1UlUMIMVIiIIM1 - American Radio History

1UlUMIMVIiIIM1 - American Radio History
the authoritative magazine about high fidelity
STEREO
EQUIPMENT
& RECORD
REVIEWS
Cassette Tape:
Pros & Cons
SEPTEMBER
1968
Private FM
Music Channels
111111
A
How Electronic
Organs Work
1
1111
II!i1iIAIIWIR11UVIi
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60##
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FM Stereo Receiver
Superior Performance, Space-Age Reliability,
Advanced Scott Technology
95
Radically new Scott Integrated
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Scott Field Effect Transistor tone
control circuitry gives you a wider
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only$Suggested Audio File Net
Scott Integrated Circuit IF
strip virtually eliminates all
interference from outside
sources.
Scott solid-state
Time- Switching
multiplex insures
lowest distortion
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separation.
Leather -grained
black vinyl
Scott all -silicon
output circuitry
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case included.
power, with
maximum reliability.
Military -type glass epoxy
printed circuit boards
with solderless connec
tors boost circuit reliability
Scott silver-plated
Field Effect Transistor
front end brings in
more stations more
clearly.
Stereo indicator light
goes on only when
tuner has automatically
switched to stereo
reception.
Precision center -tuning meter
helps you tune for best reception.
Volume compensation
switch permits full frequency
sound enjoyment, even
Front panel stereo headphone
output allows you to listen in
at very low volume levels.
privacy, with speakers turned off.
Tape monitoring control lets
you do a professional job of
transcribing your favorite programs or records on to tape.
Separate on/off switch lets you
maintain volume at a constant level.
Stereo balance control plus
separate bass and treble
controls for each channel let
you adjust the music to your
own taste and room acoustics.
Input selector control gives
you a choice of FM, records,
tape, or tape cartridge.
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Hum and noise, phono -55dB
Cross modulation rejection 80dB
Usable sensitivity 2.5µV
H.H. Scott, Inc., Dept.
Dual speaker switches turn on
Main, Remote, or both sets of
speakers; or switch all speakers off
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front end
FET
Selectivity 56dB
Tuner stereo separation 30dB
FM, IF limiting stages 9
Capture ratio 2.5dB
Signal to noise ratio 60dB
Phono sensitivity 4mV
Prices and specifications subject to change
without notice. Walnut -finish case optional.
COSCOTT
35-09, Maynard,
Mass. 01754
Export: Scott International, P.O. Box 277, Maynard, Mass. 01754
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e1968, H.H. Scott, Inc.
AUllIO
ARTHUR
P.
SALSBERG,
EDWARD TATNALL CANBY,
Successor to
RADIO
,
Est. 1911
Associate Editor
BAXTER
Production Manager
JOSEPH GIOVANELLI
ALEXANDER ROSNER
LEONARD FELDMAN
STUART TRIFF
BERTRAM STANLEIGH
BERT WHYTE
MARY CLAFFEY
Subscription Manager
FEATURE ARTICLES
Behind the ScenesCons of Cassette Tape
SCA-Private Music on Public FM
Electronic Organs-Part I
A Greek Theatre (circa 1968)
ABZ's of FM-The i.f. Amplifier
&
10
23
26
30
36
Bert Whyte
Leonard Feldman
Norman H. Crowhurst
Don Davis
Leonard Feldman
40
42
44
46
49
50
711B
Five -A
RS -761S
EQUIPMENT PROFILES
Altec FM Stereo Receiver
Electro -Voice Loudspeaker
Panasonic Tape Recorder System
Dual Automatic Turntable
Shure Dynamic Microphone
Shure Super-Cardioid Ribbon Microphone
1015
SM -60
330
RECORD/TAPE REVIEWS
Classical 56 Edward Tatnall Canby
Jazz 60 Bertram Stanleigh
Light Listening 62 Stuart Trifj
Tape Reviews 64 Bert Whyte
AUDIO IN GENERAL
Audioclinic 2 Joseph Giovanelli
What's New in Audio 6
Audio Techniques 8
Letters 14
Tape Guide 16 Herman Burstein
Editor's Review 20
IM+TITUTL
er
HIGH FIDELITY
YAMUrACTU+tb
IMC
series of discussions
Marketing Director
R. KENNETH
HERMAN BURSTEIN
e
a
by Electro -Voice engineers
C. G. McPRouD, Publisher
SANFORD L. CAHN
Design
Art Director
Contributing Editors
Pros
Number 60 in
Editor
RICHARD CLIFF
PETER RENICH
Vol. 52, No. 9
September 1968
Classified 66
Advertising Index 68
AUDIO (title registered U. S. Pat. Off.) is published monthly by North
American Publishing Co., I. J. Borowsky, President; Roger Damio, Frank
Nemeyer, C. G. McProud, and Arthur Sitner, Vice Presidents. Subscription
rates-U. S. Possessions, Canada, and Mexico, $6.00 for one year; $11.00
for two years; all other countries, $7.00 per year. Printed in U.S.A. at
Philadelphia, Pa. All rights reserved. Entire contents copyrighted 1968 by
North American Publishing Co. Second class postage paid at Phila., Pa.
REGIONAL SALES OFFICES: Sanford L. Cahn, 663 Fifth Ave., New York,
N. Y. 10022; (212) 753-8824. Louis Weber, 5201 N. Harlem Ave., Chicago,
III. 60656: (312) 775-0755. Jay Martin, 9350 Wilshire Blvd., Beverly
Hills, Calif.; (213) 273-1495.
REPRESENTATIVE: Warren Birkenhead, Inc., No. 25, 2-chome, Shiba Hamamatsu -cho, Minato-ku, Tokyo, Japan.
AUDIO Editorial and Publishing Offices, 134 N. 13th St., Philadelphia, Pa. 19107
Postmaster: Send Form 3579 to the above address.
Testing of microphones ordinarily takes two
distinct forms: laboratory tests and field tests.
The former is basically objective in nature and
results in performance specifications, while the
latter provides a subjective evaluation of the
microphone under actual use conditions. Both
forms of testing are valuable, but on occasion
the field results do not seem to fully support
the laboratory tests.
The difference, of course, lies in the "idealized" conditions that consistently form the
basis for laboratory tests. No such uniformity
exists in the field, yet the need for correlation
between specifications and actual performance
is increasingly felt.
In order to more thoroughly explore the
causes for deviation from laboratory response,
Electro -Voice has undergone a series of tests
of varying types of microphones using its
large anechoic chamber as a research tool. To
date the investigation has concentrated on
effective polar response, effects of distance on
frequency response, and the results of multiple
in -phase and out -of -phase microphone pickups. While the studies have just begun, causes
of several common problems have been pinpointed.
Polar response was investigated by rotating
the microphone in the anechoic chamber, while
speaking at constant volume. This test pointed
up the necessity for uniform response off-axis
as well as on -axis. With microphones such as
the Model RE15, level changed with rotation
of the microphone, but voice quality (hence
frequency response) remained constant. However with directional microphones that did not
offer uniform off-axis response, sound quality
quickly became unacceptable. Using such a
microphone to reduce unwanted pickup to
reasonable levels can alter the tonal character
of the unwanted sound, as well as distort the
apparent acoustical characteristics of the studio or hall.
It was also noted that many omni-directional
microphones exhibited directional characteristics that were quite audible at an angle as
small as 80° off axis. This proved to result
from interference of the microphone case, and
was directly related to increasing case diameter.
In another series of tests, the effect of distance
on frequency response and articulation was investigated. A male voice was recorded at distances from 2' to 25' in the anechoic chamber.
Levels were then equalized, and tonal quality
and articulation was compared. No significant
difference could be noted as distance increased. It is evident that the "loss" of highs
with distance is not due to reduction in actual
intensity. Rather the changing phase relationships determined by environment acoustics
has an increasing effect with rising frequency.
This is interpreted subjectively as a loss of
intensity.
Further tests of this type will be discussed in
future columns, and suggestions for other
areas of investigation are welcome.
For reprints of other discussions in this series,
or technical data on any E-V product, write:
ELECTRO -VOICE, INC., Dept. 983A
602 Cecil St., Buchanan, Michigan 49107
gkeee
A SUBSIDIARY OF GULTON INDUSTRIES, INC.
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1
Coming in
October
Special Hi-Fi Show Issue
The '69 HOT ONES-Audio's
special "New York High Fidelity Music Show Issue"
covers the outsanding, new
stereo/hi-fi components and
systems to be presented to
the public (September 19
through 22, Statler Hilton
Hotel, New York City).
Readers will get a preview of
what can be expected to line
local hi-fi dealers' shelves in
late 1968 and the following
year.
Among other feature articles
will be:
SMALL ROOMS FOR STEREO
MUSIC
Michael Rettinger
discusses how music reproduction is affected by a
room's dimensions and furnishings.
-
AN
AUDIO
LOOKS
AT
ENGINEER
RUSSIAN RETECHNIQUES
-
CORDING
Dr. Ray Dolby's professional
recording experiences at Melodiya Studios and the Russian Radio and Television
Studios.
EQUIPMENT PROFILES: AR 3a speaker system, Sansui
Model 2000 AM/FM Stereo
Receiver, Benjamin Model
1050 Compact Stereo System, and more.
Regular departments
and recorded music reviews.
PLUS:
ABOUT THE COVER: Here's a view (photographed with a "fish-eye" lens) of 3M's anechoic chamber, an echo -free environment
for acoustical testing of loudspeakers and
microphones. The chamber is built from
12 -in. poured concrete, is r.f. shielded, and
has about 3000 34 -in. glass wool wedges on
all six surfaces to absorb more than 99 per
cent of the sound.
Audio clinic
JOSEPH GIOVANELLI
If you have a problem or question on
audio, write to Mr. Joseph Giovanelli
at AUDIO, 134 North Thirteenth Street,
Philadelphia, Pa. 19107. All letters are
answered. Please enclose a stamped,
self-addressed envelope.
Electronic Crossover Systems
Q. I have seen several stereo systems
which use separate amplifiers for high
and low frequencies.
I would like to know what the advantages and disadvantages of this type of
arrangement are.-Thomas Hitt III,
Chanute AFB, Ill.
A. The obvious disadvantage of having the speaker system divided so that
each speaker within is driven by its own
separate power amplifier, fed from an
electronic crossover, is that the arrangement is both costly and space consuming. However, in most of the
tests that I have observed, this system
does provide superior sound over that
which you can normally obtain by a
conventional LC network. Apparently
the LC (inductance-capacitance) arrangement in a network "rings" at the
crossover frequency, imparting a roughness to the sound which is hard to
eliminate without degrading the slope
of the crossover curve.
There is something else which might
play at least a small part in contributing to what I think is better sound produced by an electronic crossover
arrangement. Each amplifier does not
have to handle material covering a
wide frequency range. Because each
amplifier handles less of the overall
program than is true of a more conventional setup, the number of IM
distortion products will be reduced.
Therefore, a lot of this "soup" will not
be passed on to the loudspeakers.
This about sums up the two arguments. I have thought of one more
against the electronic scheme, however.
If something should happen to the
high -frequency amplifier which could
result in the production of a high power transient, this transient will be
transmitted into the tweeter as an impulse having a wide frequency distribution. A tweeter should not be exposed
to such a pulse, of course. Such exposure will probably damage it. But
tweeters do not require real power to
drive them, as is the case with low frequency speakers. Most of the power
is concentrated in the low frequencies.
Therefore, I would think that the am-
2
plifier feeding the high frequency
speaker can be less powerful. This will
overcome the possible damage to a
tweeter; at least to some degree.
I can think of some experimental approaches which might be worth investigating further. How about putting a
capacitor in series with the tweeter
whose value is such that its reactance
would be out of the picture at or just
below the crossover frequency, but
which would be appreciable at lower
frequencies. I don't know how much
coloration it might add to the sound,
but it should not be too bad. Of course,
in the case of a tube amplifier, the
amplifier would not be loaded very
much at lower frequencies. This might
cause some damage to the amplifier
when a transient occurs. You probably
would need to use some kind of extra
load in the form of a resistor whose
value is perhaps twice the impedance
of the speaker being used. Some power
would be wasted, but this is not too
important inasmuch as the tweeter does
not require much power anyway.
I rather doubt that any kind of fusing could be fast enough to prevent
damage. I would imagine that the ultimate in protection can be provided by
a Zener diode, two of them connected
"back-to-back," or perhaps some kind
of bridge arrangement.
While I recognize that we are drifting somewhat away from the main idea
of the question, I think the idea of
protecting our tweeters is a real issue
here.
Some observers have wondered about
the phase relationship between lows
and highs with this kind of electronic
crossover system. Personally, I believe
that matter is relatively unimportant,
so long as the phase relationship between channels is maintained. I can expect considerable disagreement on this,
and will welcome comments.
In the days before stereo, electronic
crossover systems were rather popular.
However, they went out of favor when
stereo came along, presumably because
the amount of equipment required was
doubled. With solid-state equipment
becoming more and more compact, this
gives rise to a renewed interest in electronic crossover systems.
Damping
Q. My questions concern the "damping factor" specifications given for
amplifiers: (1) What is the definition
of damping factor? (2) How is the optimum value of damping factor determined? (3) What is the procedure for
altering an amplifier's damping factor?
(4) Is an amplifier's damping factor a
function of frequency?-Robert J. De
Jonge, Sodus, N. Y.
(Continued on page 4)
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A. Before we define damping factor,
it might be appropriate to dwell for a
bit on the nature of damping.
If you tap a speaker cone you will
get a characteristic tone. This sound
will depend upon the stiffness and mass
of the cone and the nature of its inner
and outer suspensions. Two things are
determined by these conditions: the
frequency of the sound produced by
your tapping the cone, and the duration
of the cone's vibratory motion.
The latter consideration is of interest
to this discussion. Naturally, if we have
a moving speaker and we suddenly stop
feeding signal into it, we would want
the speaker to stop moving immediately. Otherwise, it is producing sounds
not fed to it by the amplifier.
Now short the two input terminals
of the speaker together. Tap the cone
again. Notice that the speaker no
longer produces much of its characteristic sound, or free -air resonant frequency. We say that under these
conditions the speaker is damped. Why
did shorting the input terminals help?
It works this way because the moving coil speaker is a generator. When it is
tapped, the movement of the voice coil
through its magnetic field produces a
voltage. Shorting the speaker terminals
means that this voltage is shorted. This
is the same as saying that our generator has a heavy load on it. This is
translated to the speaker's moving mass
as work. It takes work to supply this
voltage under these short-circuit conditions, and the force available to accomplish this work can be derived only
from the motion of the cone imparted
to it when you tapped it. Because of
the extra work now placed on the moving system, the speaker stops moving
sooner. I guess we could say that it's
similar to adding friction to the moving system. It is a case of the energy
being dissipated more quickly now that
a load has been added to the moving
system.
Even when there is no load placed
on the speaker by shorting the voice coil leads, the speaker's motion won't
continue forever. There is still work
involved in overcoming air resistance
and frictional components in the suspension. In other words, no matter
what you do or don't do, the oscillations of the speaker cone are always
damped to some extent. Of course, this
action is less than ideal when the voice
coil is not well loaded.
Naturally, if the magnetic fields
acting on the voice coil are weak the
damping factor with the voice -coil terminals shorted will not be as dramatic
as would otherwise be the case.
The suspension systems of the better
speakers are designed to have the ability to damp out unwanted cone motion
mechanically. Notice that when the
speaker is well damped, it ceases motion more in accordance with the
motion imparted to it by the driving
amplifier.
If we compare the connection of the
speaker to an amplifier with a direct
voice -coil short circuit, we find that the
damping is not quite as good with
the amplifier connected as it is under
short-circuit conditions, though the difference is slight. This is reasonable
when you consider that the speaker,
when connected to the amplifier, is not
a "dead" short. The amplifier acts as a
very low resistance, but not so low as
a direct short. All this leads to the
damping factor of an amplifier. This is
simply the impedance of the speaker
divided by the output impedance of the
amplifier.
Unfortunately, this gets us into another subject. When you connect an
eight -ohm speaker to an amplifier rated
as having an impedance of eight ohms,
you would have to conclude from my
last statement that the damping factor
of the amplifier is 1. This is likely not
to be the case at all. We are all brainwashed into worrying about impedance
matching. Actually, all you really know
about an amplifier's output impedance
is that when a load having a given impedance is connected to an amplifier
specified as having that same impedance, you will get the power indicated
by the designer of the amplifier. You
probably don't have anything even
close to a match. The true output impedance is quite a bit lower than the
impedance of the load to which it is
connected. The greater this ratio, the
higher will be the damping factor. We
can increase the ability of the amplifier
to perform this damping function as
much as we like. Beyond a certain
point, however, we just do not register
much improvement.
The way I see it, by the time the resistance of the interconnecting cable is
figured into the problem, it becomes
the dominant factor once the output
impedance of the amplifier has fallen
below that resistance. This is why I
have always advocated very heavy wire
between the speaker and the amplifier:
No. 16 or even No. 14 lamp cord.
(2) The optimum amount of damping will depend upon the total speaker
design, including the effect of the enclosure. It is often best to have a speaker
damped below the maximum value
which can be achieved. The sound obtained by changes in damping is rather
subtle in most cases. Therefore, I have
never felt it necessary to have an amplifier with variable damping. As far as
I am concerned, there is no really optimum amount of damping. There are
too many variables, and the difference
between optimum and somewhat removed from optimum is not great
4
enough for me to worry about.
(3) We can alter the damping factor in two ways. We can increase the
amount of negative feedback around
the output stage of the amplifier,
thereby increasing the damping factor.
This is reasonable because increasing
the amount of feedback effectively
lowers the impedance of the output
stage. We can decrease the negative
feedback, bringing about the opposite
result. We can reduce the damping factor in a much better way, and that is
by introducing current feedback. This
is achieved by placing a small resistance between the low side of the
output transformer of a tube -type amplifier and ground. Perhaps someone
will write in and show us how this
might be accomplished with a solidstate amplifier. It is the voltage drop
across this resistor which is added to
the feedback circuit of the amplifier
and is in such a direction as to decrease
the damping factor.
(4) Assuming that the amplifier is
properly designed, the damping of the
amplifier should not be determined by
frequency of the signal being fed to it.
However, the requirement of the load
will change with frequency. At the
fundamental resonance of the speaker,
damping will be most needed, and it is
there, ready and waiting.
Note: This whole area of discussion
is loaded with controversy. I hope some
of you will rise to the occasion and submit your thoughts. I will try to include
at least some of them.
Choosing an Amplifier
Q. I bought a pair of AR3 speaker
systems. I would like to know which of
the following amplifiers is the best to
match the AR3.
JBL Model SA600,
40 WIch rms at 8 ohms
McIntosh Model MA230,
30 WIch rms at 8 ohms
Scott Model 260 B,
40 WIch rms at 8 ohms
The AR3 requires an amplifier of at
least 25 WIch rms.-H. M. Chan, Hong
Kong.
A. I would say that any of the amplifiers you have listed should work well
with the AR3.
To my way of thinking, if an amplifier is basically good, and if it meets the
power requirements of the load, then
that is all there is to it. All you need
to do is choose the amplifier that you
like best.
You cannot judge a speaker or an
amplifier by written specifications
alone, of course, you must hear it. This
is especially true of transducers, but it
does also hold for amplifiers. So listen
to your AR3 driven by the amplifiers
you're interested in, playing familiar
source material.
AUDIO
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SEPTEMBER 1968
Humanized because ...
research on th3 physiological reaction
of the human ear to sound pressure
led to the deve opment of a headphone
driver which functions with the human
ear as a unit, and is capable of gen
erating full fidelity sound at close proximity to the en -rance of the ear.
Humanized because ...
of their seeming weightlessness.
Humanized because ...
of their comfcrtable fit which allows
you to enjoy burs of listening pleasure without discomfort.
Humanized be:ause .. .
it permits you to enjoy transparent
reproduction cf music and voice and
still remain in partial contact with your
surroundings.
TYPICAL CUSTOMER COMMENTS
"Unbelievably fantastic."
"Superior musically to six other
types tesbd."
"Best sound yet."
"Best headphone at any price."
"Very comfortable to wear."
"Pleasure is now mine."
"Excellent sound and comfort."
"The Best!'
"Prefer it tc speakers."
"Very realistic sound."
Listen to the AKG K-20 or K-60 at your
dealer and convince yourself.
MIC3OPHONESHEADPHONES
BSTIETE.0 BY
NORTH AMERICAN PHILIPS COMPANY. INC.
AUDIO
Check No. 5 on Reader Service Card
SEPTEMBER 1968
5
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What's New
In Audio
New York was a summer festival for
the electronics trade. Two industry
shows-the NEW show and the Consumer Electronics Show-gave dealers
and distributors an eyeful of what's
coming up during the '68-'69 buying
season.
A substantial number of hi-fi component equipment manufacturers participated in both shows, joining parts
manufacturers at the NEW Show and
packaged equipment manufacturers at
the CES Show.
Some products will undoubtedly not
be available to the public for some time
(and some not at all should marketing
plans change, sales to dealers and distributors turn sour, and so on). Nevertheless, many will be available in the
near future. So let's take a look at
some of the highlights.
Tape recorders were hot items.
Seems like everybody is on the bandwagon. Aside from the myriad types
and models displayed, there were a few
recorders that impressed us due to apparent high quality and/or appealing
innovations. For example, Roberts introduced a combination video and
stereo (audio) tape recorder that uses
standard 1/4 -in. recording tape. It's expected to be priced at under $1000.
KLH entered its first tape unit, a
stereo, open -reel tape deck that incorporates an audio noise-reduction
system) for use with the recorder's
33/4-ips speed) under an agreement with
Dolby Laboratories. A 71/2-ips speed is
also provided. Expected price is about
$600. Sony Superscope topped its new
reel-to-reel recorders with a professional portable stereo tape recorder,
the model 770. It operates on a.c. or
d.c. (includes a rechargeable nickel cadmium battery pack) and boasts four
tape heads. Priced at $750. Among
Sony's new cassette machines, the
model 125, an a.c.-powered stereo cassette deck, provides an end-of -cassette
alarm system, actually a light that
starts to blink on and off as the cassette approaches the end of each side.
If you've ever squinted through a cassette machine's window to determine
if you're near the end of the tape, you
would appreciate such a useful facility.
TEAC demonstrated a cleverly designed tape deck which had seveninch reels positioned diagonally instead of in a straight line, thereby
reducing the width of the machine.
Top to bottom: Roberts Model 1000 video/
audio tape recorder. KLH tape deck with
Dolby audio - noise - reduction system.
Sony/Superscope Model 770 professional
portable stereo tape recorder.
Its new A-7030 tape deck features
reel capacity ($749.50).
101/2 -in.
Uher's new Royal Deluxe model
10,000, at $550, features two- and four track head assembly modules that may
be interchanged quickly. HarmanKardon showed its receiver/tape deck
combination, model TDC-33, which retails for less than $489.50. 3M's Wollensak unveiled new open -reel tape
machines. A new tape transport system
is said to provide more rapid forward
and rewind operations, and gentler
braking. Model 6100, a tape deck, is
priced at $159.95. Also introduced by
3M was a new stereo cassette recorder,
model 4800, that features heavy-duty
components to improve wow -and -flutter performance (less than 0.3% at 17/8
ips) . With separate speaker systems,
it will be priced under $200. Ampex'
new compact tape deck, model 1450,
features automatic reversing and replay, sound -with-sound, and tape monitoring, at a $299.95 price. Bell &
Howell exhibited its full line of reel-toreel tape recorders and cassette tape
units. Two new reel-to-reel machines
feature automatic threading and automatic reversing for playback. Revox,
in a location near the CES Show, demonstrated its new model 77A 3 -motor
deck. Sterling showed off its Nordmende stereo recorder/deck with
built-in slide -type mixers, as did Dy naco with its B&O recorder. Panasonic
had a broad, complete line of tape recorders, in addition to TV receivers
(including a 11/2" -screen pocket portable) and a component 90 -watt AM/
FM stereo receiver ($349.95). BASF
magnetic recording tape, both PVC and
polyester backed, were shown, as well
as two editing kits.
Speaker systems were given a big
play by a number of companies. Jensen Manufacturing and University
Sound both displayed speaker systems
for music instrument applications, as
well as those for use with stereo hi-fi
systems. University Sound's new Alhambra III 4 -way, 3 -speaker floor standing speaker system includes a
two-position switch for electrically adjusting the system's bass -response
characteristics over a range of 5 dB.
Marantz introduced a speaker system
for the first time. It's a three-way design with five speakers, available in
two enclosure styles. The Imperial I,
a walnut cabinet with hand -rubbed
French lacquer finish is expected to retail for about $299; Imperial II, with a
distressed antique finish, will be priced
at about $369. Yamaha presented el (Continued on page 54)
6
AUDIO
www.americanradiohistory.com
AmericanRadioHistory.Com
SEPTEMBER 1968
The new
Sansui 5000
is
now available
at Sansui
Franchised Audio Centers
across the country
...
Inputs for 3 sets of stereo speaker systems
Selective monitoring for up to 4 stereo tape decks or
recorders
180 watts (IHF) of music power
FET FM
Front End ... Integrated circuits ... FM Sensitivity 1.8, v
(IHF) ... Just to name a few of the features .
You are invited to test the new Sansui 5000 at your
favorite Sansui Audio Center ... Do it today for a
truly great experience.
...
...
$449.95
r
wi1TMG
-"atID#%td4>.
M STEv.:y
1ti:. RïVPS4 M.:k:t
[LL
Q/1_S
Sansui Electronics Corporation
34-43 56th Street
Woodside, N.Y. 11377
Sansui Electric Company, Ltd. Tokyo, Japan
AUDIO
SEPTEMBER 1968
Check No. 7 on Reader Service Card
www.americanradiohistory.com
AmericanRadioHistory.Com
Phone: (212) 446-6300
Electronic Distributors (Canada) British Columbia
7
Audio
Techniques
Convenient Multiple
Load Panel
At one time or another, every experimenter needs a Load Resistor. And
in this day of stereo amplifiers, he
needs two load resistors. And furthermore, he needs a number of values to
make comparative tests of solid-state
amplifiers, which are usually rated at
what is their best value-such as 8 or
4 ohms. Requiring these resistors on
almost a day-to-day basis, and tiring
of adding up an assortment of power
412
8
COM
/<,,,,
`la
812
16
812
Fig. 1-Wiring diagram for the three -value
load resistor panel described. Both channels are identical.
resistors every time a load resistor was
needed, the unit shown herein was put
together and given a convenient location on our test bench where it would
be readily accessible to an amplifier
under test, and readily patchable to
output and distortion meters.
The unit consists of six 50 -watt, 3%
power resistors-two of 4 ohms each,
and four of 8 ohms each. These are
Got any hints or aids to enhance
equipment performance? Simplify
operation? Construction shortcuts?
Audio invites readers to send them in
to Mr. Joseph Giovanelli at AUDIO,
134 North Thirteenth St., Philadelphia, Pa. 19107. Please enclose
stamped, self-addressed envelope.
a
mounted on a %6 -in. bracket, along
with eight binding posts in the schematic of Fig. 1.
Since the use of double banana plugs
is standard in our lab, the four posts
for each channel were mounted as
shown in Fig. 2. The ground post is at
the center of a 3/4 -in. arc, and the remaining three posts are mounted on
the arc, one directly above the common
ground post, and the others 45 deg. to
the right and left of it. Labeled 4, 8,
and 16, they permit immediate choice
of termination. Stackable double banana plugs permit extensions to the remaining equipment-distortion meters,
output meters, and an oscilloscope.
The ground post is connected direct
to the chassis, which is grounded. It
could have been insulated, and perhaps would have been had it been made
two years ago, when some stereo amplifiers had outputs which could not be
connected together. However, practically all amplifiers at present now have
a common ground for both channels, so
no problem has arisen. In the present
form, the load unit can accommodate
50 watts at both 4 and 8 ohms, and
100 watts at 16 ohms in each channel.
Note that the wiring is with #14 solid
copper wire. Since each of these resistors can accommodate a 100% overload
for a short time, this choice has proved
ideal. The 3% resistors were obtained
from surplus stocks-only 1% resistors
are listed in current mail-order catalogs, and they cost considerably more.
Figure 3 shows the rear of the unit.
Fig. 2 (Left)-Panel view of the load resistor unit. This is permanently mounted under the
test equipment panel. Fig. 3 (Right)- Rear view of the author's load panel.
8
Fig. 4-One method
which will minimize the inductance
of a wire -wound
power resistor. The
resistor should have
a value of four
times the desired
load.
Resistance --
R/4
Inductive load resistors
The purist may argue that these resistors, being spiral wound, have some
inductance, and should not therefore be
used for crucial terminations. However, non -inductive load resistors are
hard to find in high -wattage values. In
the past we have used a single wire wound adjustable type 50 -watt resistor
by tying the two ends together for one
terminal, and using a center -tapping
band for the other terminal. The lead
connecting the two ends together
passes through the tube. In this arrangement, shown in Fig. 4, the two
halves are thus connected in opposition, and the inductance cancels outwell, almost. In a 75 -ohm, 50 -watt resistor, with the two halves connected
in parallel as shown to provide approximately 16 ohms, we measured an
inductance of less than 10 micro henries, which is an improvement over
the series inductance of the untapped
and unparalleled resistor which measured 125 microhenries. The only problem which exists is that there are no
16, 32, and 64 -ohm resistors in the catalogs, so it is difficult to get 4, 8, and
16 ohms. It can be done with an extra
clip band on each resistor, but that's
a lot of trouble.
At the time of writing this, no problem has been encountered with the
small inductance which is inherent in
the 50 -watt Dalohm resistors used in
the unit described, and no rebuilding is
contemplated.
Æ
AUDIO
www.americanradiohistory.com
AmericanRadioHistory.Com
SEPTEMBER 1968
Anybody
can
Iw
build a
turntable.
(This
is
a public service message from Marantz.)
There are ¶wo ways to build a turntable. The ordinary way.
And the Marantz straight-line tracking way.
Only straight-line tracking makes it possible for a home
turntable system to reproduce the sound on a phonograph
record exactly as it was originally etched by the cutting head.
And only Marantz has it.
Straight -Vine tracking keeps the tone -arm precisely tangent to the grooves-not sloppily sloshing around in them.
That's why it is the only known
way to give you absolutely uniform stereo separation and
frequency response from the
outermost groove to the innermost (where distortion is greatest). In addition, straight-line
tracking also eliminates tracking error distortion, uneven
stylus wear. and skating force.
positive cueing control, ends accidental record scratch
forever. One simple control knob lets you set the stylus in
any groove you desire-without touching the tone arm.
The Marantz Model SLT-12U turntable is equipped with
a universal pick-up head which is adaptable to a broad
selection of popular cartridges. No wonder-feature for
feature-it is the ideal instrument to enable you to enjoy
perfect stereo sound in your
own home-exactly as heard
in the finest recording studios.
And best of all, it is priced at
just $295.
There is so much that goes
into making
a
Marantz
Another Marantz feature,
Designed to be number one in performance... not sales.
©MARANTZ CO.. INC.,
AUDIO
SEPTEMBER
1968
1968. MARANTZ IS A SUBSIDIARY CF SUPERSCOPE. INC. P.O. BOX 99C
a
Marantz, that your local franchised Marantz dealer will be
pleased to furnish you with
complete details together with
a demonstration. Then let your
ears make up your mind.
SUN VALLEY, CALIFORNIA 91352
Check No. 9 on Reader Service Card
www.americanradiohistory.com
AmericanRadioHistory.Com
SEND FOR FREE CATALOG.
9
ratory conditions the frequency range
of a stereo cassette can be 40 to 12,000
Hz with a signal-to-noise ratio (S/N)
of 45 to 48 dB (unweighted) . Under
12EIEW
Min
Scotch MAGNETIC
TAPE CASSETTE
NO
BERT WHYTE
The Cassette Tape Format:
Pros & Cons
At the recent Consumer Electronics
Show (an industry trade show) in New
York it was well nigh impossible to
walk into a manufacturer's exhibit that
did not feature some form of cassette
recorder. The proliferation of new
units, especially from the Japanese
companies, was of amazing proportions. It was very obvious that the
cassette format had "arrived." There
were tiny battery -operated portable
mono and even stereo cassette recorders; recorders combined with AM and
FM radios; recorders built into elaborate "entertainment" consoles; integrated stereo cassette recorders with
amplifiers and speakers. There were
stereo cassette playback decks, even
stereo cassette changers from Norelco
and Aiwa which automatically played
back up to six cassettes. Every manufacturer I talked with outlined his
extensive and elaborate marketing
plans for maximum exploitation of the
cassette concept.
While the 8-track cartridge is generally regarded as a playback medium,
the cassette has been touted for its recording capabilities as much as for its
function for playback of pre-recorded
music. In fact, I would say that at the
Show, the emphasis was on the "hardware" and the recording aspects of the
cassette. The attitude of many people
I talked with was that the "plus" of the
recording facility in the cassette system had a great attraction for the con-
10
sumer, even if his primary interest was
in pre-recorded cassettes. It was also
felt that this was the reason why the
cassette system would eventually prevail over the 8 -track cartridge. This of
course, remains to be seen. With the
accelerated pace of developments in
magnetic recording technology over
the past few years, prognostication is
a very precarious pursuit.
Admitting the values of the recording function, it is also apparent from
the ever-mounting sales figures that
the pre-recorded stereo cassette is a
resounding success. Let's take a look
at this plastic phenomenon and discuss
some of its positive and negative qualities.
Advantages and disadvantages
The stereo cassette is indisputably
small, light, easy to handle and easy
to store. It is rugged and, unless grossly
abused, should last almost indefinitely.
Its tiny size stimulates miniaturization of drive mechanisms and electronics. The narrow 150 -mil tape can
be had in an ultra -thin configuration
which will afford 120 minutes of playing time at its 17/8-ips speed. The cassette permits the use of fast -forward
and rewind, which allows a certain degree of program selectivity when combined with a footage counter. The two
pairs of stereo tracks are well separated so there is no crosstalk problem.
There is crosstalk between the tracks
in each stereo pair, but since the
tracks both run in the same direction,
the crosstalk isn't audible. Under labo-
optimum playback conditions in the
home, regular production -run cassettes
afford 60 to 9ö00 Hz with S/N ratios
of 40 to 45 dB (unweighted). It should
be noted here that this S/N ratio is
better than the levels of many cassette playback units!
Needless to say, like any other developing technology, the cassette has
various problems. Some of these problems are in the cassette itself, others
are in the playback units. For example,
in the standard cassette there is a mu metal shield to reduce stray hum
fields. In practice it has been found
that with certain drive mechanisms the
shielding is inadequate and, try as you
might, you just can't ground out the
hum. In new cassettes which should be
on the market very soon, the mu -metal
shield has been extended in a "wraparound" style; with a very slight additional cost to the pre-recorded cassette manufacturer, this has reduced
hum significantly. There are also some
new playback units which use synchronous motors. Unfortunately, the
narrow width of cassette tape contributes to playback noise on a ratio of
almost 2 to 1 compared to standard 1/4 in. tape. The cassette tape has a 0.5 -mil
base and a 0.2-mil coating of magnetic
oxide. Standard 1/4 -in. tape has a 0.4 mil coating. This difference in oxide
thickness produces about a 5 dB loss
in the cassette tape because of the very
short wavelengths at the 17/8-ips speed.
The cassette tape must have the thin
base and coating to ensure a supple
tape which permits good head "wrap"
and contact to maintain good frequency response. It is also a matter of
sheer space and playing time, an important factor in the tiny confines of
the cassette. One bright spot is the production of a new oxide which is reported to gain back about 3 to 4 dB of
the loss attributed to the thin coating
on cassette tapes. As far as the "Cronar" chromium oxide tape is concerned, it is not available at present.
In any case, it is too thick, is somewhat abrasive, and could cause accelerated wear in the type of heads furnished with cassette playback units.
Further, it would require the bias frequency to be almost doubled. In the
considered opinion of some engineers,
there has been and there is such rapid
progress in the development of iron
oxides that they doubt chromium oxide would be much of an advantage
Check No.
11
on Reader Service Card
-
The cartridge looms large
for a simple reason:
It
is the point of contact between the entire hi-fi system and the recording. What happens at the tip of
its tiny stylus determines what will happen in all those big and impressive components that are so obvious
to the eye and, in the aggregate, so apparent to the pocketbook. Worldwide, experts and critics have
hailed the discovery of Trackability as the definitive measurement of cartridge performance. When
evaluated against this measurement, the superb Shure V-15 Type
Shure Brothers, Inc., 222 Hartrey Ave., Evanston, Illinois 60204
II Super Track
stands alone.
The analog -computer -designed Shure V-15 Type Il Super-Trackability cartridge maintains contact between the stylus
and record groove at tracking forces from 3/, to 11/2 grams throughout and beyond the audible spectrum (20-25,000
Hz). Independent critics say it will make all of your records, stereo and mono, sound better and last longer.
Tracks 18 cm/sec. and up at 400 Hz; tracks 26 cm/sec. and up at 5,000 Hz; tracks 18 cm/sec. and up at 10,000 Hz.
This minimum trackability is well above the theoretical limiis of outing velocities found in quality records. $67.50.
© 1968 Shure Brothers, Inc.
www.americanradiohistory.com
AmericanRadioHistory.Com
.... at least not in the area of home
audio.
Another thing that plagues the duplicators of pre-recorded stereo cassettes is the variation in the width of
their duplicating tape. The standard
calls for 150 mils with a tolerance of
plus zero and minus 2 thousandths. If
the tape is slightly narrower, it cuts
into the edge track (which is the left
channel) and may cause a loss of 3 to 4
dB in signal. There is an appreciable
number of pre-recorded stereo cassettes which are down in level on the
left channel. It is usually not your
machine which is out of kilter, but this
tape variation
so you will have to
use your balance control. You will also
encounter dropouts in pre-recorded
cassettes. Much of this is caused by
fingerprint residues on the thin coating, but this is expected to be eliminated by the use of automatic machinery instead of the hand assembly of
cassettes.
The wow -and -flutter content of most
pre-recorded stereo cassettes is usually
quite a bit less than the wow -and -flutter of the various playback units. This
is one of the penalties of the 1%-ips
speed and is likely to remain a problem until the development of an inexpensive servo -control drive. It should
be noted that there are two new cassette recorders made by 3M/Wollensak and Harman-Kardon which use
full-sized drive components, large flywheel, etc., and are in general built to
"professional" standards, and for
which excellent figures are quoted for
...
wow and flutter. I saw and heard both
units at the Consumer Electronics
Show and they seem to hold much
promise. I hope to obtain sample units
and give them the "lived with for
awhile" treatment.
There seem to be two schools of
thought regarding the duplication of
stereo cassette tapes. One method is
the Ampex -style use of multiple -slave
tape machines. The other is what is
known as the "common mandrel" system. The mandrel is the equivalent of
a large -diameter, massively heavy axle
on which are mounted many large
take-up reels which pull the tape over
one to each reel.
a recording head
Since the reels are all driven by the
same mandrel or "axle," it is claimed
there is very little difference in wow and -flutter content between the tapes
on each reel, and a low overall figure
for wow and flutter. The Dubbings Co.
of Copiague, New York uses the common mandrel system; I am indebted
to Chief Engineer Trevor Campbell for
a most fascinating and instructive tour
of his plant. Mr. Campbell says that,
under optimum conditions, wow and
flutter are about equal between the
multiple -slave tape -machine system
and the common-mandrel system, but
he feels the latter system is easier to
maintain to specifications. He also
feels that scrape flutter is easier to control, especially since he is using dubbing ratios of 16 to one and is currently
experimenting with ratios of 24 to one.
This drops the scrape -flutter frequency
much further into the bass range, with
subsequently less effect on transient
response. Mr. Campbell uses the Ferrite heads which wear very little and
thus avoids "lipping" and tape skew
which could cause track misalignment.
At the present time, any evaluation
of the pre-recorded stereo cassette
must be considered in the light of several different kinds of listeners. For
the mass market-those with integrated or "compact" systems with
small limited-range speakers, who audition mainly "pop" type material, at
relatively low playback levels in small
apartments or homes-the stereo cassette affords them a quality of sound
equal if not superior to what can be
obtained from a disc system in the
same price range. With the added advantages of longevity and non"scratchability" of their recorded material and the recording capability of
their cassette unit, the appeal of the
cassette system is readily apparent and
the burgeoning sales not surprising.
For the serious audio buff, especially
those oriented to classical music, the
...
12
stereo cassette leaves much to be desired. For one thing, the number of
classical cassettes is comparatively
limited. Ampex, for example, issues
but one classical cassette to every 15
or 20 pop productions. It is true that
D.G.G. and a few other companies are
trying to build up fairly extensive catalogs of classical cassettes, but this still
makes for scant classical representation. Far more serious than the lack of
material is the quality of sound to be
found on classical stereo cassettes. To
put it bluntly, it is not remotely competitive with the high -quality stereo
disc or 71/2-ips stereo tape, and only
marginally and occasionally equal to
33/4-ips material. The restriction of frequency response, especially in the bass
range, the dropouts and the all -too frequent distortions of various type,
and above all, the almost traumatic
hiss caused by the poor S/N ratio,
simply negates its virtues of size and
handling. When "pop" cassettes are
played over a high -quality system the
results are somewhat better, but the
hiss still is too high. I must admit that
the present cassette playback units add
their increments of noise, and some of
the newer units may help the overall
noise picture. I will also admit I heard
some remarkably quiet stereo cassettes
of generally good quality under laboratory conditions, and presumably this
kind of quality will be forthcoming in
the not -too -distant future. As things
stand now, with the currently available quality of sound on stereo cassettes, the audio buff will most likely
use them for background music.
Over the past months we have discussed various formats of slow -speed
tape. The quality picture with all of
them is not particularly bright, at least
as far as the devotee of high -quality
sound is concerned. A friend of mine,
one of the most respected engineers in
the tape field, who chooses to remain
anonymous, sums up the slow speed
there are
tape situation thusly:
many avenues of approach to upgrade
the slow -speed tape where it can
eventually begin to compare with topquality disc and tape. But all of the
effort expanded in doing this will prove
that reaching this goal will be very expensive and that, except for certain
convenience factors, it will not be as
good as a 71/2-ips tape. The factors
needed to improve 71/2-ips tape are far
easier of accomplishment and far less
costly. The extra tape required on a
71/2-ips tape is cheap and is getting
cheaper all the time." A radical view
in this age? Unquestionably, and only
time will tell.
Æ
...
AUDIO
www.americanradiohistory.com
AmericanRadioHistory.Com
SEPTEMBER 1968
STVD.D PNC ,NO SOL
STA. -re. REC. E/VCR
MO
12
O4
M6
M8
1;,IIItMIIh (,i!121t!(,elii!II(tWIi11,IkNF:t'
4,Oa.s
r,
If you don't mind paying a lot less
for a lot more,
try the n.ew University deceiver
If we had priced our new Studio Pro -120 Solid -State FM/Stereo Receiver
at half again more than its $379.50, the whole thing would have been
deceptively simple. Then no one, not even the most spend -thrifty status
seeker, could question its modest price versus its immodest quality,
If the thought of paying a lot less to get a lot more bothers you, we'll tell
you why the Studio Pro -120 is such a value. For over 35 years, we've built
some of the world's finest speakers and sold them at prices lower than
anything comparable. We're famous for that. But who ever
heard of a University receiver?
The Studio Pro -120 is our first, so we put everything we could into it,
including our many years of experience in designing sophisticated audio
electronics for the military.
The results turned out to be so fantastic, we had every spec certified
by a leading independent testing lab. That way, when you compare
our middle -of -the-line price with quality that's quite comparable
to the top -of -The -line of the Big 5, you'll know both are for real.
And if that isn't enough, how about asking your dealer for a re -print
of the three -page article on the Studio Pro -120 from
the January, 1968, issue of Audio Magazine.
Better yet, play with the Pro -120. Listen to it. And by all means compare
it to any much higher -priced receiver in the store. We'll bet
you'll wind up with our magnificent deceiver, as long as you don't
mind paying a lot less while getting a lot more.
l
UNIVERSITY
SOUND
DIVISION Of LTV LING ALTEC. INC
A
9500 West Reno . Oklahoma City, Oklahoma 73126
AMPLIFIER SECTION: IHF Power Output: 120 watts total, IHF Standard at 0.8% THD, 4 ohms (60 watts per channel). RMS Power Output: 8
ohms 30 watts per channel at 0.3% THD. Frequency Response: +0, -3 dB from 10 Hz to 100 kHz. Power Bandwidth: 10 Hz to 40 kHz, IHF
Standard. Intermodulation Distortion: Less than 0.5% at any combination of frequencies up to rated output. Tone Control Range: ±18 dB
at 20 Hz and 20 kHz. Damping Factor: 50 to 1. Noise Level: (Below rated output) Tape monitor: -83 dB-Auxiliary: -80 dB-Phono: -60 dBTape Head: -63 dB. Input Sensitivity: (For rated output) Tape Monitor: 0.4 Volts-Auxiliary: 0.4 Volts-Tape Head: mV at 500 Hz-Phono:
4 mV at
kHz. Input Impedance: Phono and Tape Head.: 47,000 ohms-Tape Monitor: 250,000 ohms-Auxiliary: 10,000 ohms. Load Impedance: 4 to 16 ohms. FM TUNER SECTION: Sensitivity: 6µV for 20 dB of quieting, 2.3 µV for 30 dB of quieting, IHF. Frequency Response:
% dB from 20 to 20,000 Hz. Capture Ratio: Less than dB. Image Rejection: Greater than 90 dB. IF Rejection: Greater than 90 dB. Separation: 40 dB at kHz. Selectivity, Alternate Channel: 55 dB. Drift: .01%. Distortion: Less than 0.5% at 100%modulation ±75 kHz deviation.
Multiplex Switching: Fully automatic logic circuit. GENERAL: Dimensions: 4%" H x 16%" W x 12" D (including knobs). Weight: 17 lbs.
Amplifier Protection: Three -ampere circuit breakers. -Complement: 31 Silicon & MOSFET transistors, 21 Diodes, 2 Integrated circuits
(each containing 10 transistors, 7 diodes, 11 resistors).
1
1
1
1
1
1
UNIVERSITY saving money never sounded better
Check No. 13 on Reader Service Card
AUDIO
SEPTEMBER 1968
13
www.americanradiohistory.com
AmericanRadioHistory.Com
Letters
Stylus Size
We read with some interest the advice given to Mr. Paul E. Scraggs on
the subject of Styli and Records in your
April 1968 issue; and while agreeing
with most of the recommendations
made, we feel that the question of
stylus -tip size needs clarification.
In accordance with the International
Standard for Processed Disk Records
and Reproducing Equipment (IEC
Publication 98 Second Edition 1964,
Clause E.1.1.2, including amendment
No. 1 of August 1967), the frontal tip
radius of reproducing styli for stereophonic records must be between 0.5 and
0.7 mil. The lower limit is set by the
bottom radius of the groove while the
upper limit is set by the instantaneous
minimum groove width on stereophonic
records. In accordance with "Dimensional Standards, Disc Phonograph
Records for Home Use, Bulletin E4"
published by the Record Industry Association of America, the instantaneous
minimum groove width on stereophonic
records is 1 mil.
Simple geometric considerations
show that a stylus of frontal tip radius
greater than 0.7 mil will not fit into a
groove having a minimum width of
1 mil, and will therefore be subject to
severe mistracking or groove jumping.
For these reasons we consider it essential that the frontal tip radius of styli
for stereophonic records should be
strictly limited to between 0.5 and
0.7 mil.
Finally, we should like to draw your
attention to the fact that it is the tip
radius, not the diameter, which must
lie between 0.5 and 0.7 mil for stereo.
G. M. NATHAN
The Decca Record Co., Ltd.
W. Hampstead, England
"Pro -Recorded" Tape
If you must have a prefix on the
word tape to indicate one recorded
with music, why not use the term
"Pro" Recorded, meaning, of course,
Professionally Recorded.
LEWIS DICKENSHEETS
Wichita Falls, Texas
Telex Encore
Stereophones
Made in America
Unbelievable at
$9.95
(Clever, these Americans)
You'll become a believer once
you look and listen. Dramatic
sound. 50 to 18,000 Hz. response.
Light weight. Comfortable. Tough
Cycolac plastic. Removable foam
filled vinyl cushions. Rugged 8'
Superflex cord. Hearing is believing. See your Telex dealer.
TELEX
9600 Aldrich Avenue South
Minneapolis, Minnesota 55420
A Shocker
I read your article on TV sound in
the Audioclinic section of AUDIO, July
1968, with considerable concern. I have
added cathode -follower circuits to several TV sets in the past. There are
many TV sets around that do not have
an isolation power transformer between the chassis (audio ground) and
the power line. Installing a cathode
follower between the TV audio and an
external hi-fi system via shielded cable
could result in the metal parts of the
hi-fi system, phonograph, tuner, tape
recorder, etc., all being connected directly to the hot side of the power line.
If a component in the hi-fi system is
grounded, smoke and sparks may appear in TV or in the grounded component. If a component is not
grounded, a deadly trap awaits someone who touches the system and a
ground at the same time.
Don't be fooled by sets with a power
transformer in them. I have a set with
a 6.3 V power transformer, but it is
only for the tube filaments. The power
line goes directly to the chassis and
selenium rectifiers are used in a voltage -doubler circuit for the B+. The
TV is safe for normal use because the
chassis is insulated from the cabinet,
knobs, etc.
These sets offer you a 50-50 chance
of getting a shock depending on how
the plug is oriented in the wall. If you
are lucky, the chassis could be connected to the ground side bf the power
line instead of the hot side. Reverse
the plug and you won't be so lucky.
Try using a 1: 1 line isolation transformer and avoid this hazard; that's
what I do.
ROGER H. RUSSELL
Binghamton, N. Y.
The technical information submitted
with AKG K-60 headphones (reviewed
in the July issue) when introduced late
last year did not include details on the
unusual efficiency of' the mylar diaphragm driver unit. The headphones
require only one milliwatt to reproduce
a sound pressure level of 112 dB. This
high sensitivity provides ample reserve
output for versatile, direct connection
to virtually any source-from amplifier
speaker circuits to the high -impedance
outlets provided on many transistorized tape decks for monitoring. Also,
both K-60 and the budget -priced K-20
version may be used on any impedance
from four ohms to 10,000 ohms without
a transformer.
R. W. MILLER
AKG Microphones -Headphones
New York, N. Y.
Check No. 14 on Reader Service Card
14
AUDIO
SEPTEMBER 1968
If saving money sounds "in" to you,
yoù ought to hear
the sounds of University.
High quality, fair price. That's what makes University the "in" itne. If the quality is no good...why
even bother about the price, right? Right" But if the quality is outstanding, wouldn t you like to
save a little moola too? Then you owe it to yourself and your pocket -book to check out
University speakers. Here's how to dc it the hard way:
Take any one of University's many spea>ter systems. For example, try the luxurious Sorrento
or the classic -styled Mediterranean. Ask your dealer to play either one along side another
speaker listed at the same price. Next, compare University's quality with a little higher
priced speaker. Then try still a higher priced speaker. `our ears will teil you to
stop comparing, and your eyes will tell you the bargain you got.
If you go along witn the idea that saving money is "in", even with hi-fi equipment, you'll be amazed at how sensational University speakers really do
sound, dollar -wise and sound wise.
While you're at it, check out University's one and only Studio Pro -120
Solid -State FM/Stereo Receiver. The specs are so unbelievably good,
we had them certified by an independent testing lab. They meet or
beat any of the top -of -the line receivers of the Big 5, at a most
attractive middle-of-tne-line price!
Now you know why/ University is the "in" fine. Check it
out. It's -a good way to cash in.
!`l
UNIVERSI1Ys0UND
O/V/SIGN
LTV LING ALTEC. !NC
OF
A
503 West
Reno
Oklahoma City, Oklahoma 73126
UNIVERSITY saving money never sounded better
Check No. 15 on Reader Service Card
AUDIO
15
SEPTEMBER 1%8
www.americanradiohistory.com
AmericanRadioHistory.Com
Tape Guide
HERMAN BURSTEIN
If you have a problem or question on
tape recording write to Mr. Herman
Burstein at AUDIO, 134 North Thirteenth Street, Philadelphia, Pa.19107.
Please enclose a stamped, selfaddressed envelope.
Tape Electronics
Q. I am considering the purchase of
a used tape transport. How should I go
about building it into a deck? Would
another make tape preamp be good to
use with this transport? What heads
would you suggest? About what would
the transport be worth?-Hal Weinberger, Ithaca, N. Y.
A. I can make the general statement
that I am prejudiced against the idea
of trying to hook up a tape transport
with separate record electronics not
matched for it. Even separate playback
electronics under this circumstance is
not highly recommended.
Separate electronics present a variety of problems to those not technically
qualified and equipped. These problems
include proper adjustment of bias current, adjustment of recording current,
adjustment of recording-level indication, matching the circuit impedance to
the head impedances, and proper
equalization, including compensation
for frequency irregularities of the record and playback heads (or of the
record/playback head) As witness that
these problems cannot be lightly taken,
there are extremely few tape preamplifiers today offered for sale as separate
items for matching with transports in
general.
.
High -Speed Duplication
Q. When duplicating a prerecorded
3.75-ips tape, and doing so at 15 ips,
thereby cutting recording time to minimum, should the new recording be distorted when played back at normal
speed? If so, is it due to misadjustment
of the line and mike volume controls,
or is it due to the very high frequencies? I notice while duplicating that the
VU meter registers above 0 VU a great
deal of the time. When I decrease the
record volume control to diminish distortion, the playback level is not loud
enough. When recording, is it best to
just monitor the recording to obtain the
best volume and balance, or should one
use the VU meter indications as well?B. S. Powell, APO San Francisco, Calif.
A. In multiplying playback speed
and therefore all recorded frequencies
by a factor of four, you are increasing
the output of high -frequency energy.
Thereby you may be overtaxing the
capabilities of the playback head, the
playback electronics, the record electronics, and the record head. For cleaner tape duplication, record at a level
that keeps the pointer of the VU meter
in the proper range-presumably below 0 VU. Although this will reduce the
recorded signal level, what counts is
the eventual signal-to-noise ratio. If
S/N becomes unsatisfactory, try dropping to a lower duplication speed.
Ordinarily one relies heavily on the
VU meter in order to record at proper
level. But you should also monitor the
tape to make sure that, whatever the
VU meter indicates, the recording level
is not so high as to produce noticeable
distortion, nor excessively low so as to
cause an inferior S/N ratio.
Running Correspondence
The series of questions and answers
below resulted from correspondence
with an overseas reader, Domingo
Riego, Jr., Manila, Philippines.
Q. The manufacturer of my tape recorder says that the cause of clicks
recorded on the tape may be removed
at the factory. How can this be done at
home or in a radio shop?
A. There are various possible causes
of recorded clicks. The click may be
due to a power switch, and placing a
capacitor in parallel with the switch
contacts might be the remedy. In another case, a high -value resistor, say,
10 megohms, between a switch contact
and ground may be the answer.
Q. Almost all better quality speakers
on the market are rated at 8 ohms impedance. My tape recorder has a 3.2
ohm output, and I find it difficult to
obtain good quality 4 -ohm speakers
to match the recorder's output impedance. How may my recorder's output
impedance be changed to 8 ohms?
A. I think you will find that 8 -ohm
speakers will generally work satisfactorily when fed from your machine's
3.2 -ohm output. An upward mismatch
(amplifier impedance lower than the
speaker impedance) is not apt to result
in perceptible losses, provided you do
not attempt to drive the speakers to
very high volume. If you do operate
at high volume, choose speakers of
relatively high efficiency. A number of
high -quality 8 -ohm speakers have
rather low efficiency.
Q. Will lowering the bias voltage in
my tape recorder, say from 55 volts to
45 volts, lower the volume in recording
or playback?
A. Lowering the bias voltage (as
measured at a prescribed point designated by the tape recorder manufacturer) , which really means reducing
the bias current through the record
head, will result in reduced magnitude
of the signal recorded on the tape. Of
course you will therefore also have a
lower signal in playback. Reduced bias
will also result in exaggerated treble
response.
Q. My tape recorder is properly
fused for operation on 117 volts a.c.
However, if plugged accidentally into
a 220-volt line, the voltage used in the
Philippines, the fuse blows only after
a length of time, almost always after at
least one tube has been damaged beyond use. I would like to have a fuse
or mini -breaker installed in the circuit
which will instantaneously blow or
break the instant 220 volts is applied.
In what part of the recorder's circuit
may it be installed, if applicable? What
should be the rating of the fuse or mini breaker, in amperes (my recorder is
rated at 100 watts). Will the addition
of a mini -breaker affect volume and
frequency response?
A. I would suggest trying a fuse with
slightly lower amperage rating than the
one you are now using. And install it
in the same place as the present one.
Presumably the manufacturer of your
tape machine has already chosen the
best fuse location. I would guess that
the proper fuse value is about 1 ampere
or slightly less. If by any chance your
present fuse is of the slow-blow type,
replace it with a conventional fast acting fuse. I don't see how the mini breaker could affect volume or frequency response.
Q. My tape recorder is rated at 117
volts a.c. Can it be modified for use
with 220 volts merely by changing the
power transformer and solenoid shunt,
without disturbing the other components?
A. To convert to 220 volts you also
need to change the transport motor.
Duplication
Q. Is the Cross Field head of any
value in recording or copying at 7.5
ips? Which is the more important to
someone like me, who does a lot of
copying: a Cross Field head with good
accuracy and wow -and -flutter specifi-
AUDIO
16
www.americanradiohistory.com
AmericanRadioHistory.Com
SEPTEMBER 1968
How to
recognize
a stacked
deck.
The Choice of Experts. This is the improved
successor to the famous Sony Model 350
which was picked as "a best buy" by the
nation's leadingconsumerreportingservice!
Scrape Flutter Filter. Special precision idler
mechanism located between erase and
record/playback heads eliminates tape
modulation distortion. This feature formerly
found only on professional studio equip-
MOW
ment!
Professional 3 -Head Design. The ultimate in
versatility. Such wanted features as Tape
and Source Monitoring, Sound -on -Sound,
Sound -with -Sound, and other special
effects!
Non -Magnetizing Heads. Head magnetization
buildup-the most common cause of tape
hiss-has been eliminated by an exclusive
Sony circuit which prevents any transient
surge of bias current to the heads!
Instant Tape Threading. Exclusive Sony
Retractomatic pinch roller permits simple
one -hand tape threading. An automatic tape
lifter protects heads from wear during fast
forward and reverse!
Unprecedented Frequency Response.
Achieves true high fidélity performance
even at slower speeds!
20-22,000 Hz @ 71/2 ips
20-17,000 Hz @ 33/4 ips
20- 9,000 Hz @ 1'/e ips
Noise Suppressor Switch. Special
Vibration -Free Motor. An important new Sony
filter
eliminates undesirable hiss that may exist
on older recorded tapes. Filter does not
affect the quality of sound reproduction!
development utilizing "floating" shock
absorber action to completely isolate any
motor vibration from the tape mechanism!
Sony Model 355. Priced under $229.50. For
your free copy of our latest tape recorder
catalog, please write to Mr. Phillips, Sony/
Superscope, Inc., 8142 Vineland Avenue,
Sun Valley, California 91352.
Three Speeds. 71/2, 33/4 and 1'/e ips. Additional features include: Four -track Stereophonic and Monophonic recordingand playback. Seven-inch reel capacity. Stereo
Headphone Jack. Automatic Sentinel Shutoff.TwoVU Meters. Pause Control. Four -Digit
Tape Counter. Record Interlock. Vertical or
Horizontal Operation. And more!
You never heard it so good.
SONY SUPERSCOPE
The
Taperai to Stereo
©sueqe<aP6 iHc.. uee
Check No. 17 on Readeir Service Card
AUDIO
SEPTEMBER 1968
17
www.americanradiohistory.com
AmericanRadioHistory.Com
t
1:1
e.
NORTRONICS
HAS
THE REPLACEMENT
TAPE HEAD
YOU NEED
FOR
ANY
TRACK
STYLE
°RFUNCTION!
To keep getting optimum perform-
ance from your tape recording
equipment you must regularly
replace worn tape heads. With Nortronics heads, adapters, and brackets,
it can be done quickly and easily...
and you can also convert track styles
in minutes.
Replacements for
MAGNECORD
AMPEX
RCA
CONCERTONE
CROWN
as well as 1500 popular
priced recorders
REEL-TO-REEL OR
CARTRIDGE TYPES
MONO/STEREO
FULL TRACK
HALF TRACK
QUARTER TRACK
EIGHTH TRACK
RECORD
PLAYBACK
ERASE
RECORD
PLAYBACK
RECORD
ERASE
NORTRONICS Bulletin 7230A
describes the complete line of
Nortronics replacement heads,
conversion and mounting kits, and
accessories. Write for free copy.
7/o,fronues
CO PANY INC.
INA
8101 Tenth Avenue North
Minneapolis, Minnesota 55427
cations, or the very best in thesg specifications without the Cross Field head?
When you do a lot of copying, is it
important to stay with machines of the
same model and make, or can I still get
the best results even though I buy two
different machines, both of high quality? One day I took music recorded at
3.75 ips and played it at 7.5 ips, and
copied it at 7.5 ips on my second recorder. The result when replayed at
3.75 ips wasn't too good. To speed up
the copying process, could music recorded at 7.5 ips be copied using two
machines designed to operate at 15 ips?
Would it come out sounding all right
on the 7.5 ips replay?-M. Glen Bair,
Idaho Falls, Idaho
A. The Cross Field head claims to
permit better treble response at low
speeds. While this is of course desirable, nevertheless I feel it is a secondary consideration compared with
low wow and flutter, low noise, and low
distortion.
In copying tapes you can get good
results with two machines of different
makes and/or models if they are both
of high quality and conform to the same
equalization practices.
A 7.5 ips tape can be copied at 15 ips
(that is, played at 15 ips, recorded at
15 ips, and eventually played at 7.5 ips)
with good results if the tape amplifiers
have frequency response to at least
30,000 Hz and if the bias frequency of
the copying machines is satisfactorily
high, say about 150,000 Hz.
Amplitude Fluctuation & Warble
Q. In the recording mode, with a very
constant voltage input from a frequency generator, the monitor output
of my tape recorder fluctuates as indicated by its VU meters. A VTVM confirms this random fluctuation. Various
audio frequencies give the same erratic
output. So do various tapes. Heads
were cleaned and demagnetized, and
springs controlling tape tension were
adjusted per the instruction book. The
pressure roller seems reasonably round
and smooth. All tracks give similar results. An oscilloscope shows about 5%
fluctuation in amplitude. Using earphones, a warble tone is heard. Your
interpretation of the difficulty and suggestions to correct the trouble would be
appreciated.-William E. Shenk, Philadelphia, Pennsylvania
A. All tape machines exhibit amplitude fluctuations, due in part or all to
the tape and to varying contact between the head and the tape. A 5%
fluctuation in amplitude is less than
1 dB and rather moderate. The warble
tone may be due to excessive recording
level, particularly at high frequencies.
At upper frequencies the VU meter
should indicate at least -10 dB when
recording a steady tone.
Using Two Recorders in Tandem
Q. I own two tape recorders, both
stereo. I am using them with a packaged set. Both recorders have a preamplifier, but the packaged set does
not. I would like to hook both recorders
into my audio system in tandem, so
that I can tape long broadcasts without reel change interruptions, and also
so that I can duplicate tapes. I have
tried a Y -adapter to each channel's
tape recorder output jack, but this does
not work. The signal cuts out completely. Yet both recorders work well
when hooked up individually.
Another problem is that there is no
left -right mode switch on my audio set,
so that when using one of my tape
machines and playing back a 4 -track
mono tape, I have to unhook one of the
output leads from the tape machine.
Can a switching arrangement be made
to eliminate this problem?-William J.
Zinn, Hanover, Ontario
A. In the absence of schematics of
your audio set and your tape machines,
it is difficult to suggest with certainty
how to feed the two tape recorders
simultaneously from your audio set
outputs. Seemingly one of the tape machines loads down the other, shorting
out the input signal to them. Perhaps
the following might work to isolate the
machines from each other: Connect isolating resistors between the Y -adaptors' hot leads and the inputs of the
tape recorders. Use the lowest value
that produces acceptable results. Start
with about.10,000 ohms, but try to avoid
going above 100,000 ohms. Instead of
using two isolating resistors, one for
each machine, a single resistor to one
machine or the other might do. Perhaps you can mount these resistors inside the tape recorders, at their input
jacks.
As for cutting out one of your channels in playback, does either of your
tape machines have separate playback
volume controls for its two channels?
If yes, just turn down the volume for
the undesired channel. If no, does
either of your tape recorders have a
left -right mode switch? If yes, use it.
If both answers are no, you or a technician can install in the tape machine
a simple toggle or slide switch to short
out the playback signal of the undesired channel. The shorting can be
done at the site of the playback volume
control.
Check No. 18 on Reader Service Card
AUDIO
18
www.americanradiohistory.com
AmericanRadioHistory.Com
SEPTEMBER 1968
few new reasons
you should see
the Pioneer line now!
a
every area of high fidelity, new
components by Pioneer are making
listening more enjoyable ... a richer
experience. Although these components represent the newest and
most advanced technology in audio
electronics, each is backed by the
30 years' experience of the world's
largest manufacturer devoted solely
to high fidelity and audio components, Here is a sampling of some
of the things to come in the next
In
few months.
SX-1000TD-130-watt AM -FM Stereo
Receiver with an FET front end and
4 IC's
A powerful 130 -watt (8 ohms, IHF)
receiver with most advanced circuitry, boasts 1.7 uy FM sensitivity
'IHF), excellent selectivity, capture
ratio of 1 dB (at 98 mHz), and S/N
ratio of 65 dB (IHF). Automatic
stereo switching, frequency response: 20 to 50,000 Hz ± 1 dB.
CS -52T -Compact 2 -way Speaker
System
Brilliant sound reproduction from a
very small
81"W
enclosure (13%"H x
x 85/8"D). Driven by a 61/2 -
inch woofer with extra large and
heavy magnet, and 21/2 -inch cone type tweeter. Excellent transient response and sparkling highs with
very wide dispersion.
I5 -31 -Basic Music Programmer for
Integrated Systems
Pioneer has led the way in advanced
concepts of bi -amplification and
electronic crossovers
the Pioneer
Integrated Systems. Hailed as the
ultimate approach to perfect sound
reproduction, Pioneer introduces
for 1969 (available now!) this basic
music programmer
an AM -FM
stereo tuner, a transcription turntable, and preamplifier, in one integrated module to couple with bi amplified speaker systems such as
the IS -80, Beautifully designed in
walnut, charcoal, and white gold,
with smoked acrylic cover.
-
-
PL -25 -Semi -automatic Transcription
Turntable
The turntable perfectionists have
been waiting for
the precision of
-
manual transcription turntable
with automatic cueing, automatic
shut-off, and automatic arm return.
The turntable with the conveniences
people want.
a
CS -5 -Intermediate -sized, Budget
priced Speaker System
An intermediate -sized speaker system at the lowest possible price,
from the world's largest manufacturer of loudspeakers. The CS -5 is
a convenient bookshelf -size system, using the most advanced transducers for full range reproduction,
to fit anyone's budget. Measure-
ments: 211/4"H
8
13/16"D,
x 11
7/16"W
x
See these and other fine components by Pioneer at your nearest
Pioneer franchised dealer. Or write
directly to Pioneer for free literature.
PIONEER ELECTRONICS U.S.A.
CORP. 140 Smith Street, Farmingdale, L.I., New York 11735.
Pl OIVEER
,.,(1,I)
...More Value All -Ways!
SX-1000TD
AUDIO
SEPTEMBER 1968
Check No. 19 on Reader Service Card
www.americanradiohistory.com
AmericanRadioHistory.Com
19
1965, could this mean that the interest in "rock"
music and/or "folk" music, the prime stimuli of
guitar sales, has leveled off and is now in decline?
Or does it simply point to a trend toward more
listening and less instrument playing?
For the fourteenth consecutive year, the number of stations broadcasting FM has grown. As of
February 28, 1968, there are 1804 FM broadcast
stations, according to the Electronic Industries
1968 Yearbook. This is an increase of 173 stations
over 1966 (at year end) . In contrast, commercial
AM broadcast stations evidenced a continuous
increase every year since 1949 (2006 stations at
mid-year) to its present (as of February 28, 1968)
4180 stations. This is an increase of 65 stations
over year-end 1966.
FDITOR'S
HEVIEW
For the Birds
Recording bird songs is not an uncommon avocation, though our British cousins have a greater
affinity for this hobby. Any tape recordists interested in taking a turn at this would do well to get
Dover Publications' recent record release, Common Bird Songs ($2.50) , which makes it possible
to identify songs and calls of 60 different and
widely distributed birds of Eastern and Central
United States, and Canada. An accompanying
32 -page booklet contains a picture of each bird,
together with comments on its sounds. The Company's address is 180 Varick St., New York, N.Y.
Coming Up
The New York High Fidelity Music Show is
coming up fast. It will be held at the Statler Hilton
Hotel, Seventh Ave., 32nd to 33rd Streets, in New
York City. Admission charges are $2.00 for adults,
500 for children under twelve years of age. Mark
these show dates on your calendar:
GENERAL PUBLIC
Thursday, Sept. 19
Friday, Sept. 20
Saturday, Sept. 21
Sunday, Sept. 22
Statistics
4. 00 P.M. to 10:30 P.M.
4. 00 P.M. to 10:30 P.M.
1. 00 P.M. to 10:30 P.M.
1.00 P.M. to 9:00 P.M.
DEALERS
For the first time since 1949, sales of musical instruments showed a decline compared to the
previous year. Whereas 1966 retail sales were $954
million, 1967 sales dropped to $924 million. However, its per cent of personal consumption, 0.187
per cent, was exceeded only in 1965 and 1966.
According to a report by The American Music
Conference, the number of music -making adults
and students continued to rise in 1967 from over
41 million to almost 44 million persons. Not surprising, the piano was the leading instrument, with
231/2 million people playing the instrument (ten
years ago it was nearly 20 million) . This was followed by the guitar, which numbered 11 million
players (ten years ago it was close to 3 million) .
Both leaders exhibited a decline in unit sales in
1967.
Guitar unit sales, in particular, slumped from
1.43 -million unit sales in 1966 to 1.04 million, a loss
of almost 400 thousand guitar sales. On top of a
70 -thousand loss in unit sales in 1966 compared to
Wednesday, Sept. 18
Thursday, Sept. 19
Friday, Sept. 20
5. 00 P.M. to 9: 00 P.M.
00 P.M. to 4: 00 P.M.
1. 00 P.M. to 4: 00 P.M.
l'
George Dubé was named to the newly created
post of Executive Director of the Institute of High
Fidelity. He joins the IHF directly from the Consumer Products Division of the Electronic Industries Association.
Address Unknown
On occasion, readers forget to enclose a stamped,
self-addressed envelope with their inquiries to
AUDIO columnists. Every letter directed to them
for assistance on a hi-fi problem is answered. If
you do not receive a reply within a reasonable
time (1 to 2 months?) , please send a duplicate of
your letter with another stamped, self-addressed
envelope. (Some readers omit their address on the
letter itself, making it impossible for columnists
A.P.S.
to respond.) Thanks.
20
AUDIO
www.americanradiohistory.com
AmericanRadioHistory.Com
SEPTEMBER 1968
The X factor in the new Pickering XV15.
The X in the new Pickering XV -15 stands for the
numerical solution for correct "Engineered Application." We call it the Dynamic Coupling Factor
(DCF).5M
DCF is an index of maximum stylus performance
when a cartridge is related to a particular type of
playback equipment. This resultant number is derived from a Dimensional Analysis of all the parameters involved.
For an ordinary record changer, the DCF is 100.
For a transcription quality tonearm the DCF is 400.
Like other complex engineering problems, such as
s'
Dynamic Coupling Factor and DCF are service marks of Pickering
Check No.
AUDIO
SEPTEMBER 1968
the egg, the end result can be presented quite simply.
So can the superior performance of the XV -15 series.
Its linear response assures 100% music power at all
frequencies.
Lab measurements aside, this means all your favorite records, not just test records, will sound much
cleaner and more open than ever before.
All five DCF-rated XV -15 models include the patented V -Guard stylus assembly and the Dustamatic
brush.
For free literature, write to Pickering & Co., Plainview, L.I., N.Y.
21
&
Co.
on Reader Service Card
21
First of a
is what high performance is all about. A bold and beautiful new FM Stereo
new breed This
Receiver bred to leave the others behind. 160 crisp, clean watts-power in
-from
Sherwood
circuitry featuring Field-Effect Transistors and
microcircuitry. Front -panel, push-button command of main, remote, or mono
extension speakers and loudness contour. Sherwood high-fidelity-where the
action is-long on reliability with a three-year warranty.
reserve. Up -front, ultra -now
1111110
OD
..
Model S-8800a
$399.50
-Sieuuoar,t-Sherwood Electronic Laboratories, Inc.
22
4300 North California Avenue,
Check No. 22 on Reader Service Card
Chicago, Illinois 60618
Write Dept. A-9
AUDIO
SEPTEMBER 1968
SCA
Private Music Channels
on FM Stereo
LEONARD FELDMAN
How background music broadcasts are hidden on
public FM stereo broadcasts
IT
WILL COME as no surprise to
many owners of stereo FM receiving equipment that there
exists, within the public FM frequency band, a service which is anything but public, known as SCA
(Subsidiary Communications Authorization) . Manufacturers of stereo
FM receiving equipment are even
more aware of the existence of this
ancillary service, for they must
painstakingly filter out this additional sub -carrier by adding circuitry to their receivers' stereo FM
decoders. Earlier in the brief history
of stereo FM, many manufacturers
learned the hard way that failure to
provide adequate SCA rejection filters resulted in a combination
"swishing-whistle" on certain stereo
FM stations which rendered some
just about un-listenable.
Additional sub-carriers (other
than the supressed double-sideband,
audio modulated one used for transmitting the L
information of a
stereo program) are used by some
broadcast stations to transmit
"background music"-the music you
so often hear in restaurants, bowling
alleys, factories, and many other
public places. In most instances, the
station owner merely "leases" this
additional facility to another entrepreneur who is engaged solely in the
sale of this innocuous, commercial free music. Actually, that's all that
is sold. The necessary FM receiver
and decoder are seldom, if ever, sold
to the user. Rather, equipment is
leased to the customer, installed by
the background music firm, and serviced by that firm as well. Usually,
the receivers so leased are fix -tuned
units (crystals are usually used
to tune the main r.f. frequency)
-R
AUDIO
SEPTEMBER 1968
capable of receiving only the background music service, to the exclusion of main channel programming
of the given station or any other station.
SCA Standards
Figure 1 details the spectrum distribution of the various services
authorized by the FCC to be transmitted over a single FM transmitter.
Note that the horizontal axis represents frequency, while the vertical
axis represents percentage of modulation or deviation of the main carrier. The band of frequencies from
50 Hz to 15,000 Hz represents "main
channel" or L + R monophonic
public programming. This is followed by the well-known 19 -kHz
"pilot" carrier, needed to establish
a 38 -kHz reference carrier in the
stereo decoder section of the receiver. Next come the upper and
lower sidebands of the suppressed
38 -kHz subcarrier which constitute
stereo information. These
the L
extend from a low of 23 kHz to a top
frequency of 53 kHz. If the station
is not engaged in SCA service, the
sum of all these modulations will
equal 100% (or 75 kHz) deviation
of the main carrier. (Note that both
information are
L + R and L
shown to cause a maximum modulation of 90%, while the pilot signal
provides the other 10%. Actually,
because of the so-called "interleav-
-R
-R
ing" action associated with the FCC approved FM stereo system, L + R
never reach 90% deviaand L
tion at the same instant, so that the
instantaneous sum of the two never
exceeds the 90% deviation figure.)
In the event that a station is to
transmit SCA service as well, L + R
-R
and L
-R modulations are "backed
off" to 80%, the "pilot" remaining
at 10%. This leaves an additional
10% available for the SCA service,
which, as can be seen in the diagram
of Fig. 1, is nestled in at 67 kHz, extending upward to approximately 72
kHz and downward to about 62 kHz
when modulating information is applied. Note that unlike the L
-R
stereo subcarrier, this additional
subcarrier is frequency modulated.
Thus, if you think of this subcarrier
as a sort of FM station all over again,
its "r.f. center frequency" is 67 kHz.
Its amplitude remains constant at all
times, but its frequency is caused to
vary in accordance with the desired
program material. This entire sub carrier then modulates the main r.f.
carrier. Since this subcarrier is quite
different in makeup from any part of
the stereo composite signal, the progamming imparted to it by FM modulation of its center frequency (67
kHz) is not audible on a standard
FM receiver nor on a standard stereo
FM receiver. About all a stereo FM
receiver can do is reproduce the annoying whistling sound described
earlier if SCA rejection filters have
not been adequately designed.
Several months ago, Mr. Murray
G. Crosby (the noted inventor in the
FM field, and one of the pioneers in
the development of stereo FM broadcasting) suggested a novel way to
demodulate this frequency-modulated 67 -kHz subcarrier, once it has
been recovered intact at the output
of the detector of a conventional FM
tuner. In order to appreciate the
sophistication of his approach, it is
necessary to first consider how this
decoding job is generally accomplished by most manufacturers of
23
100
_
If
If
block diagram of which is shown in
Fig. 3. In this approach (still used,
by the way), the 67 -kHz subcarrier
is processed "as is."
The first stage is for isolation, followed by a band-pass filter that is
employed to remove everything but
the desired 67 kHz. Amplified further, the 67 -kHz signal is used to key
a "Schmitt Trigger" type of multivibrator which produces square
waves of large constant amplitude,
the frequency of which follows the
frequencies of the incoming 67 kHz
subcarrier as it is modulated, ± 4
kHz based upon program audio. The
square waves are then differentiated
to form narrow width pulses, which
are then "counted" or integrated by
a form of counter detector. In this
form of detector, the more closely
spaced pulses will cause a greater
output (instantaneous d.c. level)
while more widely spaced pulses
(corresponding to the downward deviation away from 67 kHz) will
cause reduced d.c. level. The movement above and below a nominal
No SCA Channel Used
SCA Channel Used
ô
° 80
z
º
60
Main Channel
(L+R)
20
Stereo
Pilot
15
19
Sub
-
Channel
23
FREQUENCY
tribution of information on FM
channel.
SCA
Sub -
Channel
Channel
53
38
62 172
67
(KILOHERTZ)
SCA decoding equipment. Perhaps
the most -often -used approach is illustrated in the block diagram of
Fig. 2.
The small amount of 67 kHz sub carrier recovered at the detector
(either a discriminator or a ratio detector type) of the standard FM
tuner is first passed through a 67
kHz resonant circuit of moderate
selectivity which rejects some (but
not all) of the other material present. A stage of isolation usually follows (such as an emitter follower),
to prevent circuit loading of the
main FM detector (not shown) . A
local oscillator (often, but not always crystal controlled) produces a
frequency which is 455 kHz above
that of the incoming subcarrier.
Thus, for a 67 -kHz subcarrier, the
local oscillator would be tuned to
522 kHz. The two signals are heterodyned in much the same way as is
done in any AM radio, producing an
"i.f." frequency of 455 kHz. This
choice enables the use of very ordinary "AM i.f." transformers, and a
sufficient number of stages of gain
employing such interstage transformers are used to both reject anything other than 455 kHz and to
build up the signal to a well -limited
one.
Finally, since we are dealing with
FM (despite the use of a familiar
"AM" frequency) , detection is accomplished by a discriminator tuned
to a center frequency of 455 kHz.
Ratio of deviation to total frequency
is not unlike that associated with
regular FM. Here we have a deviation of approximately 4 kHz about a
new center frequency of 455 kHz, as
opposed to the more familiar 75 kHz
about a frequency of 10.7 mHz.
24
Upper
Sideband Sideband
Of Stereo Of Stereo
(L -R)
(L -R)
40
o
g
Fig. 1-Spectral dis-
Lower
Audio recovery is fair, usually running about 0.1 volts rms for 4 -kHz
deviation. Cost, however, is quite
high, since several stages of 455-kHz
amplification are required, not to
mention crystal control of local oscillator, and a converter stage, "i.f."
transformers, a rather expensive,
specially made discriminator, and
so on.
Back in October 1958, in the
Avnio edition of that month, I
described an alternate method of
FM subcarrier demodulation, a
Fig.
2-One approach to
67 -kHz decoder
circuit utilizes heterodyning and an AM-type
i.f. strip.
455 kHz
STAGES
"IF"
67 kHz FILTER
FROM
FM} DETECTOR
)(i
.
T
ISOLATION
->-
MIXER
STAGE
111[
1111
455 kHz
522 kHz
OSCILLATOR
DISCRIMINATOR
I--r-I
>AUDIO OUT
Fig.
3-An early
SCA decoder described by the author (AUDIO, October 1958).
DIFFERENTIATOR
6Hz
AMPLIFIERS
FROM
FM> - ISOLATION
STAGE
DETECTOR
fJ
COUNTER
AMPLIFIER
->-
-,\ AT
SCHMITT
TRIGGER
Fig.
4-Block diagram of new
BAND-PASS
FILTER
FROM.
FM >-DETECTOR
T
T
AMPLIFIERS
OUTPUT
I
NTEGRATING
N ETWORK
SCA decoding system.
LIMITERS
SERIES
RESONANT
CIRCUIT
AND GATE"
INTEGRATING
NETWORK
OUTPUT
I
4
AUDIO
I
SEPTEMBER 1968
"DIRECT" INPUT
"PHASE SHIFTED"
INPUT @
RESONANCE
RESULTANT OUTPUT
PULSES
"DIRECT" INPUT
i
"OFF RESONANCE"
PHASE SHIFTED
INPUT
RESULTANT OUTPUT
PULSES
Fig. 5-Principle of "Gate" FM detector. Output pulses at (A) are for unmodulated condition of sub -carrier, while tP,ose in (B) represent departure of sub -carrier from center
frequency.
d.c. center point, with changing frequency above and below the nominal
67 kHz, represents the detected
audio output of the system. Extremely linear output is a known
characteristic of such counter -
detectors. In this instance, because
of the relatively small difference in
"integrated area" of pulses as one
goes from 63 kHz to 71 kHz, the actual audio output using this system
is extremely low, measuring much
less than 0.1 volt for the parameters
involved in SCA transmission.
Though the circuit is less costly than
the 455 kHz type already described,
the very low output more than offsets this advantage since extra stages
of gain must follow detection and
these, unfortunately, can do nothing
to improve signal-to-noise factor.
The system of decoding suggested
by Mr. Crosby is shown as part of
the block diagram of Fig. 4. It is
based upon one of the most common
of "logic" circuits used in computers, but perhaps unfamiliar to
AUDIO
those in the audio and communications field-the "AND" gate. An AND
gate is simply a device that produces
an output, "C," only when two inputs, "A" and "B," are present. With
only input "A" or only input "B"
present, no output will be produced.
With this idea in mind, let us examine Fig. 4.
The first block represents a simple
band-pass filter, which rejects all
frequencies other than those at or
near the desired 67 -kHz center. Two
stages of amplification follow, which
utilize high-input impedance FET's.
The signal is then further amplified
and limited by a pair of IC's. The
output of the second IC is a fully
limited signal which closely resembles a square wave. This signal
is passed along two paths. The first,
via simple capacitive coupling, applies the signal to one transistor of
the pair making up the AND gate. The
second path includes a resonant circuit tuned approximately to 67 kHz
(L3 and C18 in Fig. 4) . The voltage
applied to the alternate transistor of
the Arm -gate pair is taken from the
voltage appearing across the capacitor element of the series resonant
circuit. This voltage therefore differs
in phase from that directly fed to the
other input by approximately 90 degrees.
From the previous explanation of
gating action it is obvious that an
output will be present for only that
period of time in which both inputs
are positive and overlap in time (or,
90 degrees out of a possible 360).
Thus, the output will be a series of
pulses having a fundamental frequency of 67 kHz and a duty cycle
of 90 degrees.
Now suppose we depart from 67
kHz (as would be the case when the
signal is modulated with program
information) . Since we are now feeding frequencies which are on either
side of resonance, the phase difference between the directly fed signal
and that taken from across the capacitor of the series resonant circuit
will no longer be 90 degrees, but will
vary above and below that angle.
This means that the period during
which both inputs are positive and
applied to the gate will be shorter
when the angular difference increases,
and longer when the angular difference decreases. As a result, the area
or width of the output pulses will
vary, too. And variance is considerable compared to the area difference
arising merely from the slight
change of frequency (as might be the
case in a conventional counter detector). A simple integrating network (in this case, an R -C network
which would be needed to provide
de -emphasis anyway) is all that is
required to translate this changing
pulse area into a whopping audio
signal.
Fig. 5 illustrates the "gate FM detector principle" just discussed. The
"Q" of the series resonant circuit
need not be very great to take advantage of this principle. For example,
fractional detuning of 4 kHz above
or below resonant frequency (67
kHz) results in a phase lag or lead
of nearly 50 degrees with a circuit
"Q" of only about 10 or so!
A practical SCA adapter , using
the above principle, will be examined next month.
25
SEPTEMBER 1968
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AmericanRadioHistory.Com
Electronic
Organs
PART
1
of a series
NORMAN H. CROWHURST
Introduction to how
electronic organs work
AN UNDERSTANDING of electronic
organs involves a wedding of two
kinds of knowledge: musical and
electronic.
From the electronic viewpoint,
and to some extent in the music department also, organs can be divided
according to the way the tones are
generated. In grandfather's days,
home organs used reeds, driven by
air pressure or vacuum which was
obtained by foot -operated bellows.
Modern adaptations use electrical
power to blow the reeds, relieving
the feet of all that work, and they
provide electronic amplification of
the vibrations to make the sound
louder, and allow loudness control.
As amplifiers are not electronic tone
generators, we'll not consider this
group to be true electronic organs for
the purposes of this discussion.
In the same category with this
kind of organ is the so-called electronic piano, to which we will also
give only passing mention. Instead
of using the bridge and sound board
to radiate sound, this instrument
uses neither, but employs pickups
and electronic amplification to get
the desired volume of sound. With
the amplifier off, such a piano is very
nearly silent.
uses magnetic tone wheels driven at
different speeds, using pickups to
give the electrical output. As we
shall discuss later, the Hammond
uses electronics to a far greater extent than the mere use of pickups
and amplification from a mechanical-type source.
The other electromechanical type
hasn't been seen too much in the
U. S. The Compton organ uses it.
The pickup is capacitive, and the
complete waveforms are etched on
tone wheels driven in a manner similar to the Hammond (Fig. 1-1) .
The main difference between these
two types, apart from the type of
pickup used, is that the Hammond
synthesizes tone quality electronically, while the Compton has the
waveform physically built into the
tone wheel.
Individual tones generated on the
Hammond are basically close to
sinusoidal. They are very nearly perfect sine waves. Overtones or harmonics, to give timbre, are added by
electrically adding the outputs from
different tone wheels. In the Compton, the compositive waveform, complete with all its harmonics, is
etched on the tone wheel.
Electronic Generators
Having briefly dispensed, for the
time being, with the types that may
be considered partially electronic,
we now turn to the fully electronic
types of oscillator, which have no
mechanical moving parts of any
kind. These use some kind of elecFig. 1-2
-
SINE WAVE
OUTPUT
COMPOSITE WAVE
OUTPUT
TONE WHEEL
CAPACITOR
PICKUP
1-1-Two types of electromechanical
tone generator: (a) The magnetic, used by
Hammond, generates a sinusoidal output.
Timbre is achieved by mixing the outputs
from as many as 9 tone wheels. (b) The
electric (sometimes called "electrostatic"),
used by Compton. Here, each tone wheel
generates a composite wave, with a wave
form etched into the original wheel.
Fig.
tronic oscillator as tone generator.
Two basic kinds can be distinguished, depending on the way the
pitch of the tones generated is determined. Some oscillators use a tuned
circuit, the waveform of which is
basically sinusoidal. If it oscillates
too hard, the sine wave goes out
of shape, but it is still basically
sinusoidal.
When it oscillates too hard, the
frequency is less definitely fixed by
the circuit L and C values, so frequency stability is more likely to be
a problem. But stability is a complicated question, which we will come
to in a later installment.
The other type of oscillator works
on time intervals, and is exemplified
Essential
difference in basic
waveforms generated by two types
of generator: (Top)
The sine wave, generated by tuned cir-
cuit oscillators.
(Bottom) The
SINE WAVE
VARIATIONS FROM SINE WAVE
SQUARE WAVE
VARIATIONS FROM SQUARE WAVE
square wave, generated by multivi-
Electromechanical
Tone Generators
brator-type oscillators. In each case,
the basic, or theo-
Next we come to two varieties of
organ that are truly electronic, although the pitch of the notes is determined mechanically. This type
we will call "electromechanical."
Best known is the Hammond, which
retical waveform is
at the extreme left,
while the other
waveforms
are
practical variations
of it, within the
type.
26
AUDIO
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SEPTEMBER 1968
1-3-A simple generator circuit for the
type of solo organ used as an add-on unit
for attaching to a piano.
organ richer in overall tone quality, or it's one way of achieving that
effect.
With organs of this type, only the
top octave has actual tone generators. Octaves below that are obtained by using frequency dividers.
Each octave gets its notes by halving
the frequency of the notes in the
octave above. When the top octave
has been tuned, the whole organ is
in tune, automatically.
An essential feature of this kind
of organ is that all generators must
be oscillating all the time, as are the
frequency dividers performing their
dividing function. With this type,
keying must essentially consist of
switching the outputs of the oscillators and dividers that are always
running.
Individual Oscillators. The final type
of organ uses a separate oscillator,
or more than one, for every note on
the keyboards. Only the best organs
can afford to include this much electronics and the work involves tuning
every one. But when such an organ
is tuned, it sounds like a lot more
organ.
Fig.
SUPPLY
Fig. 1-4-Arrangement of some earlier organs had groups of two or three (the latter shown here) notes sharing each
KEYS
OUTPUT
oscillator. Only one note of any group of
three could be played at one time. Thus
a C minor chord could be played, consisting of C in the first group, D# in the second group, G in the third group, and C in
the fifth group.
OUTPUT
11
OSCILLATORS
dl
C
C# D D# E
F'
I
I
F# G G# A A#B
1<I If II
C
C# Dp#;E
F
F#
G
II
4A,A##8
in the multivibrator. The basic output of a multivibrator is square, although a variety of other waveforms
can be "found" around a multi vibrator circuit, or easily developed
from it.
Fig. 1-2 shows the distinction, together with the essential difference
in the waveforms, as generated. Frequency of a sine wave is basically
related to a rate of movement, of the
harmonic motion type. Period of a
square wave is a question of timing
between movements, such as switching, whose rate has no essential connection with frequency.
From the musical viewpoint, the
quantities of frequency and time interval, or period, are inseparably related, but in considering kinds of
generator, this significant difference
exists.
C C#(D D# E F
AUDIO
A#1
B
Some of the earlier organs used
this method, possibly with more sophistication for part of the organ,
the part intended to be played as
solo, one note at a time. Other earlier
organs wired one keyboard in a sort
of hybrid fashion, where one oscillator sèrves two or three notes rather
than having one for every note (Fig.
1-4).
With these organs, only one of
any group of notes using the same
oscillator will sound at a time. Not
many of these are still in use.
Master Oscillators. The most inexpensive organ capable of playing any
combination of notes, as well as
being the easiest organ to tune, uses
an arrangement with just 12 tone
generators or oscillators (Fig. 1-5).
Some organs of this type may have
more than one master set of 12 oscillators, but the idea is the same.
Using more than one set makes the
Generator Arrangement
Now we have the basic parts from
which to build an organ. But still
there are different ways of going to
work with these parts, of stacking
them up, as it were. We can use varying generator arrangements.
The simplest kind of "organ" is
sometimes supplied as a solo unit
for affixing to the front of a piano
keyboard to give extra effects. This
uses just one tone generator, which
the keyboard switches to a variety
of frequencies. It can play only one
note at a time. A simple form of
generator uses no more than a neon
tube, capacitor and different charge
resistors for every note (Fig. 1-3).
II
II
F# Ggi# A
Fig.
1-5-The master oscillator system
uses
Timbre or Tone Quality
The next step in designing an
organ is to find a way of varying the
tone quality or timbre of the notes.
An organ may employ one of three
different ways to achieve this, although each way is limited, or more
readily adaptable, to certain kinds
of generator.
Frequency Synthesis. The first type
literally puts together the component fundamental and all the haronly
12 generators (at the
right). Lower octaves
are obtained by frequency dividers working successively.
SECOND DIVIDERS
Ir
MASTER OSCILLATORS
FIRST DIVIDERS
1I
-- ---
KEYS
7
TTTT`T-TT--TTFJTYTT
B C C# D D# E
F
F#
G
G# A A# B C C# D D# E
F#
G
G# A A# B
CC
J
C
C#
D
D#
E
Ìfir`
F
F#
G G4# A
A#
B
27
SEPTEMBER 1968
www.americanradiohistory.com
AmericanRadioHistory.Com
monies needed to produce the
desired tone quality in each note
played (Fig. 1-6). This approach
can only be applied to sine -waveform generators.
The only well-known organ employing it today is the Hammond,
which uses drawbars to mix harmonics in the desired proportion.
Each drawbar works a set of potentiometers in the outputs of the harmonic that the drawbar represents.
This approach provides virtually infinite variety to the overtone structures that can be used.
Formants. The remaining types of
tone formant work on the output
waveform are already produced by
whichever type of generator is used.
The commonest and simplest is the
response formant type. This takes
the output from the whole range of
oscillators, after they are keyed, and
feeds it through a filter that weights
lower or higher frequencies. Thus
the overall output of the organ is
"colored." Different filters can work
in parallel to combine effects (Fig.
1-7).
Wave Shaping. The third type of formant works on waveform, rather
than on frequency content. It can
best be understood by assuming it as
used with the multivibrator type of
generator, whose waveform is first
changed from square wave to triangular (Fig. 1-8) . Then the triangular
waveform is fed into the waveform forming networks, which shape it
into any desired form. This is much
more complicated, but also much
more versatile in the kinds of output
waveform it can produce.
Integrated circuits have made it
feasible for medium-priced organs,
where before it would have been prohibitive for any but really highpriced organs. Although we illustrate
it applied to the multivibrator form
of output, this is not the only type
that can use it or an adaptation of it.
Each method of changing tone
quality has its merits or range of
uses. Some organs use more than one
form.
T
f
NOTE
PLAYED
m
m
H
4
II 11111 III
u
I
11111
1 -6 --Frequency synthesis as a way of developing timbre. This
C is played. The drawbars (Hammond method) control how much
Fig.
diagram assumes note
tone is taken from the
various other wheels indicated. In ascending order, the bars illustrated represent: sub harmonic, sub -third, fundamental, second harmonic, third harmonic, fourth harmonic,
fifth harmonic, sixth harmonic, and eighth harmonic.
much you want to spend. Organs today include a lot more of them for
less money than earlier organs would
have cost.
Unless you're interested in church
organ music only, with a baroque
quality, your organ is certain to have
some form of vibrato or tremolo that
gives the notes that wavery effect.
Many of the better organs have more
than one vibrato or tremolo; some a
choice and some the possibility of
combining effects.
Most modern organs have something in the percussion, sustain and
reverberation department. The simplest of these is sustain. The keying
is designed so that the tone dies
away electronically when the pressure of the finger on a key is released.
The earliest organs to include this
feature called it "percussion." Actually it is not. Percussion applies
not to the way the note dies away,
but to the way it begins. True percussive effects use further electronic
means that add something to the beginning of the note when the key is
first pressed. A sort of extra attack,
rather than just "switching the note
on" (Fig. 1-9).
Reverberation has an effect somewhat similar to "sustain." The difference is that it works after all the
notes are mixed together; more like
a reverberation effect in a large hall.
This uses the same kind of reverb
units that are used to add that quality to recordings.
Finally come the real "luxury"
trimmings, mostly reserved for the
4 Fig. 1-7-Arrangement of the formant type
of timbre control.
Fig. 1-8-The wave -shaping method: The
square wave is first made triangular; then
electronic shaping controls alter this to
desired shape.
AMPL.
Other Features
That gives us the basic elements
of the organ. Now come the trimmings, which may be used in varying quantities, according to how
BUS FROM
INDIVIDUAL
TONES
T
FORMANT FORMANT FORMANT
NETWORKS
INPUT
OUTPUT
BUS
BUS
28
TONE
GENERATOR
INTEGRATING
NETWORK
OTHER
ONE FOR EVERY NOTE
AUDIO
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SHAPING
NETWORK
SHAPING
NETWORK
OUTPUT
BUS
SEPTEMBER 1%8
KEY
KEY
PRESSED
RELEASES
RE,
PRESSES
NEE
RELEASED
selecting appropriate chords. This is
for those who have difficulty reading
music well enough to get their fingers
in position to pick out the right notes
to play the full chords themselves.
Not to be confused with this relatively simple chord -making feature,
although related to it, is another
kind of extra that makes automatic
arpeggios, which play the notes in
a chord in sequence, like a strum,
rather than all at once.
That wraps up most of what goes
into the electronics of an organ.
We've stayed away from manuals
and pedal claviers, the mechanical
details associated with playing, for
the time being. We'll have to go into
that too, when we get down to details. In future installments we'll
progress into details, beginning with
the next issue, on what goes to make
an electronic organ musically satisÆ
fying.
PERCUSSION
PERCUSSION
WITH SUSTAIN
AN ASTOUNDING NEW
KEY
PRESSED
REY
KEY
RELEASED
RELEASED
KEY
AUDIO NOISE REDUCTION
PRESSEC
SYSTEM WHICH IS
MAKING BACKGROUND NOISE
YESTERDAY'S PROBLEM.
The Dolby System gives
10dB increase in
usable dynamic range
A 10-15dB hiss reduction
A 10dB print -through and
cross -talk reduction
A 10dB hum reduction
A
Fig. 1-9-The difference between percussion and sustain. Top left shows the en-
velope of a wave keyed with no electronic
effect added. Top right shows the addition
of electronic sustain to the keying. Bottom
left shows the addition of one form of
electronic percussion to the keying. Bottom right puts the two together.
highest-priced models in the manufacturers' lines, although one of them
also comes as an alternative on many
of the lower cost organs.
One that only comes as an extra
on the best organs is the side-effect
department. This has a variety of
special names used for promotion
purposes, but its effect is to add
drums, traps, cymbals and other
non -tonal effects.
Some of them take their cue from
the player, using electronic means to
automatically synchronize the electronic "drummer" with the music
you play at the moment. Others can
be set to provide a regular beat or
rhythm, which they will hold until
you change it. With these the organist keeps time with the drummer,
rather than vice versa.
Many of the low-cost organs provide some means for automatically
PLUS generally cleaner, more
transparent recordings-with
unaltered frequency response
and signal dynamics.
Recording engineers and musical directors are
so enthusiastic about the Dolby S/N Stretcher
system that the network of users is growing at
an astonishing rate-on an international scale.
Master tapes made with the system now fly
regularly between the major recording centers of
the world, such as New York, London, Rome,
and Vienna.
The basic principle of the system is simple.
Low-level signals are amplified in four independent frequency bands during recording and
attenuated in a complementary way during playback-recording noises being reduced in the
process. High-level signals are unaffected by
this procedure (no distortion or overshooting),
and the symmetrical design of the circuitry
ensures that the signal is restored exactly in all
details-high-level and low-level, amplitudes and
phases. The result is a noise reduction system
with ideal characteristics-perfect signal handling
capability which can pass any line -in, line-out
A -B test, and a genuine 10dB noise reduction.
In short, the Dolby system offers an entirely
new area of sound for the recording engineer.
Get to know more about it fast by writing directly
to Dolby Laboratories or contacting your nearest
agent.
DOLBY
LABORATORIES
SIXTH AVENUE
Telephone: (2121 243.2525
333
INC.
NEW YORK N.Y. 10014
Cables: Dolbylabs New York
Check No. 29 on Reader Service Cord
AUDIO
29
SEPTEMBER 1968
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AmericanRadioHistory.Com
Fig. 1-View of the
seating area and
stage of the openair theater in which
the sound system
installation described in the text
was. made. A closeup of the loudspeaker array is
shown in the inset
photograph.
A Greek Theater
(circa 1968)
DON DAVIS*
Sound installation for a modem
open-air theater
THE
open-air amphitheater has presented acoustic
problems since its inception in antiquity. Witness the works of Vitruvius, the tuned resonant vases found
in the risers of the ancient theaters,
and the use of the megaphone concept designed into the masks worn
by the actors.
Recently, a modern Greek-style
theater in Hollywood, California
employed up-to-date electro -acoustic techniques to achieve startling
results as compared to the ancients,
and remarkable results as compared
to modern contemporaries.
Five
CLASSIC GREEK
Guidelines
The requirements to fulfill the performance promise inherent in the
latest electro -acoustic equipment
break down into the following interlocking steps:
*Manager, "Acousta Voicing," Altec Lansing,
Div. LTV Ling Altec Inc.
Correct acoustical design of the
loudspeaker enclosure and cluster. This includes time -difference
relationships from a cluster to
audience vs. performer to audience, acoustic gain potential, and
realistic coverage patterns at
properly adjusted gain differences that compensate for the
inverse -square -law effect of dispersion.
2. Proper electronic system design
that provides sufficient electrical
power to ensure generation of the
required acoustic power.
3. Correct electronic design to provide full flexibility of source-type
and location.
4. Full electro-acoustic equalization
to insure optimum acoustic gain
and high -quality full -range program reinforcement.
5. A system survey that measures in
detail the electrical and acoustical adherence to the design standards set for the system.
This article covers briefly how one
professional sound contractors went
1.
'Hannon Engineering, Inc., Los Angeles, Calif.
30
about meeting the spirit of these five
guidelines in an actual installation.
Site Survey
The first step taken was a site survey of the theater. Tools used were
a 100 -ft. tape measure, an inclinometer, a sound -level meter, and a Polaroid camera. These tools were used
to determine the following data:
(1) Find the height of the proscenium arch. The loudspeaker
would be at its optimum, from a
placement viewpoint, if this location
were used. The listener's tendency
to think that the sound was emanating from the stage itself would be at
a maximum.
(2) The height also was needed to
calculate the acoustic gain achievable from a loudspeaker located at
that position relative to the required
microphone locations on the stage.
Through the use of the tape measure
and the inclinometer, highly accurate height readings were achieved
by simple triangulation.
(3) Next, the width, length, and
rise of the audience area were re -
AUDIO
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AmericanRadioHistory.Com
SEPTEMBER 1968
corded. This allowed a simple plan
and a section view of the theater to
be drawn for use in laying out loudspeaker projection angles.
(4) The SLM was then used to
read the typical overall ambient
noise levels at the site on the "C"
and "A" scales.
(5) The Polaroid camera was
used to photograph the total site and
any of the architectural details that
might require further study. Such
simple photographs can often save
additional trips to the site by showing the detail desired but not recorded in the written data.
All the data gathered on the site
survey were taken back to the engineering offices of the sound contractor and translated into a sound
system layout. Using the plan view
and section view developed from the
tape and inclinometer measurements, the number and type of
multicellular horns were determined. Consideration of the ambient
noise levels and type of program
material and audience encountered
determined the maximum sound pressure level goal at the rear of the
seating area. This can vary over a
20- to 40 -dB range, from reinforcement of poetry readings to providing
"enhanced" reinforcement of Rock
& Roll bands. Twenty- to 40-dB differences become meaningful when
translated to electrical power required by the sound system.
If the poetry reading can be carried off with a Mo -watt peak electrical power in a high -efficiency system
(30% or better), then the Rock &
Roll group will require 1,000 peak
electrical watts. These are not fanciful figures, but are derived from
actual system data. The peak figures
naturally reflect an expected average
program power of approximately
-10 dB or Mo the peak power. In
very high quality, conservatively designed sound systems, a 15 to 20 dB
peaking ratio can be employed.
Typical System Planning
Obviously, the projected sound pressure -level (SPL) goal will determine the number of loudspeaker
drivers required to handle the
power. Thus the necessity of high
efficiency in reinforcement work becomes glaringly important. A simple
example from this installation can
suffice here, as follows:
The Altec 288-C high -frequency
driver chosen yields 112 dB-SPL at
four ft. with one electrical watt of
input power. Its maximum power
rating is 40 watts. Therefore, it will
give a peak acoustical level at four
feet distance of 128 dB-SPL. It is
200 feet from the loudspeaker location to the rear of the seating area
2-The power -amplifier rack with complement of four Altec
160 -watt power amplifiers. There is sufficient power to allow for
moderate expansion of the loudspeaker sÿstem.
Fig.
AUDIO
SEPTEMBER 1968
and, being outdoors, the inverse
square law dispersion effects are
fairly reliable indicators. Therefore,
we would expect a peak acoustic
SPL of 82 dB, or an average program level of 72 dB. Since the theater handles primarily legitimate
stage plays and the site is known for
its woodsy tranquility (confirmed
by the very low sound-level -meter
(SLM) readings of 45 to 50 dB) ,
these become quite satisfactory figures.
Two Altec 203B twin -cell multi cellular horns are used to cover the
upper -rear audience seating area
with high -quality, low-distortion
program levels of 75 dB. (The two
horns combine for a 3 -dB increase in
SPL over the single horn. This information gives us the requirement
for one 80 -watt power amplifier.)
Looking further into the projection angles of our drawings, we find,
due to the width of the house, a need
for two 18 -cell multicellular horns if
good coverage is to be maintained.
Due to this area being 1/2 the distance at its extreme from the loudspeaker array as the rear listening
area, these horns require 6 dB less
input power than the rear area
horns. However, the rear area horns,
having a narrower coverage angle,
produce a higher SPL per watt. And,
the wider horns' greater dispersion
3-View of the Altec 9200 console, custom built for the Greek
Theatre. Should expansion be required at a later time, different
strip modules can be installed.
Fig.
31
angle means that slightly less than
a 6 -dB power differential will be
applied. At this point, these four
multicellular horns provide full
high -frequency coverage for the
major part of the seating area. It is
now necessary to match enough low frequency energy to them so that the
audience will hear a natural balance
of both high and low frequencies.
Using the specified efficiency ratings of the drivers involved plus
their enclosures led us to select
four 15 -in. low -frequency drivers
mounted in four large combination type enclosures. To achieve the
proper sound pressure level in this
case required 160 watts of power.
The four drivers chosen can handle
up to 200 watts safely. This leaves
only the front side areas uncovered.
Two Altec 300 -Hz sectoral horns
mounted above the main array supply this need. A 40 -watt power amplifier safely supplies the necessary
electrical power here.
Planning for Power Amplifiers
It can now be seen that, in developing the proper loudspeaker
coverage for the audience seating
area, we have also accurately determined the maximum electrical
power required and how to best
divide it among several amplifiers.
We have:
Two (2) 80-watt amplifiers for the four (4)
multicellular horns
160 watts
One (1) 160 -watt amplifier for the four (4)
15-in. woofers
160 watts
One (1) 40-watt amplifier
for the two (2) sectoral
horns
40 watts
TOTAL
360 watts
If Rock and Roll groups were to
be handled in this theater, the magnitude of the problem can be realized by visualizing the size of the
loudspeaker array capable of safely
handling 3600 watts at the same efficiencies as provided in this array. It
should also be apparent why professional sound engineers do not use
low -efficiency column speaker systems.
32
Planning for Speech -Input
Equipment
The speech -input equipment is
largely determined by the number of mixing positions required,
the desired dynamic range, and the
amount of total hum, noise and distortion that can be tolerated.
In the case of the system illustrated here, no compromises were to
be tolerated; a 24 -microphone
plus one-phono and one -tape-input
Altec 9200A console was constructed. The equivalent input noise
level was -128 dBm, +27 dBm the
maximum output level, and maximum operator comfort with speed
and versatility were to be maintained. Slide wire attenuators were
chosen because more of them can be
mounted within a normal operator's
arm span than can equivalent rotary
controls, and also because they feature 0.1 -dB increments and extremely low noise in use.
When designing complex speech input systems, the temptation is
great to include all the current
"cheese keepers." The seasoned professional, however, restricts the controls on his panel to only those
actually required at the present
time. Note that on the console illustrated here, provision has been made
for additional controls if the need
arises later, but only the actual
needed controls now used are
mounted and connected.
Two forms of equalization are included in this console. The first is
individual dialogue equalizers on
three of the microphone inputs plus
one for the main program channel.
In addition to this, a graphic equalizer is used to shape the overall
acoustic response of the sound system to as close to uniform amplitude
as possible, thus allowing maximum
acoustic gain to be developed before
dialogue equalization is attempted.
Proofing the System
Once the system was designed,
constructed, and carefully shop
tested for conformity to its electrical
specifications in regard to equivalent
input noise, total harmonic distortion, frequency response, maximum
power output, proper grounding,
freedom from spurious oscillations,
hum, and noise, it was ready for installation on the site.
Installed at the site, these same
electrical specifications were again
confirmed. It is at this point that
the acoustic tests of the sound system begin, and it is here that many
present-day sound contractors are
remiss in their duty. To leave the
sound system as finished after the
electrical tests are completed is
about as satisfactory as connecting
a magnetic cartridge into a linear
preamplifier and expecting good results without the benefit of proper
equalization. The interaction of the
acoustic with the sound system
always requires more complex
equalization than any cartridge
manufacturer ever contemplated.
For example, the following acoustical tests were performed:
1. The measurement of the distribution of the sound system's
acoustical energy throughout the
audience area, as measured in
the 4000 -Hz octave band.
2. The measurement of the acoustical frequency response of the
sound system taken in the audience area.
3. The equalization of the measured
frequency response until maximum acoustical gain is obtained.
In this case, 32 dB of acoustic
gain was achieved. If there had
not been sufficient acoustic gain
after the use of the graphic equalizer, then the system would have
been Acousta-Voiced2 using the
9014A Filter Set. But, achieving
adequate acoustic gain outdoors
is seldom the problem that it is
indoors, thanks to the absence of
multiple reflective paths.
Increasingly, the better sound contractors now own sound -level meters,
octave-band and 1/3 -octave -band
analyzers, graphic level recorders,
random -noise generators, pink-noise
filters, tone -burst generators, oscilloscopes, oscilloscope cameras, impedance bridges, and elaborate
sound -system equalization facilities
-all used or available on the Greek
Theater job.
Æ
'Trade Mark, Altec Lansing.
Check No. 33 on Reader Service Card
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The Sony Side of the Street
it's any place they're showing the new 6060 receiver
The Sony 6060 receiver is the brightest thing
that's happened to stereo hi-fi in a long while. A
superb performer on FM stereo; FM and AM
broadcasts; records and tapes. It will brighten up
the music in your life.
Here's what Sony built:Amplifier-110 watts IHF
power into 8 ohms. Distortion less than 0.2% at
rated output. The tuner-sensitivity 1.8uV; selec-.
tivity, 80 dB; capture ratio, 1.5 dB; spurious signal
rejection, 90 dB. Abundant control facilities: auto -
matic stereo reception; zero -center tuning meter;
front panel headphone jack; switches for tape
monitoring, muting, speaker selection, tape or Aux.
input, loudness-the works.
At $399.50 (suggested list) the 6060 outshines
receivers costing up to $500. Get a Sony disposition. Just direct your feet to one of .the Sony hi-fi
dealers listed below. Sony Corporation of America,
47-47 Van Dam Street, Long Island City, N.Y. 11101
ALABAMA BIRMINGHAM: Likis Stereo Center, 2018 11th
Int), 4549
Ave. So.
ILLINOIS CHICAGO:Allied Radio, 111 N. Campbell Ave.
Musiccraft, 2035 W. 95th St. Musiccraft, 48 E. Oak St.
Schwartz Bros., 8533 S. Cottage Grove
ARIZONA PHOENIX: Bruce's World of Sound Inc., 2711
E. Indian School Rd.
CALIFORNIA ANAHEIM: Henry Radio, 931 N. Euclid
Stereo Mart, 979 S. Anaheim Blvd. AZUSA: Rancho
Sound, 18532 E. Alosta Ave. CANOGA PARK: Wallichs
Music City, 6600 Topanga Cyn. LAKEWOOD: Wallichs
Music City, 5255 Lakewood Blvd. LONG BEACH:
Humphrey's Music Co., 135 E. Third St. Wallichs Music
City, 1501 N. Vine St. Winstead Cameras, 5015 E.
.Second LOS ANGELES: Bel -Air Camera & Hi Fi, 927
Westwood Blvd. Crenshaw Hi Fi, 4051 Marlton Ave.
Henry Radio, 11240 W. Olympic Blvd. Henry's Camera,
516 W. 8th St. Jonas Miller Stores, 3025 Crenshaw
Magnetic Recorders, 7120 Melrose Ave. Schireson Bros.
344 So. Broadway Winstead Cameras, 724 So. Broadway PALM SPRINGS: Palm Springs Music, 360 W. Palm
Canyon Dr. Pat Barbara Music, 121 So. Palm Canyon Dr.
PALO ALTO:Yamaha Peninsula, 3731 El Camino Real
PASADENA: High Fidelity House, 563 S. Fair Oaks Ave.
Stereo Mart, 3205 Foothill Blvd. REDONDO BEACH:
Bay Elect., 2315 Artesia Blvd. SAN DIEGO: Milo Double
"E:' 3686 El Cajon Blvd. SAN FRANCISCO:Skinner
Hirsch & Kaye, 229 Kearney St. Tokyo Electronics,
1766 Buchanan St. SANTA ANA: Hi Fi Assoc., 2220 No.
Main SANTA MONICA: Bob Pilot's Stereo Ctr., 2201
Santa Monica Blvd. SUN VALLEY: Electronics Division,
7562 San Fernando Rd. TARZANA: Stereo Mart, 18410
Ventura Blvd. TORRANCE: Griffey's Elect., 3840
Sepulveda Blvd. Wallichs Music City, 17540 Hawthorne
WEST COVINA: Wallichs Music City, 2917 E. Garvey Ave.
WHITTIER: Oxbow Elect., 15914 E. Whittier Blvd.
COLORADO BOULDER: Lloyds Hi Fi, 1134 -13th St.
DENVER: Empire Audio Exchange, 1100 Broadway
Lloyds Hi Fi, 1599 S. Colorado Blvd.
CONNECTICUT NEW HAVEN: David Bean Smith, 262
Elm St. NORWALK:Arrow Elect., 18 Isaac St.
WESTPORT: Klein's, 44-50 Main St.
WASHINGTON, D.C., Glen Music & Audio, 1204 "G"
St., N.W.
DELAWARE WILMINGTON: High Fidelity House, 3910
Concord Pike
FLORIDA MERRITT ISLAND:Stereo Assoc. (Helene's
Int), 545 N. Courtenay Pike MIAMI: Electronic Wholesalers, 9390 N.W. 27th Ave. Hi Fi Associates, 3188
Biscayne Blvd. ORLANDO: Electronic Wholesalers,
345 Graham Ave. TAMPA:Viviano Hi Fi Center, 1538 So.
Dale Mabry Hwy. TITUSVILLE;Stereo Assoc. (Helene's
AUDIO
SEPTEMBER 1968
S.
Hopkins Ave.
LOUISIANA BATON ROUGE: Kadair's Inc., 226
W.
State
MARYLAND BETHESDA:Audio Center, 4962 Fairmont Ave
MASSACHUSETTS CAMBRIDGE:Audio Lab, 16 Eliot St.
Minute Man Radio, 30 Boylston St., Harvard Sq.
SPRINGFIELD: Consumer Audionics of Springfield,
461 Summer Ave.
MICHIGAN DEARBORN: Mamas Hi Fi Stereo, 15031
Michigan Ave., DETROIT: Pecar Electronics, 11201
MorangDr. Stereoland, 17131
20746 Mack Ave.
W.
McNicols,
MINNESOTA MINNEAPOLIS:Audio King, 7010 France
Ave., So.
MISSOURI KANSAS CITY: David Beatty Hi Fi, 1616 W.
43 St. ST. LOUIS: Hi-Fi West Inc., 8217 Delmar Blvd.
NEW JERSEY CHERRY HILL: High Fidelity House,
244 W. Marleton Pike NEW BRUNSWICK: Hi Fi Haven,
28 Easton Ave. NORTHFIELD: Rainbow Electronics,
318 Tilton Rd. PARAMUS:SamGoody, Garden St.
Shopping Plaza SPRINGFIELD: Federated Purchaser,
155 Rt. 22 TRENTON: House of Hi Fi, 1819 No. Olden
Ave., Ext. TOTOWA: Arrow Electronics, 255 Rt. 46
NEW MEXICO ALBUQUERQUE: H. Cook, 308 Central
Ave., S.W.
NEW YORK NEW YORK CITY:Arrow Elect., 97 Chambers
Audio East, Inc., 310 E. 79 St. Audio Exchange,
1305 Second Ave.; 415 Lex. Ave.; 110 W. 32nd St.
Electronic Workshop Sales, 26 W. 8th St. Grand Central
Radio, 124 E. 44 St. Harmony House, 197 E. 76 St.
Harvey Radio, 2 W.45 St. Interiors & Sound, 1307
Second Ave. Leonard Radio, Inc., 18 Warren St.;
1163 Ave. of the Americas Liberty Music Shop,
450 Madison Ave. Lyric Hi Fi Center, 1221 Lexington Ave.
Sam Goody East, 666 3rd Ave. Sam Goody West, 250 W.
49 St. G. Schirmer Inc., 4 E. 49 St. Sonocraft Corp.
(Asco Sound), 115 W. 45 St. Wexler & Sporty Inc.,
125-127 Lafayette St. BRONX: Arista Camera
Specialists, 2194 White Plains Rd. BROOKLYN: Audio
Exchange, 1065 Flatbush Ave. Kitcraft (Dyna Tech
Labs), 738 Washington Ave. FARMINGDALE: Arrow
Elect., 900 Broad Hollow Rd. HUNTINGTO.N: Sam
Goody, Walt Whitman Shopping Ctr. JAMAICA: Audio
Exchange, I53-21 Hillside Ave. MINEOLA: Arrow Elect.,
525 Jericho Tpke. NAN UET: Electronics 59, 346 W.
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Rt. 59 ROSLYN: Audio Exchange, 1040 Northern Blvd.
SYRACUSE: Audio World Hi Fi, 2910 Erie Blvd.
Q-Tronics, 3461 Erie Blvd. E. VALLEY STREAM: Sam
Goody, Green Acres Shopping Cr. WAPPINGER FALLS:
Arnee Audio Designs, Nine Mall Rt. #9 WHITE PLAINS:
Audio Exchange, 239 Mamaroneck Ave. WOODBURY:
Harvey Radio, 60 Crossways Pk.
W.
OHIO AKRON: Electronic Eng. Co., Audio Hall, 362 W.
Bowery St. CINCINNATI: Hi Fi Audio Co., E. McMillian at
Woodburn CLEVELAND:Winteradio, 4432 Mayfield Rd.
COLUMBUS:Anderson Hi Fi, 2244 Neil Ave. Custom
Stereo Electronics, 1391 So. Hamilton DAYTON: Hauer
Music Co., 4421 Salem Ave. KETTERING: Hauer Music
Co., 3140 Far Hills Ave. PARMA: Winteradio, 5373 Ridge
Rd. SPRINGFIELD:Bradley Kincaid Music, 130 So.
Fountain TOLEDO: World of Sound, 3139 W. Central Ave.
YOUNGSTOWN: Audio Arts, 4224 Market St.
OKLAHOMA OKLAHOMA CITY: Sonax Co., 1200 E.
Britton Rd. TULSA: Sound Unlimited, 3745 So. Peoria
PENNSYLVANIA ARDMORE: Soundex, 45 W. Lancaster
Ave. FAIRLESS HILLS: C.A. Rogers Audio Lab, 312
Oxford Valley Rd. PHILADELPHIA: Danby Radio Corp.,
19 So. 21 St. Sam Goody, 1125 Chestnut St.
PITTSBURGH: House of Audio, Terrace Level, 218
Allegheny Ctr. Radio Parts Co., 6401 Penn. Ave.;
929 Liberty Ave. Solar Elect., 2354 No. Mall POTTSTOWN: Amity Supply Co., 216 River Rd., So. WAYNE:
High Fidelity House, 167 W. Lancaster Ave. YORK:
Sol Kessler, 126 So. George St.
RHODE ISLAND WOONSOCKET:Sound Products,
230 West School St.
TENNESSEE MEMPHIS: Opus Two, 404 So. Perkins St.
TEXAS AUSTIN: Home Entertainment Ctr. 4803 Burnet
Rd. DALLAS: Gramaphone Shop, 2800 Routh DENTON:
Music City EL PASO: Ayoub & Wardy, 218 S. Stanton
HOUSTON: Audio Center, 1424 Westheimer Home
Entertainment, 5310 Kirby Dr.; Nassau Bay Shopping
Ctr. Mall, 18091 Upper Bay Rd. LAREDO:Cowl's Music
Center, 1212 Hidalgo St. SAN ANTONIO: Vandergrift,
6740 San Pedro Vision Elect., 1116 E. Houston St.
UTAH SALT LAKE CITY: House of Music, 156 So. Main
St.; 4835 Highland Dr.
VERMONT BURLINGTON: Concert Elect., 40 Church St.
WASHINGTON SEATTLE: Standard Records & Hi Fi,
1028 N.E. 65 St.
WISCONSIN MADISON: Specialized Sound, 621 Gammon
Rd.; 411 State St. MILWAUKEE: Wack Sales Co.,
5722
W.
North Ave.
35
ABZs of FM
LEONARD FELDMAN
I.F. Amplifiers
many factors to be
considered in discussing FM i.f. performance, design and desired specifications, an entire book might be devoted
to this subject alone. All we can hope
to do in a quick treatment is to acquaint the reader with some of the high
points of design and operation of this
most vital section of an FM tuner or
receiver.
The need for an i.f. section arises
from the use of the superheterodyne
principle common to both AM and FM
equipment. By reducing all incoming
signal frequencies to a single, lower frequency (by the conversion or mixing
process discussed last month), subsequent amplification is relatively simpler and more stable, and reliable
designs can be produced. Actually, the
lower the i.f. frequency, the easier it is
to come up with an effective design.
Why, then, did the industry choose 10.7
MHz as the universally accepted i.f.
frequency for FM, as opposed to, say,
455 kHz (used for AM i.f. stages) or
some other low frequency? For one
thing, such a small spread between
local oscillator frequency and incoming signal frequency might well cause
a strong incoming signal to "pull" the
frequency of the local oscillator, until
both were "locked" at the same frequency. Result: no i.f. output from the
converter for the i.f. stages to amplify!
Still, an i.f. frequency of a couple of
megahertz would eliminate this problem. So why 40.7 MHz?
Well, suppose, for the moment, that
we were to choose an i.f. frequency of
4.5 MHz (as is, in fact, done for the
sound portion of some TV receivers),
and suppose we were tuned to a signal
frequency of 95.0 MHz. If our oscillator were designed to operate above
incoming frequency, it would be oscillating at 99.5 MHz. Next, assume there
were another station (and a strong one
at that) in the vicinity, transmitting at
a frequency of 104 mHz. Despite the
selectivity of the tuned r.f. stage (assuming there is one), this higher frequency would beat with the 99.5 MHz
of the local oscillator to produce a second signal, also at 4.5 MHz. Before you
LOCAL
OSCILLATOR
THERE ARE SO
DESIRED
STATION
f
-+
POSSIBLE
"IMAGE"
(MHz)
99.5
95
fo>c
=
104
decide that the local oscillator should
have been designed to operate below
the incoming signal frequency, take a
look at Fig. 1B, which shows that the
same thing can happen, only this time
with the desired stations at the high
end of the dial and the undesired station 9 MHz lower.
It's pretty obvious, therefore, that
given an FM band of 20 MHz (from
88 MHz to 108 MHz), the least i.f. frequency necessary to avoid "image responses" would be some frequency
greater than 10 MHz. The last major
consideration which led, specifically, to
the choice of 10.7 MHz has -to do with
"direct i.f. response." If some station
is transmitting at the chosen i.f. frequency itself, such a received signal
could easily reach the i.f. circuits either
through the usual input channels
(which might lack sufficient selectivity
to exclude them) or by the appearance
-
Schematic
representation
of
i.f. interstage transformer. Arrows indicate "slug" or
Fig. 3
4.5 MHz
®LOCAL
OSCILLATOR
Prim.
Sec.
permeability tuning
of both primary and
POSSIBLE
DES RED
"IMAGE"
STATION
secondary.
of i.f. signal voltage directly at the
input of the first i.f. stage when adequate shielding is not provided. To
95
99.5
104
fotc=4.5MHz
Fig. 1 -Examples of "image" frequencies
which would occur if local oscillator were
(A) 4.5 MHz above desired station frequency or (9) 4.5 MHz below desired station frequency.
Fig. 2 -"Idealized" i.f. response
(output
and phase shift) for the "perfect" i.f. sys-
tem.
Relative Response
o 0
o 1.0 ó
M N N
0
I
o
0 o o o 0
o in o ILI ó
+
+
+
{ N+
FREQUENCY (KILOHERTZ)
36
+
forego this possibility, the chosen frequency (10.7 MHz) is one that is never
or seldom used for commercial transmission. This choice does not eliminate
every type of spurious response possible, but it seems to be the best compromise choice available.
Having established the frequency of
the FM i.f. "strip," we can now con-
sider the additional characteristics
which must be considered. They are
really surprisingly few in number
(though often, a design can be quite
difficult to achieve). Gain, of course, is
one. Bandwidth is another, phase response a third, and that's really about
all there is. Remember, we are excluding limiter stages from the discussion,
even though many consider them to be
part of the i.f. strip (structurally, they
usually are). We shall deal with
limiters and their special additional requirements next month.
While you might suppose that a
bandwidth of 150 kHz is all that would
ever be required of an i.f. stage (based
upon the maximum allowable modulation of ±75 kHz), recall that sidebands
may actually exist well beyond these
superficial limits. This is especially
true now, since the advent of stereo
FM (multiplex), which involves higher
modulating frequencies. A bandwidth
of 6 dB (attenuation) for around 250
AUDIO
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AmericanRadioHistory.Com
SEPTEMBER 1%8
press
comment
on the
AMERICAN
record
guide
(Larry Zide)
"In choral works and other music of relatively 'heavy' content, the AR -3a simply
eliminates any mid -range lack of clarity ... find myself repeating what said in 1959
[about the AR -3I. The AR -3a ... easily succeeds its prototype as a speaker that
consider as close to musical realism in the home ... as the present state of the
art permits.' In a word, It's superb."
I
I
I
HIGH FIDELITY
(Norman Eisenberg)
"Our reaction on first hearing the AR -3a was [anl ... enthusiastic one which has
not diminished after weeks of listening ... in normal use, predominantly fundamental
bass is evident to about 30 Hz ... Tones in the 13 to 14 kHz region can be heard
clearly at least 60 degrees off axis ... at !high] levels, the speakers sounded
magnificent ... On any material we fed to them, our pair of AR-3a's responded
neutrally, lending no coloration of their own to the sound."
Hill/Stereo Review
(Hirsch -Houck Laboratories)
... the best speaker frequency response curve we have ever measured using our
present test set-up ... virtually perfect dispersion at all frequencies
perhaps the
most non -directional forward -facing speaker we have ever tested ...
AR speakers set new standards for low -distortion, low -frequency reproduction,
and in our view have never been surpassed in this respect."
'
-
Chicago's AMERICAN
(Roger Dettmer)
"I have not encountered truer 'fidelity'
...
in three decades of home
The AR -3a is priced from $225 to $250, depending on cabinet finish.
listening."
Literature is available
for the asking.
ACOUSTIC RESEARCH, INC.,
24 Thorndike Street,
Cambridge, Mass. 02141
Check No. 37 on Reader Service Card
AUDIO
37
SEPTEMBER 1968
www.americanradiohistory.com
AmericanRadioHistory.Com
to 300 kHz is now accepted as being
4-Typical i.f.
response and phase
shift achieved by
using transformer Fig.
coupled circuits.
0
In ó o
It)
ó
N
+
óM 0 0N0 0 00 ó
Ion
N
o
0
f+)
(KILOHERTZ)
FREQUENCY
I.F.
1st I.F.
TRANSFORMER 6 8A6
I.F.
TRANSFORMER
TO
--r-
.005
µF
.005,
1
k
'
I
100
µF
A.G.C.
=001
B+
.005 µF
-µF
B+
250 V
100 V
I.F. TRANSFORMER
1
NEXT
STAGE
Fig.
5-Typical
stage using
a
i.f.
pen-
tode tube amplifier
with agc.
005
µF
B+
250 V
I.F. TRANSFORMER
6-
-
Fig.
Typical i.f.
stage utilizing discrete, bi -polar transistors.
'
.1
56 k
µF
22k
B+
10.5 V
A.G.C.
TO
A.G.C.
RF
-
Fig. 7 New integrated circuit (CA 3012) used in i.f.
systems of some FM
receivers today.
with
High
gain
good stability and
-I-10 V
+10V
excellent limiting
characteristics are
claimed for these
new designs. See
Fig. 8 for "contents" of the IC.
38
adequate for high quality, stereo FM
reception. Ideally, the shape of the "response curve" of the i.f. system should
be that shown in Fig. 2. Generally,
however, the expense involved in attempting to come close to such perfect
response is prohibitive. There is at least
one manufacturer we know of who
comes mighty close to this ideal by
means of complex, multiple -section
filter networks. Most manufacturers
achieve their response by means of
double -tuned, interstage i.f. transformers, as represented in Fig. 3.
Depending upon the number of
stages used and the excellence of the
particular design, the resultant response curve might be something like
that shown in Fig. 4. It should be noted
that when we speak of a 6 -dB loss for
a bandwidth of 250 kHz we mean the
total attenuation of the entire i.f. system, not simply to a single stage. Thus,
in the example cited, if there were
three tuned circuits in the i.f. system,
each circuit would contribute 2 dB of
attenuation at the "end points," but
the total response of the entire system
would then be "down" 6 dB at 250 kHz.
Still another method of achieving a
desired bandwidth characteristic involves the use of newly devised "crystal
filters" between amplifying stages. Still
relatively new in FM use, these "mechanical filters" are actually already
in use in the i.f. system produced by
one well-known receiver manufacturer.
Rapid progress in this field is sure to
occur in the very near future.
All tuned amplifiers exhibit phase
shift between secondary current at resonance and secondary currents at frequencies off -resonance. At resonance,
this current is in phase with the i.f.
transformer's secondary voltage. Above
resonance, secondary current leads the
secondary voltage, while below resonance the converse is true. If this
phase shift does not vary linearly with
changes in frequency within the i.f.
pass -band, time -delay errors in the received FM signal can occur. Though
not terribly serious in monophonic FM
reception, such delays can be disastrous
in the case of stereo FM, where so
much depends upon phase relationships between main -channel audio, 19
kHz pilot sub-carrier and the stereo
sub -carrier information. Proper selection of coefficients of coupling, Q's of
the various stages, and required bandwidths help to achieve a proper frequency/phase relationship.
Gain in an i.f. system (as with any
amplifying system) is achieved by
means of active amplifying devices,
(Continued on page 63)
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-*
High FidElity starts here.
BSR McDONALD
PRECISION CRAFTED IN GREAT BRITAIN
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BER (USA) LTD., BLAUVELT, N.Y. 10913
This Month:
Equipment
Profiles
Altec Lansing 711B FM Stereo Receiver
Electro -Voice Model E -V Five -A Speaker
System
Panasonic
RS -761S
Stereo Tape Recorder
Dual Model 1015 Automatic Turntable
Shure Model SM -60 Dynamic Microphone
Shure Model 330 Super-Cardioid Ribbon
Microphone
Altec Lansing Model 711B
FM Stereo Receiver
MANUFACTURER'S SPECIFICATIONS(Tuner Section): IHF Usable Sensitivity: 1.9
AV. Image Rejection: 80 dB. Frequency
Response: 20 to 20,000 Hz ±1 dB. Capture
Ratio: 2.5 dB. Separation: 35 dB.
(Amplifier Section) Power Output: 100
watts IHF total music power @ 0.5°/o THD
(4 -ohm load); 70 watts (8 ohms); 60 watts
(rms) total continuous power (8 ohms).
Power Bandwidth: 15 Hz to 25,000 Hz.
Frequency Response: 15 to 30,000 Hz
±1 dB. Tone Control Range: ±15 dB at
20 Hz and 20,000 Hz. Damping Factor:
50. Noise Levels (IHF): Tape Head:
-58 dB; Phono: -65 dB; Extra: -88 dB.
Dimensions: 53/e" H x 163/8" W x 12" D.
Weight: 19 lbs. Price: $399.50.
This solid-state entry from Altec
Lansing is a medium-priced complete
receiver containing virtually all of the
facilities needed for a home music
center. For its compact size, it delivers
a goodly amount of power-a common
characteristic of the latest crop of
solid-state integrated receivers. For
those who favor a quiet, almost aristocratic subdued look, the physical appearance of the Altec 711B will have
instant "shelf appeal."
The front panel, with the exception
of the heavy gold framing around its
efficiencies which exist among popular
speaker systems. The "amp gain"
switch provides two settings of amplifier gain not total power capability,
which is the same for either setting).
Thus the user who has highly efficient
speakers need not limit himself to just
"cracking open" the volume control before he is drowned in loud sound. He
would set the switch to the "lo" position.
rim and is colored a very soft, matte
charcoal grey, which makes the gold screened control designations extremely legible. Approximately seven inches
of frequency spread, with a tuning
control that includes a ball -bearing flywheel arrangement, makes for one of
the smoothest and easiest-to -tune
dials we have encountered in' some
time. The upper half of the panel also
contains a peak -reading tuning meter
and the usual stereo FM indicator
light mounted behind the dial glass.
Functionally arranged controls located at the lower portion of the panel
include a five -position selector switch,
a dual volume control (simultaneously
controlling both channel levels), a balance control, and the usual bass and
treble controls. Secondary controls, all
activated by means of rocker switches,
include a high -frequency filter, the
tape monitor switch, a "stereo -mono"
mode switch, a loudness in/out switch,
speaker switches for "main" and "remote" speaker installations, and the
power on/off switch. A stereo headphone jack completes the layout of the
front panel, which may be seen in
Fig.
Circuitry
Circuitry layout, viewed from under
the set, can also be seen in Fig. 3. The
totally shielded "front end" employs
one FET as a first r.f. amplifier, followed by a second bi -polar device used
as an additional r.f. amplifier, and
separate transistors for local oscillator
and mixer. Thus, the front end has
four tuned circuits, rather unusual for
a unit in this price class. With this fine
front end, which could not be overloaded under any signal conditions, we
wonder why Altec bothered to include
the "local" -"distant" terminal arrange-
ment?
The i.f. circuit module contains two
RCA CA -3012 integrated circuits, a
balanced ratio detector and a meteramplifier transistor.
The multiplex demodulator circuit
board is of fairly conventional design,
containing four active transistors, plus
one for indicator light activation, as
well as for a balanced -diode -bridge demodulator. Encapsulated bridged -T
filters eliminate much of the residual
38 kHz and its harmonics at the output
of this module.
Fig.
2-Rear panel connections of the
711B.
1.
The rear connection panel, shown in
Fig. 2, offers very widely spaced screw
terminals for connection of main and
remote sets of speakers, FM antenna
screw terminals (for both "local" and
"distant" reception), input pairs of
jacks for tape head, phono, "extra,"
and tape monitor and output jacks for
recorder output and a center channel,
the latter intended to feed a separate
monophonic amplifier, not a center channel speaker directly. One final feature at the rear of this receiver is a
little slide switch called "amp gainlo/hi." This feature is extremely useful
in light of the great range of speaker
40
3-View of the inside, showing combination of circuit board and direct -wirFig.
ing layout.
AUDIO
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SEPTEMBER 1968
Performance
1
Measured performance agreed very
closely with published specifications.
IHF FM usable sensitivity measured
2.3 j,(,V, well within manufacturing tolerances to be expected. Maximum
quieting was a very respectable 70 dB,
as shown in the curves of Fig. 4. Measured separation of our sample fell
somewhat short of the specified 35 dB
at 1 kHz by a few decibels, but it was
certainly more than adequate at this
frequency. Separation at the high end
of the spectrum, however, fell off a bit
too rapidly to below 20 dB at 10 kHz.
The FM tuning meter is of the peak reading type, common to many receivers. As mentioned here in the past, this
makes it slightly more difficult to tune
to center of channel compared with the
center -reading types. The meter circuit
is not designed to operate truly as a
signal -strength indicator of received
stations as some peak -reading types
are.
As for amplifier measurements, just
about every one was better than the
published specifications. The 0.5%
total -harmonic -distortion (THD) figure was reached at 34 watts per channel with 8 -ohm load) against the 30
watts claimed by the manufacturer. A
curve of THD is shown in Fig. 5, along
with IM distortion, which reaches
2.2% at 36 watts per channel.
Tone -control action is plotted in Fig.
6, along with that of the high -frequency filter. Note that this filter has
only a 6-dB -per -octave slope, and
really does no more than counterclockwise rotation of the treble control.
Loudness compensation, when switched
into the circuit, produces bass boost of
+5 dB at 50 Hz at one-half rotation
of the volume control and + 11 dB at
50 Hz for one -quarter volume control
setting. Power bandwidth is shown in
Fig. 7, while Fig. 8 illustrates square wave response at 100 Hz and 10 kHz.
Listening to FM and FM stereo on
the Altec 711B, we were able to pick
up 35 clear FM stations with just a
simple dipole antenna. Just to see if
CO
+10
aW0
0
"H(Filter-
-20
100
1k
FREQUENY (HERTZ)
AUDIO
4
-
quieting
FM
-40
char-
-50
-60
acteristics
of
the 7118.
Ik
10k 20k
Residual
Dist(=0.3%)
Max.
Quieting
70dB
siduai Noise
-70
0.2
100
10.0
1.0
RF
200
INPUT (MICROVOLTS)
2.5
2.0
Fig. 5-THD and
IM curves with
both channels
1.5
IM
.
1.0
driven.
5
THD (8 -ohm load
channel)
20
40
30
POWER OUTPUT (WATTS)
1
10
the local -distant antenna connections
meant much, we then connected our
antenna to the "local" terminals, only
to find that we still picked up the same
35 stations. In fact, one station (a
local) exhibited minor interference
from an even stronger local adjacent
station when the antenna was connected to the distant terminals. This
cleared up considerably using the
"local" terminals, but aside from this
single phenomenon, all other stations
seemed about the same regardless of
antenna connection.
Of the stations received, eleven were
broadcasting in FM stereo. All of these
"gated" the circuits into the stereo
mode with no popping or noise of any
kind, and no erratic illumination of the
stereo indicator lamp was noted at any
Fig.
-10
2Ó
Fig.
H F Usable
Sens.(2.3pV)
Output
I
-20
-30
6- (left).
Tone -
control range. Dotted
line shows effect of
"HI" filter.
U
W
CI
-10
Fig.
+20
-dB Limiting(2.7pV)
0
7- (right). Power
bandwidth curve.
-
Fig. 8
(far right).
Square -wave response
-upper, 100 Hz; lower, 10 kHz.
60
50
point on the dial. Operating the receiver with the muting circuits "in" reduced the number of received stations
to 31. A few of these were marginal in
that high orders of distortion were
noted, until the muting switch was
turned back to the "off" position.
The sound we heard (using fairly
inefficient speaker systems) was full
bodied and very pleasing. Settings of
about 11 o'clock produced room -filling
sound, and as we "pushed harder"
there was no evidence of break-up. At
a suggested retail price of $399.50, the
Altec 711B has come up with a design
that does not scrimp on latest circuit
components or quality of parts used,
combining this with attractive appearance.
Check No. 40 on Reader Service Card
OI
10A
50 -
Iá
j"
40-
,,
34 W
1-30--..
20-
10
15W15 Hz
15W/25kHz-"
100
1k
10k
100k
FREQUENCY (HERTZ)
41
SEPTEMBER 1968
www.americanradiohistory.com
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Equipment Profiles (continued)
Electro -Voice
Model E-V Five -A
Speaker System
MANUFACTURER'S SPECIFICATIONSFrequency Response: 30 to 20,000 Hz. Impedance: 8 ohms. Power -Handling Capacity: Program, 30 watts; Peak, 60 watts.
Dimensions: 121/4" H, 213/4" W, 103/2" D.
Finish: Polymer -coated walnut veneer.
Weight: 27 pounds. Price: $88.00.
The new E -V Five -A is a small- to
medium -size bookshelf speaker of impressive performance that belies its
price. It is a straightforward, well put
together two-way system, using a 10 in.
acoustic -suspension woofer. An LCR
network crosses over at about 1100 Hz
Fig. 1-Electro-Voice
-V Five -A speaker
system.
E
to a 21/2 -in. dome tweeter which takes
over from that frequency and upwards.
Two more layers of wire have been
added to the woofer's voice coil, offsetting the inefficiency caused by the
greater moving mass of an acoustic
suspension design. The result is higher
efficiency than is expected from a unit
of this construction. This means that a
smaller power amplifier will adequately
drive these speakers. (We found that a
clean 20 watt amplifier does it just
fine.)
The tweeter has a dust dome
mounted centrally on its cone. In the
lower portion of its frequency range
the tweeter cone and dome function together. As the frequency increases, a
progressively smaller area of the cone
radiates sound. The dome is radiating
only at the highest frequencies. Since
the dome is hemispherical, it radiates
widely, thereby aiding dispersion. The
resonant frequency of the tweeter is
just below the crossover point, no doubt
for rapid rolloff. Also, a viscous -damping compound is injected between the
voice -coil form and the magnetic structure. The jelly -like stuff dampens cone
movement at resonance, with the inten-
tion of eliminating intended spurious
responses and breakup. From the lack
of these undesirable hobgoblins, we'd
saw that the viscous damping is successfully used here.
Both the woofer and tweeter are
front mounted, the rear of the %-in.
fiakeboard cabinet being completely
sealed. Fiberglass fills most of the inside, and duckseal is used around the
speakers to inhibit air leaks. The light tan grille cloth is affixed to a thin
wooden panel that comes off with a pull
and goes back on with a push. (Velcro,
again.) The high -frequency control is
recessed in back of the cabinet and is
adjustable only with a screwdrivercan't be changed accidentally that way.
It is a 20 -ohm wirewound potentiometer that represents part of a voltage
divider of the crossover network. Its
range at 10 kHz is about 8 dB. In our
listening room we found it best up all
the way. A mark atop the control says
NORMAL, but there's no corresponding
pointer on the shaft of the control. A
minor quibble.
A vinyl coating protects the walnut
surface so that dust cannot collect in
the wood grain to dull the appearance;
it also makes it more scuff-resistant. A
wax can be applied to get a glossier
finish, or fine steel wool can be used to
reduce the surface sheen for a duller
look. The "as is" surface looks exactly
like standard oiled walnut.
angle of radiated sound converging
slowly above 13 kHz. Distortion was
low all the way down.
We were especially pleased, though,
when we listened to music reproduced
via these speakers. After all, speaker
measurement techniques have not yet
been sufficiently standardized. Therefore, subjective evaluation still yields
the most meaningful data.
The E - V Five- A (a stereo
pair) sounded forward, open and big.
The highs were crisp and balanced.
The bass was very full and resonant -more so than we expected from a unit
of this size and price. The speaker system, in fact, was just a pleasure to listen through in both small and large
room. Anyone who still thinks he can
judge size of speakers by their sound
ought to put a couple of EV Five-A's
behind an acoustically transparent
curtain and then try it.
We agree with E -V when they say:
"The Five -A provides performance formerly found only in far more expensive
systems." The increased efficiency is a
bonus.
Performance
MANUFACTURER'S SPECIFICATIONSFour-tracks. Record -playback system. Tape
Our averaged measurements of frequency response showed that the E -V
Five -A covered 50 to 16,000 Hz within
5 dB. It put out clean bass down to 40
Hz, below which doubling could be induced. E -V's engineering data sheet
shows the response right out to 20 kHz,
with only a small drop. We don't doubt
it. The speaker's tone -burst response,
as shown in Fig. 2, is excellent, with
only one small ringing node. Dispersion was good all the way up, with the
Fig.
2-Oscilloscope
photos of tone
bursts at 300, 4500,
and 10,000 Hz ilthe E -V
lustrate
excellent
Five -A's
transient response.
300
10,000
vMW.wwAS
Check No. 42 on Reader Service Card
Panasonic Model RS -761S
Stereo Tape Recorder
speeds: 71/2, 33/4, 1'/e ips. Frequency Response: 30-18,000 Hz at 7'/2, 30-13,000 at
33/4, 30-16,000 at 11e. Signal -to -Noise
Ratio: more than 52 dB. A.C. Bias: 50 kHz.
Weight: approx. 22 lbs. Dimensions:
x 61/2 x 11'/4 in. Speakers: Two 81/2 x
5'/2 x 11 in. enclosures. Price, with speakers,
microphones, connecting cables:
178
$269.95.
Every time we encounter a new tape
recorder, it's like a new ball gamethey are similar in many respects, but
vastly different in detail. The RS -761S
is a tape recording system, in that it
includes everything one needs to start
recording immediately-microphones,
speakers, etc.
The unit is a three -speed, 7 -in. reelto-reel machine, designed for four -track
stereo recording, four- or two -track
stereo playback, and four tracks of
mono recording and playback. The
small speaker systems, each of which
contains a 61/2 -in. woofer and 2% -in.
tweeter, have provisions for wall
mounting.
AUDIO
42
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SEPTEMBER 1968
the new ELPA PE-2020 Automatic turntable lets you
escape
from the
ordinary
Here's why
(1) The Exclusive 15° Vertical Tracking Angle Adjustment.
For critical listening and perfect sound reproduction,
records should be played with the stylus at a 15°
vertical tracking angle. The new ELPA PE -2020 is
the only automatic turntable that permits the
critical listener to do this for a single record,
in single manual play
or for any record in a
stack in multiple automatic play. This feature
gives the ELPA PE -2020 the precision of a fine
manual turntable, and a greater precision in
...
-
multiple play than any other automatic turntable.
(2) Stylus Protection. It is impossible to damage
the stylus of the ELPA PE -2020 by lowering -he
tonearm onto an empty platter. Should the turntable be
switched on accidentally, the tonearm will refuse to descend
if no record is on the platter.
(3) Automatic Scanning. You don't need to adjust the new ELPA
PE -2020 for various size records. The scanninc device automatically determines the size of the first record-on the platter
and automatically adjusts the tonearm to descend in the proper
play position.
(4) Simplicity Of Operation. One lever controls all modes of
operation: Start, Stop, Repeat, Cueing, Pause, and Lift
making
the ELPA PE -2020 the easiest automatic turntable to operate.
The single control is located at the front of the turntable and is
easily accessible even in confined quarters.
(5) Anti -Skating. The most sensitive anti -skating device on any
automatic turntable. Combined with an exact adjustment dial
to compensate for stylus shape, size, and tracking weight. Less
wear on your records, more perfect sound reproduction.
-
AUDIO
SEPTEMBER 1968
(6) Motor Driven Cueing. The most advanced form of cueing
today. No extra levers, no viscous -damped hand controlled
manual devices. Eliminates accidental slips of hand striking
the tonearm.
AND THERE ARE MANY, MANY MORE SUPERLATIVE FEATURES ON THE NEW ELPA PE -2020.
Don't make a buying decision on an automatic turntable without
seeing the finest ... the new ELPA PE -2020. See it at your high
fidelity dealer, or write for full literature and name of nearest
franchised dealer. ELPA MARKETING INDUSTRIES, INC.
New Hyde Park, N.Y. 11040
Check No. 43 on Reader Service Card
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43
Equipment Profiles (continued)
Fig.
1-The Panasonic
RS -761S
The panel of the recorder properthe amplifier panel occupies the 31/2 -in.
at the right of the recorder chassishas the usual supply and take-up
spindles, with the speed selector between them and a 4 -digit counter at the
lower left. The control section is fitted
with two record -level meters which also
indicate during playback, and two record-level controls at the left. Below
these are two pushbuttons for the record function. These buttons are covered
by a plastic slide which helps to prevent unauthorized or inadvertent operation. To the right is the transport and
head section, and below this is the pair
of microphone jacks, using the miniature phone plugs. A push-on, push -off
power switch is next, and farthest right
is the control lever. The rest position
of the function lever is STOP; one position to the left is REWIND and one position to the right is PLAY. Next to the
right is the PAUSE position, and farthest
right is the FAST FORWARD position. The
pause position between fast forward
and play practically eliminates any
possibility of breaking the tape in
switching from F.F. to PLAY.
The unit employs one motor, with
a stepped motor pulley providing the
speed changes, and idlers between
the motor shaft and the reel -spindle
turntables. All of the action is mechanically controlled by a series of levers
and wires. The head shields, on which
Stereo Tape Recorder System.
are mounted the pressure pads, are
raised automatically when the control
lever is placed at PLAY, hinging outward when the lever is in any other
position.
The amplifier section, mounted at the
right of the deck, has a three -position
slide switch at the top. In the center
position, the machine is in the stereo
mode, and at either right or left positions feeds the speakers from either
right or left channels-desirable when
playing monophonically recorded material. Progressing downward are the
treble control, bass control, volume control, balance control, and a headphone
jack.
On the rear is a panel which offers
access to the auxiliary inputs, line-out
phono jacks (high impedance), and
two miniature phone jacks for the
speaker connections. The power cord
also enters the unit from this panel.
Circuitry
The Panasonic RS -761S employs a
total of 19 germanium pnp transistors
and six diodes in its electronic circuitry.
The amplifier consists of the bass
boost control, followed by a transistor
stage, with its output going to the
speaker switch which selects the source
channel for the monitor signal. This
is followed by the treble control, the
driver transistor stage, transformer coupled to the two-trans;stor output
2-View of the
mechanism of the
Panasonic RS -761S
with the front panel removed.
Fig.
44
stage, which is a single -ended push-pull
configuration, with the output being
taken from the intermediate point,
going first to the headphone jack which
cuts off the following speakers when
the usual three -circuit plug is inserted.
The balance control is a 20k pot connected from the bases of the driver
stages, with its arm grounded.
The bias/erase oscillator uses two
more transistors in a balanced oscillator which feeds a 50 -kHz signal to
the erase heads from a tap on the secondary of the oscillator coil, and bias
voltage from the entire coil through
adjustable trimmers. When only one
channel is being recorded, a load resistor is switched into the circuit to
simulate the unused head.
D.c. is supplied to the low-level
stages through a regulating transistor,
while the full rectified output voltage
is fed to the audio amplifier sections.
A pilot light, which illuminates the
record-level meters, is fed from a tap
on the secondary of the power transformer.
Switching from play to record is done
entirely by the push buttons used to
select the channel on which recording
is to be done, while separate switches
short out the audio signal to the amplifier when the machine is stopped or
in either of the fast-wind positions. In
addition, the line outputs are shorted
out during recording. A tape -sensing
switch shuts off the drive motor when
the end of the tape passes through the
head assembly.
Performance
In operation, the Panasonic gives a
good account of itself. Its one -knob
function control and vertical stacking
of amplifier controls simplifies operation.
It has a comparatively low hum -and noise figure of 49 dB below the 3%
distortion point when measured according to NAB standards at 71/2 ips.
At 33/4 ips, S/N is 50 dB, and at 17/s
ips it is 47. Wow and flutter measure
0.13% at 71/2, 0.17% at 3%, and 0.25%
at
11/2.
The record -level meters are calibrated at a zero which is 10 dB below
the 3% distortion point, and the output at the overload point is 3 volts
at the line output and 1 watt at the
speaker jacks-enough for a reasonably
loud signal with the speakers furnished.
To reach the meter zero in recording,
a signal of 0.14 V is required at the line
inputs, and only 0.25 mV at the microphone jacks. One great convenience is
the fact that the meters operate in the
AUDIO
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SEPTEMBER 1968
Shown here are several good reasons wily Altec audio
equipment is being used by more and more recording and
broadcast studios and auditoriums. And for all sound re-
inforcement applications.
Altec microphones are engineered and manufactured to
the same high standards of quality that have made "Mace
of the Theatre"® speaker systems, Altec audio controls,
monitors and other sound equipment the standard of the
industry for so many years.
Take our Solid State Condenser Microphone Systems
(M49 Series), for example. Extremely wide, smooth frequency response. Front -to -back discrimination of 20 dB.
Omnidirectional or cardioid types. Battery or AC operated.
Lightweight but rugged, with power supplies to match. Altogether, these fine, precision -made instruments are the
most advanced profess oval mikes on the market today.
The M49 is typical of the complete Altec n-ike line which
includes selectable pattern types, miniature leveller's,
close -talking models and other solid-state condenser types.
Plus mounts, wind screens and accessories.
So go ahead and put Altec on. Why not start by asking
your Aitec Sound Contractor for complete technical data?
He's listed in the Yellow Pages under
"Sound Systems." Or, if you prefer,
write direct to us at 1515 S. ManLANSING«
chester Ave., Anaheim, Calif. 92803.
1g ARec. Inc.
ALTE[
Now we know why
you're putting us on. %-ige-
Stereo Ensemb'es for the Home / Microphones,
World's Largest Manufacturers of Sound Equipment Exclusively: Stereo Receivers Speakers, Speaker Systems,
/ Audio Controls, Consoles, Amplifiers.
Control Consoles, Amplifiers, Speakers, Speaker Systems for Public Address Systems / Acousta-voice Equalization
Amplifiers & Associated Wire & Microwave
Microphones, Monitors for Professional Broadcast, Recording & Motion Picture Studios & Theatre / Telephone
Transmission Equipment / Power Supplies & Transformers / Doctors, Nurses & Hospital Call Systems.
in New York October 21-25."
"Visit Altec Lansing at the Audio Engineering Society Show at the Park Sheraton being held
AUDIO . SEPTEMBER 1968
Check Ne. 45 on Reader Service Card
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45
Dual Model 1015
Automatic Turntable
Equipment Profiles (continued)
-
MANUFACTURER'S SPECIFICATIONS
Speeds: 162/3, 331/3, 45, and 78 rpm.
Operation: Manual, auto-single, or autochanger. Pickup Arm: Dynamically balanced. Tracking Force; 0 to 5 grams.
7
......
..
Fig. 3-Record/play
curves for the Pan-
asonic
RS
-761S
Tape Recorder.
1%
a
20
100
1
FREQUENCY
k
(HERTZ)
ú
Ampex Std Tape 31331-01
Ae.
100
7
playback mode as well as when recording.
The electrical signal output from a
standard frequency tape shows the response to be within ±3 dB from 40 to
15,000 Hz at 71/2 ips, and ±2 dB from
40 to 5000 at 3%-these frequencies
being the limits of our standard tapes.
With signals recorded at a constant
input level and played back, the response was within ±5 dB from 40 to
16,000 Hz at 71/2 on the left channel,
and within ±7 dB on the right channel. At 3% ips, the response measured
±5 dB from 30 to 8000 Hz, with the
two channels differing by not more than
2 dB. At We, response was within ±5
dB from 30 to 2200 Hz. The manufacturer's specs do not indicate any
tolerances, unfortunately, so our measurements cannot be compared. These
figures are respectable for a complete
system in the RS-761S's price category, however.
Tone -control action was relatively
gentle, providing very little bass boost
and about 8 dB of cut at the low end,
and about 3 dB of boost and 10 dB of
cut at the high end. While these tonecontrol figures do not sound very impressive, it is surprising how effectil e
they are with the system's speakers.
(Tone -control circuits were modified
in early production to meet the follow -
on.
i ips
Fig. 4 -Playback re-
sponse from
Am-
pex Standard
3i ips
Tapes.
10k
1k
FREQUENCY
Transcription turntable / tone- arm
combinations probably received their
first real challenge from record changers when changers' tone arms were de coupled during play from the crude
springs, levers, and cams of their armlifting and record-changing mechanisms. A host of other improvements
reduced wow and flutter,
followed
lower rumble, less tone -arm pivot friction to permit tracking with newest
phono cartridges, anti -skating compensation to further reduce tracking-force
requirements, cueing devices, and so
-
1Ók 2Ók
Ampex Std Tape 31321-01
Price: $89.50.
(HERTZ)
ing specifications, according to the
manufacturer: Bass, ±10 dB at 100
Hz; Treble, +10, -15 dB at 10 kHz.
-Ed.)
Rewind time clocked 2:58 for a
1200 -ft. reel of tape, while fast forward
required 3:25 for the same reel. These
figures are slower than normal for machines in this general category. The
50 -kHz bias frequency is lower than
generally used for modern tape recorders; if it appears on the tape it
might show up on a stereo recording
from a tuner as a 12 -kHz squeal.
Crosstalk between channels measured slightly better than 40 dB at
1000 Hz, and about 34 dB at 10 kHz,
which is good. Distortion measured
below 3% at the speaker jacks up to
1 W output, rising to 5% at 3 W. An
output of 1 W provided an adequate
listening level with the system's highly
efficient speakers.
In summation, the Panasonic RS 761S is a handsome machine, with dark
wood, chrome, and black employed
tastefully in both the recorder and the
loudspeakers. The machine is easy to
thread, and easy to operate, with a
transport that handles tape gently.
Panasonic's RS -761S certainly offers
one a nice, complete tape package at
$269.95.
Check No. 44 on Reader Service Card
46
Today, there are few practical advantages of the finest manual turntable/tone-arm combinations over the
finest automatic changers in the manual playing mode). The former is less
complex mechanically, of course, and
therefore potentially more reliable.
Manual types also remain more flexible in being able to be mated to various
tone arms to achieve optimum performance. Additionally manual types are
designed for operation with one record
only, rather than from one to, say, 10,
so that the weight imposed on the turntable platter remains constant, and the
tone arm always "rides" parallel to the
record. The changer, on the other
hand, offers the convenience of automatic start and stop, not to mention
the ability to play several record sides
in sequence when desired. And catching up in many respects to performance capabilities of the manual types,
changers indeed have earned the appellation, "automatic turntables." Depending on applications, then, we
need both types.
The Dual automatic turntables, as
they are sometimes called, have been
in the forefront of the record changer's
challenge to manual turntables. The
Dual Model 1015 continues this tradition. (A new version of the 1015, the
1015F, is identical to the model examined here with the following exceptions: It has a variable -speed control
which permits each speed to be varied
over a 6% range, and the 16% speed
is eliminated. The price remains the
same. Ed.)
Similar in appearance and operation
to the costlier Dual 1009SK ($20.00
more) , it is a nicely made piece of ma -
AUDIO
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SEPTEMBER 1968
The most
independent, independent
testing laboratory
announces its findings
on the Elac 444-E
Fifty of the most knowledge and discerning high fidelity salesmen have just completed a thorough testing of the new Elac
444-E cartridge. They tried it with their
home systems and compared it with the
cartridge they are now using. Here are
samples of their findings:
(Be A great groove -tamerfor the straightfrom -the -studio sound to ver!All of today's
terms won't describe the utmost enjoyment
I experienced Fine response, clarity, were
soon taken for granted"
"This is probably one of the finest cartridges I've had the privilege to evaluate.
Ifind it superior in all respects."
"The over-all impression of this cartridge
is more than delightful. It's tonal quality
is probably the closest to the original
sound. It should be a great asset to the
better turntable."
"This is about as good a cartridge as is
presentlyavailable!Full, rich, clean sound
More than half of these demanding critics
rated the performance of the Elac 444-E
as equal to or better than any cartridge
they'd ever heard-regardless of price.
Why don't you put the 444-E through
your own demanding test at your hi-fi
dealer. Elac cartridges are priced from
$69.50 for the 444-E to a modest $24.95.
Benjamin Electronic Sound Corp.,
Farmingdale, New York 11735
r
Elac
444-E
It may be the finest
cartridge you
ever heard
Check No. 47 on Reader Service Card
AUDIO
se
SEPTEMBER 1968
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47
Equipment Profiles (continued)
chinery that performs exceptionally
well by standards for both manual and
automatic units. The price differential
between it and the 1009SK is due to a
single -play spindle that does not revolve with the record; a two-piece vs.
one-piece cast platter; a different arm
counterweight, and a different motor.
An idler wheel, driven by the stepped
pulley on the motor's shaft, connects
to the inside rim of a cylindrical sub platen, riveted to the main one. The
4 -lb., cast, non-ferrous turntable platen
is not dynamically balanced (at least
it shows no signs of balancing holes or
slugs) and uses a ball -bearing thrust
brace support for the brass sleeve on
which it rests. Teeth cast into the outside of the shaft form a gear which
drives the record-changing mechanism.
same number appearing on the stylus
force dial. Dual uses about 12% as the
ratio of the anti -skating force and
stylus force (playing weight). Naturally, the ratio can be changed by altering the anti -skating dial setting relative
to the tracking force. We found this
anti -skating compensator as effective
as any that we have seen thus far. For
those who have forgotten, skating force
is a term used to describe an undesirable inward force exerted on the stylus
(therefore the tone arm).
The arm's cartridge holder accepts
all cartridges with the standard halfinch mounting -screw spacing (which
includes just about every cartridge).
The cartridge holder drops out of the
tone arm when the arm's finger lift is
pushed to the rear. A plastic gauge,
1-Dual Model
1015 Automatic
Fig.
turntable.
record #1, if he so chooses.
The Dual 1015 can be operated
manually, automatically, or anywhere
in between. It has a fabulous manual
lever -actuated lowering and raising de vie, that gently and accurately lowers
arid raises the tone arm for use when
playing a certain portion of a disc, for
instance. The control was so true in its
lift and drop that, barring an off -center
record and other variables, it was possible to lower the arm so that the
stylus descended back into the same
groove from which it was lifted. (However, a two- or three-groove variation
would generally be expected due to
eccentricity of grooves, etc.) The anti skating force doesn't seem to affect the
lift here, though it does affect lifts in
some other tone arms that we have
tried. Aside from the manual cue control, a single lever controls all start,
stop, and reject functions of the unit.
During changer operation, the large
"elevator action" spindle, which holds
up to 10 records, lifts the stack except
for the bottom disc, which is released
to drop to the turntable. A silent cam operated muting switch shorts the
phono output during cycling.
Performance
A ribbed rubber pad with raised "gunwales" to support the record is fixed
to the turntable. The "gunwale," together with two other concentric smaller ribs, help in supporting warped
records. The turntable itself is 10% -in
in diameter.
The tubular tone arm, with a sliding
counterweight that is lockable in any
position, is supported by hardened steel
points, each supported by ball bearings.
In the horizontal plane, double ball bearing races are used. Tracking force
is applied at the pivot point by a multiple -coiled mainspring. A calibrated
dial sets in the desired tension. This
dial was found to be accurate to within
0.1 gram.
The anti -skating compensation is applied by means of a spring which pulls
on a finger extended from behind the
arm pivot. Though the spring is
stretched as the arm moves toward
the disc's center, compensation remains essentially constant due to the
angle which correspondingly reduces
the pull of the spring. The amount of
anti -skating compensation is set with a
second calibrated dial located in front
of the base of the tone -arm pedesetal
post. One simply turns this dial to the
which snaps over the cartridge holder,
allows accurate overhang adjustment
by acting as a benchmark for sliding
the cartridge forward and backward. A
tapered wedge, also supplied, provides
optimum 15 -deg. tracking angle when
one record is on the turntable-in case
one plays a single record exclusively or
primarily. Dual thought of everything,
it seems. The vertical tracking angle of
the stylus increases as the stack of
records already on the turntable increases, and the object is to remain as
close to 15 deg., the current standard,
as possible. In order for the stylus to
maintain a 15 -deg. angle at every disc
up to, say, 10 discs, either the arm or
the cartridge would somehow have to
be raised by increments proportional
to the record stack. But many records
have been cut not at the standard 15 deg. angle but anywhere between 0 and
25 deg. Furthermore, pickup cartridges
vary also, though not as much anymore. Therefore, the 15 -deg. requirement is not too critical and could be
set up to average out in the record
stack-which is what Dual does in the
1015. The difference between the first
and the 5th record is just a few degrees. The purist can still set it to
48
We tested this unit using two popular phono cartridges. The horizontal
and vertical friction of the arm pivot
were too low for us to measure, which
makes it an exceptionally low friction
(Dual claims .04 horizontal and .01
vertical). The sideways arm thrust
required to trip the changing mechanism at the run -out grooves measured
under half a gram (Dual says it's
1/4 gram). In any case, the unit is suit-
able for the most compliant of high compliance cartridges around these
days. A cartridge tracking at just 1/2
gram trips the mechanism, which is a
neat feat.
Rumble, including vertical and lateral components, came out to -33 dB
and -38 dB with vertical components
cancelled (mono operation). This is
unweighted rumble, referred to 3.54
cm/sec 45 -deg. velocity at 1000 Hz, the
standard NAB reference for rumble
measurement. These are excellent figures, surpassed only by the very best
manual turntables and Dual's own
higher -priced automatic units. Wow
and flutter was checked at .07%, which
is also a very good figure.
At 331/3 rpm and one record playing,
the turntable of our sample was more
than 1% fast. (The upcoming 1015F
has a variable speed control to cor-
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SEPTEMBER 1968
rect for such a deficiency.-Ed.)
Speed was constant over line -voltage
variations between 95 and 125 volts.
We got perfect 33% rpm speed at 85
volts input from a Variac.
Tone arm tracking error, a function
of length and offset angle of the cartridge, was very low.
In playing records at a tracking force
of 2.5 grams, the Dual 1015 performed flawlessly, though slightly fast.
The arm has a smooth feel to it, the
motor is quiet, and the changing mechanism is gentle. When using a cart-
ridge that was not well shielded, the
changer's motor induced some hum
through a wide -range stereo system.
When the changer is mounted on a
base, it rests in its three soft, damped
springs for isolation from vibrations
and acoustic feedback. We found this
quite effective. But the main reason for
the excellent vibration resistance of the
1015 is its tone -arm design. This was
proved by mounting the unit in several
different ways while subjecting it to
feedback and vibration -inducing conditions. One mounting technique was to
Shure Model SM60
anode current for the cathode follower
(in more recent models, a source of
current for the FET, which is taking
over from the vacuum tube in the latest
models) .
The ribbon microphone, long the
standard in the broadcast industry, is
still used for certain applications where
its "Figure -8" pattern is desirable, but
even that pattern can be duplicated by
either dynamic or condenser microphones. The dynamic, however, is the
workhorse of radio and TV studios, and
it has become the standard for public
address uses, and is practically universal in the home recording field. Its
simplicity and reliability have earned
for it the "workhorse" cognomen.
There are many grades of dynamic
microphones, however-some can be
purchased for as little as $7.00, and
some cost as much as $150.00. This one
has a practical price at $49.20 net, but
is a quality product, listed by Shure
as a professional model. The SM60 is
essentially omnidirectional, showing
only a slight directionality in the
higher frequency range, largely due to
its physical construction (the body of
the unit provides some shielding
against high -frequency sounds coming
directly from the rear.)
The microphone body is 7/8 -in. in
diameter, (the same diameter as the
Cannon plug) expanding to a maximum of 11/4 -in., and then tapering
down to its 1 -in. business end. Its overall length is 61/4 -in. giving it attractive
proportions. The body is a steel tube,
Dynamic Microphone
-
MANUFACTURER'S SPECIFICATIONS
Polar Pattern: Omnidirectional. ImpedFrequency Response: 45 to 15,000 Hz.
ance: 150 ohms (matches inputs from 50
through 250 ohms). Output level: -59 dB
(0 dB = 1 mW with 10 microbars.) EIA
Sensitivity Rating: -153 dB. Net weight:
6 oz. (less cable). Dimensions: 1'/a" diam.,
6h/4" long. Cable: 20-ft. 2 -conductor
shielded broadcast type, with Cannon
XLR-3-11C connector on microphone end.
Accessories furnished: Swivel "snap -in"
adapter; cloth protective cover. Net Price:
$49.20.
The dynamic microphone has
proved itself for applications where
rugged, self-contained, and versatile
transducers are required. While the
condenser microphone has become the
standard for measurement purposes, as
well as for applications requiring the
highest possible quality, it does have
the disadvantage of requiring a source
of polarizing voltage for the capsule
and another source for the heater and
AUDIO
leave it in its starchy styrofoam packing material, which, incidentally,
makes an excellent temporary base.
In all, the Dual 1015 is an exceptionally fine medium-priced automatic
turntable. Considering the soon -to -be introduced 1015F's addition of a variable speed control, while eliminating
the generally useless 163/4-rpm speed,
it's worth waiting for. Price of the new
version remains the same ($89.50).
Check No. 46 on Reader Service Card
0
210
1kHz
180
4kHz___
10kHz
Fig. 3 -Polar -response curves for the SM 60 microphone at three different frequencies.
with a non-ferrous tapering section
topped by a steel protective grille,
which houses the built-in wind and pop
filter which eliminates the need for
add-on windscreens for outdoor use.
Finish is matte chrome. Because of the
low impedance, no transformer is required, which eliminates one possible
source of distortion. The cartridge
ground and case ground are connected
to terminal 1 of the Cannon receptacle
(the usual professional practice), with
the two coil leads appearing on terminals 2 and 3.
The microphone is provided with a
plastic snap -in swivel adapter adjustable from vertical to horizontal, and
threaded to fit the usual %-27 microphone stand.
+10
Fig.
2 -Frequency
response of Shure
SM -60 microphone
on axis.
o
-10
-15
20
50
100
FREQUENCY
10k
k
(HERTZ) -
20k
ON AXIS
49
SEPTEMBER 1968
www.americanradiohistory.com
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Equipment Profiles (continued)
Performance
The response curve of the microphone is shown in Fig. 2 and its polar
response is shown in Fig. 3. Note that
there is little departure from omnidirrctionality, and that only at 10,000
Hz. These measurements were made
in comparison with a calibrated condenser microphone and a suitable
speaker source in an outdoor location
free from reflections nearer than 50
Model 330 "Uni -Ron"
Shure Uni -Directional
Super-Cardioid Ribbon
Microphone
MANUFACTURER'S SPECIFICATIONSFrequency Response: 30 to 15,000 Hz
±21/2 dB. Impedance: multi -impedance
switch furnishes choice of three-50, 150,
and 250 ohms. Rated Sensitivity: 50-ohm
position, -60 dB; 150 -ohm and 250-ohm
positions, -58.5 dB: (0 dB = 1 mW with
10 microbars.) EIA Sensitivity: 50- and 150 ohm positions, -152.5 dB; 250 ohms,
-150.5 dB. Weight, 1'/2 lbs. (less cable).
Dimensions: Height, overall, 79/32"; Width,
overall, 17/2"; Depth, 1%". Cable: 20-foot,
broadcast type 2 -conductor shielded, with
Cannon XL -type cable receptacle. Net
Price: $72.00.
In the previous section, we commented on the usual "Fig. 8" pattern
of the ribbon microphone. This pattern results when both sides of the
ribbon are exposed to the sound field.
Sound originating at 90 deg. from the
axis impinges on both sides of the ribbon at the same time and with the
same intensity, thereby cancelling out
Fig. 1-Shure Model 330 Super-Cardioid
Ribbon Microphone.
feet, and at a level where reflections
would not affect the measurements
anyhow.
In actual recording use, the smoothness of the unit was evident. The wind
filter was particularly effective, although it did not completely filter out
breath "pops" when used at 3 to 4
inches. (It was also ineffective in filtering out airplanes flying overhead-one
of the disadvantages of outdoor testing,
as well as recording.)
any motion of the ribbon and consequently reducing the output to zero, in
theory. This is borne out in practice
where the microphone is tested in anechoic chambers, but in normal studio
use the effect of reverberation modifies
this response somewhat. There is sufficient reduction in output from sounds
originating at the sides that it was
common in the days of radio plays,
soap operas, and the like, for two performers to work on opposite faces of
the microphone, and the prompter
could stand at the side without being
heard.
In the 330, however, the back of the
ribbon is covered by a phase -shifting
enclosure, much as is done with dynamic units to produce the cardioid
pattern. In the ribbon, the pattern
which results as a combination of the
newly designed acoustic phase -shift
network and an improved ribbon element is the super-cardioid, which is
somewhat sharper than the usual cardioid obtained with dynamic units, and
the reduction in rear response is of the
order of 26 dB at 9000 Hz, and 15 dB
at 4000 Hz. The 300 is claimed to reduce reverberation, reflection, and
pick-up of undesired random sound by
73%. Sound enters the microphone
through nearly 2500 tiny apertures in
the protective housing and impinges on
the element through further filtering.
The back of the ribbon is connected to
the phase -shifting volume, and similarly protected from wind and breath blast pressures.
The impedance -changing system involves the use of a transformer with
three taps on its secondary (a transformer is always necessary with a ribbon microphone because the impedance of the ribbon itself is of the
order of 1/4 ohm) to give the proper
output impedance. The transformer is
located in the microphone housing,
with the four leads brought through
a spring-like shield to the switch which
is located in the isolation unit, and
accessible to a screwdriver blade
through a small hole on the front of
the unit.
50
On the whole, we found the SM60 to
be a neat, compact unit which is sufficiently versatile for practically any
application. Its high -frequency rise is
particularly helpful in providing clear,
intelligible speech, making it especially
useful in recording interviews or for
announcing. Its overall smoothness
permits boosting the lows for ideal
musical recording.
Check No. 49 on Reader Service Card
+10
-J0
w
a1
0
U
w
C1-10,
20
100
(HERTZ)
0
270
90
180
-1kHz
---4kHz
10kHz
2-(upper). Frequency-response curve
of the 330.
Fig. 3-(lower). Polar -response curves of
the 330 at three different frequencies.
Fig.
Performance
The response of the microphone is
smooth and reasonably flat from 30 to
10,000 Hz, as shown in Fig. 1, and the
polar curves exhibit the type of directionality commonly described a
"supercardioid." The rejection from
the 180 -deg. point is slightly less than
at the 90- and 135 -deg. points, so that
the exact rear need not be placed toward the interfering sounds. The
unit is remarkably free from breath
sounds, and because of its directionality it would not normally be used as
close to a sound source as would the
usual cardioid or omnidirectional microphone. It is rather too heavy for
hand-held use, which is not normally
recommended for ribbon microphones
anyway. The weight is largely due to
the heavy magnets, as well as to the
die-cast case, which is sturdy.
For studio use, however, the 330 "Uni -Ron" provides excellent response,
and is sufficiently directional to reduce
feedback and to eliminate unwanted
noises arising from the rear of the unit.
Check No. 50 on Reader Service Card
AUDIO
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10k 20k
1k
FREQUENCY
SEPTEMBER 1968
World's
greatest
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AUDIO
53
SEPTEMBER 1968
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What's New In Audio
(Continued from page 6)
liptical-shaped, flat speaker, (7-in.
cabinet depth) with two bookshelf
models, NS -15 and NS -10. Benjamin
showed off its latest EMI speaker
systems, too, which ranged from the
Jensen Mfg. Vibranto® power column.
EMI
SCO
small, bookshelf model 55, at $54.95, to
two under -$350 floor -standing consoles,
each of which includes a 15 -in. woofer
as part of a three-way system.
Both Koss Electronics and Telex
broke out with new headphones. Koss
demonstrated its new electrostatic
headphone, model ESP -6, priced at
$95. Each unit is accompanied by an
individually measured response curve.
Telex announced a new, low-cost
headphone, the Encore, priced at $9.95.
H. H. Scott and Fisher Radio each
displayed long, long lines of component equipment, component consoles
and modular systems. Benjamin displayed its new Elac phono cartridges
and a new, under-$200, portable stereo
unit. Koss entered what is said to be
the first of a line of hi-fi component
kits, called KossKits. The new model
600-K AM/FM stereo features 500
watts total power (IHF) with a 4 -ohm
Series.
Koss' Model 600-K AM/FM stereo receiver
kit.
load. Its digital read-out dials for AM
Marantz Imperial
University Sound's Alhambra Ill
II
and FM and a "go/no-go" lamp tuning system were among its impressive
innovations. Kenwood featured its latest addition, a stereo receiver/speaker
system, the 30 -watt AM/FM KS -33,
at $199.95. Sansui showed an electronic
crossover. Nivico displayed an amplifier with an elaborate tone -control section that uses slider controls.
Packard Bell's "component" color
television receiver, the 23 -in. model
CC9000, caught many eyes. Designed
for installation in a flush wall mounting or in a custom cabinet, the new set
incorporates cathode followers for
audio and a video tape recorder output. $750. Panasonic introduced a
novel FM radio-wrist-watch styling.
The battery -operated model RF -120
Panasonic FM wrist -watch radio.
Model RF -120.
Clairtone psychedelic light and control
equipment.
measures only 11/4" x 11%6" x 2%2" and
contains five ICs, two transistors and
two diodes. Tuning is electrical through
use of a "Capistor." EICO, Clairtone,
and Aztec demonstrated psychedelic
lighting units, with low, medium and
high frequencies activating different
color lights. Jerrold featured its first
antenna rotator, an in -line design.
Toujay Designs had its line of audio
cabinets, including its "Sound -X Pander" cabinet. A Canadian furniture
company, Backhaus, demonstrated
audio cabinets that incorporate power operated speaker enclosures that can
be positioned for optimum sound dispersion. Uses a 24 -volt motor and reduction gear box.
Garrard's top model, SL95, with its
newly developed synchronous motor,
was featured by British Industries,
along with Garrard's Module SLx,
which is a complete record playing
section with cartridge, base and dust
cover. Garrard also showed its new,
sleek bases and dust covers. BSR presented its space -saving "Minichanger"
module, SX5H, for compact installations, at the NEW Show. A re -styled
line of BSR McDonald record playing
equipment was shown at the CES
Show. Dual introduced its new 1212
automatic turntable ($74.50) , which incorporates a varable pitch control. See burg's "Audiomation" record playing/
selecting system, which plays 100 LP record sides automatically, also included a model with an AM/FM tuner and
speakers, as well as a component unit.
More details on the foregoing equipment will be presented here in future
Æ
issues.
54
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SEPTEMBER 1968
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55
AUDIO
Classical
56
1\iUSTC
Jazz
Light Listening
Recorded Tapes
60
REVIEW
62
64
,..
r.., .._.._.._.._.._.._.._.._.._.._.._..._.._.._.
j
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own musical
Classical
Record
formed.
The Nine -Cent Record
1
O.
1.
I keep trying to remember to put
down the prices on my record reviews. I'm reminded; I forget.
My reason for going blank on
prices is: I tend to wonder what
prices mean. I've wondered even
ago, when
since a week
nine-cent LP
I
my
I likekt my nine-centfirs record! Let's review it right now, and price no
consideration.
-d.
I
I
Handel: Two Italian Cantatas. No. 6,
Cecilia, wolgi un sguardo. No. 8,
Dalla guerra amorosa. Dora van Doorn,
Leo Larsen David Hollestelle; Orch.
Netherlands Handel Society, Loorij.
Rarities Collection 304 mono.
I
i
Handel, ever versatile, wrote a
long chain of beautifully tailored
Italian works of the solo cantata
type, part of that large body of
music which he turned out mainly
to show the Italians how easily he
could out -perform them at their
Ç
i
It's a Lulu
Alban Berg: Lulu (Hamburg State Opera
Production).
Rothenberger, Steiner,
Meyer, Wohlfahrt, Unger, Borg, Kusche,
et. al., Hamburg Philh. State Orch.,
Ludwig.
Angel SCL 3726 stereo (3)
There has been much excitement
among the musical cognoscenti over
this production of "Lulu," and another
new one on records from DGG, supplementing an older Columbia recording.
The excitement is real enough. "Lulu"
is a twentieth century musical landmark, even though unfinished at Berg's
singing too loud at close range. This
is the only recording of the first of
the cantatas.
Performance:
B-
Sound:
B-
That isn't easy, these days.
ReviewsHandel's singers, Italian or otherwise, were very good at the sort of
EDWARD TATNALL CANBY
Ì
games-any game.
Nothing deep or profound, but superb music, nevertheless, and deeply enjoyable whenever well per-
Reading that review, could you
guess at a proper current price?
Wouldn't you say, maybe, $2.50, the
music he wrote for them, full of
standard list price for imported
leaps and jumps and high notes,
European Baroque with lessertrills, runs, acrobatics, all to be
league soloists. (And for reissue taken in ever -so-casual stride,
type rarities, too.) But nine cents!
vocally speaking. Show any sweat
Of course, that $2.50 price is sub and you're ruined. So we can be
ject to certain highly pervasive
grateful when a singer today manpressures in the market place.
ages to turn in a reasonably con-gThat'd do it. Not all market places.
wincing version of this type of
Just a few, though large in their
music.
volume of sales. Go to these big-city
These two cantatas are done
spots and you'll find the pressures
middling-well-which means pretty
in action. But go to your home town
good, considering. Three soloists,
record store, comfortably close and
soprano, tenor, and bass, between
convenient, and you won't find
the two works. Plus a muscular
them. List prices, whether high or
continuo -type accompaniment and
a few strings, basic orchestra. The
first cantata features tenor and soprano; the tenor holds forth mightily and he is, alas, both too loud
and too close. Lower the volume and
he's passable. The soprano is much
better; and when (flip side) they
join in duet the music becomes positively charming. The second work,
shorter, is all bass, a good solid one
who sings about the War of Love in
suitably potent tones. Nice, if not
overwhelming. Good modern sound,
in mono, but the balance is faulty,
the tenor being most at fault, for
1927 death. This Hamburg Opera performance has been on tour and hit the
Big Time in New York last year at
Lincoln Center. Tie-in for public relations, natch.
What strikes the average you -and me listener in this music, I think, will
be not so much its modern idiom-it is
"twelve tone" or serial music-as,
paradoxically, its old-fashioned quality, straight out of Wagner, and then
the German opera of Johann and Richard Strauss which, oddly enough, it remarkably resembles in all but the actual harmonies (if that is a word to
use in this case).
56
L
I
ç
j
3i
t
1
Lj
t
low.
Even there you have an alterna tive. Mail order. There, too, pervasive pressure tends to rubberize
prices, and mail-order discs are
available in every small town merely
for the trouble you care to take. If
you care to. But do you?
Now all this is supposed to be a
big, dark secret, at least in print,
I'm not letting any secrets out, not
me. Except for my nine -cent record.
I'm just saying that a price is a
price, and it all depends. How
should I know where you do your
depending, if you follow me?
1
t
1.
L
i
1
i
Here is the big post-Romantic orchestra, here are the big Romantic
opera voices, rich and wobbly and full
of dramatic expression. Here, too, is
that fast -paced sung "conversation"
which is so excellent a feature of Richard Strauss's operas, in contrast to the
dead -slow pace of the Wagnerian
opera.
But most of all, "Lulu" continues
and augments that nightmare-ish atmosphere which one finds in the first
Strauss operas, in "Salome" (with the
leering head of John the Baptist visible on a platter), in "Elektra"-full of
the anguished caterwauling of women
AUDIO
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i
j
SEPTEMBER 1968
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AUDIO
57
SEPTEMBER 1968
www.americanradiohistory.com
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demented by violence and murder.
That grisly tradition goes right on into
"Lulu"-somebody dies within the
very first moments of the first act, and
plenty more to come. Moving, yes!
Powerful. But grisly.
"Lulu" then is an early twentieth
century opera of the end of the Romantic school, and the fact that its
music is serial is both pioneering and,
oddly, almost incidental. That's why it
is so accessible, of course.
That
is-if
you like deadly serious late -German
opera, the Valkyries gone psychotic.
Some do-some don't.
Performance:
A-
Sound: B+
Weill -Brecht: The Three Penny Opera (in
German). Stars of the Vienna Opera, F.
Charles Adler.
Vanguard Everyman
SRV 273 SD el stereo ($2.50)
Though not the performance-any
of several, both in German and English, featuring Kurt Weill's wife the
singer Lotte Lenya-this version of the
famed popular operetta of the German
1920s has its values. One of those values is not, I would say, the presence of
famed and beloved stars of the Vienna
opera; instead, the show goes on and
is listenable in spite of their slightly
unsuitable voices-for this is like, perhaps, a Metropolitan Opera production
of "Porgy and Bess," though the gap
between popular and "grand" opera, to
be sure, is much less in Vienna than
in New York.
The performance is good because it
is heartfelt, the orchestra (with its unforgettable blatty brasses out of the
Twenties) is excellent, if discreet, and
above all, the heroine, Polly Peacham,
is not an opera star, but a Viennese
pops artist! Excellent decision on
somebody's part, and the other singers
generally are able to follow her lead.
An elderly recording, given the synthetic stereo treatment and released at
half price (the original was still in the
catalogues the month this was released), the new disc has a somewhat
dull sound but is otherwise clean and
intelligible in the all-important Brecht
text (translation provided).
Performance: B+
Sound: C+
from the earlier nineteenth centurythat's the one that would sell this disc
to me in a hurry. Berwald.
Nationalism looks good on a cover,
of course, and this is, after all, a Swedish performance out of Stockholm. (The
newly Swedish Dorati, you'll remember, was not long ago making hi-fi
spectaculars for Mercury out in Minneapolis.) But the musical items on this
record merely swear at each other's
styles. Play 'em separately, I warn you.
Blomdahl, the youngest, is an expertly academic middle-aged contemporary whose grandiose opera about a
space trip came out a few years ago.
I found it sort of painful. And though
I admire the skilled orchestral writing
in this "Sisyphos" suite (originally a
species of ballet) , a lot of swankly sardonic dissonance, very neo-classic, I
still find that the Blomdahl technique
is 'way ahead of the content. Skillful
yet somehow pretentious. As for Rosenberg, the grand old man (b. 1892) of
Swedish music, his "Voyage" doesn't
cut very much American ice, except
that to an experienced ear-it oddly
sounds like a good deal of late -Impressionist American music of the pre World War I era. Loeffler, Chadwick,
John Knowles Paine. Probably a coincidence. Slightly nutty, too; Rosen berg's "Voyage" music (from an opera
of that name) dates from 1932, a quar-
ter century later.
Ah, but Berwald! A recent discovery
for those of us outside Sweden, he turns
out to be a fascinatingly real musical
personality of the early Romantic era
-this little symphony dates from 1842.
Such quirky, elfin, high-tension, explosive music, so honestly, so deftly written. Such superbly catchy little ideas,
such a wispy sort of thinking, andfor its date-such modernity! The man
was a year older than Schubert, born
1796, and there is much that reminds
us of late Schubert in his work-yet
also we hear Berlioz, and Mendelssohn,
even a bit of Liszt.
Buy the record for Berwald, decidedly. Throw in the others for curiosity.
Performance:
A-
Sound: B+
Modern Twists
Microtonal Fantasy. The Music of John
Swedish Suite
Music from Sweden. (Blomdahl: Suite
from "Sisyphos"; Rosenberg: Voyage to
America; Berwald: Sinfonie capricieuse.) Stockholm Philharmonic, Dorati.
RCA Victrola VICS 1319 stereo
Two mildly modern items and one
Eaton.
Decca DL 710154 stereo ($5.79)
The determinedly advanced and
difficult music of this young man-very
much on the classical side-is given a
lot of general interest by the Syn-Ket,
appearing in a number of works here.
It is a live electronic synthesizer,
58
played on the spot, in performance,
and it produces what sounds like and,
in fact, is electronic music. The gadget
is semi-accident, not having originally
been intended for live performance, but
it works and the idea is very important. Nearest relative is the now well
known Moog Synthesizer. But has
anyone yet played the Moog machine
in a live performance?
Most excruciating music here is that
sung by a hard-working Japanese soprano, who practically busts herself
screaming out the incredible high
notes. Next to her comes the piece for
two pianos tuned a quarter tone apart.
Oof-what a sick sound, for our overly
halftone -trained ears. Tough stuff.
New Music in Quarter-tones. (Ives, Hampton, Lybbert, Macero). Chamber Ensemble and Two Quarter -Tone Pianos.
Odyssey 32 160162 stereo ($2.50)
There are ways to break down our
half -tone system, including the familiar noises of the all -electronic medium.
When the breakdown occurs via live
instruments, especially the piano, it is
catastrophic on the ears. And yet-go
far enough and the sound begins to
sound almost OK. This disc will take
you over the bumps, from Charles
Ives' early and out -of -tune experiment
(that's how it sounds) to recent works
by thirty -year -olds, who know how to
make quarter tones sound persuasive.
Dockstader and Reichert: Omniphony I.
Owl ORLP-11 stereo
(1229 University Ave., Boulder, Colo.)
For a number of years, Tod Dockstader has been a part-time independent creator of electronic music on tape
in spare time from his work as a studio
sound engineer. Now he has found a
"classically trained" musical colleague
and the two have combined forces for
this enormous operation in 5 movements, and evidently only a beginning,
at that. The technique is indeed unusual. The music is largely produced
by live instruments-but instead of a
performance, the musicians prepared
blocks of recorded sound for later treatment, along with other natural sounds
and sounds electronically generated.
The pieces was organized out of four
categories of these-pure instrumental
sounds; the same, electronically transmuted; natural sounds, and electronic
sounds. Much of the work was done
via Moog processing equipment.
No use trying to "describe" the work!
Try it for yourself. A weird cross
between recognizably "live music"
sounds and now -familiar electronic
effects.
(Continued on page 61)
AUDIO
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SEPTEMBER 1968
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AUDIO
59
SEPTEMBER 1968
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......._... s ... » ..... »......-....«..........._.....»-«.«.«....
Is There an
Eighth
Dimension?
BERTRAM STANLEIGH
Early in March, the producers of
Command Records herded a collection of record dealers, disc jockeys,
and critics into the large studio of
Fine Recordings for an advance
demonstration of their newest innovation in sound -recording technique. Such demonstrations sometimes precede really monumental
strides in recording. Both the longplaying record and the 45 -rpm disc
were first announced at similar press
previews, and curiosity was understandably at a high pitch regarding
the new sound method considered so
important by its prqducers that it
could only be introduced at a special
preview.
First, Loren Becker, co -producer
of Command Records, recounted the
previous sound triumphs of his label,
beginning with the now historic
Persuasive Percussion, Stereo 35/
MM, and Dimension 3. Then he
described the careful planning that
he, Bobby Byrne, and engineer Bob
Fine had devoted to the development of this new sound. How the
tapes of the first sessions, in January
1967, had been discarded as unsatisfactory. How arranger Jack Andrews had been called in to prepare
special scoring utilizing new electronic instruments. How the final
music tracks had been mixed with
effects tracks at the Todd Studios in
California, utilizing the world's largest mixing panel, and how by January 1968, Command was confident
that it had a worthy product to release. One last modest note crept in
as Becker declared, "We hope to do
better in six months to a year."
After that, at ear-splitting level, a
half dozen of the new disc's eleven
selections were played. Unfortu-
nately, the audience contained a
high percentage of those strange
characters who begin: to talk as soon
as a recording starts to play. Since
the music was loud, they shouted.
In the midst of the turmoil, it was
quite impossible to reach any conclusions. But I left the conference
clutching a copy of Sound in the
Eighth Dimension, resolved to put
this new contender to the test.
A study of the liner notes revealed
just what was meant by the eighth
dimension. Instead of the usual left
and right positions, with a center
spot between the two, the new Command technique has as its goal the
establishment of six firm positions
from left to right, plus a solo position in front of the orchestral sound
curtain, and a percussion and
rhythm position behind the band.
Home listening on my own familiar system immediately made it
clear that it was possible to audit
this disc at more normal listening
levels than had been played at its
preview without any diminution of
its sonic merits. In fact it was
pleasantly surprising to note that in
contrast to its very notable loud
passages, the disc also had some real
pianissimo sections. To this listener,
the clarity of sound through this
very wide dynamic range is one of
the very real virtues of the new technique.
The solidity of "fill" between the
speakers was also quite apparent,
and there was no question about the
stable positions of various sections
and solo instruments. Each sound
emerged with clarity from ite own
fixed position, and it was quite possible to detect a half-dozen or more
different instrumental locations at
the same moment. If one wanted to,
one could sit in one's favorite chair
and diagram the seating position of
the orchestra for each selection.
Other records with somewhat smaller instrumental groups have come
very close to the clarity and positional stability of this new Command breakthrough, but I can't
think of a single recording of a group
of forty or more instruments that
has succeeded to such a marked extent. The technique really works!
Now, what about the use to which
it has been put? The present disc is
manifestly a "high fidelity showcase" type of affair. Its selections
,
60
have been chosen for their flashy
effects and variety of styles. Lime house Blues and South Rampart
Street Parade are cheek by jowl
with Ebb Tide and Blue Hawaii.
Spanish Eyes and El Gato Montes
provide the Latin flavor. La belle
France is evoked in Michel Le Grand's This Heart (Paris), show
biz is represented by The Sound of
Music and Get Me to the Church on
Time. The sound of a marching
band is provided in March of the
Space Cadets, and the kiddies get
their nod with Talk to the Animals.
There is, indeed, something for
everyone from the aficionado to the
jazz buff, but the only central theme
running through the entire disc is its
recording technique. Anyone is
bound to find a band or two that he
admires-for me El Gato Montes is
an absolute smasher, a fine performance with marvelous brass sounds
and a spine tingling re-creation of
the sounds of a bull -fight crowd. But
I'm thoroughly uncomfortable with
the arrangements that sandwich it
in. The only way I can cope with
this platter is to sit close to my turntable and pick the bands I enjoy.
Mark you, there's not a thing
wrong with any one of the performances, provided you like the style.
Robert Byrne, who conducts the first
rate studio orchestra, is a thoroughly
accomplished professional who can
get exactly what he wants from a
group. He led one of the spritelier
groups back in the "big band" era,
and he continues to keep things moving in a bright, youthful manner.
What about the new recording
technique? Is it the revolutionary
breakthrough it's claimed to be?
Well, it's certainly splendid. As good
or better than anything I've heard
to date. But I wouldn't classify it as
more than a particularly well
planned, well engineered recording
that utilizes all of the familiar
present-day techniques. It will take
subsequent releases with more substantial musical interest to reveal
any startling new dimensions. We'll
be waiting to see just how good those
new releases are.
Sound in the Eighth Dimension. Command Stereo RS 928 SD
Performance: B
Sound: A
AUDIO
www.americanradiohistory.com
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SEPTEMBER 1968
Classical Record Reviews
(Continued from page 58)
Capsule Comments
Boulez Conducts Debussy (La Mer; L'ApresMidi d'un Faune; Jeux). New Philharmonia
Orch. CBS 21 11 0055 stereo.
2r
Mr}
Unusual performances-hailed right and
left. I found the familiar music rather too
different, sounding more modern, less impressionistic, the "insides" oddly showing.
Interesting, and the seldom -heard late
"Jeux" is especially valuable. Definitely a
young -generation achievement.
U
Schumann: Piano Concerto; Novelettes. Artur
Rubinstein; Chicago Symphony, Guilini. RCA
LSC 2997 stereo.
The sprawling Schumann concerto is tough
to interpret-Rubinstein has it in hand as
few still do. Guilini is excellent too, but of
a younger generation. A fine performance,
though there is some noticeable disagreement
between the two, not entirely resolved when
passages echo, piano vs. orchestra.
Victor
Mozart; The Last Six Symphonies. Sir Thomas
Beecham, Royal Philharmonic. Odyssey 32 3
0009 mono.
True (as Odyssey notes)-Beecham was
Mozart for years. Now, his resurrected recordings are still meticulously accurate in
detail, but the concept seems heavy, often too
slow by our standards, the orchestra over-
weight, the eccentricities of ritard, etc., rather
hard to take. Still, these are fine documents
of an era now departed.
Music for Maximilian.
Rias Ch.
L
CONVENTION and EXHIBITION
PROFESSIONAL AUDIO EQUIPMENT
FOR STUDIO AND LABORATORY
OCTOBER 21
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24
PARK SHERATON HOTEL, NEW YORK CITY
Orch., asst.
soloists. Angel 36379 stereo.
The Triumph of Maximilian. London AmbroSingers, Vienna Renaissance Players.
Sian
Nonesuch HB -73016 stereo.
Suddenly, the Emperor Maximilian (d.
rediscovered-he of the fabulous wood prints, Albrecht Dürer and others,
the splendid processions, creator of the Habsburg empire-because his equally important
music, once too "early," is now again coming back for listening. Here are two surveys,
Nonesuch's on two records, with such now revived names as Isaac, Senfl, Des Prez,
Finck. Voices, instruments, solo and ensembles of various sorts.
1519) has been
P.D.Q. Bach on the Air. With John Ferrante,
Virtuosi di Hoople, Prof.
counter -tenor,
Peter Schickele. Vanguard VSD 79268 stereo.
I
Prof. Schickele's third spoof -record shows
him as persistently seeking the big laugh as
ever; he is not noted for extreme musical
subtlety. This hysteric take-off of "good
music" on the air, nevertheless, will double
up anyone who fancies Baroque music. The
works, including announcers, commercials,
"remotes" all in Baroque -modern! The counter -tenor sings the station breaks and time
signals. The P.D.Q. music isn't half bad. As
music, I mean. I've heard worse.
Haydn: The Six Paris Symphonies, Nos. 82-87.
N. Y. Philharmonic, Bernstein. Columbia D3S
769 (3) stereo.
This splendid big album of six superb and
formerly little known late Haydn symphonies
does not put Nonesuch's parallel album (H73911, Leslie Jones) out of the running-try
both. Bernstein's is bigger in sound, more
polished, more "symphonic," and occasionally a bit old fashioned. Jones -Nonesuch
gives a surer, more intimate look at these
splendid works. Between the two sets, you
are set for a year's good listening.
TECHNICAL SESSIONS INCLUDE: Solid State TransSound Reinforcement Symposium, Audio
ducers
Engineering and the Environment Disc Recording.
Magnetic Recording Audio in Medical Practice and
Audio Apparatus and Communications
Research
Systems C. J. LeBel Memorial Symposium (next 20
Developments
Audio Abroad (2)
years in Audio)
in Electronic Music Systems
SPECIAL APPLICATION SESSIONS: "From Studio
to Microphone to Listener,' Tuesday Evening at 7:30.
No admission charge.
HOURS OF SESSIONS: Monday -Thursday, 9:30 a.m.,
1:30 p.m. and 7:30 p.m. except Tuesday, 7:15 p.m. and
Wednesday, 9:30 a.m. and 1:30 p.m. only.
HOURS OF EXHIBIT: Monday and Tuesday, 12 noon 9:00 p.m.; Wednesday and Thursday, 12 noon -5:00 p.m.
AWARDS BANQUET: Wednesday evening, 7:00 p.m.,
preceded by Social Hour, 6:00 p.m., Boston Symphony
conductor Eric Leinsdorf, speaker.
Write, telephone for program and banquet information
Angel S-36472 stereo.
AUDIO ENGINEERING SOCIETY, INC., Dept. 35
Room 428, The Lincoln Building, 60 East 42nd Street
New York, New York 10017 (212-661-8528)
Brahma chamber music is so obviously not
background music --even on records! The
Menuhins, violin -brother and piano -sister,
steer a leisurely Romantic course through
these two works, with a fine horn in one and
a fine cello in the other. Excellent if you pay
close attention, but a recorded performance
generally needs more drive and push. Yehudi
is getting wobbly and inaccurate, though still
musical. Hepsibah's piano is miked too distantly in the horn work, OK in the other
one. In sum: not bad, if plenty mellow.
20TH
Brahms: Horn Trio, Op. 40; Trio No. 2 for vl.,
cello and pf., op. 87. Yehudi and Hepsibah
Menuhin, Alan Civil, horn, M. Gendron, cello.
AUDIO
ANNIVERSARY
61
SEPTEMBER 1968
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WORTH
WAITING
Light
Listening
STUART TRIFF
... The Old
FOR!
DYNACO
STEREO
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The combined distortion of
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does not exceed 1/10 of 1%
from 20 to 20,000 cycles at
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Ethel Waters.
Columbia (mono only) CL-2792 ($4.79)
Another outstanding reissue in
Columbia's "Hall Of Fame Series" is
this release devoted to the incomparable Ethel Waters. The selections trace
the singer's remarkable career, from
1925 to 1940, in night clubs (Plantation and Cotton Club), movies ("On
With the Show"), Broadway revues
("Blackbirds Of 1930," "As Thousands
Cheer," "At Home Abroad"), to her
memorable starring role in "Cabin In
the Sky." The performances are treasures and the songs speak for themselves: "Dinah," "Am I Blue?"
"Stormy Weather," "Heat Wave,"
"Taking a Chance On Love," et al.
Once again, engineer George Engfer
has achieved remarkably good sound in
transferring these faded 78's to LP.
Performance: A
Sound: B+
... And the New
Dawn of a New Day-Margie Day, vocal.;
arr. & cond. by Ray Ellis, Chuck Sagle,
Jimmy Wisner.
RCA Victor LSP-3899 ($4.79)
This aptly -titled collections marks
the album debut of Margie Day, an
exciting young singer from Norfolk,
Virginia, who for the past seven years
has been serving an apprenticeship
warbling in a night spot in her home
town. Judging from this disc, I'd say
that RCA has a hot property on its
hands.
Miss Day's is not a big voice, but it's
a flexible one, capable of producing a
variety of colors with sensitive and expressive phrasing. She has some strikingly original approaches to her songs,
and though not all of them work (as
in "Wouldn't It Be Loverly" and "Let's
Do It") she's never less than interesting.
Seven of the ten songs are from
1928 to 1968. I especially enjoyed the
torchy rendition of "Walk Away," one
of the better Elmer Bernstein tunes
from "How Now, Dow Jones," and her
driving, bongo -punctuated delivery of
"Over the Rainbow." "Am I Blue?" introduced by Ethel Waters in an early
film musical, is sung in a style reminiscent, but not imitative of the great
Billie Holiday; and Cole Porter's "It's
All Right With Me" is given the most
electric interpretation I've ever heard,
complimented by a fine Ray Ellis setting.
The Burt Bacharach-Hal David
song, "In Times Like These," is another
highlight of this impressive recital. The
three arranger -conductors provide excellent accompaniments. The reproduction is sharp and full, with good stereo
effects. Miss Margie Day should have
a long and very bright career ahead.
Sound: B+
Performance: A
Fiddlesticks
Fiddle Faddle and Other Leroy Anderson
Favorites: Utah Symphony Orchestra/
Maurice Abravanel.
Vanguard VCS -10016 ($3.50)
Fifteen selections comprise this collection of thrice -familiar Andersoniana,
offered by Vanguard in their commendable, low-priced Cardinal Series, in
compatible stereo. Employing the new
Dolby noise -reduction system, this disc
is a joy to listen to. Smooth response
over the entire frequency range, noise free surfaces and a burnished orchestral sound clarify every detail of Leroy
Anderson's delightfully imaginative orchestration.
If only the performances were as
good as the reproduction of them.
Though the Utah orchestra plays
beautifully, the conducting is heavyhanded; almost everything is played
tqo slow, thus robbing these pieces of
the necessary snap, sparkle, and verve
the composer brings to them in his own
infectiously impudent renditions. With
Anderson at the reins of his "Sleigh
Ride," the journey ends at 2:44, while
Abravanel's leisurely trip takes 3:05.
In "Song Of the Bells," the composer
is finished at 2:58; Abravanel chimes on
for 3:44. There's a statement preceding
the liner notes, calling attention to the
fact that this is the first time a major
symphony orchestra has recorded an
album of Leroy Anderson. This claim,
while technically correct, is hardly reason enough to ignore the 85 virtuosi of
the Boston Pops Orchestra, and Arthur Fiedler, for whom many of Anderson's compositions were originally
written. The recorded performances by
the "Pops" are almost on a par with
those by the composer.
Sound: A+
Performance: C
IN EUROPE WRITE:
DYNACO A/S, HUMLUM, STRUER, DENMARK
62
AUDIO
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SEPTEMBER 1968
problem
solving
microphones
by
Fig.
PROBLEM:
8-The CA -3012 "IC"contains all the elements shown here.
ABZ's of FM
(continued from page 38)
whether tubes, transistors, or integrated -circuit linear amplifiers. A typical i.f. stage utilizing a pentode as the
"active" amplifying element is shown
in Fig. 5. Pentodes were often used because they could be constructed to provide a high transconductance while
exhibiting relatively low interelectrode
capacitances. In a tuned circuit, a high
Q means a high L/C ratio. Thus, if
high Q circuits are desired (and they
are, for gain and for fashioning desired
response curves), we should seek to
make L as high as possible. If the "C"
in the picture consists not only of a
fixed, selected value, but also of the
"stray" interelectrode capacitances, we
are immediately limited as to how
"high" we can choose L to be. The need
for a high value of "L" also led, indirectly, to the use of inductive tuning
rather than capacitive tuning for interstage i.f. transformers, for with permeability tuning a wider frequency range
can be covered without resorting to
relatively large variable capacitor
values which would again restrict the
value of L in the resonant circuit.
The i.f. stage illustrated schematically in Fig. 6 shows the use of a transistor as the active device. Notice, that
because of the low input impedance
characteristic of "common emitter"
stages, it becomes necessary to alter
the construction of the secondary of
the interstage transformer. A tap is
brought out near the "bottom" of the
winding to provide a proper impedance
match to the transistor base input and
to prevent "loading" of the entire secondary with subsequent reduction in Q.
S HV R E
overload
Often (though not in this illustration),
even the primary winding is connected
to the previous collector by "tapping
down" on the coil, for pretty much the
same reason insufficiently high impedance at the collector output of the
previous transistor.
Finally, in Fig. 7, we see the use of
an integrated circuit in an i.f. stage.
The "contents" of this tiny chip stagger the imagination (as shown in Fig.
8), for what we see are ten transistors,
eleven resistors and seven diodes. What
you don't immediately see is that not
all these microscopic devices are contributing directly towards amplification. For example, the "triplets"
Q1 -Q2 -Q3, Q4 -Q5 -Q6 and Q7 -Q8 -Q9
each constitute only a single stage of
moderate, though highly stable amplification, while Q-10 and all those diodes
act as a voltage regulator for the rest
of the "innards." These wonderful new
devices enable construction with fewer
external components and, properly employed, they can and are being used in
truly great i.f. designs, but let us not
succumb to the overenthusiastic claims
which state "... equals ten transistors,
nine resistors and umpteen diodes if
discrete components were used." At
least let's understand what is really
meant by such claims. What is not
needed is a return to the days when
tubes were used (often in profusion)
as series dropping resistors, so that advertisers could claim radios having
"more tubes than anybody." (In line
with this, the FTC recently clamped
down on claims made for the number
of "transistors" used in radios. Seems
that solid-state devices used for other
than amplifying or oscillating purposes
were numbered as transistors.
-
Ed.)
&
"pop"
SOLUTION:
adjustable-volume
Unisphere® A
MODEL 585SAV
One of the most ingenious microphones ever designed. The volume control
is right on the microphone
case. Enables the user to
reduce output if audio break-up due to overload
occurs. Also, enables a
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are inaccessible. Model
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vibration a problem?
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list.
write for data sheets:
SHURE BROTHERS, INC.
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Hartrey Ave.
Evanston, Ill. 60204
Check No. 63 on Reader Service Card
AUDIO
63
SEPTEMBER 1968
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1-10VII
REVEALS
TEETEEm
1RU1m4-1-
TEE
m
lG
VV'l{:1L7
1Ru1m4-1-
still considerable remove from the
quality of the best 7%-ips tapes. The
acoustic perspective is the familiar
spaciousness of the RCA Italiana Studio, with microphone placement just
about right to ensure a nice blend of
direct and reflected sound, affording
a
41 KLIR5C4-1URN®
Recorded
Tape
Reviews
BERT WHYTE
NU7'EING BUT
TI-1E mRUmel
Opera in
33/4 ips
good presense and fine definition.
Orchestral/choral/vocal balances are
good; clever use of the voices for stage
movement, not exaggerated, but tasteful and effective. Frequency response
extends to at least 9-10 kHz and the
dynamic range was unusually wide.
Transient response, most always one
of the drawbacks of 3%-ips tape, was
surprisingly good, with bright clean
Verdi: Ernani (Opera in four acts). Leontyne Price, Carlo Bergonzi, Mario Sereni, Ezio Flagello. Thomas Schippers
cond. the RCA Italiana Opera Orch. &
Chorus.
RCA Victor TR38004, open reel,
4 tr., 33/4 ips ($17.95)
The reproduction of
true hound is the sole
purpose of a Klipschorn loudspeaker.
You'll like the sounds you hear from
a Klipschorn only if you like the
sounds that were recorded. It has
no sound of its own. If you're looking
for exaggerated bass, sensational
treble, or dramatic "hi-fi" effects,
don't depend on your sound reproducing system, tell the recording
artists. Strictly speaking, there is no
such thing as "high fidelity;' only
"fidelity" or "infidelity:'
Our speakers are designed and built
for but one purpose-fidelity.
They're built in Hope, Arkansas,
under the personal supervision of
Paul W. Klipsch by a small group
of dedicated craftsmen. They're sold
by dealers who are concerned that
you get a system with fidelity.
KLIPSCH
& ASSOCIATES
BOX 280 A-9
HOPE, ARKANSAS 71801
Please send me the whole truth about the
KLIPSCHORN loudspeaker system. Also
include the name of my nearest Klipsch
authorized audio expert.
Name
Address
City
State
Zip...
Age
Occupation ..
[]Enclosed is $3.50 for a complete set of
17 technical papers on sound reproduction and stereo.
The first complete recording in
stereo of Verdi's Ernani is a resounding success. The cast and their generally superb singing, the conductor,
and the splendid sound combine to
make this one of the top operatic recordings in recent years. Most certainly it is one of Leontyne Price's
most triumphant roles. She is nigh
perfect as Elvira, her voice a fantastically responsive instrument, dazzling
in its beauty, in its power, and in its
sheer eloquence. Such a warm, golden
sound coupled with rock-ribbed control is something you have to hear to
believe. This stunning performance
re -affirms her position of eminence
among today's most illustrious prima
donnas.
Carlo Bergonzi as Emani turns in a
most convincing portrayal; his rich
sumptuous voice and tasteful style are
well suited to the role. Ezio Flagello is
a richly sonorous Silva, and Mario Sereni serves admirably as Don Carlo, albeit with less emotional involvement
than desirable.Even the minor roles are
well cast, using artists of more than
routine ability. Conductor Schippers,
on loan from Columbia, makes an impressive case for his briskly paced,
super -charged view of the music. His
handling of the chorus and his painstaking care with inner balance is masterful. He gets good support in the
excellent playing of the RCA Italiana
Opera orchestra, who are old hands in
the matter of operatic accompaniment.
This is just about the best -sounding
3%-ips tape I have heard. It proves
that careful processing and rigid quality control can make this slow -speed
tape a respectable product, although at
Leontyne Price
cymbals and solid weighty tympani.
Crosstalk virtually absent, hiss low in
level, but pre and post print -through
was in evidence. As you have gathered,
I am much impressed with the virtues
of this recording and I think your ears
will confirm my judgment.
A Brahms Winner
Brahms: A German Requiem. Agnes Giebel, soprano; Hermann Prey, baritone;
Alto Rhapsody: Helen Watts, contralto;
Nanie. Les Choeurs de la Suisse Romande et Pro Arte de Lausanna. Ernest
Ansermet cond. L'Orchestre de la Suisse
Romande London/Ampex LOH90135,
open -reel, 4 tr., 7 1/2 ips ($12.95)
The "Alto Rhapsody" and the rarely
heard "Nanie" are well -performed on
this tape and the sound is quite good.
It is the "Requiem," afforded a superb
performance by Ansermet, that makes
this tape worth acquiring. Ansermet
sets a leisurely pace, stresses orchestral/choral balances and builds to climaxes of massive power. His reading
has great warmth, and many exquisitely
lovely moments, yet he carefully avoids
any excess of sentiment. It is really a
sort of `old-fashioned" performance,
best characterized as grandiose, and
Check No. 64 on Reader Service Card
64
AUDIO
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SEPTEMBER 1968
the great outpourings from chorus and
orchestra are sonically exciting. It is a
performance in marked contrast to the
high -tensioned von Karajan reading,
being closer to the Klemperer recording. Soloists Agnes Giebel and Hermann Prey are excellent; they stand up
well in comparison to the illustrious
Schwarzkopf and Fischer-Dieskau on
Angel and outshine the soloists in the
von Karajan recording.
The sound is splendidly embellished
with all the stereo attributes. Lateral
interplay between voices is very effective. It is possible to easily differentiate
the various choirs in the chorus, yet
they are a well-blended sonic entity.
The acoustics are fairly spacious, miking medium close. Orchestral definition
generally good, chorus quite articulate
except for some infrequent blurring and
diffusion in the fortes. Orchestral/
choral/soloist balances are very good
and dynamic range is wide. The important organ pedal in the third movement
is big and solid. Overall, a thrilling recording with plenty of presence. Hiss,
crosstalk, and print -through are low in
level.
Sterling Pop
What The World Needs Now
Is
Love:
Jack Jones
Kapp/Ampex KTC3551, open reel,
Bogen's new RX200 120 -watt FM/AM receiver.
You buy a receiver for its sound.
Which is why, at every stage in the
RX200 receiver's design, we
listened to it. Through
speakers of every size,
shape, price and quality.
In our factory and in our
homes. Until we were abso-
lation rejection. Naturally, we've
used Bogen's all-silicon modular
design, and included push-but-
ton function selection
and inter-station muting.
And when our chief engineer took the RX200
home for a final listening test,
his wife was happy, too.
"I like lit," she said.
"But I haven't plugged it in yet,"
he answered.
"I know. But it's so beautiful."
The RX200 AM/FM stereo receiver. 120
watts. Only $369.95.At your Bogen dealer.
DESIGNED
lutely happy with its sound.
Because its distortion is low:
only 0.8% at full 120 watt output,
only 0.2% at 110 watts or less. And
its sound is clean and crisp at
every frequency from 10 to 35,000 Hz.
We're equally proud of its performance
as a tuner. Our FET front end gives the
RX200 excellent sensitivity (2.0 microvolts on FM, 75 microvolts per meter on
AM), yet still has 80 db of cross-modula -
Dept. 15-3-9
LEAR SIEGLER. INC.
/ LSi
BOGEN
RCLEN COMMUNICATIONS DIVISION
PARAMUS, NEW JERSEY arcsº
Check No. 60 on Reader Service Card
4 tr. 71/2 ips ($7.95)
As you probably know, Jack Jones
is now an RCA Victor artist. This tape
is presumably the last of his output
on Kapp. As with most of his Kapp
recordings, this is characterized by
top-flight singing and exemplary
sound. Jack splits his chores between
some aggressive "swingers" and smooth
ballads, which I insist is what he does
best and which made (and sustains
still) his reputation. In addition to the
title song Jack sings such familiar
numbers as "True Love," "I Only
Have Eyes For You," "The One I Love
Belongs To Somebody Else," as well
as more modern stuff such as "The
Eyes Of Love," "Yesterday," and similar material. Some intimate, "singin'just-for-you" style, dead -on -pitch,
cleanly articulate vocalizing and masterful phrasing are the trademarks of
this superb entertainer.
First class stereo sound throughout
this tape without much of the usual
pop exaggeration of direction and re verb. One of the most impressive
things is the signal-to-noise ratio .. .
this is one of the most noise -free tapes
I've ever heard. Almost no hiss, very
low pre and post print -through, crosstalk not a factor. Would that all tapes
had such sterling qualities!
It's Crown's model SHC55 high
fidelity stereo instrument with
AM/FM/FM stereo tuner, stereo
phonograph, 30 watt stereo amplifier
and professional type stereo tape
cassette desk. Compact stereo components-a complete tape home
entertainment system, engineered
and manufactured by Crown, the
tape recorder professionals. Super
compact and super attractive in a
rich handsome walnut table -top cabinet. You select the speaker system
that YOU want. Our CPS7's are
Only $349.95.
optional.
Ask about our new Model SHC51/
FM500*, too. This 30 watt, combination stereo cassette recorder and
AM/FM/FM stereo tuner is an industry first! Only $299.95 including
handsome walnut case.
"Not illustrated.
See your local Crown Dealer or write INDUSTRIAL SUPPLIERS COMPANY
755 Folsom Street, San Francisco, California 94107
AUDIO
SEPTEMBER 1968
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CLASSIFIED
Rates: 250 per word per insertion for noncommercial advertisements; 500 per
word for commercial advertisements. Frequency discounts as follows: 2 times,
less 15°/o; 6 times, less 203/o; 12 time s, less 30°/o. Closing date is the FIRST of
the second month preceding the date of issue.
SERVICES
FOR SALE
12" LP's MADE from any half-hour tape
-$4.50-ARG, 341 Cooper Station, NYC
MUSIC LOVERS, background music, con-
10003.
HIGH FIDELITY SPEAKERS REPAIRED
MULTICOREERBIN
AMPRITE SPEAKER SERVICE
168 W. 23rd St., New York, N. Y. 10011
CH 3-4812
PROTECT YOUR LPS-Heavy poly sleeves
for jackets 5¢, Round bottom for records
J
New LP jackets, White 20¢, Colors
25g. Min. order $5.00. LP Supplies, Hill burn, P.O. New York.
31/2¢ ea.
69C
ONLY
CUSTOM RECORDING SERVICE-Tape or
disc recordings made from live or recorded material. High quality. Reasonable
rates. Audio -Tech Laboratories, 2819 Newkirk Avenue, Brooklyn, N. Y. IN 9-7134.
BUY IT AT RADIO-TV PARTS STORES
Check No. 58 on Reader Service Card
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P.O. Box 4398, Chicago, III. 60680
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RENT STEREO TAPES -75¢ week. Catalog.
Art's 16131/2 N. Mariposa Ave., Hollywood, Calif. 90027.
Simple modification
improves Dynaco Stereo 70 (parts $2.00).
Regulated power supply improves Stereo
70 ($15.00). Modification improves PAS -3
(x) ($5.00). Send $1.00 each for instructions. (No kits for last two). David Hada way, 11151/2 Mechanic, Galveston, Texas
77550.
ACOUSTIC RESEARCH, Dyna, Koss, Shure
discount specialists. Write for free catalog.
SCS Corp., 95 Vassar St., Cambridge, Mass.
02139.
Test Instruments
TV Antennas
& Tubes
ALLIED RADIO, Dept. 132
Fast
784-3985.
PERFECTIONISTS:
536
SAVE
M. RETTINGER, Consultant on Acoustics.
Analysis. Room Design. Noise Reduction.
5007 Haskell Ave., Encino, Calif. Tel: (213)
ZIP
Please
Pm,t
FOR SALE
HARPSICHORD: Same as owned by Philadelphia Orchestra and RCA Victor. In kit
form for home workshop assembly, $150.
Clavichord kit, $100. Free brochure. Write:
Zuckermann Harpsichords, Dept. R. 115
Christopher St., New York, N. Y. 10014.
SLIGHTLY USED Tandberg 74B Tape Recorder, Oiled Walnut AR -3 Speakers, AR
Turntable. Make offer to W. R. Foster,
USNAB Coronado, San Diego, Calif. 92155.
tinuous, uninterrupted, from your FM
radio, using new inexpensive adaptor. Free
literature. R. Clifton, 11500-E N.W. 7th
Ave., Miami, Florida 33168.
DISC RECORDING EQUIPMENT: Cutter heads, Recording Amplifiers, and Lathes.
New and used. From Rek-O-Kut to Scully.
Send requirements. Wiegand Audio Labs,
3402 Windsor Rd., Wall, N. J. 07719.
for money saving stereo catalog AM and lowest quotations on your individual component, tape recorder, or system requirements. Electronic Values, Inc.,
200 West 20th St., New York, N. Y. 10011.
FREE! Send
FREE
CATALOGS Broadcasts, Sound Tracks
of Thirties. ARG, 341 Cooper Station, New
York City 10003.
DECCA/LONDON FFss Cartridges, individually checked, guaranteed. Creighton
Audio Labs., Haven Place, Linden, N. J.
07036.
TAPE RECORDING MAGAZINE-Enthusiasts monthly magazine for amateurs and
professionals. Send $3.75 for 1 year sub-
scription to 14-18 Holborn, London,
E.
C.1.
England.
TAPE
RECORDER SALE. Brand new na-
tionally advertised brands, $10 above cost.
Amazing discounts on stereo components.
Arkay Electronics, 1028-H Commonwealth
Avenue, Boston, Mass. 02215.
SCULLY Professional Tape Recorders, from
1 to 12 tracks, complete recording studios
available in prewired console cabinets
starting at $8,000.00. 70°/o financing. WIEGAND AUDIO LABORATORIES, 3402
Windsor Rd., Wall, N. J. 07719.
MAGNECORD 1024, 1/4 track, 33/4 and
71/2 in./sec. Tape Deck. New Sept. '67. Excellent Condition. 36 81/4 reels in boxes.
Best offer. Steve Shepard, Box 4302, State
College, Miss. 39762. Phone 601-323-2756.
SCOTCH
RECORDING
TAPE,
lowest
prices. Tape Center, Box 4305, Washington, D. C. 20012.
Check No. 66 on Reader Service Card
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SEPTEMBER 1968
condition.
KG -415. Excellent
$220. Albert W. Stump, 610 S. 13th Ave.,
Maywood, III. 60153.
KNIGHT
KLIPSCH selected SAHF, $16; Ampex 601,
$190; RCA 44BX mike, $39; Marantz pre amp 7, $110; Scott 121 preamp (mono),
$65. Tom Groom, 324 N. Spring, Murfreesboro, Tenn.
VARNER'S PIANO SHOP. In business over
Impeccable reputation and
25 years.
knowledgeable audio advice. Low quotes
with friendly, sincere service. Special: two
AR tax speakers, one ARXA turntable, one
AR Model A amplifier, one Shure V15
Type II cartridge, and Sherwood Model
S-2300FET AM/FM tuner, $620, not including freight. Varner's Piano Shop, Box 215,
Delaware, Okla. 74027.
ROBERTS 770X RECORDER. New Condition, $275. L. Wannamaker, 2407A Fan-
tasia Cir., Huntsville, Ala. 35805.
JAPAN PRODUCTS SERVICE. US $5 per
inquiry or US $30 yearly. Intercontinental,
CPO 1717, Tokyo, Japan.
WANTED: Marantz electronic crossovers.
Send price and condition. AU8-1.
BERLANT model BR1 or BR2 tape recorder;
also EV 649B & RE -15. Ray Kline, Mars, Pa.
16046.
get
the
KLIPSCH CORNWALL or Heresy. Marantz
7T,15. Janszen 350 woofers. Sony electronic xover. Tom Groom, 324 North
Spring, Murfreesboro, Tenn.
WANTED: Stephens 108 or 216 Driver and
8 compartment or segmented horn for
same. 800 cycle. M. E. Brown, 1032 Lee
Ave., San Leandro, Calif. 94577.
NEWS FREE
TRADE NEW McINTOSH C-24 (immaculate; under warranty) for tube C-22 if in
equally superb condition. Foster Action,
Grinnell College, Grinnell, Iowa 50112.
WANTED: Stephens P-35 Driver, 16 ohms;
214 Hi-freq. Tweeter; 103 LX Woofer.
A. Fisher, 723 N. Oakhurst Dr., Beverly
Hills, Calif. 90210.
WANTED: JBL 150-4C, 275 & 375 units.
Give serial number, condition & price.
McIntosh Solid State
MC 2505
POWER AMPLIFIER
RCA 77 -DX MICROPHONES. Used, with
covers and RCA stands. Pair, $200. (New
77's cost $210 apiece.) T. J. Immel, 1524D
Spartan Village, E. Lansing, Mich. 48823.
(517) 355-3115.
AS18-1.
Matched JBL 375 drivers with Hartsfield
horns. Western Electric 594A drivers.
Wanted: JBL D131, 130B, 075, LE8T,
EV 18WK. Paul Lambidakis, 7213 Cedar
Ave., Takoma Park, Md. 20012.
CHIEF AMPLIFIER ENGINEER. One of the
largest manufacturers of amplifiers and
guitars is in need of an engineer to head
up its solid-state operation. Reply held
confidential. Box AS8-2.
KUHN 361C AUDIO EQUALIZER. $32 each
like new. S. Drelinger, 1436 Lexington
Ave., New York, N. Y. 10028.
EXPERIENCED HI-FI, HAM, CB salesmen
wanted. J. S. Draper, Lafayette Radio Electronics, All Cape Shoppers Bazaar, Rt. 132,
Hyannis, Mass. 02601.
addition, you'll receive absolutely free a complete up-todate FM Station Directory.
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send to: William & Diffay, 19 W. 020 13th
St., Lombard, III. 60148.
HELP WANTED
MANUFACTURER sought for patented,
revolutionary tone -arm design. Box AL8-2.
-
"FOR SALE"
Garrard MK -40 turntable
with Lafayette 100 -watt Stereo Tuner in
Walnut cabinet, only $225. Call 617-686591 (Mass.)
KLIPSCHORN, Tannoy, Altec, Rectilinear
AR, Inc., Wharfedale, Dynaco, Sherwood,
Kenwood, Teac, Uher, Garrard, Benjamin,
Superior Sound, 621 5. Main St., N. Syracuse, N. Y. 13212.
EQUIPMENT WANTED
WANTED: New or Used Grado MARK IV
stereo cartridge. Robert Bezak, 303 Mapeat
Lane, New Castle, Pa. 16101.
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19
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