db Magazine - American Radio History
SOUND ENGINEERING MAGAZINE
MAY 1976
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IN THIS ISSUE:
The
Digital Delay Line Revisited
A VSO Switching System
Digital Clocks & Things
S1.00
Next best thing
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Shure's new headset microphones are coming through loud and clear. With
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In
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Manufacturers of high fidelity components, microphones, sound systems and related circuitry.
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Rock and roll is in it's third
decade and there are mountains
of blown diaphragms and
discarded speaker systems
as evidence of the difficulties
loudspeaker manufacturers
have had in meeting the
challenge. The SP1 was
designed and tooled by a new
loudspeaker company dedicated
to solving the basic difficulties
of high level sound
reinforcement in order to meet
that challenge.
Our two -way is a compact,
powerful, reliable, high fidelity
loudspeaker with dispersion and
power response so uniform that
the "sound" of the system is
stable in different environments.
The SP1's multi -flare
radial horn is the most
significant advance in the
control of high frequency
dispersion since the invention
of the radial horn half a century
ago. Undoubtedly the design
will become the industry
standard.
The real marvel of the SP1
system, however, is the
Model 22 Compression Driver.
We have been producing it since
August 1975 demonstrating
that it is possible to combme
adequate high end
response (13 KHz),
efficiency (30% midband),
high power handling (40 watts
pink noise 8 hours continous),
reliability (6 forms of on-line
analysis plus listening),
and good sound in a
compression driver. Until "22"
a high performance 2 -way like
the SP1 was not possible.
The low-end of the system is
provided by a 15" horn loaded
cone speaker covering the
range of 60 - 500 Hz.
The extensive Q.C. system
devised for the driver has been
expanded to allow the same
scrutiny of the SP1.
Some strong statements have
been made here, but we know
we can deliver. The demand is
so great for a system with the
SP1's performance that
our dealers have ordered over
1,200 units (as of Dec. 1,'75)
based on word of mouth from
the few people who have heard
samples from pilot production.
The SP1.
AN ALTERNATIVE TO
THE ESTABLISHED WAY
$499.50* Soon at your
Peavey Electronics Dealer.
Peavey Electronics, Corp.
PO Box 2898
Meridian, Ms 39301
*suggested retail
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STL Offers The Most
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looking for precision test tapes.
look no further. STL can serve all your needs with
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and find out where your system really is.
0_0
THE EDITOR:
I am interested in obtaining schematics of electronic effects for guitar
-such as octave box or phase shifter.
I would appreciate any available in-
formation.
MICHAEL FATH
Ri 2, Box 198
If you are
Write for a free brochure and the dealer in your area.
Distributed exclusively by Taber Manufacturing & Engineering Co.
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THE EDITOR:
I would like to take exception to a
portion of Pat Finnegan's otherwise
excellent article on f.m. stereo separation in the March, 1976 issue.
Two channels with different response curves, even if out of phase,
will not, in fact, affect channel sepa-
ration in a properly operating f.m.
stereo transmission and receiving system. Once the two channels enter the
matrix in a stereo generator, you must
stop talking about two channels. Only
after the f.m. signal has been dematrixed in the receiver can you start
talking two channels again. If there is
a problem in the bandpass of the
stereo generator, transmitter, or receiver, separation may indeed be affected. But remember, we are not talking about two channels; rather, a composite signal containing L
R and
L
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Let us imagine two channels with
non -identical response curves. One has
a flat response from 50 Hz to 15 kHz
The other has no response at all (i.e.
it is shorted out). In the transmission
system L + R will equal L - R and
the receiver will decode just one channel. Separation is good.
Changes in channel phase relationships from the original will indeed affect what the monophonic (L + R)
listener hears and will indeed alter
what the stereo listener hears, perhaps
as apparent poor separation, but actual measured separation of the system should not he affected.
I believe Mr. Finnegan is confusing
the L and R signals in the audio lines
with the L
R signals in
R and L
the transmission system.
{
DAVID E. DOUGHTY.
Chief Engineer
WTLB
Utica, N.Y.
Mr. Finnegan replies:
There can be a big difference between measured separation and the
separation (or lack of it) that we hear
on program material which has passed
over our station. As broadcasters, we
must also be concerned for this pro-
A
PHOENIX
ENTERPRISE
COMPANY
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gram separation. The left and right
AUDIO channels ahead of the stereo
generator can have considerable effect
on the separation of this program material even though our measured separation of the system is good. Our sine
wave method of measurement which
uses only one channel at a time cannot adequately measure the effect of
the audio channels on program separation. About the only real method we
have available is a critical listening
test on a good receiver.
Good separation at the output of
the stereo generator requires that the
generator he adjusted and balanced
properly. This is done with sine wave
(usually 400 Hz) at a fixed amplitude
to one and then the other inputs of
the generator. The inputs are balanced, the SUM and DIFFERENCE
signals balanced and separation controls adjusted for best separation. Under these test conditions, the response
curve of either channel will have little
effect, for as Dave says, shorting out
one channel is immaterial to the measurements. The stations left and right
audio channels are really extensions of
the generator's left and right inputs
and should he included in the balancing and adjustment process of the setup procedures.
During programming, however, a
different situation exists. Now both
left and right audio channels are very
much active and at the same time.
Phase and amplitude discrepancies of
these channels will affect and change
the original signal as it appears at the
matrix and poor separation can result.
Or we may look at this in a different
way: since our generator was balanced
against fixed input signals, then when
program signal voltages appear on the
audio lines in those areas of the hand pass where the discrepancies occur, the
stereo generator is now actually unbalanced as far as these signal voltages are concerned and the separation
can suffer. This poor separation of
program signals can occur in spite of
the fact that we have measured good
separation of the system with sine
wave signals.
Copies of db
Copies of all issues of db -The
Sound Engineering Magazine starting with the November 1967 issue
are now available on 35 mm. microfilm. For further information or to
place your order please write directly to:
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FREE LITERATURE
CONSUMER FRAUD BROADCASTS
A circular describes 2'2 minute
broadcasts under the overall topic
"Have You Been Taken Lately?" available to broadcasters. Mfr: National
Broadcasters Group.
Circle 94 on R. S. Card.
CITIZEN'S BAND CHANNELS
A pocket -sized pamphlet lists most
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Mfr: Siltronix.
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INVERTER SCRS
Two new 250 amp rms fast- switching inverter scrs are described in this
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ELECTRONIC EYELETS
28 questions regarding electronic
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Inc.
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TELEPHONE COUPLING
TRANSFORMERS
New telephone coupling transformfor interconnect to the
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ENGINEERING SEMINARS
A 6 -page brochure gives details of
three -day nationwide sound engineering training seminars. Mfr: Synergetic
Audio Concepts.
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EXTENSION
SPEAKERS
Application and technical information regarding six models of environment- resistant loudspeakers is contained in this data sheet. Mfr: Atlas
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RAM PROGRAMMER /CONTROLLERS
An estensive booklet details specifications of digital timers. Mfr: ESE
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HORNS, SPEAKERS, DRIVERS
Horns, speakers, drivers, and sound
columns with complete specifications
are described in a six -page condensed
catalog. Mfr: University Sound.
Circle 83 on R.S. Card.
WIRE AND CABLE
Specs, illustrations and applications
for wire and cable, insulation, cord electronic accessory products
a 48 -page catalog. Mfr:
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sets, and
are covered in
CALIBRATING DEVICES
This technical paper reviews the
various methods for calibrating accelerometers. microphones, and hydro phones. Mfr: B. & K. Instruments,
Inc.
Circle 85 on R.S. Card.
INSULATED WIRE AND CABLE
A data sheet includes description,
qualifications. performance characteristics, photographs and specifications
of Maser wire and cable insulated
products. Mir: Addington Laboratories, Inc.
Circle 95 on R.S. Card.
PHASE RESPONSE
A six -page engineering application
reports on "Phase Response Characteristics of a Butterworth Filter." The
report contains illustrations and graphs
for calculating gain and phase shift
through a high -pass, low -pass, band pass or hand- reject filter. Mfr: Krohn Hite.
Circle 87 on R.S. Card.
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25 -27
Contact: B &K Instruments, 5111 W. 164th St.,
Cleveland, Ohio 44142. (216)
267 -4800.
27 Mobile Radio Market Seminar.
New York City. Contact: Frost
& Sullivan, 106 Fulton St.,
New York, N.Y. 10038. (212)
233 -1080.
25 -27 Synergetic Audio Concepts
Training Session, Chicago, Ill.
Contact: Don Davis, P.O. Box
1134, Tustin, Ca. 92680. (714)
838 -2288.
28 -31 Sound and Vision '76. Birmingham, England.
tics.
JUNE
B & K Seminar: Industrial
Noise Control, Contact: B &K
Instruments, 5111 W. 164th
St., Cleveland, Ohio 44142.
(216) 267 -4800.
8 -10 Synergetic Audio Concepts
Training Session. Columbus.
7 -11
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92680. (714) 838 -2288.
8 -11 Communications '76, Brighton. England. Contact: British
Information
Services,
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Third Ave., New York, N.Y.
10022. (212) 752 -8400.
8 -11 Information Retrieval Exhibition, London, England. Contact: British Information Services.
International Audio- Visual
Aids, London, England. Contact: British Information Services.
21- Audio Recording Technology
July 9 Workshop, Brigham Young
University. Contact: Special
Courses & Conferences, Brigham Young University, Audio
Recording Technology Course.
242 HRCB, Provo, Utah
84602.
8 -11
Copies of all issues of db -The
Sound Engineering Magazine starting with the November 1967 issue
are now available on 35 mm. microfilm. For further information or to
placa your order please write directly to: University Microfilm, Inc.
300 North Zeeb Road
Ann Arbor, Michigan 48106
All 1/3 Octave Levels Are Not Recreated Equal!!!
That is why professionals equalize
recording studios, auditoria and
special masking installations. But the
job of equalization must not be left to
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frequency -amplitude unbalance.
Therefore, precision acoustic instrumentation must be used.
Equalizing procedures require portable instruments which can be pow-
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Instruments
/LIB
Number 99 in a series of discussions
by Electro -Voice engineers.
o
O
NORMAN H. CROWHURST
HORNS
OF
Impulse response
PLENTY
Frequency response
amplitude (dB)
D. (DON) B. KEELE, JR.
Senior Engineer
Loudspeakers
venical scale
x
8
frequency (kHZ)
..
1
vertical scale x 64
time (res)
frequency !kHz)
phase
Figure
1.
Cumulative decay spectra.
In last month's column, we talked
about loudspeaker testing and briefly
outlined the problems of taking a
meaningful frequency response, indicative of how the unit sounds. The traditional method analyzes the performance of the unit in terms of amplitude
and phase, measured against frequency,
as the independent variable.
There are two things a little unrealistic about this, both related to the
fact that a sine waveform is used.
First, in everyday life, a sine wave is
not representative of most of the
sounds we hear. Secondly, by using a
sine wave, we commit ourselves to a
purity of that waveform, any departure from which represents distortion.
Now, it is true that any departure
from the pure sine wave does introduce components that audibly alter the
sound. And, unless the spurious frequencies have a precise harmonic relationship to the test frequency, a quite
small departure from the original sine
waveform makes an audible difference.
The main problem with using a sine
wave for testing loudspeakers in their
natural acoustic environment (and nobody listens to program in an anechoic
room, does he ?) is that a pure sine
wave must also have duration, for the
response to it to be measurable.
This is one of the problems that
those who have tried to present a frequency response as a repetitive display
will have encountered. If you hold frequencies down at the lower end, say,
20 hertz, for long enough to enable
the system to produce a reading at
that frequency, you will take up considerable time taking these readings.
True, the higher frequencies can be
read more quickly. But the time necessary to read the low frequency response makes presentation in this form
a slow business.
Figure 2. 110 mm. moving coil bass/
mid -range unit in a 7 liter closed box.
That is not all. When you hold each
frequency long enough, or change the
frequency slowly enough, to get good
readings, you will also be sustaining
the sine wave radiated long enough to
build up standing waves, which make
the result spurious for a different
reason.
Some practical program material
may have notes that last long enough
to allow standing waves to form. But
the way we hear the program is more
apt to resolve the sound differently
from that. What we hear is the initial
impact of the waves, while any buildup of standing waves tends to be at
least partially disregarded, as part of
the reverberation that is characteristic of the listening room.
TIME DOMAIN
While it is true that our hearing
faculty does seem to analyze the
sounds we hear on a frequency basis,
it also seems that the response is quite
different from, say a wave analyzer.
Our hearing also analyzes what we
hear in the time domain, so it can
more readily separate direct sound
waves from reverberant build -up.
The human hearing faculty is a
highly sophisticated system! Because it
relies much more heavily on time domain information than any electronic wave analyzer so far built, many
have sought to find a way to use time
domain testing of loudspeakers.
As any mathematician can tell you,
a waveform can be analyzed in one of
two ways. Either it can be resolved
into a number of frequency components, of varying amplitude and phase,
or else it can be analyzed in terms of
just varying amplitude against time.
This can then, perhaps, be reduced to
a succession of time constant growth
and decay curves.
A few years ago, if you were to ask most
sound practitioners questions about horn design, each answer would probably be much
like the next. A set of assumptions about the
value of hyperbolic and exponential horns
had taken full root. And products available
to the field reflected this unanimity of opinion.
Certain shapes and sizes were "best" and
differences in horn design were almost exclusively related to materials and minor variations
in loading plug and throat characteristics.
Recently, however, intensive restudy of basic
horn shape options has led to some new conclusions at E -V. The study aided in the design
of new horns (patent pending) with performance differences that can provide meaningful
improvements in sound quality if properly
utilized.
One study concentrated on determining optimum horn mouth size. Popular belief suggested that "the larger the better" but our studies
revealed this to be untrue. When horn mouth
size is optimized, internal reflections are significantly reduced compared to both larger
and smaller horns. The result is higher acoustic efficiency, especially near and even below
the cutoff frequency.
Horn flares also underwent intensive study,
with some fascinating results. It was found
that the polar lobes typical of most exponential and multicell horns could be virtually
eliminated with a multi -flare conical section
horn. The conical flare rate is doubled near
the mouth to eliminate mid-range beaming
typical of exponential horns. The conical
flares are combined with an exponential flare
near the throat to maintain good response
down to horn cutoff. In this new class of
horns, constant response throughout the radiation angle, plus uniform beam width at all
frequencies is achieved without the complex
structure and loading plug problems required
by multicell types.
With this new class of horns, plus appropriate
drivers, the sound industry enjoys the use of
more precise tools for the control of radiated
sound. The products assist in more predictable system design, lessen installation problems, and meet the highest performance
standards. And the concept has been proven
in such recent installations as Pontiac Stadium, Disney World, and Yankee Stadium
among others.
This continual challenge of basic assumptions
has long been a tradition at E -V. From the
unique CDP dual -horn speaker -still valid
decades later
the current technology of
the Sentry speaker, our products reflect a
willingness to upset favorite notions when
they stand in the way of industry progress.
-to
Elecfroi/oiceù.
0
gukton company
Dept. 563BD, 686 Cecil Street
Buchanan, Michigan 49107
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theory
&
practice (cont.)
Any particular waveform, however
complex, will have a unique representation in each form. Thus it would
theoretically be possible to translate
one to the other, either way. But as
we have said before in this column,
while a video waveform is vitally dependent on its shape -its amplitude
variation in the time domain -an
audio waveform has always been believed not to matter, as far as its shape
is concerned, so much as its precise
frequency content. Are we now saying something else?
No, not exactly. In the sense that
shape was unimportant to the sound
of the wave, provided the frequency
content is unchanged, that is still true.
The main trouble is, we tend to think
in "either/or" terms. If phase doesn't
matter, then why bother with it?
Phase, in the order that can occur
along the propagation line of a wave,
cannot matter, because the waveshape
will vary at every point, measured
spacially along the wave. At no two
points, will the wave have the same
shape.
We in the West welcome
Sparta was asked, "Can you make a console which does more, in
less space, better, than you've ever built before ?"
the 3000
Our response was the Western double -barrel above
Series consoles!
Both the Models 3310 Mono and 3410 Stereo Consoles are all
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FREQUENCY CONTENT
But it will have the same frequency
should have -instant by
instant. If a plucked tone, for instance,
starts very harmonically rich, and settles into a tone with dominance of
fundamental and lower harmonics, this
time varying relationship between the
frequency content will also be unchanged along the propagation line of
the wave, although the waveshape will
not be the same at any two points.
content
-or
The point to realize is that the wave shape at every point must be one possible variation of the same time -varying frequency content. Thus although,
in one sense, phase will vary, and in
varying, does not change the characteristic of the sound, in another sense,
the content of the wave, as regards
frequencies present, and in what amplitude, does not vary, at any instant,
along the wave.
To use a simple example, much
simpler than you would ever encounter
in an actual program, suppose a sound
consists of fundamental and second
harmonic, both of which start suddenly, at the same instant. Where the
wave originates, let us say, both waves
start up from the zero line at the same
instant.
The fundamental will travel at the
speed of sound, as will the harmonic.
In quarter of the fundamental's period,
the harmonic will have moved through
half its period. So the phase will now
be different. But at all points along the
path of the outgoing wave, the two
will start at the same instant in time,
regardless of the momentary phase
relationship.
After the initial wavefront moves
out, two kinds of thing can happen.
The source of sound may change its
composition, so that the two component frequencies do not decay at the
same rate. Or, standing waves can
build up, due to the acoustic environment of the room.
If you place a single pressure microphone at some point in the room, it
is not easy to separate these effects.
You pick up a composite wave that
has varying amplitudes of the component frequencies due to both causes.
But your hearing faculty can tell the
difference. It can virtually ignore the
variations caused by the build -up of
reverberant energy, standing waves,
while being quite conscious of the
savener9Y
changing composition of the direct
sound.
It seems fairly obvious that our
judgment of loudspeaker performance,
as opposed to its measured response.
is based on the apparent realism with
which it can convey to us the content
of the original program.
What we have been saying about
modification of the content of the wave
with time and space, could apply
equally well to sound from an original
performance, say an orchestra or a
small group, or to reproduction of
such sound by a loudspeaker. Our
impression of realism depends on how
well the second replicates the first, as
judged by our hearing. That is the
catch.
FUNCTION OF THE
LOUDSPEAKER
The loudspeaker can do some of the
same things to sound that the other
two causes can. In short then, it can
modify either the apparent character
of the original sound source, or the
effect of reverberation or, more likely,
both. And virtually none of this capability is taken into account when you
take the frequency response of a loudspeaker in an anechoic room. If its
average output of energy, by the time
it
has reached a steady state at each
A67...
frequency measured, is the same at all
frequencies measured, it looks like a
good, "flat" loudspeaker.
On actual material, our ears may
tell a quite different story. This has
been realized for a long time. The
first attempt to do something about it
was square wave testing. Next came
tone burst testing. Both seemed to
have some validity for testing ampli-
The important thing is that it gives
information on both a frequency and
time base, frequency being shown
from left to right, and time from
back to front, the response being
shown upward. It gets closer to telling
us something about how it will sound,
because it uses a computer, with
Fourier transforms, to generate the
information from data obtained from
fiers, but became almost meaningless.
when a transducer link, such as a
loudspeaker, was included in the test.
some 500 impulses, at intervals long
enough to allow the response to die
down about 60 dB.
Anyone conversant with this kind
of measurement will know that measuring response over an amplitude
range of 60 dB is going to run into
DIGITAL TESTING
Nov, another form of testing has
come into the picture and initial work
with it shows great promise. This is
the application of digital techniques.
We show here, courtesy of KEF Electronics, of Maidstone, England, a
comparison of three forms of test on
the same unit.
At top left is a plot of decay spectra
to an impulse signal. The response is
successfully amplified, to get more
detail of the "tail." At top right are
amplitude and phase responses of the
same unit. Then below is a 3- dimensional plot of cumulative decay spec tra.You will see that this gives much
more information than any of the
other forms of presentation.
noise problems. The average anechoic
room is not good enough. A better
place is outdoors, preferably at the top
of a high tower, and in a locality well
away from airports and other sources
of noise.
Then, of course, the prevailing
source of noise will be the birds singing! Whoever would call that noise?
But, seriously, averaging over some
500 impulses will reduce incidence of
bird sounds at any particular point on
the decay curve, by at least 54 dB,
which means that quite meaningful results can be obtained, in spite of the
birds!
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Circle 24 on Reader Service Card
www.americanradiohistory.com
o
0
the sync tads
For those who were fortunate
enough to miss the October 1975 Sync
Track, I offered some ill-chosen words
about some of the less-than -glorious
guitar amplifiers that sometimes show
up in the recording studio. When the
amp is really gross, the engineer may
perhaps in desperation
suggest
"What about using an acoustic guitar?" That snappy bit of snide humor
prompted the following letter from
Dennis Melton of MDM Communications in Wilmington, Delaware.
I am writing to comment on your
discussion, What About Guitar Amps?
Your first deduction "What about using an acoustic guitar?" really threw
me. You must realize that a musician
usually chooses the type of instrument
carefully and for artistic reasons,
whether it sounds dirty or not. Very
few musicians wish to change the
sound they've worked hard to get, on
the day of recording. I agree that
grounding problems should be investigated first, but let's not alter the musician's sound by asking him to use a
direct box or an acoustic guitar. My
suggestion would be to use a noise
gate, and the engineer's talents with
the fader during the mix. Also, in
many cases, the guitar and other instruments on the tape will mask the
hum.
I feel that musicians using electronic
equipment should be educated to the
ways of getting a clean sound, for
they can certainly distort it, beginning
with a clean sound. The reverse rarely
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-
works.
I would appreciate any feedback
on my comments.
I've really got mixed emotions about
what to say. After almost every other
sentence, I want to remark, "You're
right, but . . ." For instance, about
that musician who chooses his instrument carefully and for artistic reasons.
I think there's a double negative
tucked away in there somewhere. If he
chose it thusly, it wouldn't sound dirty.
Or at least not all the time. With all
the special effects controls at rest, the
instrument should sound clean, clean,
clean. If it doesn't, the artist should
buy another axe, or get the one he
owns fixed. Then, and only then, he
should come into the studio and-with
all the fuzz, wah -wah, tremolo and reverb he can carry- create his "sound."
But he should begin with a decent instrument, one that hums, buzzes and
whistles only on command. The perpetually dirty instrument has no more
Circle 25 on Reader Service Card
www.americanradiohistory.com
excuse for existence than the dirty
console or tape recorder, and its user
has no right to call himself an artist.
WHEN AN AMP GOES SOUR
Of course, this is the real world, and
sometimes an amplifier goes sour
without warning. It can happen to a
musician or to an engineer. The pro
makes the best of the situation by
whatever means are available, and
practical. This might mean using a
direct box, putting in a noise gate, or
gain riding. But in this context, all of
these devices are crutches, used in an
emergency situation. When the engineer is forced to use them to salvage
an otherwise intolerable sound, there'll
be neither time nor equipment left for
creative recording.
"Very few musicians wish to change
the sound they've worked hard to get,
on the day of recording." That's true
enough, if the musician has only one
sound in his repertoire. However, the
true artist uses his ears to evaluate his
sound in context with everyone else's,
and is ready (and able) to change it
when that becomes necessary. This
may be for an artistic reason or because his amplifier goes beserk. In the
latter case, I think the pro would opt
for an acoustic guitar rather than hope
that the guitar and other instruments
on the tape will mask the hum. As
for getting the best sound possible under normal circumstances, Mr. Melton
sums it all up by saying that musicians should be educated to the ways
of getting a clean sound. For that matter, so should engineers.
AND SO TO LITERATURE
Speaking of education, I've
got
another book to review (How's that
for a smooth transition ?)
HOW TO BE A RECORDING
ENGINEER, by Phil York. Attainment Research Books, $6.95.
If that title doesn't raise your suspicions, you're much too gullible. For
surely, it must take more than $6.95
to become a recording engineer. My
mind wanders to other titles in an
imaginary series of "How to" books:
a Brain Surgeon
a Crooked President
a Millionaire
$13.50
$ 5.98
$27.50
a Nuclear Physicist
$ 9.75
But you're a trusting soul, so you
order the book. Surprise! It's a pamphlet of 28 pages, stapled into a blue
paper cover. The cover itself counts
Be
Be
Be
Be
for four of those 28 pages.
Inside, the information ranges from
misleading to interesting to outrageous, with a little comic relief here and
there. For instance,
/ can tell you with certainty that
its not necessary to spend years "getting into" the business . . . I've personally tutored intelligent candidates
from scratch -less than a year later
they were working full time turning
out records and jingles. It could be
done in a couple of months, but who
has the tinte or facilities for that?
Long ago, before Bob Newhart
married Suzanne Pleshette and became a psychologist. he used to do a
monologue about putting an infinite
number of monkeys in front of an infinite number of typewriters. The idea
was that, due to the law of averages,
sooner or later one of them would
turn out some great literature. Sure
enough, one day one of the monkeys
wrote, "To he or not to he, that is the
gezuornigplatx"
That was the end of the skit. But
now that Newhart is finished with that
chimp, let's give him a contract to
write a monthly column for db Magazine. What are the odds that he'll
ever turn out anything worth reading
again?
Of course, people are smarter than
monkeys (sometimes). so let's now
take an infinite number of eager beginners and put them in front on an
infinite number of consoles. We'll also
buy each one of them a lottery ticket.
Sure enough, one of them will eventually turn out a hit record, and one
will win a lot of money. But no one
will hail the lottery winner as a financial genius. Neither was that monkey
great writer. And how would you
rate that eager beginner who happened
to be in the control room the day a hit
record was born? if you want to think
of him as a great engineer, go right
ahead.
If you want to become a recording
engineer, Mr. York advises, "If you
are starting from near scratch and
have almost no experience with audio
equipment, the very first thing to do
is to buy a very good electronic or
audio dictionary." Also, it is handy to
have played an instrument and done
some wiring and soldering.
I suppose he's right. There are
many who have gotten launched in
just such a way. But i think those who
are seeking guidance in entering such
a relatively small and highly competitive field as recording shouldn't be
misled into thinking that all they need
is a book, a soldering iron, and some
music lessons.
There is a five page section entitled
How I Entered, in which York describes his personal experiences since
he first visited a small studio in 1959.
It's very interesting, and the author's
good humor shows through, but it's
got nothing to do with how to be a
recording engineer.
Next come some interviews with a
few recording engineers. Here's a little sample:
Q. Did you go to any of the trade
schools that are available for this?
A. No, 1 was lucky enough to get the
experience without going to any
schools. That's what the schools
try to give you isn't it?
Engineer S. F. describes his natural
gifts; 1 can hear things nobody else
can
can pick out something and
figure out how they did it in the studio
. 1 know every EQ setting on the
console just by listening to the record.
... i
.
.
No comment.
In the section, Setting up for a Session, Mr. York offers this bit of advice, There is a good reason to store
your tape tails out
take my word
for it. Besides, if you don't, many people will think you don't know what
you're doing.
In the section on schools, he says,
In case you want to gain some skills
before attacking the joh problem, you
may want to check the following
schools. The first one has branches all
...
over the U.S.A.
Institute of Audio Research
64 University Place
New York, N. Y. 10003
Well, the address is right, but everything else isn't. Skill is the ability to
do something well. You con 't get that
in school; not at the Institute of Audio
Research nor at any other school. You
might get an education, but you'll
have to develop the skills yourself,
after graduation. Also, the school with
branches all over the U.S.A. is the
Recording Institute of America, not
the I. of A.R.
For an informative book on what
microphones to use where, I recommend "Microphones: Design and Application."
Wrong again! Burroughs' microphone
book doesn't have a word to say about
what microphone to use where. In
fact, he took very great pains to avoid
any mention of specific microphones,
since that aspect of microphone usage
is entirely up to the taste of the user.
And finally, the correct address for
Stax SRX -III is quite simply the
finest sound reproduction system you
The
can buy. Period.
Much better than any speaker system at
any price. Literally the standard for
"other" headphone manufacturers.
Compare the facts you can measure: flat
frequency response from 25 - 30,000
Hz (± 1.5 dB): distortion is essentially
unmeasurable.
Now compare the facts that really
matter. The SRX -III is entirely hand assembled and evaluated by the family
company who created the first electrostatic headphone. A company dedicated
to research
to ultimate sound. So
every SRX is the product of detailed
effort. Even the low mass diaphrams
both by elecare individually paired
tronic testing and by listening.
-
-
Listen to an SRX system with program
material you "know ". You will be in the
front row
the same room
the recording studio. You will hear perfection.
The truest, clearest, most transparent
reproduction ever possible. A reality
now at audio dealers nationwide.
-
-
STAX
Backed by American Audioport, Inc.
909 University
Columbia, Mo. 65201
Billboard Publications' International
Directory of Recording Studios is 1515
Broadway, New York, N.Y. 10036.
(It costs $10.00)
Ironically, there is some good advice interspersed in all of the above
nonsense. In fact, I suspect that Phil
York is indeed well- intentioned, but
that Attainment Research needs a
good copy editor. Although, at $6.95,
it makes one wonder!
Circle 26 on Reader Service Card
www.americanradiohistory.com
DON'T MIX THE GOOD
SOUND WITH ANYTHING
BUT THE BEST
o
o
sound with
If you expected to read something
in this column this month about video
tape editing as indicated in last month's
"Things to Come" . . April Fool.
(Well, almost!) When work was first
begun on this column, after a short
hiatus last month, the material was
going to include information on video
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01 01 01 01
Circle 27 on Reader Service Card
tape editing and video projection with
some details on a few of the pieces
of equipment that have become available in the recent past. The subject
became voluminous in material and
will be included in a near future column. Meanwhile, so many other
things have been happening, also
worthy of your awareness, that it
might be better to catch up on a thing
or two. Since it's spring, how about
video fun for the home?
For instance, you might already be
familiar with the latest from Sony
the Betamax system for home t.v. recording.
Betamax was launched some time
ago when Sony decided that the UMatic system with which they had all
but inundated industry, education, and
training facilities would not reach into
homes. That market seemed to need
something different. The video disc
was a hot item and just about ready
for marketing, but Sony's idea was to
stay with tape.
Two other giants had recently tried
to introduce a video tape system for
the home-Sears, with Cartravision,
and RCA with MagTape. You may recall that the Sears system was a complete package with the deck and t.v.
set in one cabinet. This meant that
the owner of a color t.v. set had to
buy another one in order to have the
deck. At the time, the electronic system in the tape deck was not compatible with standard t.v. sets and required its own special unit to play
video material. Whether or not for
this reason, there was non- acceptance
by the public, and Sears decided not
to continue with the unit. This all
came about shortly after Sony started
pushing its 3/4 -in: U machines which
could stand alone and feed into almost any standard color set.
After its first venture with SelectaVision, a film type of material, RCA
began work on the MagTape system
which would utilize magnetic tape, the
up- and -coming medium, made popular with the realization that it was
necessary for the public to be able to
record as well as play back previously
recorded material. After much devel-
-
www.americanradiohistory.com
images
opment and investment, RCA decided
not to continue with this approach.
and to return to a playback -only type
of home device. They felt that the
tape unit pricing would probably have
to be higher than anticipated, and
went to work on their video disc instead.
Sony, with its know -how in development and marketing, decided that
this was the time to get its product
into the home. The system they developed used, until now, a total package with the tape recorder /player and
t.v. set in one cabinet. The impact of
advertising was to impress on potential owners that they no longer had to
miss any program that was on the air
at the same time as another favorite
show, or that went on when the viewer
would not be home to watch. By incorporating two tuners, the owner
could watch one program while the
other was being recorded for future
viewing, or, by using the unit's timer,
a not- to -be- missed telecast could be
recorded while no one was home to
watch. (Of course, this also provided
the person who owned a recorder the
opportunity to watch a program and
record it at the same time just in case
a repeat performance might be desired.)
BETAMAX
As with the 3/4 -i.n. -U cassette system, Sony was again innovative with
its Betamax. In the full console model,
the unit was provided with a camera
input, a microphone input for high impedance, and two cassettes. (When the
unit was first demonstrated, there was
no camera input.) The unit also is furnished with an earphone, an antenna
splitter, two 75 ohm coax cables, and
a 300 ohm to 75 ohm matching transformer. The system has a video s/n
ratio of better than 40 dB sand an
audio s/n ratio better than 43 dB. The
audio frequency response is given as
50 Hz to 10 kHz. Resolution horizontally is more than 280 lines monochrome and more than 240 lines in
color. The t.v. set is Sony's 19 in.
Trinitron. Cost is a bit over $2,000.
Don't let the fact that a cassette is
used fool you into thinking that this
means that the system is similar to the
U -matic 3/4 -in. system. The tape in the
Betamax is t/s in. wide. This makes
the cassette smaller, which is better
for handling and storing. However,
the previous 1/2-in systems conformed
with existing systems using the same
width tape. EIA -J standards, to which
the previous 1/2-in system conformed,
runs the tape at 71/2 in /sec. Betamax
uses a speed of 4.0 cm /sec., equivalent to about 1.6 in /sec. At present,
the maximum recording time in a
Betamax cassette is 60 minutes. (Incidentally, the model number for the
Betamax is LV- 1901.)
The complete Betamax console was
first put on the market in New York
at the end of last year, then was distributed elsewhere. At that time, since
the system was being touted as a two program device (view one, record the
other), there was no mention of a
free -standing unit or already- recorded
cassettes. Things have changed since
then. Early this year, there emerged
a possibility of a separate player machine, and there was talk of a pre -recorded tape. By the time you read
this, the player unit may be on the
market and plans may be far along on
getting movies and other programs
into production. By working out deals
with other manufacturers, Sony may
get the Betamax to be the "standard"
for the home as it did for the U -system for industry and education. The
unit will also, no doubt, get attention
from those users of video as well, for
applications where the double-program
idea can be beneficial.
As a semi -final note (there will be
more detail in the near future), a
camera is also being offered as an
accessory to the Betamax system
model AVC 1420. It is a black -andwhite unit, made to go with the Betamax. There is also the possibility that
in the very near future there will be
a cassette available which will be
longer than the present 60 minutes in
length- perhaps up to 2 hours.
-
T.V. GAMES
In the past year, the public was
given an opportunity, or two, or three,
to use the t.v. set for something other
than to watch programming that was
not to their liking. A device could be
purchased that could be hooked into
the antenna terminals that would provide the owner with a game he (or
she) might enjoy better. Similar to
the stand -alone type found in game
areas of amusement parks, these devices offered several choices, each usually requiring the competition between
two players, or at least two hands.
Among the games were ping -pong,
tennis, and auto racing. Then there
were others with planes or sharks.
Prices for the devices ranged around
$100. At the end of the year, color
games were introduced. Most major
department stores offer one type or
another, and the number of manufacturers is growing in leaps and bounds,
or is it pings- and -pongs?
This year, there will be several new
game developments. It is expected that
the simple games will remain but will
fade in novelty and importance. The
next generation will introduce computer action. This offers opportunities
for more sophisticated games like
chess, word games, number or math
games, and the ultimate situation, for
the present, anyway, an opportunity
to program the computer to play
games of the owner's own choosing
and even with changing rules. Possibilities of this diversion seem limitless.
There's even the chance that the consumer will he able to communicate
with a large computer by phone line
to get desired information, perhaps
for projects the customer can do himself from instructions on a readout
screen.
MICROPROCESSOR
The new word in the home game
field is microprocessor. Through the
use of the multi-function chip, the
more usual games of hockey, football,
handball, and squash will be joined
by the solitaire feature, as it is called
a provision built in for the user to
play against the machine itself. The
device will analyze moves, counter
against all steps taken by the just human player, and in full color, too,
and the player can even set the level
of expertise at which the machine will
play. In games where a certain amount
of speed is required, like handball, the
device will include a variable speed
control. (Well, the human has to be
able to win somehow, doesn't he ?)
Depending on the sophistication of
the game and the device, the pricing
will be from somewhere above $100
upwards to close to $1,000. (Some
of the devices will also include the
sound of the ball being hit, on- screen
score keeping, and even a remote control unit.)
Pricing will go down on the less
complex games as a result of improved
manufacturing practice, development
of less expensive material, and the
entry into the field of toy manufacturers, who always seem to know how
to introduce new "toys" for less than
they cost when they were called games.
So, this year, you have a number
of choices, for home amusement-you
can watch two programs that are on
at the same time (watch one now,
one later) play a pre- recorded tape
or make your own programs, or use
your old t.v. set for the amusement of
your own selection and programming.
Think of all the fun you've just been
introduced to. With several t.v. sets,
several different games, a few of
the Betamax units-drive you crazy,
couldn't it? No fooling!
-
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Circle 29 on Reader Service Card
o
o
bradc:ast
PATRICK S.
Optimizing the Remote Pickup Audio
0
FM TRANSMITTER
CARRIER
-
DOUBLE
SUPER HETRODYNE
GUARD
BAND
RECEIVER
BANDPASS
MICROPHONE
FILTER
AUDIO
n
PHASE
MODULATOR
Figure
1.
BASIC SYSTEM
Co
The portable transmitter does not
broadcast directly to the public, but
instead, to a receiver back at the
studios, where the audio is demodulated, and then coupled to the station's
regular facilities. The system then, is
made up of both a transmitter and a
receiver. At the remote site, there is
a transmitter and an antenna. Audio
is picked up by the system's microphone and used to modulate the transmitter. The modulation process is
usually achieved by phase modulation
so that direct crystal control of the
carrier may be maintained. The signal
is an f.m. signal.
+DEVIATION
1
Ir
/
I
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SPEAKER
Qá9
iR
i
DISCRIMINATOR
(
I
1
)
ir1
GUARD
BAND
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SIDE BAN DS
-<1
The basic system.
Many broadcast stations use small
portable radio transmitters for on-thespot news reports and similar broadcasts. The type of unit used in most
cases, is the small two -way radio system designed for voice communications. The audio specifications for
these small systems may seem rather
limited as compared to our large
broadcast facilities, but they do provide a good voice channel, and this is
quite adequate for the purpose. There
are many natural as well as regulatory
limitations which can either directly
or indirectly affect the audio whieh
can be recovered from these systems.
In this column, we will discuss a few
of the important areas which can
directly effect the system's audio.
DEVIATION
60 KHz
CHANNEL WIDTH
Figure 2. A typical remote pickup
channel.
Transmitters may be licensed in
many bands, from short wave to UHF.
Very few channels (let alone bands)
are allocated specifically for remote
pickup use. Generally, the remote
pickup shares the band with industrial
or safety services. The particular band
in use will have its own characteristics
that will limit the distance the signal
will travel and contribute noise and
other factors to the recovered audio.
The transmitting antenna is usually
at a low height, so to make up for
this, the receiving antenna will be
mounted high above the ground and
connected to the receiver with a coaxial transmission line. The receiver
is usually a double superheterodyne
type (2 i.f. frequencies) and will contain a bandpass filter. This filter is
intended for rejection of adjacent
channel interference, but it will also
automatically limit the maximum band pass of the system. Limiters are used
for noise suppression and detection is
effected by a discriminator. The recovered audio passes through a deemphasis network and on to the receiver's local speaker.
There are several areas in the system where the audio can be directly
affected. The main ones are the microphone, the modulation process and
bandwidth, receiver bandpass filter,
demodulation process and then the
interface of the audio to the station's
facilities.
www.americanradiohistory.com
The system bandwidth is determined
by the equipment capabilities and by
FCC rules. The permitted bandwidth
varies with different bands, and in
some cases, with specific channels
within a band.
BANDWIDTH
The bandwidth is based on a mathematical formula: B. = 2D -I- 2M
x K. D = the deviation on one side
of the carrier; M = the highest audio
modulating frequency; K = a constant
that, for this service, is usually 1. Narrowband telephony, for example, is
permitted a deviation of 5 kHz, and
the highest audio frequency is 3 kHz.
Thus: 2 (5 kHz) + 2 (3 kHz) = 16
kHz. Adding the FCC emission designator F3, this becomes 16F3. This
means: the bandwidth is 16 kHz, the
modulation is f.m., and the operation
is telephony (voice). A wideband
communications channel is permitted
a deviation of 15 kHz. Using this in
the formula: 2 (15) + 2 (3) = 36
kHz, or 36F3.
Since the bandwidth is the product
of the deviation and the audio modulating frequency, the actual bandwidth
may be higher or lower in operation
than the licensed value. All the emissions (including all the sidebands created during modulation) must fit within the channel. So, if you are attempt-
TRANSMITTER
MICROPHONE
AUDIO
DEVIATION
METER
1
I
AUDIO
OUTPUT
D
-15KHz
1
+ DEVIATION
I+
i5 KHz
DEVIATION
NORMAL
CONTROL
V
NARRO W BAND
FILTER
RESPONSE
CURVE
AUDIO
SIGNAL
GENERATOR
Figure
3. The
setup to measure and
I
OSCILLOSCOPE
adjust
ing to extend the audio bandpass to
a
Figure 4. The narrowband filter in the
receiver can reduce the output of a
wideband system.
transmitter deviation.
5
sions out of the channel can cause
adjacent channel interference to other
AUDIO INPUT
stations.
The system bandwidth can be exceeded in two ways. In the first case,
the entire system has been tuned too
narrowly and the bandpass filter in
the receiver is for narrowband. This
narrow bandpass of the system will
have a filtering effect on the signal,
so that the reproduced audio can be
low, have a poor response curve, or
be distorted. It all depends upon the
actual conditions at the time. I.n the
second case, the modulator and the
kHz instead of 3 kHz, the actual
bandwidth can exceed the licensed
channel width. For example, the audio
is now 5 kHz and the deviation is
adjusted for 15 kHz. Thus, 2 (15) -I(2 (5) = 40 kHz. If the licensed
bandwidth is 60 kHz, you are okay,
but if it is 25 kHz, then the signal is
out of channel. It would be necessary
to reduce the deviation to 7.5 kHz to
accommodate 5 kHz in your channel.
Thus: 2 (7.5) + 2 (5) = 25 kHz.
RECOVERED
Au DIC
modulated stage may be called upon
to deviate for more than it has the
capability. This can cause non- linearity of the audio signal or outright
clipping. Both will produce distortion.
The deviation is a very important factor in audio quality, so it should be
adjusted carefully and properly.
ADJUSTING DEVIATION
The actual amount of deviation
should be measured; using a deviation
meter is the best method. This is a
test instrument that serves in the same
capacity as the station's modulation
The microphone has a direct bearing upon the quality of the audio. The
usual microphone supplied with these
units is designed to produce audio on
a speaker which can cut through noise
at the receiver location. This type of
mic does not provide the best quality
for broadcast purposes; select one of
the better grade microphones that are
available for these systems. This will
be either a variable reluctance or dynamic -type microphone and may have
its own transistorized preamp inside
its case.
Internally, there will be one or two
audio stages (in the transmitter) for
amplification, and then a speech clipper. This clipper is required to provide
a "brute force" limit on transmitter
deviation by clipping off any excess
audio peaks. This clipper needs proper
adjustment, and of course, the audio
should be kept below the point where
clipping will occur or there will be
distortion.
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DEVIATION
The deviation of the carrier has a
direct effect on the recovered audio
and its quality. If the deviation is too
low, then the recovered audio will be
low and the system signal -to -noise
ratio will suffer. Should the deviation
be set too high, the system bandwidth
can be exceeded and there can be
emissions outside the channel. Emis-
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Circle 30 on Reader Service Card
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N.Y.C. 10036
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Circle 31 on Reader Service Card
monitor. Deviation can also be measured by a communications receiver or
a heterodyne frequency meter and
the tone modulation of the carrier,
although this is a more cumbersome
method. Tone modulation is applied
to the carrier and the deviation adjusted while listening for the carrier
nulls. When the correct null occurs,
then deviation is correct. The deviation meter is the better arrangement;
an oscilloscope attached to its audio
output can be useful.
Make the preliminary adjustment,
using 1 kHz tone modulation of the
carrier. This will allow getting all the
adjustments within the ballpark and
the oscilloscope, at the same time, can
observe if there is non -linearity or
clipping by the modulator. The speech
clipper should be adjusted out of the
way at this time so that it does not
enter the considerations.
Once the preliminary adjustments
have been made, connect up the regular microphone that will be used with
this transmitter. The signal peaks for
voice are 8 to 10 dB higher than sine
wave peaks, so the final adjustments
should always be made with voice
transmissions. If the adjustments are
made only with tone, these voice peaks
can be driving the unit into severe
distortion. Speak into the microphone
at normal announcer delivery levels.
Adjust the audio gain control and the
deviation for the correct amount. It
is best also to pull back the audio
control because these peaks may be
high enough to cause distortion in the
audio stages.
When the correct deviation is observed on peaks, then observe the
oscilloscope that is viewing the audio
after the deviation meter. If any of
the peaks are clipped, then back off
the deviation or the audio control until
the peaks are clean. Those clipped
peaks mean that either the audio or
the modulator is being overloaded and
causing clipping. When the deviation
has been set to the maximum undistorted amount, adjust the speech clipper to begin to clip at that deviation
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4200 North 48th St.
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Phone 402 464 -5911
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Circle 34 on Reader Service Card
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WITH ALL
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ROBINS /FAIRCHILD Model 659A,
REVERBERTRON, is a complete dy-
The
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enhance Broadcast /Production or Recording Studio sound.
With solid state electronics and high
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REVERBERTRON is compact in size yet
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A
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Robins Industries Corporation
Austin Boulevard, Commack, N.Y. 11725
(516) 543.5200
Circle 39 on Reader Service Card
level. Leave the settings in these positions.
Another important aspect is microphone technique. Since there are no
operating audio gain controls, announcers should practice their mic
technique until they can determine the
correct distance to hold the mic from
their mouths for their normal delivery
levels. They should develop a technique that will provide strong, full
deviation, that is just below the clipping point.
RECEIVER
The bandpass filter is intended to
reject adjacent channel interference,
but it will also effect the system band pass. If the filter is for a narrowband
systems and you are trying to operate
wideband, then the filter will remove
most of the wideband deviation you
so painstakingly coaxed into the transmitter. If you plan to operate wide band, then order the receiver with a
wideband filter.
The discriminator response curve
should be centered exactly on carrier
(which should be right down the
center of the entire system bandpass).
During receiver alignment, these adjustments will have been made with a
signal generator. But the final adjustment of the discriminator should be
made with the carrier itself and modulating with voice. Tweak up the adjustments so the reproduced voice
sounds good. This is only a touchup
adjustment, so don't overdo it.
The industrial unit is designed only
to supply audio to its own speaker.
For remote pickup use, this audio
must be coupled to the regular system
audio. Unless this interfacing is done
properly, the audio can be deteriorated and hum can be introduced.
The best method is through a line -tovoice-coil transformer. The transformer will provide both a match and
isolation. Attach the voice coil side
to the speaker output of the unit and
the 600 ohm side to the system. So
the regular speaker can operate at
normal volume, add a pad on the line
side of the transformer to reduce the
signal level to system requirements.
reel to reel
audio recording
SUMMARY
The small, industrial-type communications transmitter systems can be
used for remote pickup use, and the
results will be satisfactory for voice
broadcasts. But there are many possibilities where the audio can be deteriorated, so the units must be tuned and
adjusted properly, especially the deviation, and the interfacing to the station's audio system done with care.
TAPE
EMPTY
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Circle 32 on Reader Service Card
You oughts have
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Jerry has lived and
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His ability to modify
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And, of course, all
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Circle 33 on Reader Service Card
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Circle 50 on Reader Service Card
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Circle 52 on Reader Service Card
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RAMKO RESEARCH
3516 C LaGrande Blvd.
Sacramento, California 95823
Telephone (916) 392 -2100
Circle 42 on Reader Service Card
A miniature signal analysis device
which constantly monitors the content of a channel and determines if information or noise is present is the
basis of Sound Off self- compensating
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be placed anywhere in the audio line
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Circle 51 on Reader Service Card
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Circle 53 on Reader Service Card
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AMAI
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CANIC)RF,A M018
Ampex MM-1Z00. A
Twenty -four tracks of
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A recorder that grows.
If your budget limits
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you can always plug in more
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N
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Multichannel Endpoint
I
amen.
2
3
sow,.
4
6
stra.
1
7
1
1
11
11
It
tut rue
later. The MM -1200 head
assembly is attached with a
single screw. The basic chassis
is identical for 8, 16, and 24track configurations.
13
11
±
11
ü
17
11
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21
21
!!
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23
21
®
spot, from either direction, at
the touch of a button. At 15
in /s, cuing accuracy is
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MM -1200 equals normal reproduce excellence. You'll
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New controls,
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A newly designed
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MM -1200 easier to use than
Small points,
any other multichannel recordbut important.
er /reproducer. It lifts out for
remote use without loss of
The MM -1200 is a
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rugged machine, with lifealso
an optional
time lubrication on all
moving parts. The master
ON /OFF switch is protected
against accidental
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"bumpers"
assure
enough
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remote
clearance
for transport
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CII tilation.
machine, LED indicators
The VU meters
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tilt
out,
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-glare.
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Search -to -Cue capability is standard equipment on
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v
More than a
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An Ampex MM -1200 in
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g11111
time.
411
Specifications.
Technical specifications
for the MM -1200 would fill
a book. So we've written
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AMPEX
N
Circle 36 on Reader Service Card
www.americanradiohistory.com
products
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services (cont.)
MIXER /PREAMPLIFIER
MATCHING AMPLIFIER/
PREAMPLIFIER
Primarily designed for discotheque
model 5880 mixer /preamp is
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Two tube components, a monophonic power amplifier, model MB3045 and matching stereo preamplifier,
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Ill
Mir: Lux Audio of America.
Price: MB -3045, $445.
CL-35 111, $745.
Circle 54 on Reader Service Card
level stereo signals and are connected
to a slide control for gradual fading
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feeds both stereo channels; an auxiliary stereo input services high -level
sound sources. Each input has an individual level control, with a master
level control and master stereo balance control. Cueing control permits
headphone previews; vu meters show
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Mfr: GLI, Inc.
Price: $600.00.
Circle 56 on Reader Service Card
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different audio DA's designed
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provides continuously variable
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switched progression, auto fade progression, sound progression, and sound
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Mfr: Sound Concepts, Inc.
Price: $600.00
Circle 55 on Reader Service Card
Mir: Meteor Light & Sound Co.
Price: $1 ,275.
Circle 57 on Reader Service Card
are pre- emphasized and compressed
for noise reduction, then enter the
ccd circuits, where a front panel con-
trol
Models & Prices
DA -6 /E 1x6 (table top)
S 145
165
DA -6R /E 1x6 (rack)
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DA -6BR /E 1x6 (rack, indiv. cont.)
179
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239
DA-6RS/E 2x12 (rack)
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RAMKO RESEARCH
3516 C LaGrande Blvd.
Sacramento, California 98523
Telephone (916) 392 -2100
Circle 43 on Reader Service Card
Four-channel Sonalite Four controller offers 1,200 watts per channel
at 120 volts a.c. Each channel is individually adjustable together with auto
171OÁ DISTORTION MEASUREMENT SYSTEM
SOUND TECHNOLOGY
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Your new automatic
distortion measuring system
for balanced measurements
-
REDUCED OPERATOR ERROR
Here's something you'll like
Sound
Tech's new distortion measuring instrument for use in balanced work.
The new 1710A is much more than
just a distortion analyzer. It's a system.
It contains its own ultra- low-distortion generator tracked with the analyzer. It's a system that greatly simplifies
measuring
gives you fast measuring
with simple operation that reduces op-
-
erator error.
For example, push the frequency buttons and you set both generator and
analyzer. Push "Distortion" and you have
your reading. Automatically. No slow,
tedious manual null -searching.
Features in the new 1710A include:
a balanced, floating output (600/
150 ohms)
a balanced (bridging) input
a high -level +26 dBm signal
+26 to -90 dBm attenuator
distortion measurements to .002%
fast 5- second measuring speed
automatic nulling, optional automatic set level.
both harmonic and optional inter modulation distortion measurements.
SPECIAL OUTPUT CIRCUIT
In the 1710A you get a transformerless audio generator output that's balanced and floating. No transformer
means no transformer distortion. Floating and balanced means you can connect
to virtually any audio circuit regardless
of configuration. And you can set the
output from +26 to -90 dBm in 0.1
dB steps.
FAST, SIMPLE MEASURING
Automatic nulling and the automatic
set level option (ASL) give you ex-
tremely fast measuring and little chance
for operator error. You can measure in
5 or 6 seconds. With ASL you can
measure distortion vs. frequency, and
distortion vs. voltage or power without
resetting level.
IM OPTION
An additional optional bonus is that
the 1710A also measures intermodulation distortion. After you've made a
harmonic measurement, just push the
"IMD" button. In 3 seconds you'll have
the IM reading. With this option you'll
be ready for future IM requirements.
CALL /SEND NOW FOR
LITERATURE
It's worth while getting the information on this major new distortion measuring system. Call Larry Maguire or
Bob Andersen now and get our new
product brochure. It's ready and waiting.
S SOUND TECHNOLOGY
1400 GELL AVENUE
CAMPBELL, CALIFORNIA
(408) 378 -6540
9500U
Circle 45 on Reader Service Card
ROBERT E. BERGLAS
Digital Clocks & Things
Electrical impluses work through a series of switching
computerized aggregations to display the flashing signals
of time. Save money by assembling your own digital timer.
of the circular dialed clock and wristwatch with the pointer pointing somewhere or
other-never quite on the nose -are numbered
due to recent advances in readout devices and
Isi (large scale integration) semiconductors. The era may
well nigh be drawing close when all means of telling time
will be digital and crystal controlled accuracy will be as
taken for granted as it was elusive yesterday.
This discussion will look at some of the various readout
devices available as well as some of the "mini- computer"
insides that do the actual calculations in digital clocks and
wristwatches.
THE DAYS
READOUTS
Probably the oldest available readout devices are the
NixieTM tubes. Every number from zero to nine in a Nixie
has its own cathode wire; the tube requires about 170 Vdc
supply voltage, putting something of a strain on the power
supply transformer. There are a few more drawbacks to the
Nixie tubes, however. First of all, the viewing angle is very
limited either side of head -on. Secondly, these tubes deteriorate markedly with age. Finally, since each number has
its own cathode, the number being viewed also illuminates
some of the other wires.
Available for a few years now, are the RCA Numitron
tubes. They operate off the standard 5 volt logic supply,
are easily plugged into ordinary sockets, and their brightness can be modulated. One of their nicest features -and a
feature that few readout devices can accomplish
that
they can be filtered to just about any color the designer
wishes. On the negative side, Numitrons require 108mW/
segment, so the power supply components and transformers
must be conservatively rated.
Probably the most recent types of readouts are the
Sperry Gas Discharge tubes, now marketed by Beckman.
These produce a striking, bright orange (they cannot be
filtered) color that is very "clean " -by that I mean the
segments are solid and fuse nicely into one another to
make up a number. Furthermore, Sperry tubes are rela-
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Robert E. Berglas is associated with radio station
WBAI -f.m. in New York City.
tively large, and require very little current, albeit they
require at least 180 volts polarizing supply. The new
Heath digital clocks, for example, use Sperry tubes.
LIGHT EMITTING DIODES
When quality, not cost, is the deciding factor, most
designers choose light emitting diodes (leds). They are
available in either common anode or common cathode
formats, and can be had today in either standard ruby red,
green, or yellow. Leds have a life expectancy of 90 to 100
years! They require only the standard 5 volt logic supply,
although care must be taken to limit the segment current
with a dropping resistor so as not to instantly frizzle the
led. Since they are now available in three colors, there is
little problem about filtering; yet a cleaner, more easily
read display will result if one uses a polarizing filter with
them.
Because leds require a relatively large amount of current
to drive each segment (between 20 and 40 mA), using
them in digital wristwatches necessitates that the readout
be off when not being viewed; the watch is turned on by
depressing a button
once a mild inconvenience and
distinctive aspect of the pulsar watches.
-at
LIQUID CRYSTALS
Perhaps the most controversial type of readout is the
liquid crystal display. Developed by RCA to complement
their cmos semiconductors, its greatest advantage is in the
incredible small amount of current it draws from the
power supply. It is meant for use primarily in devices
using batteries.
Curiously, these displays require ambient light from
the "outside world" to make them visible. Obviously, then,
they cannot be seen in the dark, and only minimally in a
dim environment.
Furthermore, liquid crystals are to an extent heat sensitive, and care must be taken when using them not to
expose the device to direct sunlight. If one were walking
outdoors or driving a car, one could easily bring these
readouts out of their safe region.
Given the present format for liquid crystal displays, they
do not read seconds when used in a digital wristwatch. Of
course, when used in digital wristwatches, they can be left
on all the time, but it appears that liquid crystal displays
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clock made up of discrete ttl chips.
have a long way to go before they achieve the popularity
RCA expects of them.
THE MINI -COMPUTER INSIDES
Perhaps the best way to introduce you to the way a
typical digital clock works is to discuss how a clock made
up of discrete ttl chips actually works. FIGURE 1 shows
such a clock.
Basically, what we want to do is divide the 60 Hz line
frequency to produce one output pulse per minute. The
count -by -six and the count -by -ten circuits count and decode /display these pulses in tens, unit minutes, and seconds, respectively, up to fifty -nine minutes. The carry
pulse from the count -by-six circuit is produced once an
hour and is passed on to the hour counter. The circuit
shown uses Texas Instruments chips, interfaced with a
gas discharge type of readout (either Nixies or Sperry's).
As mentioned above, the system is synchronized with the
60 Hz power -line frequency. The SN74121 one -shot is
triggered at its Schmitt input by 60 Hz pulses from the
bridge rectifier. The one -shot pulse width is set for 15 ms
(about 90 per cent of the 16.7 ms period of the line frequency) so that power-line noise is inhibited for 90 per
cent of the period. An indicator for a.m. and p.m., using
small incandescent lamps, is shown. If this indicator is not
desired, then the connection of flip -flop (A) to the tens -ofseconds counter and the connection of the NAND gate to
its input may be deleted.
There are five switches provided for setting the clock.
The procedure for setting is: 1) When the desired indica-
tion for seconds appears, switch SI is placed in the set position. This stops the clock by inhibiting the one -shot clock pulse generator. 2) Switch S2 is placed in the set position.
Switch S5 (a spring-loaded pushbutton) is then operated
by pushing and releasing until the desired number is obtained for the minutes unit digit. The counter transition
occurs when the pushbutton is released. Switch S2 is now
returned to the normal position. If a toggle switch is substituted for the pushbutton S5, the switch should always be
left in the position which causes the counter to step (the
grounded terminal of the switch) before S2 is returned to
the normal position. 3) The procedure of step 2 is repeated for S3 (tens -of- minutes) and then S4 (hours). S4
is also used to set the a.m. and p.m. indicator. Note that if
the hours counters are set past 12, the tens -of- minutes
counter will reset to zero. 4) With all digits set and S2,
S3, and S4 in the normal position, SI is set to the normal
position and the clock begins to run.
The unregulated 5V power supply is adequate where
good -quality line regulation exists. Note that the outputs
of the SN74141N devices that are connected to the BCD
outputs of the SN7492 counters are rearranged for connection to the Nixie tube displays. If 7-segment displays are
used, the A -B-C inputs should be used to drive the decoder /driver. An extra flip -flop package will then be
necessary.
CRYSTAL-CONTROLLED OSCILLATOR
The line frequency is not the only method of timing the
logic. For greatest accuracy, a crystal- controlled oscillator
www.americanradiohistory.com
+ 6v
Let me say a few words about the crystal itself. First,
probably appears obvious by now, the higher the basic
frequency of the oscillator, the greater the possible accuracy of the clock or wristwatch. And yet, from what I have
heard from industry sources, the availability of properly
cut crystals is the single most limiting factor in keeping
digital wristwatches from being mass produced and inexpensive enough for the average consumer (the watches
go for about $300 now). The inaccuracy of a crystal controlled unit is around five seconds a month, or about a
minute a year, while a line -timed clock achieves an accuracy of 0.05 per cent of the 60 Hz waveform. It must
be said, however, that a frequency counter is necessary to
calibrate a crystal -controlled watch. There is really no
other way to do it.
as
LARGE SCALE INTEGRATION CHIP
Recent advances in large scale integration (Isi), whereby the equivalent of several thousand transistors can
be found on one integrated circuit chip, have made the
discrete i.c. clock almost obsolete. Today, all that is needed is a single mos Isi chip, a few switching transistors,
along with a handful of resistors and capacitors, and
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a -kit-built
clock.
can be used. FIGURE 2 shows such an oscillator, taken
from RCA's battery -powered i.c. digital clock. It starts
with the crystal oscillator. This integrated circuit section is
an mos complementary inverter that provides the gain
needed to maintain oscillation. Resistor R10 self biases the
oscillator stage by providing d.c. feedback, setting the input and output at approximately half the 6 volt supply.
Although this i.c. circuitry usually draws very low currents when fast rise time signals are processed, in situations
where signal transition are slowed, the supply current sharply
increases. During a portion of the signal transitions both
the p- channel and n-channel complementary devices are
on and there is a current path directly between the power
supply and ground. The input waveform of the oscillator
has slow transitions since the crystal eliminates the high frequency components. One of the things done to keep oscillator current down is to operate it with a 6 volt supply
even though we need a higher -voltage supply in other parts
of the circuitry.
there you have it.
Several manufacturers have come out with the necessary
chip, but National Semiconductor seems to have the lead
in variety and simplicity of operation. Their chips range
from a simple four -digit display (MM 5312) to a 40 -pin
chip with both regular alarm and snooze alarm in either
a 12 or 24 -hour format (MM 5316). FIGURE 3 shows a
schematic of one such clock using the rather small DL -33
led displays. All the digital logic is performed inside the
MM 5314. The remaining circuitry supplies d.c. power
and responds to the commands from the chip to drive
the readouts.
Some caution should be mentioned before anyone attempts to work with these mos i.c.s. A low wattage soldering iron must be used (not above 20 watts), and the tip of
the iron must be either isolated from the power supply or
grounded securely. The latter is accomplished simply by
attaching a heavy duty clip from the heating element to a
good ground. The chip, then, must be protected from
static charges at all times, and it is a good idea to use
sockets and not to insert the chip until the last step.
AVAILABILITY
Below are mentioned some suppliers of digital clocks in
kit form. First, is the Heath Company (Benton Harbor,
Michigan). They have three types, with one displaying
both the date and month as well as the time. Poly Paks
(P.O. Box 942R, Lynnfield, Mass.) has a clock with several readout formats and the possibility of using a crystal
time base. I would suggest that only the experienced kit
builder use this source.
The circuitry shown in FIGURE 3 is identical to a clock
marketed by Bill Godbout Electronics (Oakland Airport,
Calif.). Another source for this clock is Solid State Time
in San Jose, California.
Finally, CEI (P.O. Box 327, Upland, Calif.) puts out
several different and interesting clocks. Quite a novelty, is
their Model SDC -1, which displays hours and minutes in
sequence with only one digit. It shows complete time repeats every four seconds, or 15 times per minute. They
also put out a crystal controlled model that uses, I believe,
Numitron tubes, as well as a large, 31 -in led display clock
that can be hung from a wall. These clocks from CEI can
also be bought assembled. And for those who go all out
for accuracy, CEI has a Standard -Time Receiver which
is tuned to NBS radio station WWV.
In sum, digital clocks and wrist watches are surely the
trend of the future.
Five monitors. One sound. Five JBL studio monitors.
You could record with any one, play back on any other,
and take your pick among the rest for mixing or mastering.
The only differences are acoustic output, size and cost.
No matter what size your studio is, you can cross reference with any other studio using JBL's.
But reading isn't knowing for sure. Come listen to
one. Or two. Or five.
JBL Studio Monitors from $303 to $1596.
James B. Lansing Sound, Inc. /Professional Division /3249 Casitas Avenue /Los Angeles 90039.
Circle 23 on Reader Service Card
www.americanradiohistory.com
:1BL
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LOW
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MULTIPLY TAPPED SHIFT
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OUTPUT
FILTER
Figure
1.
Standard delay line block diagram.
RICHARD FACTOR
The Digital Delay
Line Revisited
Random Access Memory allows greater versatility,
including flanging and pitch changing.
DON'T have to go back too far in the audio
business to remember the first digital delay line,
complete with such exotic concepts as an analog to- digital converter, magnetostrictive delay lines,
anti -aliasing filters, and such marvelous arcana as bits and
clocks (which didn't even tell time).
Well, if you've been awake in recent years, you know a
bit about digital technology by now. Your watch is digital,
you have a digital calculator (or pocket computer for a few
extra bucks), your voice is frequently digitized on the telephone, your tape machine searches digitally, and you may
have even learned to count on your fingers. Of course, if
you've done any mixing or sound reinforcement work,
you
°
Richard Factor is Vice -President of
Eventide Clockworks, Inc., New York City.
you've undoubtedly used a digital delay line for the special
effects or time synchronization of which it is uniquely
capable.
Somewhat less likely, you've had occasion to delve into
the electronic circuitry by which these units achieve their
delay. The ddl is "transparent" to the end user; i.e., an
audio signal goes in, and an audio signal comes out somewhat later. Absent curiosity or malfunction, there is no
need for the user to know what goes on inside the unit.
Ask a non-technical person what is going on inside a ddl,
and he will probably make some reference to analog to-digital converters, shift registers, and digital -to-analog
converters. Don't ask any further questions as they will
probably lead to mild embarrassment. They needn't, though,
because that last sentence is a fair summary of what really
does go on in a ddl. After a brief flirtation with magnetostrictive delay lines (very clumsy mechanical delay
lines), the industry universally adopted the integrated cir-
INSTANTANEOUS
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TIME
TIME
Delay- change glitches.
cuit shift register as its method of storing signals to be
delayed.
HOW IT WORKS
Very briefly, the principle of operation of the ddl
is
this:
1. An audio signal is low-pass filtered to eliminate super audible signals which could cause heat notes and
spurious outputs.
2. The signal is then converted into a digital format at a
rapid rate, typically 25 to 50 thousand times per second.
Each of these 25k to 50k samples is represented by a
digital word, which consists of a group of l's and 0's.
The word represents a specific voltage level as present
in the original signal.
3. This word is clocked into a digital storage medium,
such as a semiconductor shift register, in which it is
progressively moved towards the output, one storage
location per clock or sample period. The delay is thus
determined by the clock rate and the number of storage
locations available by the rather simple relationship
DELAY
Number of storage locations
- Clock
or Sampling frequency
-
After the digital word reaches the output of the shift
register, it is reconverted to an analog format and
again filtered to remove spurious frequencies, this time
primarily associated with the sampling clock.
5. The signal, thus converted and delayed, is conducted
to the outside world, ready to begin its career.
4.
The above admitted oversimplification completely ignores
the differences between delay lines from different manufacturers, which are primarily related to methods of encoding
the analog signals into digital format, and the various control features of the competing units. The method of signal
processing determines the dynamic range of the unit; depending upon the application, ranges of from 40 dB to over
90 dB are desirable. It makes little sense to purchase
more range than required because the cost is directly proportional to the dynamic range, as both the amount of
storage and circuit complexity increase with increasing
dynamic range. Likewise, a variety of units are available
ranging from those with delay switchable in narrow increments with great facility to those in which delay is completely fixed at purchase. Naturally, you pay for control
features, and for delay time.
The third major trade -off is frequency response. Within
narrow limits, the frequency response is about one -third
the sampling rate. Doubling the sampling rate doubles the
rate at which the digital samples pass through the shift
registers, and thus cuts the delay time in half. So, one
would expect a given delay line to give half as much delay
at 50 kHz as at 25 kHz. It is possible to compromise, however, so that a given delay line may have variable or selectable clock rates to allow longer delays when wide frequency
response is not necessary, such as in some special effect or
sound reinforcement applications.
SHIFT REGISTER
With all these differences, there has been one unifying
and limiting factor in ddl design. All units have used the
shift register as a storage medium. To see why this is
limiting, let's look at the shift register.
The shift register is a serial storage device. It comes in
various lengths, from 4 bits to several thousand bits. New
technology has recently made 16 kilobit registers possible.
At first glance, it would seem that shift registers are ideal
for delay, because of their very structure. They work by
transferring a packet of charge representing a digital 1 or
0 from one internal node to the next. No additional timing
circuitry is necessary -the registers accomplish the delay
all by themselves.
Furthermore, they may be connected in series to achieve
longer delays, and the points at which they are connected
can be used as delay taps. If each shift register provides,
for example, 10 milliseconds of delay, and 20 are connected
in series, 200 milliseconds are available in 10 millisecond
steps. As a practical matter, many parallel shift registers
are required to handle a full word, and the switching becomes cumbersome after a few taps are necessary. There
are many techniques for circumventing this problem which
add only minimal complexity to the entire system.
So what's the problem? Well, consider how to vary the
time delay. There are two basic choices: one is to switch
shift register taps; the other is to vary the clock rate.
Switching taps creates discontinuities in the signal. Looking
millisecond
at a signal at point A and point B at, say,
time difference creates a sharp transient at the splicing
point (see FIGURE 2). Even if the switching is accomplished
electronically, such as with an optical encoder and digital
multiplexers, this transient is unavoidable, except when
the signal level is zero, or the points to be joined coincidentally have the same amplitude. If the delay is to be
changed rapidly, this becomes a serious detriment, as many
of these splices add noise to the signal.
Varying the clock rate overcomes this problem, but
creates another one, the inability to vary the delay by more
than a certain percentage. The upper limit of variation is
governed by the allowable decrease in frequency response;
the lower limit by the capability of the A to D converter
and the timing circuitry. A typical variation of 50 per cent
is insufficient to change from short to long delays, and
since all outputs vary by the same percentage, it is impos1
10K
1K
100
10
thereof) which can store individual chunks of data, and
deliver them up upon command. It differs from the shift
register in that any of the stored data is immediately available regardless of when it was entered into the memory.
If the shift register is compared to a pipeline, the ram
may be compared to a book, in which each page is numbered and accessed without reading its neighbors. In digital
terminology, the "page numbers" are addresses. An individual ram integrated circuit may have from 16 addresses,
as used in either very old or very fast chips, up to 4,096
addresses as used in many of the newest computers. Assuming each address location holds bit, it is obvious that
one "4k ram" is the equivalent in storage capacity of four
industry standard 1k shift registers. Of course, nothing
exists in a vacuum, and the 4k ram must be economically
viable, available, and reliable. Fortunately, this is the case.
as the price of the 4k ram, which was astronomical until
mid -1975, is now in the range where it is reasonably comparable to the price of the shift registers which it replaces.
Anticipating the price reductions, we began the design of a
digital delay line using random address storage instead of
shift registers. Some of the details of the design, and the
1
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SHAFT ROTATION VS OSCILLATOR
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Figure
3.
Delay- change control operation.
possibilities of rams are described below.
sible to vary one output with respect to the othm-. The
basis of the flanging effect is the sliding of one signal past
another in time, and so this lack of capability is a great
disadvantage.
One solution to the above problems would be to have
shift registers with taps at every sample. So doing would
enable one to switch from tap to tap rapidly while encountering only insignificant splicing noise (FIGURE 2). This is
because, with normal program material, the amplitude
difference between successive samples is very small. Switching between samples in this manner produces at worst a
low amplitude tone at the switching rate which is effectively
masked by the signal. The only time you run into trouble
with this method is varying the delay of high frequency
deterministic signals, which is very unlikely in normal circumstances.
Unfortunately, tapping shift registers at every bit would
require a maze of wiring large enough to fill an ordinary
city dump, and the equipment would end up there after
one repair was attempted. (It is possible to use combinations of shift registers to achieve an arbitrary delay time,
but this is not the same and will not work, just in case
anybody is tempted to try. The reason it won't work is that
in switching individual shift registers around, it becomes
necessary to wait for them to fill up, which can take an
arbitrary length of time, much greater than one sample.
before the output is usable.)
RANDOM ACCESS MEMORIES
Another solution to the above problem is to use random
access memories. This solution does work. A random
access memory is a semiconductor chip (or assemblage
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Model 1745M digital delay line.
GETTING DELAY FROM A MEMORY
To begin with, getting delay from a memory is a bit more
involved than getting delay from a shift register. To continue with the book vs. pipeline analogy, if you put something into a pipeline, you need only wait for it to come out.
The delay is equal to the length of the pipeline. If you
wanted to get delay from a book, you would have to read
the data a certain number of pages after the beginning.
Since this is a dynamic process, the point at which the data
is written must also vary. (If it did not, data would be
overwritten at the same location. Look at an old piece of
carbon paper and try to imagine what that would sound
like!) Therefore, the way to get delay from a memory is
to employ a pointer or base address register. Every time a
new sample is writttn into the memory, the register is
decremented (decreased by 1). This register then points to
the location of the most recently written data. Since the
register is decremented once each sample period, adding 1
to the register contents points to a sample that is delayed by
a sample period. If the sampling rate is 50 kHz, then, each
sample is 20 microseconds delayed from the previous one.
If data is being written at address #150, then data being
read at address #200 is delayed by 1 millisecond. Fortunately, the actual numerical address is irrelevant, as all
data storage locations are identical. Thus, an output can be
obtained at an arbitrary delay simply by generating a number equal to the number of samples difference between
input and output. The "housekeeping" is taken care of by a
single register and arithmetic unit located on the circuit
board which contains the memory.
MULTIPLE OUTPUTS
Most delay lines, especially those used in recording
studios, have two or more outputs. Multiple outputs are
especially desirable in those applications involving choral
effects and reverberation. In order to accommodate multiple outputs, it is necessary to organize the system as a
bus, which means simply that several different signals can
share the same physical connection. Doing this requires
"3-state" logic, which differs from ordinary 2 -state digital
circuits in that not only can a 1 or a 0 be output, but the
output can also be turned "off," in which case it assumes a
high impedance. If multiple outputs are connected together,
but only one is in a low impedance state, then the bus
assumes the state of the low impedance output.
MOIL
-uNrIL
m,M. LON-PAr
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INCH
IN
MEMORY MF1TRIX
Li
EVEL
tZ
INPUT
WRITE
NERD
O
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V
RDDREES
BUFFERS
CHIP
D CLFIV
V C t7
TIMINE
DOUBLE
REPEAT
1
Figure
1745 M
4.
1
1
/
1
BCD /BIN
N. DRIVERS
1
CONVERTER
BCD /BIN
SCD/CIN
COUNTER
RDDER
DDRE
1
Diagram of the operation of the model
digital delay line.
SET
ZERO
DELRV
DELAY
REGISTER
I
'IRERDOUT
FEVEL
By using modular output cards, and activating them
sequentially, one can access several different addresses
during any given sampling interval. The number of addresses which can be accessed is determined by the access
time of the memory chip used and the sampling interval,
which, as stated above, is 20 microseconds. Most common
4k rams have access times on the order of 0.2 -0.4 microseconds, which should be sufficient for 50 to 100 outputs.
However, computing the proper address also requires time,
and common ttl circuits, which are very fast, consume quite
a bit of power. As one of the objectives of the design was
to reduce power consumption, we used all cmos circuitry,
whose power consumption decreases almost to zero as its
speed decreases. Even so, there is plenty of time to service
up to seven outputs, and module positions are provided for
up to five, leaving margin for extra functions.
Another problem arises in that rams are universally
binary devices, and human beings are generally decimal.
Some provision must be made to allow setting the delay
(and reading it out) in human -decipherable units. Since
each sample is 20 microseconds, one could simply convert
the binary number representing the delay to decimal form
and multiply by 0.020 to give milliseconds. Unfortunately,
long binary -to- decimal conversions are slow or require
much hardware. A far simpler solution involves using a
small (0 to 999) decimal -to -binary Converter, and doing
all the output module addressing in decimal form.
Each 4k ram has binary addresses frm 0 through
4,095. Then memory locations 0 through 999 (binary) are
addressed for the first 1,000 samples of delay. If 1,001
samples of delay (20.02 milliseconds) are required, the
next address used would be binary 1,024. In effect, for
convenience, 96 addresses out of every memory are
ignored and wasted. These addresses are still there, by the
way, if needed, but it is a lot cheaper to waste them than
to perform the conversions otherwise required.
Using this system and sampling rate, a 16k memory,
requiring 40 memory chips gives 319.98 milliseconds of
delay in 20 microsecond steps, as compared to our previous system requiring 108 shift registers for 199 millisecond steps. A small additional advantage is that no extra
shift registers are required for additional outputs. Assuming
comparable reliability between the rams and shift registers, the memory design should be over twice as reliable.
Furthermore, the industry has settled on two or three basic
4k ram designs, and all are multiply- sourced. We opted
UT
LP nLT
IrCRJCNTIPL
17L-ISM
111.11.11,
_
i
_
_
OUTPUT BORRD
for the 22 pin, non -multiplexed address configuration for
simplicity, and because space saving was not an urgent
criterion. We have evaluated several manufacturers' chips
and found all but one acceptable. This, hopefully, will
make delivery times independent of Silicon Valley idiosyncrasies.
OPTICAL ENCODER
One final unusual design feature: our 1745A delay line
utilized an optical encoder (see January, 1974 db Magazine) for delay switching. This eliminated the need for
coarse and fine delay controls and permitted fully incremental switching in 1 millisecond steps. The control had 20
lines, and produced 20 pulses per revolution, and could be
spun to traverse the whole control range in one spin. To do
the same with a unit which varies in 20 microsecond steps
would require an encoder with 1000 lines. Although such
devices are producible, and are used in precision mechanical systems, it was deemed impractical to use such a unit
for reasons of cost and ruggedness.
Instead, we designed an oscillator of wide frequency
range with a small deadband in the center of its control
range, and with parabolic control taper. The oscillator
frequency range is from 1 Hz to 5 kHz, which allows the
full range of delay to be spanned automatically over several
seconds to several hours. It should be noted that although
the delay varies in 20 microsecond steps, the readout is
only to the nearest millisecond. If one needs to know the
precise delay, the information is available on data lines
which may be connected to readout drivers. Other features
w
m
of the 1745A were duplicated in relatively uninteresting
ways. The delay double feature which allows doubling the
delay at the expense of frequency response was implemented by inhibiting alternate base address decrementing
pulses. The repeat feature was implemented by inhibiting
memory write pulses, thus preventing overwriting old data
and so saving it.
Superficially, then, we have a new delay line with a bit
more delay and a whole bunch of familiar features employed in a wholly new way. As stated earlier, the delay
line is, and should be, transparent to the user in that, regardless of the implementation, you put audio in and get
audio out. What does all this mean to the user?
SIGNIFICANCE OF RAMS
Nobody would waste time with rams if they didn't
mean something; of that you may be sure. They mean that
true flanging can be accomplished with a single digital
delay line. The fine delay steps allow sweeping a variable
output past a fixed output in tiny increments, thus giving
an apparent continuous variation in tonality, as opposed to
the step variations possible with other systems. Unlike
analog delay flangers, the flanging may be performed after
any fixed delay. Even "pre- flanging" is possible with a
single delay line, by taking the flanging effect from the
first two outputs and the dry signal from a third at greater
delay. Of course, as with all digital systems, there is no
degradation of signal -to-noise ratio as the delay is increased.
In addition, continuous doppler shift or pitch change
may be introduced into any signal simply by increasing or
decreasing the delay in a continuous fashion (facilitated by
the oscillator control). A rather long period of change is
REMOTE BROADCASTING
Mlib+«tbò .
y14)
REMOTE SITE CONSOLE
Use standard telephone line
Direct distance dialing
Set up and check out in minutes
High and low end frequency compensation
with automatic level control option
Lost line auto hang up option
Auto pick up on redial option
Up to 6 microphone inputs with level control option,
4 headphone outputs with level control
Output matched for standard telephone line or loop
with level control, VU meter, built -in telephone
line coupler and output for PA amplifier
AC /DC with battery test meter
Built -in telephone dial
Options In addition to those noted Include:
carrying case, microphones, headsets,
test tone generator, aux inputs, phono
cartridge input and three pin connectors
Il l6^,:
!áp.
5
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'
_
,
:i
STATION END CONSOLE
PULSE DYNAMICS MANUFACTURING CORP.
Box 355, Depot St., Colchester, III. 62326
13091
776-4111
available before an artifact is introduced by the delay recycling from 319 milliseconds back to zero, and this can be
minimized in certain ways involving interleaving more than
one output.
A wholly new effect, tunneling, can be achieved by
connecting the audio output back to the audio input, in a
manner similar to classic "tape reverb," As the delay varies,
an effect similar to flanging, but much more intense, gradually changes to rapid reverberation to variable length echo.
All the while, the pitch of previously processed material is
increasing or decreasing, depending upon the direction of
delay change. The effect is audibly similar to standing in
the center of several whirling program sources as they
spiral towards you approaching the speed of sound. This
effect is so new that you probably haven't heard it yet.
You will.
Using rams means that an auxiliary module which
computes addresses in accordance with an appropriate
program can be used to obtain an arbitrary pitch change
ratio, and maintain that ratio. Any ratio can be obtained.
By proper address manipulation, it is possible to read audio
out backwards! Think of that, special effects fans! And of
course, pitch change can be turned into tempo change in
conjunction with a tape player.
It also means that precise comb filters may be implemented with much finer control of delay. Since the system
is crystal -controlled, the delay time will not drift more than
a few parts per million, and so a null can be set for some
frequency and that frequency and its harmonics will
disappear.
This process makes it possible for largely experimental
applications, such as narrow bandwidth speech scrambling,
to be reasonably implemented. For instance, you can construct a card that will read out addresses 0 to 1,000 normally, then jump to 5,000 to 6,000, then read out 2,000 to
1.000 backwards, etc., until the whole capacity is used up!
Performing the inverse operation at a remote end will
descramble the signal. The whole process, unlike digital
encoding, does not significantly increase the bandwidth of
the output, and thus it may be put on ordinary communications channels. such as the telephone. This may also be
an aid to communications, by using the memory delay line
in conjunction with several filters, and setting each filter
band at a different time delay. This is known as timediversity transmission and can also be implemented with
non -memory delay lines.
Another possibility is that experimental applications requiring digitized audio available at various times can be
implemented with a convenient test bed. Computer time
need not be taken up implementing A to D routines and
housekeeping. Samples may be withdrawn at any computed
delay and used as the experimenter desires.
In addition to the above advantages, there is another
capability built into the system as a consequence of the
memory bus architecture. If one can hang several outputs
on a given bus, why not several inputs as well? Why not
indeed! In fact one can, and so we did. The delay register
inputs, normally set sequentially by the oscillator, can be
set in parallel by placing the desired number on the address
bus and strobing the output card which it is desired to set
in the "dead time" between the last readout and a new
sample. Provision has been made for a remote control
module which enables precision setting of any or all outputs
by digital control. Data may be furnished either from a
remote console or from an automated mixdown system.
Thus, another component can be operated in conjunction
with automation, leaving the engineer and producer even
freer to listen.
Circle 28 on Reader Service Card
www.americanradiohistory.com
JOHN WORAM
A Visit With
Uncle Horsely
elk
The quiet will drive you crazy.
-
Well, it seems there's this Doctor Adams
an electron-microscopist by specialty. Being a
doctor is okay, but playing bass is a lot more
rewarding. Perhaps not in $$, but who wants
Wtto?
Doc Adams' seaplane.
to look at electrons all day anyway?
Now Doc Adams' uncle John Horsley had a lot of property up in the lake country north of Montreal. Some time
ago, Uncle Horsley went on to his reward, and there were
all these houses on the property, and nobody was living in
them, and one of them would make a great little recording studio, and who wants to be a doctor anyway?
But you can't call a place "Doctor Adams Recording
Studio :" it sounds too clinical. "Adams Sound" doesn't
make it either. So, Uncle Horsley's it is, giving recognition where due.
Uncle Horsley's is not one of your super slick infinitely
baffled multi -track sound emporiums (emporia ?). As a
matter of fact, its a fairly small room, about right for a
combo, providing they leave their retinue of roadies, groupies, accountants, and assorted hangers -on back at the airport in Montreal. The control room is even smaller, so the
persistent session crasher can't possibly squeeze in. There's
just room for the bare necessities, like an MCI 16- tracker,
some Ampex AG 440's, dbx, a 19x16 console, and a few
bottles of wine. With the possible exception of that last
item, everything else was provided and installed by Chromacord of Montreal.
There are two windows in the studio. One looks out on
the woods behind the house, the other on the woods in
front of the house. If you want to gaze into the control
room while playing, you're going to find it tough. There's
a big brick fireplace in the way. Uncle H's man at the
knobs can keep an eye on your microphone via cctv,
and you can watch the birds outside if you don't know
how to read music.
Most visitors linger a while at Uncle Horsley's. In fact.
some three days slipped by unnoticed while this epic was
being "researched." The time was divided almost equally
between meals, walks in the woods, and long naps, plus
a brief look at the studio. For others who might find
this sort of tempo exhausting, some of the nearby houses
are being spruced up for living in while attending to recording chores.
For a change of pace, Uncle Horsley's seaplane (actually, it belongs to Doc Adams) stands ready to take you
lake hopping between sessions. Or, if you have the time,
there's a canoe and a fishing rod available.
Uncle Horsley's is mostly about music -jazz or jingles.
If you need Marshall amps for earphones, the quiet up
here will drive you crazy. Besides, you'll scare the birds.
Small, but good.
The control room, with the 19 -in, 16-out Console,
MCI 16- track, dbx, and Dolby units at hand.
www.americanradiohistory.com
SIGNAL
ELECTRONICS
IISVAC
RI
OUTPUT
/
Fl
-- 0r\-0--0Iyy
NEUTRAL --e\moo'
TAPE
HOT
F2
SI
R2
50K
POWER
AMP INPUT
TO
TRANSPORT
ELECTRONICS
S2
CAPSTAN
MOTOR
MDA SOCKET,
I
t-_?_J
t-
DUMMY PLUG
-i
-
15V
-3-1
T
L _. NJ
1
SI IS POWER SWITCH
S2 IS TAPE RUNOUT SWITCH
FI
2ir(RI+R2)C
FOR INSERTION
IN MDA POCKET
rr -2
AND F2 ARE LINE FUSES
3,
LNs___
AUDIO
OSCILLATOR
30 -100 Hz
115V AC HOT 30
POWER
AMP
BOGEN
-100 Hi
33 K
0 47µf
VALUES GIVEN PROVIDE
FREQUENCY RANGE OF
27 TO 92 Hz
1
1.
R2
RESISTORS ARE I/4 W 5%
DIODES ARE 1N914 OR IN4148
OR OTHER
POWER AMP WITH 115 VOLT
OUTPUT CAPABILITY
(AT LEAST 50 WATTS
Figure
DUAL 10K POT WITH
REVERSE LOG TAPER
(TO SPREAD OUT SCALE)
C
NEUTRAL
M0100
RI
Removing the dummy plug from the mda socket.
Figure 2. Design for an inexpensive oscillator.
ROBERT E. RUNSTEIN
A VSO
Switichng System
Using electronics already present, the complications are
taken out of connecting a variable speed oscillator.
A vso (variable speed oscillator) is
usually a bothersome task. It requires the connection of a variable frequency oscillator to a
power amp capable of delivering 115 volts to
its toad, the use of a voltmeter to measure the voltage
reaching the load while the oscillator output level is adjusted, and fumbling underneath a tape transport to remove the dummy plug from the mda (motor drive amplifier) socket so that a connector carrying the variable frequency power from the vso can be inserted (FIGURE 1).
The complexity of the situation arises from two causes.
First, the output voltage from the power amp must be
ONNECTING
Robert E. Runstein is the author of the hook. Modern
Recording Techniques.
www.americanradiohistory.com
CONNECTIONS
MDA SOCKETS
TO POWER AMP
OUTPUT -HOT
TO
AC HOT
CAPSTAN
MACHINE
I
MOTOR
- KI
2.78047µF
TO POWER AMP
OUTPUT - COMMON
'
AC
1W
400V
I
NEUTRAL
AC HOT
MACHINE
CAPSTAN
MOTOR
2.7n
--K2
0.47H.F
2
AC
NEUTRAL
IW
Figure 3. A switching
system that automatically
connects a capstan motor
into a vso.
DUMMY LOAD
400v
25W I15V
LAMP
AC HOT
MACHINE.
CAPSTAN
MOTOR
2.70.
o.47pF
o
n
AC
1W
40óV
NEUTRAL
R2
RI
n
II
n
Figure 4. Using this circuit,
the capstan motor will run
whenever vso operation is
selected, regardless of
mode.
VS0
FT,-3V-1
NC
NORMAL
DI,D2,
KI,K2,
1
1
, 1
.
.
.
.
.
.
.
.
2,
RI,R2,
Dn
Kn
1
.
.
=
=
NORMAL
IN4001
POTTER B BRUMSFIELD KHP 17DI1 OR EOUIV.
(ONLY 3 POLES NEEDED PER MACHINE)
LEDs
n
Rn
NORMAL
=
SERIES RESISTOR TO CONTROL LED CURRENT
monitored so that the oscillator output can be set to provide the proper voltage to the motor. While synchronous
motors will operate at synchronous speed (their speed will
depend on the frequency of the applied voltage) over a
fairly wide range of voltages, too low a voltage may cause
the motor to stall, while too high a voltage may overheat
the motor windings and may also exceed the power amp
output capability. That causes distortion of the waveform,
which can result in speed irregularities. Secondly, it is
desirable to be able to vary the speed of any one of several machines at the flick of a switch without having to
go to the expense of obtaining a separate power amp to
drive each one.
The answer to the first of these problems is to allocate
one oscillator to the vso system exclusively, and preset its
output level so that the power amp delivers the proper
voltage to the capstan motor. The oscillator need only be
capable of limited frequency operation; most capstan motors will stall much below 25 Hz (less than V2 normal
speed) and will reach maximum speed somewhere between
90 and 100 Hz (more than 1' times normal speed). For
smooth operation the oscillator should be capable of covering these frequencies without switching ranges, and with
the high and low limits at opposite ends of the dial for
good resolution. FIGURE 2 is a design for an inexpensive
oscillator which appeared in Operational Amplifiers Design and Application.1
The frequency of oscillation is determined by the formula f = 1/27r (R,
ROC. Resistors R_ limit the oscillator's highest frequency to that which produces the highest tape speed-determined experimentally for the machines in use. If the oscillator frequency is permitted to
exceed that frequency, slippage of the capstan motor's
rotor can actually cause tape speed to slow down a bit.
R, varies the frequency and should have a reverse log
taper to spread the values out, but a linear taper will work
adequately (settings above 60 Hz will be compressed into
approximately the last 90 degrees of the control's rotation). R, is adjusted for minimum distortion, which occurs near maximum output before clipping. Distortion is
on the order of 2 to 3 per cent, which is sufficiently low
for this application.
-1
SWITCHING SYSTEM
The answer to the second problem is the switching
system to be described (FIGURE 3). The principle is simple. The vso is left on, driving a dummy load (a 25 watt
standard light bulb) until variable speed operation is de-
4
+2a
s2A
vso
circuitry permits only one machine to be connected to
the vso at a time. The circuit illustrated in FIGURE 4 results in the capstan motor running whenever vso operation is selected, regardless of what mode of operation the
tape machine is in.
The circuit illustrated in FIGURE 5 can be substituted
if the tape machine is of the type in which capstan rotation is stopped when the machine is not in the play or
record mode. Construction is straightforward, with the
only complications being precautions in the wiring of the
115 volt vso circuitry (use at least #18 wire) and the
avoidance of ground loops.
The vso wiring is complicated by the fact that most tape
machine manufacturers send only the high side of the a.c.
line to the capstan motor through a jumper in the mda
socket's dummy plug, leaving the low or neutral side of
the line permanently connected. Thus, connection of the
vso to the mda socket means that one side of the vso's
output is connected to the a.c. power line neutral through
the tape machine selected. Most power amp manufacturers
connect the common side of the power amp's output transformer to the amp's chassis and therefore to the power
line ground (if the unit is furnished with a three wire a.c.
cord) or to one side of the power line through a capacitor
(if a two -wire a.c. cord is used).
SIhC
TO
+24V
TO
PLAY _AMP
MACHINE 2
+24V
PLAY LAMP
MACHINE
SIA
ñ NORMAL
S28
TO MACHINE
TO MACHINE n
SIB
on
I
P_AY LAMP
GROUND
PLAY LAMP
GROUND
z
TO MACHINE
2
PLAY LAMP
GROU NC
Si
3
52
DPST TOGG_E SWITCH
POLE ROTARY SWITCH
WITH n POSITIONS
Figure 5. Substitute circuit, used it the tape machine
stops capstan rotation when the machine is not in the
play or record mode.
sired. At that point, a relay disconnects the power line
from the capstan motor of the desired machine and substitutes the output of the vso. As many machines as desired may be wired into the system; the selection switch
NECESSARY PRECAUTIONS
Given these conditions, the following precautions must
be taken. The side of the output transformer connected
to the power amp's chassis must be connected to the neutral side of the wiring to the capstan motor. If the power
Reverb breakthrough!
2
e
rdowLis_-Yos
S
CH.
A
CH. B
The Clover R -500
professional quality
reverb suitable for recording,
broadcast, and P. A. applications.
Hi & low Z inputs and outputs
Four transmission lines per channel
. Decay time: 1.8 secs Signal to noise: 75dB
is a
Dealer Inquiries Invited
CLOVER SYSTEMS
P. O.
BOX 55033, SHERMAN OAKS, CA 91413. (213) 789 -9395
Circle 41 on Reader Service Card
www.americanradiohistory.com
amp does not have a three -wire line cord which would assure that the common side of its output transformer is at
ground (and therefore close to neutral) potential, the
a.c. plug should be rotated so that the side of the line
connected to the chassis through the capacitor is connected to the neutral side of the power line. The chassis
of the power amp should then be grounded to the a.c.
power ground. For additional protection, the power amp's
two -prong a.c. plug should be replaced with a polarized
three -prong plug which also provides a convenient point
for the ground connection to be made.
Since it is common studio practice for tape machine a.c.
power grounds to be left floating via the use of three- to
two -prong a.c. adapters to prevent ground loops, you must
be sure that the two -prong end of the adapter is inserted
into the wall socket in the proper direction. If it is not,
the connection labeled neutral on the mda socket will
really he the hot side, and when the vso is connected to
this machine, the hot side of the a.c. line will be connected to the a.c. neutral through the tape machine's power
switch and fuse, and through the power amp's chassis,
causing the tape machine fuse to blow. Rather than risking this, the tape machine's power cord ground wire
should be disconnected inside the machine so that the
polarized three -prong a.c. plug can be inserted directly
into the wall socket, eliminating the possibility of blown
fuses.
What's new
from MP?
DA's...
Model 4820
Distribution
Amplifier
Bridging (6K ohms), Balanced, Trans formerless (Differential) Input Configuration
Balanced. Transfornterless Outputs
(Precision Resistor Network)
8
Continuously Adjustable Gain,
+10
-90
Low Noise (Output)
to
High Output Level.
channel
Reverse
Polarity 8
Overload Pro-
tected
dBm
Miniaturized. Plug -in P.C. Card Construction
Low Distortion (Typ. 0.1 %)
+20
dBm per
Utilizes MAP 1731A Audio Opera tmnal Amplifiers
...and VCA's
The neutrals of the tape machine a.c. lines must not
be connected together by the vso switching system, for
this may cause ground loops. The relays must therefore
switch the neutral as well as the hot side of the vso power
to the capstan motor selected, as shown in FIGURE 3.
Up
dB
80 dB of isolation between Outputs
8 Output to Input
Model 5100
ç,
,,,...r,l
-,
VCA Module
130 dB Control Range
-100 dB Attenuation)
(
-30
dB Gain,
Noise, --98 dBm (Output) at
Unity Gain
Low Distortion. 0.05% Typical
Broad Frequency Response. 10 Hz to
Low
NO CONNECTION BETWEEN CONSOLE GROUND
AND POWER AMP
Since the power amp chassis is connected to the a.c.
power ground, it is necessary that there be no connection
between console ground and the power amp chassis, to
prevent ground loops. If the oscillator used has its own
power supply (rather than operating from the console's
d.c. supply) and its chassis is not electrically connected
to the console via rack mounting or to a.c. power ground
via its power cord, no ground loops will occur. When an
oscillator powered from the console or electrically connected to the console in some manner is used, an isolation
transformer will be needed to isolate console ground from
the vso power amp chassis. In the event either the oscillator output or the power amp input is already transformer coupled and floating, that is sufficient if the cable to the
power amp is shielded with the shield connected to the
power amp chassis at that end and cut off at the oscillator
end (telescoping shield).
Only one other item needs to be mentioned to prevent
some head scratching when the system is connected. Some
tape machine manufacturers insert the tape runout switch
in the neutral side of the a.c. line and wire the neutral
connection on the mda socket to the transport electronics
side of the runout switch (see FIGURE 1). As a result, when
vso operation is selected, the power amp's neutral connection bypasses the tape runout switch, preventing automatic shutoff at the end of the reel. This is a small drawback when considering the many advantages of an easily
implemented vso system.
45 kHz, ±0.25 dB
Accurate Control Linearity 8 Tracking. 20 dB /Volt
Virtual Ground Summing Input
Model 4100 -VCA Card
Self-contained. Requires No External
Circuitry
High Input level, +27 dBm
High Output Level. +20 dB into 100
ohm load
Provides Reference Voltage Supply
for External Fader
Utilizes MAP Model 5100 VCA in
Conjunction with MAP 1731A Audio
Op -Amp
Optional Built -in Output Transformer
(Model 4200)
Other MAP Pro Audio Components
Audio Op -Amps
Console Modules
Equalizers
Compressor Limiter
Precision Oscillator
PC Card Amplifiers
Audio Transformers
Power Supplies and Accessories
SEE THEM IN L.A. AT
THE AES Booth 33
Shopping for
a
Console?
Ask about our Recording 8 Broadcast Console
Consoles.
For prompt assistance call or write Rick Belmont.
Modules... and
MOEDUL.AF=1
AUDIO PRODUCTS, Inc.
REFERENCES
Tobey, Graeme, & Huelsman. Operational Amplifiers: Design
and Application. McGraw -Hill Book Co., New York, N.Y.
1971. pp. 383 -385.
A UNIT OF
MODULAR DEVICES, INC.
1385 Lakeland Ave.,
Ma-
Airport International Plaza
Bohemia. New York 11716
516- 567 -962
Circle 37 on Reader Service Card
Q
b
classified
ft
REPAIR
®
SCHOEPS (TELEFUNKEN) VACUUM TUBE
CONDENSER MICROPHONES REPAIRED.
Closing date is the fifteenth of the second month preceding the date of issue.
Send copies to: Classified Ad Dept.
db THE SOUND ENGINEERING MAGAZINE
1120 Old Country' Road, Plainview, New York 11803
,V
Original factory parts &factory calibration of capsules.
Models CM51, 61, 66; M201, 221, MK24, 26 etc.
ALBERT B. GRUNDY
64 University PI., N.Y., N.Y. 10003
MOM
(212) 929 -8364
ti
TAPCO MIXERS, graphic equalizers and
reverbs at low. low cost. Specs and
prices. Write Daugherty Audio, 7313
Inzer, Springfield, Va. 22151.
a word for commercial advertisements.
Employment offered or wanted ads are accepted at 25C per word.
Frequency discounts: 3 times, 10'7( ; 6 times, 20e ; 12 times, 33%.
Rates are 50c
INFONICS DUPLICATORS! For
-
a
bunch
of reasons. you can't afford not to con-
especially
sider lnfonics Duplicators
since factory installation and training are
included in the list price. INFONICS
DUPLICATORS, (219) 879.3381.
FOR SALE
MCI input modules, $550.00 each. Tested and Guaranteed. Paul. (312) 225-
2110.
AGFA-GEVAERT. Professional PEM Mas tertape, the international studio standard
available from TECHNIARTS, 8555 Fenton St., Silver Spring, Md. 20910. (301)
585-1118.
AVAILABLE SERVICES. Milam Audio
Co. specializes in every phase of professional studio wiring, from complete
systems to individual pre -wired parts
and components. Available from stock:
patch bays, custom mic panels, multi paired cabling and harnesses, etc.
Milam Audio Co., 1504 N. 8th St.,
Pekin, III. 61554. (309) 346 -3161.
CUSTOM CROSSOVER NETWORKS to
your specifications; a few or production
quantities. Power capacities to thousands of watts; inductors and capacitors
available separately; specify your needs
for rapid quotation. Also, PIEZO ELECTRIC TWEETERS -send for data sheet
and price schedules. TSR ENGINEERING,
5146 W. Imperial, Los Angeles, Ca.
90045. (213) 776 -6057.
PRO
AUDIO EQUIPMENT
(716) 343 -2600.
DON'T MISS THE "DISCO WAGON "!
Excellent complete line of discotheque
equipment from West Germany is available to fulfill your needs. Request your
information package today. Write to:
D.T.S., Dept. DISCO, P.O. Box 16049,
Seattle, Wa. 98116. Reserve your territory in time!
SALE: MELLOTRON 300 -D; split
keyboard; both keyboards may be played
simultaneously. 12 selections on each
keyboard. Total of 24 available sounds.
$5,500. E. Delaney, P.O. Box E -2, Altmament, N.Y. 12009. (518) 861 -5389.
FOR
&
SERVICES
O
NAB ALUMINUM FLANGES. We manufacture 8 ", 101/2 ". & 14 ". For pricing,
write or call Records Reserve Corp., 56
Harvester Ave., Batavia, N.Y. 14020.
Custom touring sound` 2 -, 4- and
8 -track studios. disco systems.
Representing Akai, AKG, Altec.
Beyer. BGW. Cetec. Cerwin -Vega.
Community Light & Sound, dbx.
Dynaco. Dokorder. E -V, Gauss.
Lamb. Langevin. 3M, Martex PM,
Maxell. Meteor. Russound, Revox.
Sennheiser. Shure, Sony, Sound craftsman, Sound Workshop, Spectra Sonics, Switchcraft, TDK,
TAPCO. TEAC. Technics. Thorens,
and more. Offering these professional services: custom cabinet
design. room equalization, loudspeaker testing. custom crossover design, electronics modification, and custom road cases. Call
or write for quotes, or drop us a
line for our latest catalogue. K & L
Sound, 75 N. Beacon St., Watertown, Mass. 02172. (617) 7874073. (Att: Ken Berger)
DUPLICATORS, blank cassettes, recorders, boxes, labels, cassette albums and
supplies; lowest prices, top quality. Write
for free brochure, "50 Tips for Better
Duplication."
Stanford
International,
Box 546, San Carlos, Ca. 94070.
MEASURE REVERB TIME IN REAL TIME
-instantly! New, easy -to -use RT -60 delivers precise, instant real time digital
readout. Eliminates chart recorder analysis. Only $460. Write: Communications
Co., Inc., 3490 Noel! St., San Diego,
Ca. 92110.
NAGY SHEAR -TYPE TAPE SPLICERS
FOR CASSETTE
1h
sS
NRPD
Va
&
IN. TAPES
HAND -CRAFTED
ELD
SLF- ACCURATEE
SELF-SHARPENING
FIO
Box 289 McLean, Va. 22101
FOR
SALE:
STUDER MODEL A80 4-
track 1/2" tape recorder. Three years
old, but with very low mileage on it.
Only six months' use. The four electronics need general checkup but otherwise in excellent condition. Spare parts
included. $5,000. Call Tony Ochoa (809)
764 -4440. Write Ochoa Recording Studios, Inc., GPO Box 3002, San Juan,
P.R. 00936.
1800 WATT ISOLATION TRANSFORMERS. $150. F.O.B. Pragmatech Sound,
70 Sheldrake PI., New Rochelle, N.Y.
10804. (914) 633 -8556.
TASCAM WARRANTY SERVICE STATION. Mixing consoles, $1,350; 1/2"
recorders, $1,950; 8 -track machines,
$2,950. All shipped prepaid & insured,
including free alignment + equalization
+ bias _ calibration + life test. Music
& Sound Ltd., 111 í Old York Rd., Willow Grove, Pa. 19090. (215) 659 -9251.
Note Special Prices
FOR SALE: 3M M -56 8 -track 1 -in. w /remote. modified and rebuilt. Call Westlake Audio. (213) 655 -0303.
CLASS D SWITCHING AMPS; B.B.C.
reference monitors; pre -equalized
J.B.L. /Altec transducers; Nakamichi
mastering cassettes; I.M.F. transmis.
sion lines; Ampex /Scully /Crown/
Revox A -700 recorders /tapes; Micmix / Orban / Multi -Track reverbs;
Eventide flangers / omnipressors;
Parasound stereo synthesizers /
parametrics; Lexicon digital delays;
dbx /Burwen N.R. companders; Little Dipper hum /buzz notch filters;
Cooper Time Cube echo send /doubler; moving coil Denon /Ortofon;
B &O /Rabco
straight line arms;
Beyer condensers /ribbons; U.R.E.I.
comp /limiters; White equalizers/filters;1,000s more. Music & Sound
Ltd., 111/2 Old York Rd., Willow
Grove, Pa. 19090. (215) 659 -9251.
Enclosure Designs Included -FREE
BODE FREQUENCY SHIFTERS
SINCE 1963
Featuring the universal model 735.
described in March issue of db.
and other special models, plus the
line of Polyfusion synthesizer
modules and equipment. For details, contact:
Harald Bode
Bode Sound Company
1344 Abington Place
N. Tonawanda, N.Y. 14120
(716) 692 -1670
MODERN RECORDING TECHNIQUES by
Robert E. Runstein. The only book covering all aspects of multi -track pop
from
microphones
music recording
through disc cutting. For engineers, producers. and musicians. $9.95 prepaid.
Robert E. Runstein, 44 Dinsmore Ave.
Apt. 610, Framingham, Mass. 01701.
[
rJ FRADFORD]
Order Radford direct from England!
Immediate dispatch by air of HD250
stereo amplifier. ZD22 zero distortion
preamp. Low Distortion Oscillator ser.
3, Distortion Measuring Set ser. 3,
speakers and crossovers. Send for
free catalogues, speaker construction
plans, etc.
WILMSLOW AUDIO
Dept. Export DB, Swan Works, Bank Square,
Wilmslow, Cheshire, England
DOLBY. Two great names!
Two great products! For authorized factory representation in the progressive
Midwest. contact Jerry Milam, Milam
Audio Co., 1504 N. 8th St., Pekin, III.
61554. (309) 346 -3161.
MCI
-
.
When precision
s
yuo/Ilr
iEnrrrttnl
AEG -TELEFUNKEN
K
TUBES
HARRISON ELECTRONICS
20 Smith St. Farmingdale. N.Y. 11735
(Dealers invIted)
TEST RECORD for equalizing stereo
systems. Helps you sell equalizers and
installation services. Pink noise in t/3
octave bands, type QR- 2011 -1 @ $18.
Use with precision sound meter. B &K
Instruments, Inc., 5111 W. 164th St.,
Cleveland, Ohio 44142.
.
SCULLY TASCAM, all major
professional audio lines. Top dollar
trade -ins. 15 minutes George Washington Bridge. Professional Audio Video
Corporation, 342 Main St., Paterson,
N.J. 07505. (201) 523 -3333.
Corners, handles. audio hardware. Tapco
mixes and EQ's. Shure SM mics. Professional Audio gear at Big Savings. Catalog 50e. Headtronix, Box 31012, Dallas 8, Texas 75231
AMPEX
-for
AMPEX 300. 352. 400, 450 USERS
greater S/N ratio. replace first playback
stage 12SJ7 with our plug -in transistor
preamp. For specifications. write VIF International, Box 1555, Mountain View,
Ca. 94042. (408) 739 -9740.
NEUMANN STEREO CUTTING SYSTEM:
2 LV -60 amps and 2 GV -2A feedback
amps; one WV -2A feedback /monitor
amp; one SI -A circuit breaker; one
Ortofon 631 h.f. limiter. $3.000. Paul
(312) 225 -2110.
CERWIN -VEGA pro. full range speaker
systems; bass horn, including the 2k
rms Earthquake double -D horn; midrange horns; high frequency horns; musical instrument speakers; stage monitors;
disco systems; power amps; equalizer
and mixers with lifetime speaker warranty. A New England exclusive at
K &
L
Sound Service, 75 N. Beacon St.,
Watertown, Mass. 02172. (617) 7874073. (Att: Ken Berger)
FOR SALE, 16 -track professional recording studio in Aspen, Colorado. MCI,
Dolby, 3M, plus musical instruments. In
business two years with excellent opportunity for future growth. E. D. Thorne,
Box 1498, Aspen, Colorado, 81611.
(303) 925.5530.
WHATEVER YOUR EQUIPMENT NEEDS
-new or used -check us first. We specialize in broadcast equipment. Send
$1.00 for our complete listings. Broadcast Equipment & Supply Co., Box 3141,
Bristol, Tenn. 37620.
STUDIO SOUND- Europe's leading professional magazine. Back issues available from June '73 through June '75. $1
each. postpaid. 3P Recording, P.O. Box
99569, San Francisco, Ca. 94109.
ORTOFON
DYNAMIC MOTIONAL FEEDBACK mono
disc cutting systems. Complete with
drive, feedback. and feedback -playback
monitor amplifiers and cutterhead. All
systems guaranteed. Spare cutterheads
available for exchange /repair. Albert B.
Grundy, 64 University Place, New York,
N.Y. 10003. (212) 929 -8364.
CROWN INTERNATIONAL. Complete repair, overhaul, and rebuilding service
for current and early model Crown tape
recorders and amplifiers. New and used
machines bought and sold. TECHNIARTS,
8555 Fenton St., Silver Spring, Md.
20910. (301) 585 -1118.
MCI JH416 CONSOLE
16 bus 24- output, included director's desk & additional cabinetry
w / @62" of rack space. Included
are twelve 440 modules & space
for 12 more. Priced for quick sale.
For more info, call Marty at
Colorado Nashville, Inc., (303)
473 -1272.
ONE STOP
FOR ALL YOUR PROFESSIONAL
AUDIO REQUIREMENTS
BOTTOM LINE ORIENTED
F. T. C. BREWER CO.
P.O. Box 8057, Pensacola, Fla. 32505
Neumann recording console, 18 input,
$14,000 (originally $35,000). Scully 8track with remote control, can be expanded to 12 tracks, $7,000. Neumann
lathe with Westrex 2 -B mono system
plus accessories, reasonable. Pentagon
cassette duplicator, reel /cassette, cassette /cassette, $1,000. Ampex AG -500
stereo, $1,250. Ampex PR 10 stereo, $600.
Paul. (312) 225 -2110.
AMPEX 440B 4- track. low usage, $4,000/
offer. Jeff (315) 463 -8631.
CUSTOMIZED TUNED ROCK P.A.'s
Expandable high intensity touring/
permanent sound systems; including narrow band (5Hz!) feedback
and ring mode suppression, detailed regenerative response environmental equalization ( ±1 dB at
your ears), room design, /measurement / treatment / our engineered
enclosures plus 18 dB crossovers.
L 15% articulation loss of consonants; 1,000s of customized professional products including: fiberglass horns. consoles. comp /rms/
peak limiters. continuously variable electronic crossovers. digital /acoustic /analog delays. omnipressors. flangers, reverb, echo.
doubling /tripling. p.a. noise reduction, piezo transducers, frequency shifters, notch filters from
J.B.L. /Altec pro. Tascam.
U.R.E.I., Eventide, Gately. Beyer.
Crown, Community, Mom's Audio,
McIntosh, Allen & Heath. Cetec,
Multi- Track, Orban, White. etc. All
shipped prepaid !- insured. Music
& Sound, Ltd., 111/2 Old York Rd.,
Willow Grove, Pa. 19090. (215)
659 -9251.
Anechoic Chamber 0.9a Working
Floor
Inventors /Engineers
.
(continued)
www.americanradiohistory.com
FOR SALE
A FEW competitively priced used Revox
A77 decks available. Completely reconditioned by Revox, virtually indistinguishable from new and have the standard Revox 90 -day warranty for rebuilt
machines. Satisfaction guaranteed. Example, A77 with Dolby, $675, plus shipping. Write requirements to ESSI, Box
854, Hicksville, N.Y. 11802. (516) 921-
2620.
16 -TRACK AMPEX MM -1000, excellent
condition. Converted to 15 -30 w /input
switching on s/s and auto. Dolby switching. $13,500. Call D. Frey, A &R Record-
WE WILL BETTER anyone's price on
new Recordex high speed cassette duplicators. Your written request can save
you a bundle. Also get our large-user
cassette deal. Tape and Production
Equipment Company, 2080 Peachtree
Industrial Court, Atlanta, Ga. 30341.
Phone (404) 458 -TAPE.
SMALL 4 -16 TRACK STUDIOS. Detailed
technical assistance + acoustical consultation, from our engineering division
to our clients-either here or via phone,
& included FREE. Music & Sound Ltd.,
111/2 Old York Rd., Willow Grove, Pa.
19090. (215) 659 -9251.
THE ONLY ONE
PATCH CORDS, new 3 ft. Switchcraft
tip- ring -sleeve (PJ -051R plugs). Com-
mercial overstock makes these available
at $5.25, which is below dealer cost.
No minimum, dealers welcome, satisfaction guaranteed. Shipped prepaid or
C.O.D. NOTE: NEW BOX NUMBER.
(Post Office error sent letters back,
please write again.) Kapes Audio Supply, P.O. Box 5045, River Station, Rochester, N.Y. 14627.
CREATIVE CASSETTE & CARTRIDGE
LABELS. Custom designed; small and
large runs; cassette, cartridge duplication. Omega Audio, 25520 Graham,
Detroit, Mich. 48239.
ing, (212) 582 -1070.
REELS AND BOXES 5" and 7" large
and small hubs; heavy duty white boxes.
W -M Sales, 1118 Dula Circle, Duncanville, Texas 75116. (214) 296 -2773.
AMPEX TAPE. Ampex Audio Studio
Mastering Tapes, 631 -641, 406 -407, and
"Grand Master" in stock for immediate
shipment, 1/4", 1/2", 1", and 2 ", factory
fresh. Best prices, BAC charge cards
accepted. TECHNIARTS, 8555 Fenton
St., Silver Spring, Md. 20910. (301)
585-1118.
THE LIBRARY
Sound effects recorded in STEREO using Dolby'
throughout. Over 350 effects on ten
discs, $100.00. Write, The library, P.O.
Box 18145, Denver, Colorado 80218.
.
.
FOR SALE: LARGE MOOG with two keyboard controllers, one ribbon controller
and custom cabinet, $4,950. Woodland
Sound Studios, Nashville, Tenn. (615)
227 -5027.
CASSETTE LABELS, 1,000 on typewriter
roll, $10.98 ppd. Other formats and custom labels. TARZAC, 638 Muskogee
Ave., Norfolk, Va. 23509.
MCI 24 x 24 console with extras. Also
MCI 16-track tape recorder. Will sacrifice. Sound Room, 300 S. 69th St.,
3/M
94109.
16 -track
tape
recorder,
M -56.
$14,500. Perfect. Paul. (312) 225 -2110.
WIRELESS MICROPHONES. Professional
hand held and lavalier wireless microphones, new and used. EDCOR, 3030
Red Hill Ave., Costa Mesa, Ca. 92626.
-
Keep db coming
without interruption!
Send in your
new address promptly.
Enclose your old
db mailing label, too.
FREE
CATALOG á AUDIO APPLICATIONS
CONSOLES
KITS S. WIRED
AMPLIFIERS
MIC., EO ACN
LINE, TAPE, DISC,
POWER
OSCILLATORS
AUDIO
®OPAMP LABS. INC.
N
TAPE BIAS
POWER SUPPLIES
3M SERIES 79 1" 8 -track headstacks,
mint condition, $1,400 or best offer.
(614) 663 -2544.
(714) 556 -2740.
MOVING?
producer's desk. Expandable. $18,000
will finance. Call Tom (213) 783 -9235
or Bill (213) 462 -8515.
DISCO MIXERS. Write for free bulletin.
Berkshire Audio Products, P.O. Box 35,
Great Neck, N.Y. 11021.
$2 MILLION USED RECORDING EQUIPMENT. Send $1.00 for list, refundable, to
The Equipment Locator, P.O. Box 99569,
San Francisco, Ca. 94109.
18510.
FOR SALE: 20 x 16 QUAD recording
console. Monitor mix, 2 cues, 4 echo,
solo, mute, 2 joy sticks, patch bay and
MAXELL TAPE. All widths. Write NOW
and SAVE! N.A.B. Audio, Box 7, Ottawa,
III. 61350.
Upper Darby, Pa. 19082. (215) 7341117.
.
ARP SYNTHESIZERS! Strings, $1,385;
2600, $2,260; Axxe, $730; Prosoloist,
$875; Odyssey, $1,165. Dickstein Distributing, 1120 Quincy, Scranton, Pa.
CASSETTE WINDERS: Ramko Research
ACL -25's; excellent condition; $256 both.
TARZAC, 638 Muskogee Ave., Norfolk,
Va. 23509.
Write to:
Eloise Beach, Circ. Mgr.
db Magazine
1120 Old Country Rd.
Plainview, N.Y. 11803
DECOURSEY
ACTIVE
ELECTRONIC
CROSSOVERS. Model 110 dividing network; complete with regulated power
supply, for bi -amp, tri -amp, or quad amp. Custom assembled to meet your
specifications. Monaural, stereo, or with
derived third channel. Plug -in Butterworth (maximally flat) filters; 6, 12 or
18 dB per octave at any desired frequency. OPTIONS: Summer for single
woofer systems, VLF hi -pass filters for
elimination of subsonic noise, derived
third channel. FOR OEM OR HOME ASSEMBLERS: Model 500 or 600 dual filters. Regulated power supplies. Write for
new brochure. DeCoursey Engineering
Laboratory, 11828 Jefferson Blvd., Culver City, Ca. 90230. (213) 397-9668.
Two can ride cheaper
than one.
A
Put* Sere. of
The Mepewe L The
ow
AO.eßtrp Counol
DYNACO RACK MOUNTS for all Dynaco
preamps, tuners, integrated amps. $24.95
postpaid in U.S., $22.50 in lots of three.
Audio by Zimet, 1038 Northern Blvd.,
Roslyn, N.Y. 11576. (516) 621 -0138.
SONIPULSE w /AKG condenser
microphone. $1,000, also Allison Kepexes, API 525 Limn /Compressors, JBL
2390 lenses in good condition. Bursting
Sun Sound Services. (413) 863 -4356.
UREI
ELECTRO -VOICE SENTRY PRODUCTS.
In stock: Sentry IV -A, Sentry III, and
Sentry II -A monitor loudspeaker systems
for professional monitoring and sound
reinforcement. Immediate air freight
shipment to any N. American destination.
National Sound Corp., Ft. Lauderdale,
Florida. (305) 462 -6862.
FREE CATALOG of studio kits, consoles,
p.a., discrete opamps. QCA, Box 1127,
Burbank, Ca. 91507.
CENTRAL MUSICIANS' SUPPLY. Instruments and sound equipment for the professional. All major brands; sound reinforcement systems custom designed;
home studio recording equipment. See
our pricelist before you buy. DJ's Music
Limited, 1401 Blanchan, La Grange
Park, III. 60525. (312) 354 -5666.
CHIEF ENGINEER
AUDIO PRODUCTS
We are seeking an audio equipment engineer who is an aggressive and innovative designer-one
who has designed consoles or
components for consoles used in
recording and broadcasting applications.
If you are this creative and product- oriented individual, looking for
a rewarding career, we would like
to talk to you.
Please send your accomplishments and salary history to:
Modular Audio Products
1385 Lakeland Ave.
Bohemia, N.Y. 11716
Sabor presents
the
MK-668C
wow and flutter meter
1
'
50
_
!MEIN
fe.
The MEGURO MK -668C. capable of
measuring DIN. IEC & ANSI at 3 15 kHz
and JIS. NAB & CCIR at 3 0 kHz. is truly
a world -wide. universally applicable Wow
& Flutter Meter. It features selectable cal
ibration to permit reading of peak. average or effective values of W /F. and tape
speed error is indicated on the built -in
RECORD COMPANY established 1953
seeks freelance recording engineer associates in all major cities, colleges, etc.
Write for very interesting offer. Educo
Records, Box 3006, Ventura, Ca. 93003.
-
digital frequency meter.
W/F range is 0 003% to 10%
at inputs above 30mVrms
and 0.01% to 10% with inputs
from 0.5mV to 30mVrms
Price is $975
12597 Crenshaw Blvd
Hawthorne. CA 90250
EUROPEAN ORGANIZATION requires
General Manager for U.S. outlet (New
York area). Outstanding opportunity for
competent sales engineer to participate
in establishing a new corporation for
the distribution of recording equipment.
Good understanding of tape equipment
and of the recording industry essential.
Send resume in confidence to Dept. 52,
db Magazine, 1120 Old Country Rd.,
Plainview, N.Y. 11803.
(213)644.8689
Sabor corporation
Circle 38 on Reader Service Card
WANTED
WANTED: ALTEC X633 microphone.
Dept. 51, db Magazine, 1120 Old
Country Rd., Plainview, N.Y. 11803.
WANTED: SONY ECM -22, ECM -377, C57, C -37A, C -37P, ECM -64P, ECM -65P,
C -22, C -500 microphones and console
cabinets for TEAC 7030 SL or 7030 GSL
recorders and remote controls. Blue
Diamond Co., Box 102C, Chubbic Rd.,
R.D #1, Canonsburg, Pa., 15317. (412)
746-2540.
EMPLOYMENT
WANTED: AUDIO ENGINEER /TECHNICIAN /JACK -OF- ALL -TRADES. Resumes
only. Bradley Recording Co., Inc., 531
N. Howard St., Baltimore, Md. 21201.
MUSIC FACULTY OPENING. The UCSD
Department of Music announces the following academic opening for 1976 -77:
A recording specialist to teach undergraduate and graduate courses in re-
cording techniques, possibly graduate
course every other year in tuning and
temperament, and supervise the departmental archiving and tape duplication.
Applicants should have a strong musical
background; BA or MA in music desirable. The UCSD Department of Music
is committed to an active, experimental
program of contemporary music. All
resumes, appropriate scores, and other
documentation
should be sent to:
Search Committee; Music Department
(B026), UCSD, La Jolla, Ca. 92093.
The University of California, San Diego,
Is an Affirmative Action /Equal Opportunity Employer. Women and minorities
are encouraged to apply.
EXPLORE SOUND!
...and meet our researcher DennisColin.
Dennis has been exploring sound for more than
He plays gigs with "Family
twenty years.
Affair ", and his 1970 paper published by the
Audio Engineering Society of America is considered classic in the field of electronic music.
Dennis' special interest these days is in finding new ways to modify both instrumental and
vocal sounds. Best of all, he helped design the
ARIES SYSTEM 300 ELECTRONIC MUSIC
SYNTHESIZER. Let us tell you about it just send the coupon for full information.
(Also available in kits for those who would
like to save money by building their own).
would like to explore sound. Please
information on the ARIES SYSTEM
300 ELECTRONIC MUSIC SYNTHESIZER.
Full information on kits too, please.
) Yes,
send free
(
I
would like a demonstration cassette of the
(
I
enclose $5.00 to cover costs.
SYSTEM 300.
I
I
SPIRIT- FILLED recording engineer /technician for 16 -track rural recording studio. Hard work, long hours. Must dig
rock /country. Contemporary Christian
ministry. (614) 663 -2544.
EXPERIENCED MUSIC MIXER
NAME------ -
For major N.Y.C. studio, expanding staff. Send resume to Box 11,
db Magazine, 1120 Old Country
Rd., Plainview, N.Y. 11803.
ADDRESSSEND TO: ARIES, Inc., 119 Foster Street
Peabody, Mass., 01960
(617) 532 -0450
W
Circle 35 on Reader Service Card
www.americanradiohistory.com
o
o
PeoPle/Places/haPPenings
tir"
(4'41
AA
SZEGHO
FAR000
Well -known electronics engineer
Dr. C. S. Szegho has been appointed
to the board of directors of the Rau and -Borg Corporation of Chicago.
Dr. Szegho, who has been associated
with Rauland-Borg research, pioneered
many advances, first in radar tube
design and later in t.v, picture tube
development. He is now serving as a
consultant to the Zenith Radio Corpo-
ration.
Abid Farooq has been appointed
senior project engineer for single side band product development at Coast com, of Concord, California. Mr. Farooq will be responsible for SSB program channels for use with both satellite and CCITT FDM networks.
Dr. Peter C. Goldmark, president
of Goldmark Communications Corp.
of Stamford, Connecticut, has been
granted a patent for a new video learning system to be used with home t.v.
sets. The new system, called Rapid
Transmission and Storage Mark II.
makes it possible to transmit pictures
and sound at extremely high speeds
for broadcasting by satellite or cable
t.v. and for storage and playback over
home television sets. The system can
provide 60 different half-hour programs from a single hour -long videotape. Up to 30 of the programs can
he selected from the single tape and
shown simultaneously on different t.v.
sets.
Omega State Institute has moved
to a new location at 237 E. Grand
Ave., Chicago, Ill. The school offers
trade school facilities in broadcasting.
FCC license training, and electronic
alarm systems.
v
Serving the Midwest, Tom S. Butler has been appointed Central sales
manager by McMartin Industries, Inc.
of Omaha. Nebraska. Mr. Butler's
responsibilities will include broadcast.
COLODNY
p}
TRUEMAN
engineered sound and background music product sales. He comes to McMartin from the Collins Radio Group,
Rockwell International.
Two new personnel changes have
taken place at CCA Electronics Corporation, of Gloucester City, N.J. Samuel H. Colodny has been promoted to
director of engineering, and A. W.
(Bill) Trueman as director of marketing. Mr. Trueman came to CCA from
RCA in 1974. Mr. Colodny. who
holds several patents for his inventions, was previously with AEL.
A new nickel /steel alloy for magnetic heads was unveiled at the NAB
Show in Chicago by Nortronics. The
alloy, a high permeability magnetic
substance named Wear -Resistant Hy
Mu 800T ", was developed by Carpenter Technology, of Reading, Pa.
The long- wearing heads are projected
as a boon to high use applications.
such as broadcasting.
Overseas orders from Egypt, Malaysia, and Hong Kong have been received by Rupert Neve and Co. of
London. The Cinema Organization of
Cairo ordered an 8036, 24- channel,
16-track music recording console.
Film Malaysia has requested a BCM
I0/2 sound control console and Radio
Hong Kong has placed an order for
three BCM 10/2 consoles.
Swiss based Eastlake Audio, recently founded by Tom Hidley, president of Westlake Audio Inc., of Los
Angeles, has commenced its operations from Montreux. Representation
for the corporation in Scandinavia and
the United Kingdom will be Scenic
Sounds Equipment. Kent Duncan of
Sierra Audio, Burbank. Ca. will represent American interests. Additional
dealers are 3M France, and Studer International in Zurich, Milan. and Tel
Aviv.
DUNN
DILLEY
The Rectilinear Research Corporation of the Bronx, N.Y. has named
Claude Dunn as Metropolitan New
York sales manager. Mr. Dunn comes
to Rectilinear from the Sony Corporation.
William G. Dilley, president of
Spectra Sonics, of Ogden, Utah, has
been selected for inclusion in The International Register of Profiles. Mr.
Dilley is a Fellow of the Audio Engineering Society, a Fellow of the Intercontinental Biographical Association,
holder of fourteen U.S. and foreign
patents and is the holder of numerous aircraft speed records.
Assigned to the design of circuits
and products in the areas of broadcast control room equipment and small
broadcast transmitters, Edward M.
Corse has joined LPB Inc. of Frazer,
Pennsylvania as staff engineer. Mr.
Corse was formerly with U. S. Electronic Services.
Cindy Guzzo has been named marketing manager at Pacific Recorders &
Engineering Corporation of San Diego,
California. Ms. Guzzo will be responsible for sales and marketing. She was
formerly with La Salle Audio.
The Plastic Reel Corporation has
a new customer service department which will work with audiovisual suppliers to develop methods of
packaging, storage, and handling new
tape products. The company is based
in Carlstadt, N.J.
established
Copies of all issues of db -The
Sound Engineering Magazine starting with the November 1967 issue
are now available on 35 mm. microfilm. For further information or to
place your order please write directly to: University Microfilm, Inc.
300 North Zeeb Road
Ann Arbor, Michigan 48106
We added your inputs to ours.
The result is the Model lOB -a good thing made better.
Now there are peak reading LED indicators on each
input, chassis mounted 1/4" phone jacks for added
stability, and the echo busses can be used with
the program busses for 8 -out capability.
An 8- channel Monitor Mixdown Module (Model 116) is
now available optionally for direct interface. Each
channel may be switched selectively to monitor buss or
tape, and individual pan and gain controls are provided.
Additionally, there is a split mono cue send (1 & 2),
and an outboard automatic switching matrix.
When you want to expand the capabilities of the
Model 116, the Model 120 Input Cue/Solo Module allows
you to mult the accessory send signals from up to
12 inputs for a mix of tape cue and input cue on the
split mono cue buss. And you can solo any of 12 active
input channels.
The Model 10B is new. But it's built with the same
design philosophy and integrity that has made the
Model 10 one of the most popular mixing consoles ever.
It's a creative tool that gives you the practical
capabilities your imagination demands.
So if you have more talent than money, look into the
Model 10B at your nearest TEAC Tascam Series dealer.
Just call toll free (800) 4474700 ** for the name and
location of the one nearest you. * *In Illinois,
call (800) 322 -4400.
Model 108
TEAC.
Model 120
TASCAM SERIES
TEA(' Corporation of America,
Telegraph Hd., Montebello. ('A 90640
TEAC 1976
77:43
Model
116
Think of ahem as
your musical instruments.
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It's not something an amateur can do. It's an art
And that's why Yamaha has designed 3 superb
mixing consoles with the qualities and range of
controls that the professional sound reinforcement
artist needs.
For instance, our exclusive 4x4 matrix with level
controls gives you more exacting mastery over
your sound than the conventional method of
driving speaker amps directly from the bus
outputs.
Features like that are years away except on the
most expensive mixers. On the Yamahas, it's
standard equipment. And so are transformer
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isolated inputs and outputs, dual echo send
busses, an input level attenuator that takes -4 dB
line level to -60 dB mike level in 11 steps, and 5frequency equalization.
Whether you choose the PM- 1000 -16, the
PM- 1000 -24 or the PM- 1000 -32, Yamaha gives you
the flexibility you need to turn your job into an art
And because they're designed from the ground
up to perform on the road, more and more
professional sound men around the United States
and the world are depending on Yamaha. night
after night, gig after gig.
If you've never thought of your mixing console
as a musical instrument, we'd like to invite you to
stop by your Yamaha dealer. Once you've
checked out the operation manual and tested for
yourself what the PM Series can do, we think you'll
come away a believer.
6600. Buena Park. CA 90620
Circle
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The audience can't see you. But they can sure
hear you.
They don't know it, but they're depending on just
one person to get the music to them. And that guy
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