cost t able combina tion which
includes a n AM receiver a nd three-speed
record ch anger.
Orradio Industries built a n intriguing
display a round the fi rm's use of colorsbrown, green, a nd r ed-to distinguish various g rades of I rish bra nd r ecording t ap e.
T he complet eness of t he Irish line is ent i r~l y in keeping with the O r radib advertisin g theme- " World's L a rgest E xclusive
Magnetic T ape M anufacturer ."
The Fair offered no more imp ressive
showing of home tap e recording equipment than tha t assembled in the suite
occupied by The Pentron Corporation. A
Pentron accessory, a 4-posit ion elect ron ic
mixer whi ch m ay be used with a ny t ap e
r ecord er, cam e in for m ore tha n due share
Of a ttenti on. Through use of this unit as
ma n y as four microphones a nd/ or tuners
and record players may be mixed into a
single input, this affording the fl exibili ty
usu ally associated only with p rofessio nal
equipment.
Clearly proved in the suite occup ied by
Permoflux Corporation was th e fact tha t
excellen t r ep rodu ction of sound does n ot
necessarily entail high cost. Permoflux,
through its excellent moderate-priced speakers, has gone a long way towa rd popula rizi ng the hobby of custom building home
music sys tem s. And, th rough the h ighfidelity headphones which are a virtual
necessity for true binau ral listening, t he
comp any has built a ' uni qu e stake in the
profess ional audio fi eld as well .
M a king a n initial Fair appearan ce,
Pickard & Burns introduced a complete
assembly of high-fidelity components which
were r emark able in their p erformance.
In cidentally, this display was uni que in
t he fact tha t its p r ime fun ction was to
bring the equipment developed by P ickard
& Burns to the a ttention of prospect ive
ma nufactu rers ra ther than end users.
If fo r no other reason, the exh ibit of
Pickering a nd Company would have excited attentio n because of the g reat inter es t
DECEMBER, 1953
65
of visitors in the Model 260 turnover-type
diamond-styli cartridge, which received its
public preview at last year's Audio Fair.
But other reasons there were aplenty ;
among them was the Pickeri ng audio input system. This company should take
justified pride in being virtually the first
to sense the need for a "front end" of professional precision for use with home music
systems, a nd to make it available at reasonable cost.
Sensational New
Pilot Radio Corporation, in its first Fair
appearance, introduced a number of new
tuners and amplifiers in the moderate price
range. Outstanding was the Model AF824 tuner, which includes among its features a built-in preamplifie r with bass and
treble tone controls, as well as variable
equalization for both domestic and foreign
recordings. Engineers and hobbyists alike
were impressed by the steps Pilot is taking
to make excellent audio performance available at prices well in keeping with modest
incomes.
FM 607 FM PILOTUNER
Portable Gramaphone Company, another
of the Fair's newcomers, introduced the
new Dorset portable phonograph, at this
writing the only portable to ~mploy a Gar-
For the first time ever at this
dramatic low price! 8 Tubes including Rectifier with two stage
Audio Amplifier and Cathode Follower Output. Audio distortion
•2% at 1 volt output. Response
±.5 DB, 20 to 20,000 cycles. Unusually sensitive. Slide rule dial
with illuminated scale permits
unit to be left open on shelf or
easily installed in cabinet. Three
simple controls .. . . .... $59.50
AA-903 AMPLIFIER
rard record changer. Other quality features of the Dorset include a 6-tube amplifier, an 8-inch high-quality speaker,
record compensator, and tone control, all
of which contribute to the Dorset's impressive performance.
Williamson Type 10 Watt Amplifier with built-in pre-amplifier. 7
tubes including Rectifier ' with
push-pull output tubes. Decorative
front panel may be removed for
cabinet installation. Frequency response ± 1 DB 15 to 40,000 cycles.
Distortion less than 1 %. Controls
include on-off volume, separate
Bass and Treble, and Equalizer
selector switch for LP, NAB, AES
and Foreign Recordings $69.50
Inc.,
whose
Precision Electronics,
Grommes Model 50PG was one of the
first amplifiers to bring true high-fid elity
performance to the moderate-price field,
gave evidence that the firm 's efforts in
this direction are unabated, with the introduction of T ype RC-l record compensator. For connection between magnetic pickups and preamplifiers which are
not equipped with controls for record
equalization, the RC-l provides correct .
playback curve for all types of recordings.
It is also equipped with a . slide switch
which changes . loading to match Pickering, G. E., and Audak pickups.
Visit ASCO-America's Largest
Tape Recorder Center
Come in to see our wide selections of
tape record.e rs . • • Ask for your FREE
copy of "Sound Advice" , 148 Pages of
new Hi-Fi data, hy Irving Greene. Or
send coupon enclosmg 10¢ (or stamps)
for handling.
8
66
A repeat hit was scored by R-J Audio
Products. Fair visitors never seem to tire
of hearing clean, fundamental bass 'way
down in the organ-pedal-note range issuing forth from an enclosure no higher
than a bookshelf and only a couple of feet
in length. This year, to animate the display, the wooden top of the R-J cabinet
had been replaced with Plexiglass, thus
disclosing constructional details.
By far the most inclusive display ever
to grace an Audio Fair was that presented
by Radio Corporation of America's RCA
Victor Division. Occupying a dozen rooms,
RCA pulled out all the stops in presenting
an exhibit which had as its focal point the
new RCA custom-built high-fidelity radiophonographs, as well as the company's new
line of amplifiers, tuners, speakers, and
tape recorders. In addition to showing
equipment which is now available, the ex~
hibit included an "in-the-future" demonstration of stereophonic sound. A number
of brief lectures by well-known RCA engineers contributed further to make this
exhibit one of lasting and pleasant impression .
The Radio Craftsmen, Inc., introduced
in its exhibit a new packaged home music
equipment assembly consisting of tuner,
amplifier, three-speed record changer, and
a coaxially-mounted dual speaker system.
Heretofore, the company has sold only
separate components. Other new Craftsmen developments shown were the C900
FM tuner with I-microvolt sensitivity, and
the C210 high-fidelity dual-chassis TV for
remote control.
Famous Williamson Type
ASCO SOUND CORP ., 115-117 W . 45 St.
New York City
Please send me copy o( "SOUND ADVICE". Enclosed 1O¢ (or handling .. 0
-FM 607 PILOTUNER @ $59.50 .•. .
- AA903 AMPLIFIER @ $69.50 .. . .
Total Amount Enclosed . . .... .
"AME . . ...................... ... ...•..
ADDRESS ..... ................... .. .. .
Aldrich, Presto's sales manager, "--disc
recording, in spite of tape, is a long way
from bowing out of the picture."
A
Support for the belief that there is going to be a big market for long-playing
tape reproducers was seen in the remarkable interest commanded by Presto Recording Corporation's Model PB-l 7A, a
unit which plays as long as eight hours
without attention. The PB-17 A makes musical prog rams, with or without commercials, available to hotels, restaurants, industrial plants, department stores, etc., at
moderate cost. Presto's other new tape
equipment, the RC-ll reco rder for example, also met with great approval, as
did its extensive line of disc recording
equipment. In the words of Thomas B.
The FM tuner to end all FM tuners was
given its first public showing by Radio
Engineering Laboratories. Known as the
REL Model 646-C, it includes virtually
every known refinement for realizing the
full potential of FM transmission and re-Geption. Adding a touch of nostalgia to
the REL suite was the original FM recciver designed and constructed by Dr.
E. H. Armstrong.
. New developments in magnetic recording materials were the center of attraction
in an inviting display by Reeves Soundcraft Corporation. Sharing featured spots
were Reeves' new Mypar Lifetime recording tape, and a strip of CinemaScope film.
Mypar is a tape of tremendous strength,
and is virtually non-breakable in normal
usage. CinemaS cope, on whose development Reeves worked in conjunction with
Twentieth-Century Fox, is largely a refinement of the Reeves Magna-Stripe process
and contains four magnetic sound tracks
as well as picture area on 35-mm film.
One item which had to be seen as well
as heard in order to be fully appreciated
was the high-fidelity amplifier ensemble
shown by the Regency Division of Industrial Development Engineering Associates.
Not inexpensive,-it sells for close to a
thousand dolla rs-the Regency system
matches in visual beauty the perfection of
its sound quality.
The Fair presented no more impressive
showing of precision record-playing equipment than that assembled by The Rek-OKut Company. The latest Rek-O-Kut turntables are supreme examples of excellence
in both mechanical and electrical construction. Also coming in for a great share of
attention was an improved version of the
Rek-O-Kut portable disc recorder.
AUDIO ENGINEERING
•
DECEMBER, 1953
In addition to displaying the excellent
characteristics of Revere tape recorders,
Revere Camera Company in its exhibit received a great play from visitors with the
, demonstration titled "Ca n You Hear 17,DOD CyCles?" Tones of 10, 12, 15, and 17
conventional r emote-.control amplifier, yet
is a complete 10-watt amplifier in every
respect, including variable record equalization and sepa rate bass and treble controls.
Audio characteristics are equal to, those of
much bulkier counterparts, a nd the price
is rema rkably low. The other, known as
the Model 12 1-A Dynaural equalizer-preamplifier, is introduced by Scott as offering "complete control a nd compensation
for any record and record condition, past,
present, and future." Not inexpensive, the
121-A is designed strictly for the dem a nding connoisseur.
A unique preamplifier-equalizer in which
the loudness control a utomatically takes
over when bass is boosted, was introduced
by Sonex, Inc. The loudness control is inactive when the bass control is in zero
position. Step-type rolloff and turnover
controls give 25 possible equalization
curves. The unit gave a thoroughly satisfying demonstration in conjunction with
the Sonex ultra-linear power amplifier.
One of the Fair's more inclusive displays
of moderate-priced r ecording equipment
was that presented by Sonocraft Corporation. Fully justified was Sonocraft's position as one of the h~adin g firms engaged in
the sale of sound equipment to schools
and colleges.
kc were recorded and played back on a
standard R evere Model T-IO r ecorder;
'participa nts in the test were split in their
curiosi ty as whether they could hear the
17-k c tone, a nd whe ther the recorder could
reproduce it. About 40 per cent of the
listeners heard the tone, which was a 100
per cent indi cation of its exis tence.
An extensive line of cabinetry rang ing
from "Kits to Consoles" fo r housing hi-fi
equ ipment and TV r.eceivers was shown by
River Edge Industries. River Edge has
secured the cooperation of many leading
equ ipment manufacturers, who furnish
pre-production drawings of audio and TV
chassis prior to distribution to dealers, and
thus is able to supply cabinets pre-drilled
a nd pre-cut for most standard amplifiers,
tuners, a nd r ecord players .
Engineering features of th e British-made
Collaro record cha nger were clea rly shown
in the exhibit conducted by Rockbar Corporation, American distributors. Highly-regarded and wid ely-used on the Continent,
the Collaro changer is well on the way
towa rd dupli cating the experience in this
country. The smoothness of Collaro
changer operation was p arti cularly a ttractive to Fair visitors.
Something new in pickups-the Titone
ceramic cartridge-was given a public
initiation by Sonotone Corporation. Demonstration brought out the wide frequency
range of the unLt, as well as the fact that
it r equires neither a preamplifier nor
equaliz-e r. Particula rly impressive to visitors was the turnover model in which only
the stylus rota tes.
Visitors to the Stephens Manufacturing
Corporation exhibit were deeply impress-e d
by the improved line of Stephens highfidelity speakers, also by the Stephens
"wireless microphone" which p ermits complete mobility to stage and TV p erformers. Among the speakers the featured spot
was occupied by the Model 628, the finest
home reproducer in the Stephens line.
Affording full rear horn loading, the 628
is a handsome piece of furniture which
may be used either in a co rner or against
a straight wall.
- combining famous BROOK
12A power amplifier, and flexible 4B pre-amplifier, at mod~r:ate cost.
.
Of the many items on d emonstra tion in
Stromberg-Carlson Company's exhibit, a
combination tuner-amplifi er a nd the RF475 coaxial speaker came in for special
attention. In its new Type SR-405 self- 30-wall basic amplifierremote control pre-amplifier
combination; I:oigher power for
fu"-qodied orchestral passages.
A Fair newcomer, Shields Laboratories,
Inc., came through with a thoroughly interesting display which embraced high-fidelity amplifiers, preamps, speaker endosures, and a number of audio measuring instruments. Observers were emphatic
in their approbation of the components
which were shown.
Exceptional attention was created by
two new amplifier developments in the
-exhibit of Hermon Hosmer Scott, Inc. One,
known as Model 99-A, resembles in app earance a nd size the " front end" of a
AUDIO ENGINEERING
•
contained units, Stromberg-Ca rlson combines in a single chassis all the fe atures of
its popular 10-wa tt hi-fi amplifier a nd a
high-quality AM-FM tuner with no duplication of controls. The result is a n assembly ideal for custom installations. The 15inch RF~475 speaker contains a 10!-pound
Alnico V magnet, which incidental intelligence tells us is en'ergized by one of the
la rgest magneti ze rs in the world.
DECEMBER, 1953
Write for full information on the complete BROOK line; also name of your.
_nearest dealer. Dept. AM-3
BROO« fLfCTRomcs, inC.
g:;l'dnl I'k
34
..fi:?~ Q..£Q'.t<{y
De~ART
.Mu:&... g;rUt;;;;"c-'
19.7';
PLACE, ELIZABETH, N. 1.
67
One of the more satisfying displays was
cbnducted by a new company-Tannoy
(Canada) Ltd., sole distributors for th e
North American continent of the Englishm ade T a nnoy Dual-Concentric loudspeaker. Aside from a n impressive demonstra ti on, visitors found g rea t interest in
the T annoy die-cast cone housing which is
equipped with interna tional-sta nda rd fi xing holes. D esign of the casting p ermits
elimi nation of frontal cavity resona nce by
providing means fo r mounting the speaker
in front of th e enclosure, as well as conven tionally on the insid e when desired .
The ideal recorder for newspaper reporti ng, reo
cording lectures, telephone monitoring, fi eld
reports traveling secretary, on-the-spot interviews, reference recording, customer intervie ws.
salesmen reports and secret recordings.
Com bines, for the first time, ease and efficiency
of operation with maximum reduction of weight.
Performs an ywhere, producing p rofessional r eo
suIts under ad verse conditions. Fly·ball governor·
con(rolled electric motor plus triple shielding
ass uies. constant speed and freedom from hash .
Weather· tight , satin · fin ished, alumin um alloy
case gives complete protection to recorder. Three
models available in speeds of 15/ 16, I Vs and
3~
ips. Check
these unusua"fea t ures :
*Records fo r 4 f ull hou rs ( Model 31 a· A)
** Oper
ates from self·cont ained dry ce lls
Immediat e playback.
"* Size: 5 /2 x 9 x 12 inc hes.
* Weight : only 8 pounds.
1
Write lor complete technical literature
and direct lactory prices to Dept. AE
•
.
AMPLIFIER CORP.
of AMERICA
'.
. 398 Broadway, N. Y. 13, N.Y.
.
T .M. R eg. U.S. Pat. Off.
RECORDINC TAPE
(PLASTIC BASE)
at NET PRICES
in .Cartons of 12
WASHINGTON , D. C.:
WHERE ELSE WOULD THE RE
Magne tic
BE MOR E RED /\ TAPE!
• 1200 ft. plastic tape with plastic r eel in·
cluded .
• Each reel individually boxed .
• Choice of nationally famous top quality
bra nds such as:
Webcor (2906) 3.20; Reeves (SPN-12) 3.20;
Audio (1251) 3.23 ; Scotch (Ill-A) 3.25;
Panacoustic (7 11-A) 3.25; Irish , Profes·
sional grade (211 RPA) 3.30.
• R ecordi ng studios, schools, radio stations
and other large quantity users-wri te for
bulk price.
************************
USED RECORDINC TAPE ( PLASTIC BASE)
1.99 fo r 7 " -1200
.99 for 5 " - 600
.59 for 4"- 300
.29 fo r 3 " - 150
PllI.!tic ree ls Included
all above sizes.
fott
foot
foot
foot
with
){on.y cheerfully refunded If you do
not Ond this tape cleanly erased ad 81
cood as n.w. (U !'<>u are .keptlcal and
from MissourI send us 12¢ In .tamps
and we' ll roll you a sample.)
New empty plasti c reels in boxes for easy
labeli ng. 3 " l Ot ; 4" 22¢ ; 5" 24¢ ; 7"
30¢; 7 " Professional re el (2 V4" hub)
45¢ ea. EMPTY BO XES: 3" 3¢ ; 4" 5¢ ;
5" 5¢; 7 " lOt ea.
IV. carry new record. rs, recordlni blanks. tape.
tape
reeonl.nI. etc. at larg. savings. PLEASE INCLUDE
SUFFICIENT POSTAGE.
COMMISSIONED ELECTRONICS CO.
2503 Cha mplai n SI. N.W•• WlI.!hl ngton 9, D. C.
68
A new li ght-weight, inexpensive t ap e
recorder was g iven its first public showing
by Telectrosonic Corporation. Easy t o
operat'e a nd di stinctive in appeara nce, the
Telectrotape record er is certain t o make
its m ark in th e a udio firm ament.
There is little t o be known a bout styli
whi ch couldn't be learned in the display of
The Tetrad Company. E xcellent photomicrogra phs were used to show the effects
of a worn stylus on records, a nd to compare the wearing qu alities of sapphire a nd
di amond. Also interesting were the color
slides showing the various steps in stylus
ma nufacture. Visitors who just happened
to bring a stylus along (could there be
such ?) were offer ed free microscope a nd
shadowgraph examination .
Never again will those who visited the
Thorens Company exhibit ta ke for granted
the precision of Swiss m a nufacturing processes. Seldom does one encounter the painstaking care which is so evident in the
Thorens line of record changers a nd single
players. History repeated itself in tha t the
featu re of the exhibit was the Thorens
model wh ich was described in the 1952
version of the p resent obse rva tion as " the
changer to end all changers."
One of the Fa ir's more informa tive displays was condu cted by Tung-Sol E lectric.
Here wer e shown receiving tubes of m any
types, including of cou rse the Tung-Soldeveloped T ype 5881-but more import ant was the fact tha t the suite was staffed
with compe tent engineers who were e ntirely g rac ious in a nswering the int rica te
q uestions wh ich tubes invariably seem to
bring on .
Thousa nd s
of
descriptive
ca ta logs
clutched in t he ha nds of F air visitors provid ed eloquent evidence of the welcome
a ccorded Uta h R adio P rodu cts Compa ny
on its r e-entry into the firm am ent which is
Hig h Fidelity. It doesn't seem lik e too
many years sin ce Uta h was among the top
kicks in t he speaker industry, a nd thi s
obserV'er joins ma ny .other old-timers in
wondering where they've b een all t hi s
time.
Attractively featured in V -M Corporat ion's exh ibit was the com pa ny's new
Model 9 35HF T r ioma tic r ecord changer.
D esig ned for use with m agnetic cartridges,
the 9 35HF is equipped with a four-pole
four-coil m otor to red uce hum , a nd a
weighted a nd bala nced turntable to assure
consta nt speed . Appearance of the unit is
especially striking . Because of low lateral
p ress ure required to opera te the cha nging
m echa nism, the 935HF will accommodate
pickups with stylus pressure as low as fi ve
g rams .
Both comp leted units a nd componen ts
were featu red by Video Corporation of
America. L est the company nam e throw
you for a loss the " units" were strictly
a udio, with nothing wh a tever to do wi th
TV. E xceptional interest was accorded the
M odel HF -90 ta ble phonograph whi ch employs a six-watt a mplifier, a C olla ro
cha nger, a nd two six-inch speakers in a
bala nced aco llstical ch amber .
W eathers Industries built an effective
exhibit arollnd a r ecord-playing assembly
whi ch is being advertised a nd merchan dised as Th e D ebonnaire. I t consists of the
Weath ers FM pickup sys tem and a m a nua l
turntable complet ely assembled a nd ready
to plug into a n ex isting aud io system . Also
shown was the new W eathers tone arm
designed for use wh ere mounting space is
li mited , a nd the W eathers p ressure gauge
for m easuring stylus pressure.
A three-speaker t able phonograph called
the W eb cor " Musicale," which in cludes in
its des ign such hi gh-fid elity features as a
loudness control, a five-watt ampl ifi er wi th
extend ed frequency ra nge a nd negli g ible
E xcell ent a udio p erforman ce, notwithsta nding its small size a nd m odera te price,
wa s easily ap parent in the new p ackaged
hi-fi phonograph introduced by U ltrasonic
Corporation. Also impress ive was the U lt rasonic Model U -25 speaker system, a
compact tria ngular enclosu re for corner
installati on .
The inheren t q uality of UTC t ransformers was well evid enced in the exh ibit of
United Transformer Corporation. Pioneer
in th e a udio industry, UTC has earned a
position of unqu estione d leadership in the
design a nd ma nufacture of t ransform ers for
high-fid elity equipment of every descrip tion.
One of th e more pleasant experiences to
those of us in the a udio indust ry has been
the witnessing of the impressive a nd welld eserved g rowth of University Loudspeakers, Inc. Universitv was among the trai lblazers in the early days of aud io, a nd today those pioneering effo r ts are well evid enced in the unive rsal dema nd for the
compan y's hi -fi speakers a nd Musico rner
enclos ures. Although a number ' of n ew
U niversi ty items were displayed a t the
Fair, interest in the famili ar M odels 620 1
a nd 6200 a nd the Dlffusico ne was unsurp assed.
di stortion, a nd a Webcor Diskc hange r
equipped with a GE m agnetic cart ridge
was star,r ed in the d isplay of Webster-Chicago Corporation. W ebcor, inciden tally,
has adopted the tripl e-sp eaker id ea in a
strik ing new tape r ecorder wh ich was introduced to a gathering of audio a uthor iti es a nd mu sic critics in N ew York shortly
after th e Fair closed .
Bela ted recognition of the Fa ir by t he
record ing indust ry as a propitious spot fo r
the display of high-fidelity r ecords was
evidenced by the presence of W estminster
Recording Compan y as a prominent exhibitor. It is initia tive of this typ e which,
along with the compa ny's m agnificent
AUDIO ENGI NEERI NG
•
DECEMBER , 1953
PBOFESSIONAI.
DmEcroBY
Custom- Built Equipment
U. S. Recording Co.
1121 Vermont Ave.. Washingtoa 5. D. 0.
Uncoln 5-2705
records, is rapidly propelling Westminster
into a position of well-deserved supremacy.
Incidentaly, the new Westminster hi-fi test
record is a humdinger.
The new amplifier circuit known as
" Powrtron," introduced to Fair visit ors for
the first time by White Sound, Inc., left no
d9ubt as to its ability to deliver ultra high
fid elity. D emonstrated in conjunction with
a White speaker enclosure, the Powrtron
amplifier delivered some of the cleanest
sou nd to be heard.
More than gratifying was the attention
paid by d yed-in-the-wool audio fans to the
ha ndsome new hig-h-fidelity combinations
which were displayed by Zenith Radio
Corporation. All of the Zenith instruments
Model 377K
• Extremely stable Wien bridge oscillator
• Sine waves from 20 to 200.000 cps in
4 bands
• Square waves from 60 to 50,000 cps
• Response fiat ± 1.5 db from 60 to
150.000 cps
• Calibration accuracy ± 3% or 1 cps.
whichever is greater
• Improved cathode follower output circuit for high output over wide load
range
• 10V out a! IKQ load (rated). 14V at
10KQ. BV a! 500Q
• Continuously variable output allenuator
• Distortion only I % of rated output
Hum less than 0.4% of rated output
• I % bridge resistors. 4 gang tuning
condenser
• Rugged steel case. deep-efched paneJ
KIT $31.95
WIRED $49.95
incorporate th e company's exclusive CobraMatic R ecord Changer with built-in stroboscope. In addition to playing all standard 7-, 10-, a nd l 2-inch records automatically, the Cobra-Matic will handle the
new "talking book" records whi ch revolve
at 16-2/3 rpm. Infinite variable speed control permits operation from 10 to 85 rpm.
If any particular Zenith model was singled for more than du e share of interest
it was the L 2894~H, a distinctive radiophono-TV combination styled in the modern trend , with an acoustically designed
bass reflex speaker enclosure.
the
the
the
the
look for this symbol on record album. vau buy '
audio
audio
audio
audio
See it at your Jobb Dr I
Write for FREE Cat. AE-12
"'/1/ !
Electr~nic Instrument Co •• Inc.
I~.".L!!~~,_~_~I~~~ 84
WIthers St .• Brooklyn. N. Y.
exchange exchanges audio
exchange exchanges audio
exchange exchanges audio
pxchanae exrhnnno c ""'/:9
Information on trading HI-FI
components on request. Write
or call for free catalog AE
HI FI ENCINEER
To evaluate hi fi equipment for home use:
tuners , amplifiers, speakers, enclosures. record players and components, etc. Strong
interest in and knowledge of field ; degree ,
good technical background and experience.
Include full resume and salary desired in
first letter. Box 00-1 Audio Engineering.
159-19 Hillside Avenue • Jamaica 32. N. Y.
OLympia 8-0445
You got troubles? Let us fix them!
COMPETENT ENGINEERS
FULLY-EQUIPPED AUDIO
LABORATORY
TECHNICIAN
Distortion, frequency-response.
a nd other
measurements; hum el imination , correction
of faulty operating conditions, performance
improvem ent to your requirements . Write,
descri bing your problems for estimate.
Box PV-l, AUDIO ENCINEERINC
AUDIO ENGINEERINC
•
Selects and correclly
comp ensates for Ihe characteristics of TV
tuner, radio tun er, crystal phonograph pick·
'up; plus magnelie phonograph pickup equal·
Ized for FIVE different reco rding character·
Istics Including the NEW ORTHOPHONIC
RECORDING CURVE.
Wide range frequency re sponse - 20 to
20,000 cycles ± 1;' db. Ten wal ts of power
outpul at less than 1% harmonic distortion.
Record er output jack permits recording
while lislening.
With knowledge of high-fidelity audio
sought by progressive New York City firm.
Will produce and market high-quality line
of amplifiers and speakers. State qualifications and salary desired . Box DD-2, Audio
Engineering.
DECEMBER, 1953
Unsurpassed In hig~ tonal definition, In
fallh fulness of reproduction, In
hearing satisfaction. Hear
it loday al your dealer's.
69
Left to right : Arrow Electron ics, Inc ., Asco Sound Corporat ion , Hudson Radio (;, T elevision Corp.
The Distributor-Exhibitors
HAT CAN BE SAID about the distributors who exhibited at the Fair?
They all have essentially the same
equipment to show, and relatively little
can be done to make the same equipment
look any different no matter how it is
placed.
Instead of extoll ing the exhibits or the
equipment showll by the distributors, we
prefer to take this space to extol these important organizations for the work they
have to do in carrying the message to the
ultimate user of audio equipment. For the
W
tuners. So both turn to the distributor's
salesman for advice, and it is these men
who are the final contact in the long line
from manufacturer to consumer.
The consulting room of a professional
man could scarcely be more enlightening
to the student of human nature than the
sales room of an audio distributor. The
questions asked, the problems outlined, and
the constant weighing of the merits of
this unit against that one all add up to an
interesting picture of the hi-fi business. T he
distributor's salesman has, over the past
few years, developed into a competent consultant on audio, and we take off our hat
to him. He has tact and patience and an
enormous fund of information on a complicated subject, and we know of few other
types of business in which so much depends
on the salesman.
Our sincere compliments, therefore, to·
this group of men who struggle to make
every newcomer to hi-fi a true convert,
men who must satisfy every customer as·
to the performance, cost, and appearance
of the merchandise they sell.
Left to right : Leonard Radio, Inc ., Radio- W ire -T elevision , Inc., Sonocraft Corporation.
distributor and his salesmen are far more
than purely a sell ing organization-each
one of the men on the "firing line" has to
be a diplomat and an engineer in addition
to being a good salesman. People shopping
for any product in the audio category are
- in most instances-in a field where they
are not too familiar, and consequenfly they
have to rely on the sales engineer to advise
them on the equipment they need. What
may be ideal for the well-to-do buyer with
a 30 x 50 foot living room may not fi t the
requirements
of
the
small-apartment
dweller. The needs of the suburbanite are
likely to differ appreciably from those of
the city fo lk, particularly with respect to
CORRECTED SCH EMATIC
The article, "A Three-Element Bass Control" by Glen Southwor th, which appear ed,
in the October issue has been the subject of considerable correspondence from readers
who were plagued by the reproduction of the schematic, Fig. 5 on page 25. Remade, the'
cut now shows the decimal points in more readable proportions. JE regrets the inconvenience caused to any of its readers.
.
Sun Rad io (;, Electronics Co. , Inc .
70
AUDIO ENGINEERING
•
DECEMBER ,
195~
!J~
N0ie4 ...
The Ampex Corporation has created a
whollY-(HV n ed s u bsidiary to be known a s
the Ampex Loudspeaker Company, according to recent a nn ouncement of Alexander
M. Poniatoff, president. Initia l o u tput w ill
consist sole ly of theatri cal speakers to
fulfi ll Am p ex commitments to equip theaters with m ulti-directional sou nd systems
used with 3-D and wide-screen techniques.
Ampex speakers are b eing built under
license from James B. Lansing Sound,
Inc., u nder management of Thomas L.
T aggart, Ampex comptroller.
Newark Electric Company, 223 W. Madison St., Chicago 6, Ill., is inaugurating its
second expansion program within a period
of eighteen months. After increasing
space from 12 to 25 thou sand sq. ft. in
May, 1 952 , Newa rk added another 10
t h o usand sq. ft. in November; la test expansion will be used la rgely to increase
sales space a nd high-fidelity d emonstration q uarters.
Pentron Corporation, Chicago, is s ub stantially increasing production faci lities
to meet the d e mand necessitated by
g r owing sales. According to announcement of Irving Rossman, P enh'on president, n ewly-leased quarter ~ wil l be devoted essentially to asse mbly operations.
Beeves Soundoraft Corporation has licensed 20th Century -Fox Film Corporation
to u se Soundcraft's Magna-Stripe process
in the produc tion of release prints for
CinemaScope productions, according to
Frank B . Rogers, R eeves vice-presid ent.
Soundcraft has installe d in the Fox Hollywood studies a Magna-Striping machine
which i s n ow working f ull time on t he
produ ction of mutistriped print stock for
a number of CinemaScope productions
soon to be released.
Personal NotesArthur Z. Adelman has joined his
fat h er's firm, Leon L. A delma n Co., manufact urers' r epresentative, as field representative . . . Entire e l ectronic industry
shar es bereavement of Burnstein-Applebee, Inc., at recent death of Joseph A.
Burnstein, company president . . . C. G.
Barker, former vice-president of Magnecord, Inc., h as been n a med distribution
manager of The National Company, Malden, Mass., Chris J. Witting, manager of
the Dumont Television Network, has been
named pres ide nt of Westinghouse Radio
Stations, Inc., effective January 1 . . .
E. W. Nielsen is new president of Best
Manufacturing Co., Inc., Irvington, N. J.
Brook Electronics, Inc., announces t he
appointment of Evelyn J. Korne to its
advertising department.
Some salient characteristics:REFERRED PRIMARY LOADINC. The standard models cover the requirements of all
popular tubes. Each half primary is brought
out separately to posts and Is tapped at
43 % of the turns.
POWER RATINC. Peak 50 watts.at 60 c.p.s.
or 14 watts at 30 c.p.s. for less than 0.5%
harmonic distortion without feedback .
LEAKACE INDUCTANCE . . 10 mH o SELF
CAPACITY . • 500 pF. full primary.
NOW for $25 duty paid you can have this p.p.
transformer specifically designed for really highquality audio equipment. Having an extended \
frequency range and low harmonic distortion it
enables a large measure of N.F.B. to be taken from
the secondary circuit and appl ied three or four
stages back. The superlative properties of the
latest strip wound grain orientated material are
used to the maximum advantage. The unit is
hermetically sealed in a deep drawn case of purposeful design .
• . • and it's AVAILABLE NOW I
from your usual jobber; if in difficulty
write direct-we'" see you are supplied
without delay.
Ask for Technical Data • •
mailed free on request.
PARTRIDGE ' TRANSFORMERS
',,:
H
, T OLWORT
'.
•
·.~" _ SURREY·
•
LTD
eNGLAND
.
In introduc ing our Audio-Con so lette, we believe
that we ha ve set a n ew standard of qual ity for
equipment of thi s type . Its top-grade components
include carbon-deposit resist o rs, Allen-Bradl ey
co ntrol s, and a high " Q" t oroi d .
Some features: 3 low level-4 high leve l inputs.
Recorder & main outputs. Cutoff filter. Independent loudness compensato r. Separate 6-position
phono equalizers for bass & treble. Unu sually low
I.M . di st ortion. Totally inaudible
hum at full gain. Ample voltage Audio Consolette
gain. Two-chass is construction .
Cabinet
Write for specifi cation s.
AUDIO ENGINEERING
•
DECEMBER, 1953
$142.50
12.50
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MONTHLY SUMMARY ot product develop·
ments and price changes of radio electronic-television parts a nd equipment,
su pplied by United Catalog Publishers, Inc.,
110 Lafayette Street, New York City, publishers of Radio's Master.
These REPORTS will keep you up-to-date In
this ever-changing industry. They will also
help you to buy and specify to best advantage.
A complete description of most products will
be found In the Official Buying Guide, Radio's
Master-available through local radio parts
wholesalers.
Audio
Broadcasting equipment
Acoustics
Home f"eproduction systems
Recording
PA systems
Psychoacoustics
(Please print)
Name
Address
........ ... . . . . . ..
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RCA- Added " Radiotron Designer's Handbook," 4th Edition,
at $7. 00 user price.
RIDER , JOHN F.-Added No. 148 "Guide to Audio Reproduction" at $3 .50 net.
RINEHART BOOKS-Added "Hlgb Fidelity Techniques" at
$7.50 net.
ACRO PRODUCTS-Added Model TO·33 0 Transformer at
$39. 75 net.
AMPEX ELECTRIC-I ncreased prices on the component
parts of the Model 450 Audio Magnetic Tape Reproducer
seri es.
BROCINER ELECTRONICS-Added model 4W wall horn at
$42 0.00 consnmer price.
BRUSH ELECTRON ICS-Added model BK45 5P " Soundmlr·
ror" high-fidelity tape recorder at $289.50 list.
FAIRCHILD RECORDING - Added model 828 automati c
_ spiralling attachment at $57 0.00 net; model 829 ~acuum
chip syStem lit $150.00 net.
GENERAL ELECTRI C-Added IJl()del A1· 200 preamplifier
control unit at $57. 95 net; model A1·a OO 10 -watt amplifier at $47.75 net; model Al-400 12·ln. dual coaxial
speaker at $41.95 net ; model Al-406 loudspeaker enclosures, blonde at $59 .95 net, mahogany at $59.95 net,
unfinished at $50 .37 net.
KINGDOM PRODUCTS-Added model LP65 2'h -io. tweeter
at $8.50 user price; model LP215 9-in. loudspeaker at
$22.50 user price.
LANSING SOUND. JAMES B.-Added model 150-4B 15-in.
low-frequency horn driver unit at $ 114.00 net.
NATIONAL HOLLYWOOD-Discontinued tbeir sapphire phono
needle series.
ORRAOIO INDUSTRIES-Increased price on " Irish" tape
195RPA, plastic base, 1200 It. on plastic or metal reel
to $3.75 net.
PENT RON - Discontinued model PB·1 tape player.
Position . . . . .. . .. . Company ... ... ... .
Name : ..... . ........ . ... . . . ... . .. . . .
FOR SALE: Fisher Master Audio Control,
model 50-C, used less than 40 hours. $55. Call
WA 7-8669 (N. Y.) or write Box CD-4, AUDIO
Address
ENGINEERING.
Position .... .. . . . . Company .. . .... .. .
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Name .. .... .. . .... ...... .. .. . ...... .
Address
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SACRIFICE: Brand-new Altec 604C in
beautiful TInimode bass-reflex ca binet. Consumer's net $300, selling f or $200. Reice
Hamel, 325 Midwood Street, Brooklyn 25 ,
N. Y. PR 2-4563.
Company .. . •. . .. . .
FOR SALE: (Phila. area only) Pres to 15-G
turnta ble in wooden ca binet; Proctor Soundex
multis12eed turntable; Proctor and Pickering
arms. :j;100 takes a ll. Call GR 3-0948.
Name .... ... . .. . .. . . . .. .. . . . . . ..... .
BROWNING RJ-12C AM-I~M tuner with
power s upply, $105. Ap t . 3M. 34-35 76th St.,
Jackson Heights, N. Y. IL 7-8649.
Position . . . . . . . . .. Company
Name ... . . . . . . . ... . . .. . . . .... .. . ...•
Address . . . ... .. . ... .. . .• . .. .
.. •. .. Company . . ... . ... .
Name
Addres s
Position
. . ..... . Company ..... . . . . .
U. S., Possessions, and Canada ' only.
RADIO MACAZINES, INC.
P. O. Box 629, Mineola, N. Y.
72
AUDIOPHILES wanted for part or full
tim e wo rk. T echnical o r secreta rial experience
desirable. Lo cation: north suburba n Philadel·
phia. Send resume of edu cation and e xpe ri e n c ~
to Box CD-I , A UDIO E NG l x EEIU NG.
PRESTO Y-3 r ecord er in new condition, lIsed
less than 15 hours, 112 and 224 lines, 1D cu t·
t er, G.El. VR play back. $400. C. F. Craig, 3802
Grand Ave., Oma ha II , Nebr.
3-W AY Klipschorn system built by Kli pschorn sales engin eer. Klipsch-type compon·
ents. Seller will provide A-B a gain s t commercial Klipsch orn. $<145. TWiuing 6-0916 Fores t
Hills, N. Y.
'
FOR SALE : Pres to 9 0B recordin g amplifier ,
guaran teed excellent condition, $285 ; Gray
603 Equalizer. $30. Louis Brown, 2217 Alexande r , ~"acO I '£exas.
FOR SALE: Lowther PW1 corner horn
$95; Lowther-Voigt PM2 driver also avail:
able. R oyal II type enclosure, with J ensen
15-in. w oofer). St ephens h .f. driver , Hoodwin
8HD horn, 8uO-cps network, complete, $175;
n ew Pilot P A-911 preamp, $2 2. All perfect
condition. FOB. Hovland, 151 Hartford Tnpk ..
Hamden, Conn .
. KITS ASSl)]MBLED: designate tuner, amplifier, test mstrument, add 25 % . Bridges
E lectronics, Randolph Rd., Rockville. Md.
CRAFTSMAN R C-10 Tun er, like new, $95.
Dupre, 16-A Glendale St .. Worces ter.
~a;;:
WANTED: Used FM t u ner, a lso tape recorder. Box CD-2, AUDIO ENGINE EIIING .
WRITE FOR FREE TRIAL and data on
our "Battleship Built" Williamson Amplifie r.
NIcely ASSOCiates, Kenton, Ohio .
SELL ': Altec 604C, McIntosh C104A, Uni verSity 440!lJ make oll'er. C. B. Parkinson 4 31
Encinitas, mon rovia, Calif.
'
UNIQUE BARGAIN. New, guaranteed in
manufacturers' cartons: Browning RV31 $88 '
Bell 2200, with pilot light, $89; Wharfedale
Super-12, $58; R-J floor model, 12-in. enclosure, unstained, $36; Ga rrard RC-80 with
base, $38; G.E. Golde n Treasure, certified
flawless diamond and sapphire, $19.50. As
complete system, rock-bott om price $315. B ox
CD-3, A UDIO E NGI NB ERING.
•••
Address
Position . "
WILLIAMSON amplifiers-buy direct f rom
factory and sa ve 50 0/0 . Prices sta r t at $56.
Send pos t card fo r lis t. Long I sla nd Sound Co ..
19 B enu ett Place, Amity ville, N. Y.
CANADIANS-Two complete systems for
sale, including Concertone recorder, Weathers
pickup R ek-O-Kut turnta ble. Write for details. L. K. Cra bt ree, 765 118th St., Shawinig an South, Quebec.
WANTED: Experienced efficien t, d ependable radIO and Hammond Organ service man
t o take over our shop and operate it as own
bu sin ess. $2000 capital r equired. Will finance
a portion if necessar y. Mu st have good r ef erences a s to cha ra cter, dependabilit y a nd
c ~edit. A highly profita ble opportunity for the
l'lght man. Pre vlO!ls Hammond organ experien ce not r eqUired if you h ave a go od working
knowledge of electroni cs. TERRY' S MUSIC
STORE, In c., 309 Ma in S t., La Crosse. Wis.
BRUSH BK-401 t a pe r eco rder chassis. Tape
transport, recording amplifi er , and playback
preamplifier only. Recently ch ecked by Brush
dealer, $65. Arthur Bunker, 4947 Ward Parkw ay , Kan sa s City, Missouri.
FOR SALE: 5-cu. ft. speaker cabiuet $10'
3-cu. ft. speaker ca binet, $8; Meissner BC FM
tuner, $38; Miller 585 tubeless tuner $7'
Jensen P8R, ST-169, $6; Triplett 666H' volt:
ohmmeter with case, $12 ; two Wes tern Electric 0-200 microamm e te r s, $18; 75 a ssorted
tubes, 10 0/0 oil' net. T. M. Olsen, 745 E . 242nd
St., Bronx 70, N. Y.
TRADE your unwanted electronics equipment for fin est new audio components at
AUDIO LABORATORIES, 2111 Camden Ave ..
Los Angeles, Calif.
FOR SALE: Magnecorder PT6-M, PT6-J,
PT6 -AH, extra equa lizer , extra t win-track
h e ~d, 2 carry.ing cases, $400. Excellent condItIOn. Assocmted Recording Studios. 1625
Broadway, New York 19, N. Y. CIrcle 5-7<151.
FOR SALE: Concerton e HOlD and 1401S
tape reco rders, brand n ew , full warra nty
usual net $345, uubelievable special $2 60:
Nation~lly advertised Williamson Amplifiers
(not kIts-fully assembled , t ested) featuring
P eerless tra n sform e rs, KT-66 output tubes
u sua l ne t $99.95, our special $75; BOZAK
3-way system, demon strato r, includi ng 12· in.
w oofer, mIdra n ge, two tweet er s, divi.din g n e t work, 8-cu. ft. sea led en clos ure, Bozak endorsed, us ually $225, close out $165' many
oth~r in teresting bu ys in uew an d secon'd hand
eqUlpme!lt, gen erou s trade-in s a llowed. Write
for detmls to : Audio Ba" gain Center Box 12
Fleetwood S t ation, Mt .. Vernon , N. Y.
'
VIRGIN Presto Thermos tyli. Box 101, St.
Alban s, N. Y.
A\JDIO ENGINEERING
•
DECEMBER, 1953
Audio Engineering-1953
SUBJECT INDEX
Allied Radio Corp., N ew Home for. O ct.,
31.
Amplifiers
Distortion in Voltage Amplifi'ers, W . B.
Bernard. Feb., 28.
Everyman's Amplifier, G. Leonard Wern er
& H enry Berlin. Oct., 40.
Feedback from Output Tr-ansformer Primary, AUDIOLOGY. May, 14.
Feedback from Output Transformer Secondary, AUDIOLOGY. July, 14.
Hum Reduction in Amplifier D evelopment,
AUDIOLOGY. June, 14.
Improvements on the Universal T ape R ccorder Amplifier. C. G. McProud. Sept.,
44.
Moderately Priced Amplifier Introduces
Loudness Control Selector, L. H. Bogen
& Alfred M. Zuckerman. May, 31.
Optimum Loading for Power Amplifiers ,
AUDIOLOGY. Aug., 12.
Pass Band of a Transformer Coupled Amplifier, Joseph F. Sodaro. June, 24.
Precision Phase Splitting, AUDIOLOGY,
Nov., 12.
R-C Coupled Amplifier Cha rts, AUDIOLOGY. Oct., 12.
Simplified Push-Pull Theory. Jul;us Postal.
I, May, 19; II, June, 21.
Stability Testing of Feedba ck Amplifiers,
AUDIOLOGY. Sept., 14.
Three-Channel Tone-Control Amplifier,
Joseph F. Dundovic. Apr., 28.
White Powrtron Amplifier, Stanley White,
Nov., 32.
Zero-Impedance Output Stage, R. G.
Anthes. Jan., 21.
Amplifiers, PreHigh-Fidelity Phonograph Preamplifier
Design, R. H. Brown. Apr., 19.
Amplifier Design
Circle Diagrams for R-C Coupled Amplifiers, Olan E. Kruse. Feb., 22.
Feedback-Degenerative and Regenerative, Rudolph L. Kuehn. Apr. 23.
New Approach to Negative Feedback D esign, N. H. Crowhurst. May, 26.
ASCO Unveils Flexible Sound Display
Room. Feb., 36. "
-Audio for Leisure Hours. July, 25.
Audio in the Year 1693, Allen H . Fry,
Mar., 25.
IE Goe; to London and Paris. June, 38.
Audio Fair, The
Audio Fair-Los Angeles. Jan. 38.
Audio Fair and AES Convention R each
New Heights. Nov., 29.
Audio Fair Review. Dec., 28.
Awards
Audio Engineering Awards. May, 24.
Review of the Audio Enginee ring Awa rds,
June, 28.
Book Reviews
Applications of the Electronic Valve, by
Dammers, Haantjes, OUe, and Va n
Suchtelen. Feb., 14.
Bas ic Electronic Test Instruments, by
Turner. Oct., 16.
Circuit Theory of Electron Devices, by
Boine. Dec., 6.
Electri cal Engineering-The ory and Practice, by Erickson and Bryant. Feb., 69.
AUDIO ENGINEERING
•
Electrophysiological T echnique, by Dickinson. June, 63 .
Fundamentals of Automatic Control Systems, by Farrington. Mar. 10.
Fundamentals of Engineering Electronics,
2nd Ed., by Dow. Feb., 69.
PhotoeJ.ectric Tubes, by Sommer. Oct., 16.
R adio Interference Suppression, by Stephens. Feb., 14.
Radiotron D esigners H andbook, 4th Ed .,
edited by Smith. Sept. 12.
Sound R eproduction, 3rd Ed ., by Briggs.
June, 63.
Thermionic V acuum Tubes and Their
Applications, by Aldous . Nov., 49.
Broadcasting
Auxiliary or Emergency Broadcast Con trol Room, Harold R eed. Mar., 26.
Auxiliary Mixer for TV Studios, George
A. Singer. Apr., 26.
Binaural R adio Broadcasting, Harold T .
Sherman. Jan., 14.
Complete Remote Control of an Ampex
300, Richard F. BIinzler. Oct., '23.
Simplified. PrograI'1 Switching Panel, Harold Reed. Feb., 25.
Cabinets
Tired Business Man's Radio Cabinet and
Speaker, C. C. Fraser. Dec., 26:
Vibration Reduction in Loudspeaker Enclosures, Gladden B. Houck. Dec., 24.
Components
Audio Transformer Design, N. H. Crowhurst. Feb., 26.
Making the Best of an Audio Transformer,
N. H. Crowhurst. Jan., 40.
Output Transformer Design Considerations, AUDIOLOGY. Apr., 14.
Construction Practice
Bread-Pan Layout, L. B. Hedge. Aug., 24.
Making a "Front End" Handsome, William H. Burke, Nov., 20.
Controls, Tone
Flexible Tone-Control Circuit, Basil T.
Ba rber. Sept., 29.
Selection of Tone-Control Parameters, Edgar M. Villchur. Mar., 22.
Three-Channel Tone-Control Amplifier,
Joseph F. Dundovic. Apr., 28.
Three-Element Bass Control, Glen Southworth. Oct., 24.
Controls, Volume
Note on Volume Controls, Charles P.
Boegli. Apr., 40.
Crossover Networks
Basic D esign of Constant Resistance Crossovers, N. H . Crowhurst. Oct. 21.
Dictating Machine-A Specialized R ecording System. Richard M. Somers. I, Aug. ,
22; II, Sept., 24.
L eak TL-1 2 Amplifier, June, 42.
Lorenz Speakers, Sept., 64.
Newcomb Classic 25 Amplifier, Feb., 38.
Pilotone AA-901 Amplifier and AF -821A
Tuner, Mar., 44.
Pilotuner, AF-824. Aug., 32.
Raul and Model 1826 with the Libretto.
Oct., 35.
Sargent-Rayment SR-68 Tuner. July, 32.
Sonocraft FM Tuner. Jan., 56.
TapeMaster HF -500 Recorder. Oct., 34.
UTC W-20 " Williamson" Kit. May, 42.
Feedback
Feedback and Loudspeaker D amping, John
A. Mulvey. Apr., 34.
Feedback-Degenerative and R egenerative,
Rudolph L. Kuehn. Apr., 23.
Feedback from Output Transformer Primary, AUDIOLOGY. May, 14.
Feedback from Output Transformer Secondary, AUDIOLOGY. JulYI 14.
New Approach to Negative Feedback Design, N. H. Crowhurst. May, 26.
Stability Testing of Feedback Amplifiers,
AUDIOLOGY. Sept. 14.
Handbook of Sound Reproduction, Edgar
M. Villchur. Chap. 8, Jan., 30; Chap.
9, Feb., 30; Chap. 10, Pt. 1, Mar., 32; Pt.
2, Apr., 29; Chap. 11, Pt. 1, May., 34;
Pt. 2, June, 30; Cha,!). 12. Pt. 1, July,
26; Pt. 2, Aug., 26; Pt. 3, Sept. 36;
Chap. 13; Oct., 42; Chap. 14, Nov., 25;
Chap. 15, Pt. 1, Dec., 34.
Hearing Aids
Design Considerations, AUDIOLOGY. Dec.,
12.
Sonotone Transistorized H earing Aid,
Harry A. Pearson. Alii!'., 19.
Hum Reduction in Amplifier Development,
AUDlOt~GY. June, 14.
Loudspeakers
75th Anniversary of First Dynamic
Speaker, Murlan S. Corrington. Feb. 12.
Basic Design of Constant-Resistance Cross'overs.' N. H. Crowhurst. Oct., 21.
Coupled Loudspeakers, Charles W. Harrison, Jr. May, 21.
Feedback and Loudspeaker Damping, John
A. Mulvey. Apr., 34.
Great Loudspeaker Mystery, H. A. Hartley. Jan., 33.
Horn Enclosure for Custom Installations,
Arnold .J. Gassan. Sept., 22.
Make Your Own Woofer, Curtiss R. Schafer. Nov., 19.
Practical Aspects of the R-J S,peaker Enclosure, William Joseph & Frank Robbins. Jan., 19.
Theatre Sound in a Small Package, Thomas
R. Hughes. I, Feb., '19; II, Mar., 30;
III, Apr., 24.
Vibration Reductioril in Loudspeaker Enclosures, Gladden B. Houck. Dec., 24.
Electronic Music
Organ for One-Finger Artists, Ri chard H.
Dorf. Sept., 19.
Measurements
New Volume Visualizer, Norman Prisament. Sept., 30.
Twin-Triple Resistance Decader and
Bridge, L. B. Keirn. Sept., 34.
Wide-Range R-C Oscilla.to~, ~ewis S.
Goodfriend . Feb., 21.
Equipment Reports
Bogen R701 AM-FM Tuner, Sept., 42.
Collaro Changer, Apr., 42.
Concertone 1501-S Tape Record er,. July,
30.
Musical Instruments
The Piano, Albert Preisman. I, Oct., 26;
II, Nov., 22.
Organ for One-Finger Artists, Richard H .
Do,f. Sept., 19.
DECEMBER, 1953
73
Patents
"First Inventor" Under the 1952 Patent
Law, Albert Woodruff Gray. Mar., 40.
P atentable Features in Radio Inventions,
Albert Woodruff Gray. June, 36.
The Protection of Ideas, Albert Woodru ff
Gray. Jan., 36.
Phase Splitters
Precision Phase Splitting, AUDIOLOGY.
Nov., 12.
Phonograph Equipment
Effect of Load Impedance on the Frequency Response of Magnetic Pickups,
Norman C. Pickering. Mar., 19.
Lateral Mechanical Impedance of Pickups,
.T. G. Woodward and J. B. H alter. J,
June, 19; II, July, 23.
.
New Wide-Range Phonograph Cartrid ge .
John F. Wood, Dec., 22.
Phonograph Records, The Best British, of
1952, H. A. Hartley: Apr., 44.
Phonograph Reproduction
The Columbia " 360," Peter C. Goldmark .
Mar., 28.
Columbia " XD" Speaker System, Peter C.
Goldmark . Oct., 36.
Effect of Load Impedance on the Frequency Response of Magnetic Pickups,
Norman C . Pickering. Mar., 19.
High Fidelity Phonograph Preamplifier
Design, R. H. Brown. Apr., 19.
Photography
Audio Photographers Check List, Eugene
F. Coriell, Mar. 14.
Power Supplies
D . G. Pack for H eaters and Bias, Allan M.
Ferres. Sept., 33.
Psychoacoustics
Binaural or Stereophonic? R. J. Tinkham.
Jan., 22.
/J
:J~~ l".r
,I
ti"i,1S
Binaural Public Address, Charles F. Adams.
Feb. 24.
Binaural Radio Broadcasting, H a rold T .
Sherman . .Tan., 14.
.
Great Mystery of Dannemora Dungeon,
Emory Cook. Oct. 50.
Two-Channel Conversion for AM-FM Receivers, C. G. McProud. Jan., 25.
Public Address Systems
Binaural Public Address, Charles F. Ad ams.
Feb., 24.
Canadian House of Commons Sound Installation by Tannoy. Apr., 38.
System Design
It Can Be Attractive, C . G . M cProud .
Nov., 30.
M atched Line of Hi-Fi Sound Equipment,
Harry F. Olson. Aug., 29.
Simplified Program Switching Panel, Harold Reed. Feb., 25.
Tools for Building Temples of Tone. Oct.,
Recording, Disc
Automatic Disc Recorder, Curtiss R. Schafer. Dec., 21.
Evolution of a Recording Characteristi c,
R. C. Moyer, July, 19.
Flexible Single Recording and Dubbing
Channel, Hal Magargle. Jan., 28,
Recording, Magnetic
"\
Complete Remote Control of an Ampex
300, Richard F. Blinzler. Oct., 23.
Correction of Frequency R esponse V ariations Caused by M ag'netic Head Wear,
Kurt Singer & M. Rettinger. July, 29.
Flexible Single Recording and Dubbing
Chamtel, H al Magargle. Jan., 28.
Improvements on the Uni versal T ape R ecorder Amplifier, C . G. McProud. Sept. ,
44.
Magnetic Transfer of Stainless Steel Wire,
Samuel 3torchheim. Dec., 19.
Multiple-Track Magneti c H eads, Kurt
Singer & M . R ettinger. Aug., 34.
Top Tape R ecording Performance,· H arold
R eed. June, 26.
Stereophonic Sound
Binaural or Stereophonic ? R. J . Tinkham.
.Tan., 22.
-t
.f
IJ&a
Volume Controls, A Note on, Charles P.
Boegli. Apr., 40.
t\~5
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This offer is good only in the U. S. and applies only to subscriptions
entered by se.n ding your request and check to the address below.
•
Tubes
Power Tube Figure of Merit, Warren G.
Bender. Mar., 21.
t:G\Ntt\\NG,,,.E
E RECE,VE
ItREFOR
'f of ~
,.~E RES
,.1'1 0 UoUS\.."i fOR
CON,.,N
~,
Transformers
Audio Transformer D esign, N. H . Crow·
hurst. Feb., 26.
Making the Best of an Audio Transformer,
N. H. Crowhurst. Jan., 40.
Output Transformer Design Considerations, . AUDIOLOGY. Apr., 14.
••
••
.,
A\lll \ \\
,1'0
Tone Controls
Flexible Tone-Control Circuit, Basil T .
Barber. Sept., 29.
Selection of Tone-Control Parameters, Edgar M. Villchur. Mar., 22.
Three-Channel Tone-Control Amplifier,
Joseph F. Dundovic. Apr., 28.
Three-Element Bass Control, Glen South·
worth. Oct., 24.
:~--------------------~----~
:)lib
Vl\\.\. 'f~
.
: The New
£. ainninf
i' b1\ttibtt ,.
IS'
54.
•
•
DO YOU HAVE
YOURS?
.
Case for Music, John H. Thomson. Sept.,
32.
.
Great Loudspeaker Mystery, H . A. Hartley . .Tan., 33.
High Futility-An Essay on Scale Distortion, Joe L. Dickey. Apr., 21.
Great Mystery of Dannemora Dungeon,
Emory Cook . Oct., 50.
•
RADIO MACAZINES, INC.,
P. O. Box 629, Mineola, N. Y.
Enclosed is check 0 money order 0 for $25 .00 for which please enter my
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Name (please print) .... .. . .. . ... . . . ... .... . . .. . ... .. . . . .. .. .
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City . . . . . . . . . . . . . . . . . . Zone . . . . . . . . State . . . ... ..... ...... .
74
$65 F.O.B. Factory
For Milar Tape, add $2
Sample splice and brochure on request.
flRESTOSEAL C~~~·.
3727 33rd st.,long Island City 1, N. V.
AUDIO ENGINEERING
•
DECEMBER, 1953
AUTHOR INDEX
Adams, Charles F.
Binaural Public Address. Feb., 24.
Anthes, R. G.
Zero-Impedance Output Stage. jan., 21.
Ayres, W. R. (AUDIOLOGY)
Feedback from Output Transformer Primary, May, 14.
Feedback from Output Transformer Secondary, July, 14.
Hearing Aid D esign Considerations.
Dec., 12.
Hum Redu ction in Amplifier Development. June, 14.
Optimum Loading for Power Amplifiers.
Aug., 12.
Output Transformer Design Con ~ id e rations. Apr., 14.
Precision Phase Splitting. Nov., 12.
R-C Coupled Amplifier Charts. Oct., 12.
Stability Testing of Feedback Amplifiers.
Sept., 14.
Barber, Basil T.
Flexible Tone-Control Circuit. Sept., 29.
Bender, Warren G.
A Power Tube Figure of M erit. Mar"
21.
Berlin, Henry & Werner, G. Leonard
Everyman's Amplifier. Oct., 40.
Bernard, W. B.
Distortion in Voltage Amplifiers. Feb.,
28.
Blinzler, Richard F.
Complete Control of an Ampex 300.
Oct., 23.
Boegli, Charles P.
A Note on Volume Controls. Apr., 40.
Bogen, L. H. & Zuckerman, Alfred M.
Moderate Priced Amplifier Introduces
Loudness Control Selector, May, 31.
Brown, R. H.
High-Fidelity Phonograph Preamplifier
Design. Apr., 19.
Burke, William H.
Making a "Front End" Handsome. Nov.,
20.
Crowhurst, N. H.
Audio Transformer Design. Feb., 26.
Basic Design of Constant R esistance
Crossovers. Oct. 21.
Maki ng the Best of an Audio Transformer. Jan., 40.
A New Approach to Negative Feedback
D esign. May, 26.
Cook, Emory
The Great Mystery of Dannemora Dungeon. Oct., 50.
Coriell, Eugene F.
Audio Photographers Check List. Mar.,
14.
Corrington, Murlan S.
75th Anniversary of
Speaker. Feb., 12.
First
D ynam i
.
Dickey, .Toe L.
H igh Futility-An Essay on Scale DIs- tortion. Apr., 21.
Dorf, Richard F.
Organ for One-Finger Artists. Sept., 19.
Dundovic, Josenh F.
Three-Channel Tone-Control Amplifier.
Apr., 28.
Ferres, Allan M.
D. C. Pack for Heaters and Bias. Sept.,
33.
Fraser C. C.
T ired Business M an's R adio Cabinet and ·
Speaker. Dec., 26.
AUDIO ENGINEERING
•
Fry, Allen H.
Audio in the Year 1693 . Mar., 25.
Gassan Arnold.J.
Horn Enclosure for Custom Installations .
Sept., 22.
Goldmark, Peter C.
,
The Columbia "360." Mar., 28.
The Columbia "XD" Speaker System.
Oct., 36.
Goodfriend, Lewis S.
A Wide-Range R-C Oscillator. Feb., 21.
Gray, Albert Woodruff
"First Inventor" Und er the 1952 Patent
Law. Mar., 40.
Patentable Features in R adio Inventions. June, 36.
The Protection of Ideas . Jan., 36.
Halter, J. B. & Woodward, J. G.
The L ateral M echani cal Impedance of
Pickups. I, June, 19; II, July, 23.
Harrison, Charles W., Jr.,
Coupled Loudspeakers. May, 21.
Hartley, H. A.
The Best British Records of 1952. Apr.,
44.
Great Loudspeaker Mystery. Jan., 33.
Hedge, L. B.
The Bread-Pan Layout. Aug., 24.
Houck, Gladden B.
Vibration Reduction in Loudspeaker Enclosures. Dec. 24.
Hughes, 'Thomas R.
Theatre Sound in a Small Package. I,
Feb., 19: II, Mar., 30; III, Apr., 24.
Joseph, William & Robbins, Frank
Practi cal Aspects of the R-J Speaker
Enclosure. Jan., 19.
Keiin, L. B.
Twin-Triple Resistance D ecader &
Bridge. Sept., 34.
Kruse, Olan E.
Circle Diagrams for R-C Coupled Amplifiers. Feb., 22.
Kuehn, Rudolph L.
F eedback-Degenerative and R egenerative. Apr., 23.
Magargle, Hal
A Flexible Single R ecording and Dubbing Channel. Jan., 28.
McProud, C. G.
Improvements on the Universal Tape
R ecorder Amplifi'e r. Sept., 44
It Can be Attractive. Nov., 30.
Two-Channel Conversion for AM-FM
R eceivers. Jan., 25.
Moyer, R. C.
The Evolution of a R ecording Characteristic. July, 19.
Mulvey, .John A.
F eedback and Loudspeaker D amping.
Apr., 34.
Olson, Harry F.
M atched Line of Hi-Fi Sound Equipment. Aug., 29.
Pearson, Harry A.
The Sonotone Trans istorized H earing
Aid. Aug., 19.
Pickering, Norman C.
The Effect of Load Impedance on the
Frequency R esponse of Magnetic
Pi ck uDS . Mar., 19.
Postal, .T ulius
Simnlified Push-Pull Theory. I, May,
19; II, June, 21.
D.ECEMBER, 1953
Preisman, Albert
The Piano. I, Oct., 26; 11, _Nov., 22.
Prisament, Norman
A New Volume Visualizer. Sept., 30.
Rettinger, M. · & Singer, Kurt
Correction of Frequency Response Variations Caused by Magnetic Head
Wear. July, 29.
Multiple Track Magnetic Heads. Aug.,
. 34.
Reed, Harold
Auxiliary or Emergency Broadcast Control Room. Mar., 26.
A Simplified Program Switching Panel.
Feb., 25.
Top Tane Recording Performance. June,
26.
Robbins, Frank & joseph, William
Practical Aspects of the R-j Speaker
Enclosure. Jan., 19.
Schafer, Curtiss R.
An Automatic Disc Recorder. Dec., 21.
Make Your Own Woofer. Nov., 19.
Sherman, Harold T.
Binaural Radio Broadcasting. Jan., 14.
Singer, George A.
Auxiliary Mixer for TV Studios. Apr.,
26.
Singer, Kurt & Rettinger, M.
Corrections of Frequency Response Vari- .
ations Caus'e d by Magnetic Head
Wear. July, 29.
Multiple-Track Magnetic Heads. Aq,g.,
34.
Sodaro, joseph F.
The Pass Band of a
Transformer
CouDled Amplifier. june, 24.
Somers, Richard M.
The Dictating Machine-A Specialized
Recording System. I, Aug., 22; II,
Sept., 24.
Storchheim, Samuel
Magnetic Transfer of Stainless Steel
Wire. Dec., 19.
Thomsom, John H .
The Case for Music. Sept., 32.
Tinkham, R. J .
Binaural or Stereophonic? Jan., 22.
Villchur, Edgar M .
Handbook of Sound Reproduction.
Chap. 8, Jan., ,30; Chap. 9, Feb., 30;
Chap. 10, Pt. 1. Mar., 32; Pt. 2, Apr.,
29; Chap. II , Pt. I, May, 34; Pt. 2,
june, 30; Chap. 12, Pt. 1, july, 26;
Pt. 2, Aug., 26; Pt. 3, Sept. 36; Chap .
13, Oct. 42; Chap. 14, Nov. 25; Chap.
15, Pt. 1, Dec. 34.
Selection of Tone-Control Pa rameters.
Mar., 22,
Werner, G. Leonard & Berlin, Henry
Everyman's Amplifier. Oct., 40.
White, Stanley
The White Powrtron Amplifier. Nov.,
32.
Wood. John F.
A New Wide-Range Phonograph Cartridge. Dec., 22.
Woodward, J. G. & H alter, J. B.
The Lateral M echani cal Imneda nce of
Pickups. I, June, 19; II, july, 23.
Zuckerman, Alfred M. & Bogen, L. H.
Moderately Priced Amplifier Introduces
Loudness Control Selec tor. May, 31.
75
,
ADVERTISING
IN DEX
WE WERE AT THE FAIR
o
. . . and what pleased us most was the number of people
who were pleased with us. "You still put out the best sounding sound", they said.
The reason is quite simple. We are more interested in producing good sound than we are in putting on a good show ..
We have devoted all our time and effort to the task of
developing a complete sound system worthy of being designated 'high fidelity'. Here are the results. We offer them
with pride.
$65.00
HARTLEY 215 Loudspeakel' . . . .. .
HARTLEY Boffle Enclosmes ..... . 45.00 to 250.00
37.50
HARTLEY Tone-Control Pl'eamplifiel'
135.00
HARTLEY 20 watt Amplifiel' ..... .
W rite for free literature.
Prices slightl y higher West of the Rockies
H.
A.
521
East
LUdlow
HARTLEY
162nd
5-4239
Street ,
CO.
B
,
INC.
ron x 51,
N.
y '.
~ ~If 'leMt4 de
44
68
7
66
43
Cover 2
69
Beam I nstruments Corp. ..
29 ,
Be lden Manufacturing Co.
Bell T elephone Laboratori es ... . . • . . .
Bogen, David, Co., I nc . . .. . . . . . .
British I ndustries Corp. . ... . . .
Briti sh Radio Electronics, Ltd.
Brook Electronics, Inc. . ..
53
Capitol Records, Inc. ... . . . .
Carter Motor Co. .. . . .. . . .
Chicago Transformer Di vis ion
Cinema Engineeri ng Co . ... . ... • • . . .
Classif ied Ads . .. . . . ... .. . . . .. . .
Commissioned Electronics Co.
Crestwood Div., Daystrom El ectri c Corp.
69
58
the 2nd audio anthology
the 2nd audio anthology continues
from where the first left off and contains reprints of articles from January
1950 through July 1952. In both
books the articles were brought up tEl
date, corrected where necessary, and
assembled by subject. the 2nd a a may
still be had with board cover,
MAIL TODAY - - - - - - - - - - - -
Book Division, Dept. 3V,
Radio Magazines, Inc.,
P. O. Box 629, Mineola, N. Y.
check 0 money order for $ . .... .. Please send
(paper cover) @
of
audio anthology
of the 2nd audio anthology (paper cover) @
of the 2nd audio anthology (board cover) @
60
67
46
12
72
68
14
54
50
Cove r 3
D & R, Ltd . . . .. . .
Dubbings Co. , Inc. . . .
Daven Co . . . .... .. .
69
Electron ic Instru ments, Co., Inc . . .
El ectro - Voice, Inc . . .... . . . . ... . .
33
Fairch i ld Recording 'Equ ipment Co.
59
Cene ral Electric Co. . . .. .. . .
64
Hartley, H . A., Co. , Inc. .. •. .
H arvey Radio Co., Inc. ... . . . ... . .
Heath Co . . . .. .. . ... . . ..... . . .
5 1,
Hollywood El ectronics ... . .. . . . ..
Hughes Research and Development
Laborator ies
. . . . . . . ... ........
Hycor Sa les C;o. . . .. .... ... . ... . .
76
Isotone Acoustic Spiral w ays, Inc. . .
62
49
59
69
1
54
Kierulff Sound Corp. .. .. .
Kingdom Products , Ltd . .. • . ..•• . . . . .
69
57
La ngevin Mfg . Corp.
Leonard Radio, Inc . . . .. . . .
9
52
Magnecord, Inc . . . .. . .. . . .. . .. . . • .
Minnesota Mining & Mfg. Co . . . . . . .
Ma rantz, S. B. . . . . . . . . .. . . . . : . '..
11
71
Pacific Transducer Corp . .. . . .. .
Partridge Transformers, Ltd . . . .. •.
Peerless Electrical Products • . ... • . .
Permoflux Corp. . . .. . .. .• .. . . . .
Pickering and Co., Inc . . . . . .
Precision Film Laboratories, Inc . .. .
Presto Recording Corp. . . . .... . . . .
Prestoseal Mfg . Corp. . . ...•.. . • .
Profess ional Directory . . .. .•• . . .
0 ' ••
Sirs: Enclosed is 0
copies
copies
copies
47
3
)
and
- - - - - - - - - - - - CUT OUT -
41
18
Jensen Mfg. Co . . ... ... . . . . .. .. . 38, 39
audio anthology
The original audio anthology is still
being ordered by people who have
worn out their first copy or who have
just learned about the book. Contains
repr.ints of 37 articles which appeared
in AUDIO ENGINEERING from May
1947 through December 1949. An invaluable reference work on audio in
the home .
60
45
A kusti sche und Kino-Cerate
Allied Radio Corp. . ... . . .
A ltec Lansing Corp. . . .. .. .
Amplif ier Corp. of Am eri ca .. . .
Arnold Engineerin g Co.
A sco Sou nd Corp. ..
Audak Co . . . . . . .
Audio Dev ices, Inc. . . .
Audio Exchange , Inc . .
me
$2.00 each
$2.00 each
$3.00 each
Name (please print )
56
71
2
61
17
10
31
74
•
Rauland - Borg Corp. . . . . .. ... . • . . . .
Reeves Soundcra ft Corp. . .•. . . • • . ..
Rek-O-Kut Co.
Rockbar Corp. . .... . .. . . . . . .. . .•.
Si gma Instruments, Inc. . ... . .• . .
Simpson, Mark , Mfg. Co., Inc. . ..
Sonotone Corp. .. . .. .... ... . . ..
Stromberg -Carlson
TA B .... .
Termina l Radi o Corp . . . . . . .. . . .. . .
Tri ad Transformer Corp. . . . .. •. .. .
Tung-Sol Electric, I nc. . .. . ... . . .
4
69
60
5
35
15
6
69
13
37
55
63
65
8
Address
City .. • .. .. ... . ...•. . .. • •.. . .• . . . . .... Zone ... ... State . .. .. •. . . . ... . • • • • •...
76
Un ited Transformer Co . . .... ... .. Cover 4
U. S. Recording Co. .. . . . .... . ..
69
AUDIO ENGINEERING
•
DECEMBER, 1953
THE
'. THESE , ARE
WHY r~14lIWJ_J 1ST H: E
LEADER
AU D 1,0
IN
THE
A T TEN U A TOR
FIE L D
INPUT TRANSFORMERS
Type
Application
No.
lS·10 low impeda nce mike .
pickup. or multiple line
to grid
lS·10X As above
lS·12 low impedan"e mike ,
pickup , or mU itiple line
to push pull grids
lS·12X As above
HJdlillllllll ltB
~
JO
)O
XXI)OO
~JOQ
r l'l.(QV['" '' · C'fCUS
0000
1'U
Primary
Impedance
50, 125/ 150,
200,250.333 ,
500/600 ohms
As above
50 , 125/ 150.
200,250, 333,
500/ 600 ohms
As above
LS·15X Three isolated lines or 30,50,200 ,
pads to one or two grid s 250 ohms
each primary
Case Size
length
Width
Height
± 1 db Max.r Relative' Un bal. DC
Secondary
Impedance
from
leve
hum
in prim'y
60,000 ohms in 20·20,000 +10 DB -74 DB
.5 MA
two sections
50 ,000 ohms
120,000 ohms
overall, in two
sections
80,000 ohms
overall, split
60,000 ohms
overall . in two
sections
Case
No.
lS·l
list
Price
$25.00
20·20,000 + 10 DB 92 DB·Q
20·20,000 +10 DB -74 DB
.5 MA
.5 MA
lS·1
35.00
lS·l . 28.00
20·20,000 +10 DB -92 DB·Q
.5 MA
lS·l
35.00
20·20,000 +10 DB -92 DB·Q
.5 MA
lS·l
37.00
Case
No.
list
Price
lS·l
$26.00
INHRSTAGE AND MATCHING TRANSFORMERS
J ..
ptR SECOf\O
Type
No.
LS·19
LS·21
LS·25
LS·30
lS·33
Application . Single plate to push pull
grids like 2A3, 6l6, 300A.
Split secondary
Single ,plate to push pull
grids. Split pri. and sec.
Push pull plates to push
pull grids. Med ium, level.
Split primary and sec.
Mixing, low impedance
mike , pickup, or multi·
pie line to multiple line
High level line matching
Primary
Impedance
15,000 ohms
Secondary
Max. t Relative' Unbal. DC
Impedance
Response
level
hum
in prim'y
95,000 ohms;
± 1 db
1.25:1 each side 20·20,000 +12 DB -50 DB
0 MA
135,000 ohms;
± 1 db
3: 1 overall
20·20,000
30,000 ohms
50,000 ohms;
± 1 db
plate to plate
turn ratio
20·20,000
1.3:1 overall
50, 125/ 150,
50, 125/ 150,200, ± 1 db
200,250,333, 250,333,
20·20,000
500/ 600 ohms 500/ 600 ohms
1.2, 2.5,5, 7.5 50, 125, 200,
±.2 db
10,15,20, 30,50250,333 ,
20·20,000
125, 200, 250 , 500/ 600 ohms
333,500/ 600
15,000 ohms
+10 DB -74 DB
o MA
lS·l
26.00
+15 DB -74 DB
1 MA
lS·l
32.00
+15 DB -74 DB
.5 MA
lS·l
26.00
lS·2
30.00
15 watts
OUTPUT TRANSFORMERS
Secondary
Max. t Relative' Unbal. DC Case
Impedance
Response
level
hum
In prim'y No.
50, 125/ 150,
± 1 db
200,250,333, 20·20,000 +15 DB -74 DB
a MA
lS·l
500/ 600
lS·52 Push pull 245 , 250, 6V6 8,000 ohms
500, 333, 250,
± .2 db
lS·2
or 245 A prime
200, 125, 50, 30, 25·20,000 15 watts
20, IS, 10, 7.5,
5,2.5, 1.2
lS·55 Push pull 2A3's , 6A5G's, 5,000 ohms
500, 333 , 250 ,
± .2 db
200,125,50,30, 25·20 ,000 20 watts
lS·2
300A's, 275A's , 6A3's , plate to plate
6l6 's, 6AS7G
and 3,000 ohms 20, IS, 10, 7.5,
plate to plate
5, 2.5, 1.2
± .2 db
lS·63 Push pull 6F6, class B 10,000 ohms
30, 20, IS , la,
46's, 6AS7G, 807·TR, plate to plate 7.5,5,2.5, 1.2 25·20,000 15 walts
lS·2
1614·TR
and 6,000 ohms
plate to plate
± 1 db
lS·151 Bridging from 50 to 500 16,000 ohms,
50 , 125/ 150,
ohm line to line
bridging
200,250,333, 15·30,000 +18 DB -74 DB
1 MA
lS·1
500/ 600
The values of unbalanced DC shown will effect a pproxi mately 1.5 DB loss at 30 cycles .
• ComparISon of hum balanced unit with sh ielding to normal uncased type . Q Multiple alloy magnetic shield .
t 6 MW as ODB reference.
Type
No.
LS·50
Primary
Application
Impedance
Single plate to multiple 15,000 ohms
line
list
Price
$26.00
35.00
35.00
25.00
27.00
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