Page 1 ISSN0011-7145 THE SOUND ENGINEERING OCTOBER

Page 1 ISSN0011-7145 THE SOUND ENGINEERING OCTOBER

ISSN0011-7145

THE SOUND ENGINEERING

OCTOBER

1978

$1

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A

Test and

Save.

simple philosophy?

Yes. But, one The heart of our

TM 500

Audio

Travel carry-on- flight luggage.

A rear interface circuit board in the TM 515 Traveler that can save you and your clients Lab is our600

St low distortion audio

Mainframe lets you interconnect the many dollars. oscillator, which generates square or

Consider this: plug

-in instruments to make gain, loss or response measurements

-

at the touch of a pushbutton.

You're recording an exciting, new spot for a new client.

The musicians and low

500 distortion sine waves from

5

Hz to kHz (0.035% THD

20 Hz

For general to

50 kHz). troubleshooting combine vocalists are set.

You're getting noise on the tape and you can't find it this compact oscillator with a full function

TM 500

Multimeter with ac. dc. current, temperature and resistance readings as well as dB capabilities.

Add anywhere. Testing with a

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Try this:

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Troubleshooting with a

TM 500 test set before the show could have found the problem.

In this world of sound. time is money.

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Reader Service Card www.americanradiohistory.com

Coming

Next

Month

The subject for this next issue is

Digital Electronics.

There will be a story from Ampex on digital recording standards

-a

sub- ject that gets more important to dis- cuss with each passing day.

John Woram is assembling a story based on visits to a new automated re- cording studio in San

Francisco aptly named the Automatt.

Digitally operated automatic loca- tion of a tape will be

A another subject. number of present day systems will be

A detailed. sophisticated digital syncronizer from

BTX is the subject of another article. Learn all about the SMPTE time code and what it can do for you.

The world's first digital tape re- corder directory will appear in this issue.

And there will be articles on micro- processors now available that can do almost everything in your studio and yet cost good almost little more than typewriter. a

All this digitally coming in

No- vember in db, The Sound Engineering

Magazine.

This month's cover shows what one of the first direct -to

-disc sessions looked like.

The illustration is taken from an early issue of Scientific Amer- ican.

For a look at the complete cover see pages

56/57. And don't forget to read our reprint of their cover story, simply titled The appearing on pages

Gramophone and

54/55.

THE

SOUND ENGINEERING MAGAZINE

OCTOBER 1978

VOLUME

12,

NUMBER

10

EDITORIAL

BASIC

GROOVE GEOMETRY

Irwin J. Diehl

A

FROM

CYBERSONICS:

NEW DISC

-MASTERING LATHE

Suzette Fiveash

CBS DISCOMPUTER

C. P.

Repka

THE GRAMOPHONE

db TEST

REPORT

-

KEITH

MONKS

RECORD CLEANING MACHINE

THE

LOGISTICS

OF DIRECT

-DISC

RECORDING

Bert Whyte

BRING YOUR OWN

LATHE

Suzette

Fiveash

A

LOOK AT

THE RECORD -PLATING

PROCESS

James

P. Shelton

LETTERS

CALENDAR

BROADCAST SOUND

Patrick

S.

Finnegan

SOUND WITH IMAGES

Martin Dickstein

THEORY

AND

PRACTICE

Norman

H. Crowhurst

NEW PRODUCTS AND SERVICES

CLASSIFIED

PEOPLE,

PLACES,

HAPPENINGS

4-' is listed in

Current Contents: Engineering and Technology

40

42

46

50

54

58

61

64

66

2

8

10

20

26

32

69

72

Larry Zide

PUBLISHER

Bob Laurie

ART DIRECTOR

Eloise Beach

CIRCULATION MANAGER

Ann

Russell

ADVERTISING PRODUCTION

John

M.

Woram

EDITOR

Hazel

Krantz

COPY EDITOR

Lydia Anderson

BOOK SALES

Suzette Fiveash

ASSOCIATE EDITOR

Crescent Art Service GRAPHICS AND LAYOUT db. the Sound contents

11803.

Engineering Magazine is published monthly by Saga more Publishing Company. Inc. Entire copyright ©

1978 by Sagamore Publishing Co., Inc..

Telephone (516)

433 6530. db is published for those individuals and firms in

(514.00 per year outside U.S. Possessions. Canada and

Controlled circulation paid at

Brattleboro,

Mexico) professional audio

- recording, broadcast, audio -visual, sound reinforcement. consultants. video recording, film sound. etc. cation should be made on the subscription form in the rear of each issue.

Subscriptions are $7.00 per year

VT

05301.

1120 in U.S. funds. Single copies are 51.00 each.

Editorial.

Old Country Road, Plainview, L.1.,

Publishing. and

Sales

Offices:

Appli-

1120

N.Y.

Country Road, Plainview,

New

York

11R03.

Postmaster: Form 3579 should be sent to above address.

Old www.americanradiohistory.com

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Reader Service

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THE

EDITOR: by

Herewith a few thoughts prompted

Marshall King's two -part article,

The Technician and His Union. He mentions the decline of the big old movie studios and the rise of the in- dependents. Popular opinion has it that unions were in part responsible for this, and that unions do not pro- mote excellence; that seniority lists eliminate competition between engi- neers and shelter incompetents.

As we all know, the recording field has undergone meteoric growth over the past ten years Along with this, the role of recording engineer has also evolved. Whereas new equipment has kept the maintenance engineer on his toes, his work has remained es- sentially the same. But the recording engineer has had to become increas- ingly involved, creatively, in the use of multi -track techniques, and of the studio itself as a giant musical instru- ment.

In general, the unions have re- sisted this trend, or responded in pure- ly reactionary fashion

To the extent that it is democratic, the union is bound to speak for the majority, that which all workers have in common rather than the attributes which make each man unique.

Not all workers are equally good at all tasks, and this fact must be reconciled with the democratic principle of equal pay for equal work. The controversy sur- rounding "job classification" is im- plicit recognition of the problem, but the paradox remains, within any cate- gory there will always be important differences between individuals, with regard to both ability and motivation.

The unions are also seen, especially by artists and producers, as being op- posed to all new technological devel- opment, resisting with featherbedding and sabotage. Once a shop gets a reputation for such activities, it may suffer loss of jobs or even extinction.

Thus, while acting to support the idea of fair treatment for workers, the union may, ironically, sacrifice the very jobs it intends to protect.

Additionally, there is a growing feel- ing that bigness is itself an enemy.

As they have gotten bigecr, the unions have begun to resemble the giant corporations they are supposed to

(continued) www.americanradiohistory.com

Accurate Sound

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AES

AKG

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26

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Altec Corporation

Ampex

Ashly Audio

Audio

Design

Recording

Audio -Technica U.S.

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Auditronics

Cover

36 -37

53

. . .

4

28

7

5

Bogen

BTX

27

55

Clear -Com

30

Community Light

&

Sound

. . .

13

Crown

International

3 dbx,

Inc

19

Dolby

Duncan Electronics

Garner Industries

Hammond Industries

Inovonics

J & R

Music World

JBL

Leader Instruments

Lexicon Inc.

Neptune

Neutrik

Northwest Sound

Orban Associates

Otari

Philips Audio

Pioneer

Pro -Audio Specialties

Recording Supply

33

31

14

4

9

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25

24

12

29

18

20

22

21

16,

18

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Shure Brothers

SM Ltd.

Sound Technology

Sound

Workshop

Standard Tape Lab

Stanton

Magnetics

Studer

-Revox

Tandberg of America

38

41

2

17

65,67

10

23

15

48 -49

TDK Electronics

35

TEAC Corp. of America

, .

Cover

3

Techniques

Tektronix by

Panasonic

.

.44

-45

Cover

2

Telex Communications

Tentel

60

63

UREI

Waters Manufacturing

White

Instruments

6

16

14

The

Crown

D-75

is all new.

Except the shape.

(And

we

invented

that.)

If the new

D

-75 professional power am-

plifier

looks familiar, it's because the shape, which we created years ago, is

truly func-

tional.

But, until now, you have never seen any

amplifier

of this size, including Crown, that performs like the

D

-75.

The Crown

D

-75 is a powerful ampli- fier.

35 watts continuous average power per

channel into

8 ohms, 20Hz to 20KHz

@

.05% THD.

45 watts into

4 ohms.

In mono, the

D

-75 provides

95 watts continuous aver- age power into

8 ohms.

The

D

-75 is

virtually distortion

-free. Fre- quency response

@

1

±0.1dB,

20Hz to

20KHz

watt into

8 ohms;

±1.2dß,

5Hz to

100KHz. Hum and noise 106dB below rated output. THD less than .001% from 20Hz to

400Hz,

increasing linearly

to

.05% at

20KHz. IMD less than .01% from

.25 to

36 watts (less than .05% from

.01 to

.25 watts).

The

D

-75 is

professionally

convenient.

Signal- presence LED's indicate peak output greater than l/a watt into

8 ohms.

Active bal- anced XLR connectors, as well as unbal-

anced'

/4" phone plugs, are standard on the

rear

panel,

plus

an switch. Gain

external dual

/mono controls

are lockable.

The

D

-75 now

includes the Crown

Input- Output Comparator

(IOC) which re- ports non

-linear behavior in the amp: over- load, TIM or

protection circuit

activation.

In

addition, separate signal

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chassis

grounds are provided to minimize ground loops.

The

D

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expect

it to be

rugged

and

reliable.

Compare it with any

competitive amplifier.

The

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value. For more information, please write or call Crown or consult your Crown dealer.

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crown

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Up

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$815 counterpose- unresponsive to local needs, and resistant to change of any kind (bureaucracy breeds more bu- reaucracy). And, like big business. some unions are seen as come dient, crime. having be- immoral, dealing, when expe- with elements of organized

Finally, there are those

(admittedly, very few) who have deep concern about the

Constitutional question posed by sentation compulsory union repre- of all workers in a closed shop.

(A recent Supreme

Court ruling on this matter affirms freedom individual.) of the

Educated people know of the great good done by the unions in this country, over the years. Whatever problems the unions have today, the solutions can cone only from the members themselves.

Mr. King is right in saving those who criticize a union should also he actively trying to do something about it.

DOUG POMEROY

Brooklyn.

NY

SPEC]

FICATIONS:

INPUT IMPEDANCE: Unbalanced, 10K ohms nominal. OUTPUT IMPEDANCE:

Unbalanced, less than 10 ohms,_ short

-20 dBm to +24 dBm; input

CURACY:

PONSE at +4

*2

%. protection circuit

60V protected. OPERATING

RMS.

CALIBRATION ACCURACY:

(CONTROLS

FLAT):

*0.5 dB

POINT: +22 dBm Into 600 ohms load.

CENTER FREQUENCY

'0.5

20Hz to dB.

LEVEL:

FREQUENCY

AC-

RES-

20kHz. OUTPUT CLIPPING

DISTORTION:

Less than 0.01%

... 1kHz dBm into a

600 ohms load; less than 0.05% ... 20Hz to 20kHz at +18 dBm into a

600 ohm load.

EQUIVALENT

INPUT NOISE:

Less than

-90 dBm unweighted,

20Hz to 20kHz.

KLARK-TEKNIH

A Member of the Hammond

Industries

Group

The Sound of

Today.

THE EDITOR:

I really find it quite disappointing. and a little hard to believe, that the error in

Patrick

Finnegan's March.

1978 piece was lute claimed as the abso- truth in the June issue.

In

Mr.

Finnegan's answer, he does peak bias at

1 refer to kHz as the common guideline it is.

In the original article. however, he stated level at 10 correctly that the kHz is much more sensi- tive to the exact bias setting.

He erred. and

Gordon Carter, in his letter. picked him up on this, when he stated that the bias is set for the

"peak audio output" with the high frequency signal.

The range of

10 kHz drop with correct bias is at least as wide as given by

Mr.

Carter. I have seen the best performance obtained with drops anywhere from

2 to

12 dB at 10 kHz.

Within that great spread levels, the great for

10 kHz majority of tapes were very close to peak bias for

400 to

1.000 Hz.

In the last two years of using a I%3- octave rta (real -time ana- lyzer) with a pink noise source for tape and tape recorder testing.

I have become convinced of such a display of the essentialty if the goal is widest and flattest response.

The levels of the highest frequen- cies and the shape so of the curve change rapidly with small changes in bias that it is close to impossible to match the possible a scheme, performance using such

if

just 1,000 Hz peak bias is used.

Anyone who has not seen the

(continued)

Circle

3/ on

Reader Service Card www.americanradiohistory.com

... five years ago, I've done all of Shaun Cassidy and

Leif Garrett on it, most of

Donny and Marie. plus Al Martino, Sammy Davis. Debby Boone. the Supremes and others."

"After 20 singles and

12 albums on this console.

25 of them gold and platinum,

I guess you could say my

Auditronics

501 (serial number 0002) is a real money- maker.

It does what

I want as well as when it was new, and i m still cutting on it today."

Independent producer

Michael

Lloyd is one of over 300 satis- fied

Auditronics console users. if you'd like to learn some of what they know about

Auditronics console quality and reliability, circle reader service number or write to

3750 Old Getwell Rood, Memphis,

Tennessee

38118 (901) 362

-1350

auditroniu inc.

Circle 42 on Reader Service Card www.americanradiohistory.com

cD

Model

927

DDL

What

Took

You

So

Long,

UREI?

4 ii

i

0 8

'-

6

.

.

. . .

MI IM IM MI

'13- octave rta being used to set up a recorder is urged to do so.

If nothing else, on you will find it very instructive the interrelationships of relative frequency, bias. eq.. tape type. and head alignment. Finally. and perhaps not so incidentally. the pink-noise /rta approach is very fast:

30 seconds is the most time needed to see what the record /playback response is.

HOWARD

A.

ROBERSON

Pittsfield. Ma.

Well, frankly, we didn't think much of the marginal perfor- mance of the we digital delay lines we'd seen to date. We vowed wouldn't get into the

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Tired of pre -emphasis /de- emphasis filters tak- ing 12dB of high end headroom just to meet the

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And are you tired of not being able to believe what you read about digital delay line specs? Well, you should be! The technology is here to eliminate that nonsense in digital audio systems.

Our Model

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write us or ask your

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Get one believe the honest and complete specs it lists. for your next delay job and prove to yourself that

-

"our time has come!"

THE

EDITOR:

I have read with great interest

Marshall King's recent articles in db.

I have found them to be a very factual and informative description of the cur- rent status in the film and video tape industry.

I would, however, like to point out two things which need further clarifica- tion. can

First, the freelance sound mixer put together. with extreme con- fidence, a total audio package for a producer by contacting one of the several rental houses who specialize in this area. The freelance mixer has the freedom that the staff mixer does not have, to call upon one of these audio one- stops, thereby providing the producer with a state

-of- the

-art audio package which is maintained to high standards, dictated by the fact that these companies make their profit by providing this equipment on an on- going basis.

Secondly, the area of rf microphones has given the audio mixer greater flexibility when they are plied, thereby giving the properly mixer ap- new found freedom along with the camera- man, lighting directors, etc.

I appreciate the opportunity

Mr.

King has given everyone to have a greater understanding of the union situation in our industry.

ROBERT

N. EsrRIN

President, Filmways

North Hollywood,

Ca.

Copies of db

Copies of all issues of db

-The

Sound ing

Engineering Magazine start- with the November

1967 issue are now film. For available on 35 mm. micro- further information or to place your order please write di- rectly to

University Microfilm,

Inc.

300

Ann

North Zeeb Road

Arbor, Michigan 48106

8460

San

Fernando Road, Sun Valley, California 91352 (213) 767 -1000

Exclusive export agent: Gotham Export

Corporation,

New

York

Circle 54 on Reader Service Card www.americanradiohistory.com

Auclio-Tecknica anunnces

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Add more than a little creative excitement in your life, with

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Circle 43 on Reader Service Card www.americanradiohistory.com

The

Bottom

Line

Problem -Solver

CO

The Bottom

Line

We're Audio Consultants.

We solve problems; and there

is

no greater problem than that of high quality at low cost.

In

our industry, that's the

"bottom line

".

When

a

client needs

a

certain sound, we respond with more than just equipment.

We respond with

a

system that's a problem -solver. And, our equipment must do the same.

That's why everything we produce functions within an area greater than its own

...

within the total system, the total solution to the problem.

Like

our systems, our equipment must solve problems at the bottom line, delivering excellence at low cost.

The

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One of our problem -solvers

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The standard of quality for the industry, the

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Its design permits quick and precise "spotting

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with maximum extension and height flexibility. The swivel devis provides

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The counter- weight balances the microphone properly; and ball bearing, rubber

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The Starbird

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"Because

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Circle

18 on

Reader Service Card www.americanradiohistory.com

Calendar

OCTOBER

24

-26 Society of Broadcast Engineers

State of the

Art

Convention,

Kentucky Chapter. Ramada Inn

Bluegrass Convention Center,

Hurstbourne,

La., Louisville,

24

-25

Ky. Contact:

R. J. Klein

KY

ETV, 600 Cooper Dr., Lexing- ton, Ky. 40502. (606)

233-

0666.

Institute of High Fidelity Top

Management Seminar. Doral

Inn, New York, N.Y. Contact:

Gertrude Murphy,

IHF,

489

Fifth

Ave.,

New York, N.Y.

10017. (212) 682 -5131.

29- Society of Motion Picture

&

11/2

Television Engineers Confer- ence, New York

City, Ameri- cana Hotel. Contact: SMPTE

Conference, 862 Scarsdale

Ave., Scarsdale,

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CD

PATRICK

S.

FINNEGAN

4VBroackast

Sound

Transmission Distortions

its

Broadcasting is an aural medium: end product is audio at the receiv- ing set. The program audio is created in the studios and then delivered to the listening audience by an rf transmis- sion system. The rf system has short- comings that place limitations upon the audio it can carry. Aside from these limitations, faulty components and op- eration can put back into the recov- ered audio many of the distortions we worked so hard to eliminate from the original audio signal. This month

I will touch upon some of the ways the transmission can degrade the audio signal.

1

FC

(A)

(B)

'

(C)

r

CARRIER WITH

MODULATION

F2

L..\GOOD

1

BANDPASS

\

VERY POOR

BANDPASS

SOME BASICS

The audio signal is placed on the rf carrier by a modulation process. Once on the carrier, it is no longer audio per se: it is rf. Although now an rf signal. it must still retain its internal relation- ships as well as those to the rf carrier.

Figure

1.

(A) Modulation creates bandwidth to the wave.

All circuits which follow must have an adequate bandpass.

(B) shows the circuit with a good bandpass for a typical wideband signal. while (C) is a very poor bandpass for that signal.

Should any of these relationships he altered, the recovered audio will he affected in some manner. Once im- pressed on the carrier, the entire entity becomes a modulated wave.

A modu- lated wave requires far more spectrum space than an unmodulated carrier

-

how much space depends upon the type of modulation and the character- istics of the wave. The f.m. wave re- quires considerably more space than the a.m. wave.

In a.m., there are two equal sidehands spaced from the car- rier according to the frequency of the audio signal

In f.m., the amplitude of the audio directly modulates the mas- ter oscillator and causes the carrier to deviate above and below its normal resting space in the spectrum. At the same time, many sidehands are cre- ated. The space taken up in the spec- trum by the modulated wave is the wave's bandwidth.

Since the audio, through the modu- lation process, creates the widening of the spectrum space, it becomes an in- tegral part of that wave. Every circuit through which this modulated wave must pass on its way to the detector in the receiver must have a flat response curve across a bandpass at least equal to the bandwidth of the wave.

Faulty components. mistuning, or anything else which can restrict or distort the system bandpass, will limit and de- grade the modulated wave

-and

the recovered audio in some manner.

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I

NTERFACE in

We can have a perfect audio system the studio and a perfect rf transmis- sion system, yet end up with degraded audio from the receiver. This can hap- pen if there is a mismatch between the rf and the audio systems.

Transmitter inputs are designed around standard impedance values: for audio only, 600 ohms balanced. For stereo composite and

SCA. these are high impedance. unbalanced circuits.

Mismatch at this junction is purely an audio problem, even though one side of the circuit is the transmitter.

And the same ensue audio problems can

-poor

response curve, phase shifts, poor signal level transfer. Match- ing is not ordinarily an operational factor, but one of set

-up or test pro- cedures. Making measurements and feeding the audio generator directly into the transmitter can result in erro- neous indications and adjustments if the generator is not properly matched to the transmitter. Mismatching could occur if the limiting amplifier or unit which normally drives the transmitter has failed and the substitute unit used as a replacement has been set up dif- ferently, in another application, in the station.

(continued)

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SIGNAL LEVELS

Perhaps the most common cause of transmission distortions result from overmodulation of the carrier. The modulator requires a given level of input audio to produce the

100 per cent FCC limit on modulation. This is the design objective, and if the audio input exceeds this amount, distortions can be created right here at the modu- lator as well as down along the rf transmission system. Besides standard input impedances, the transmitter is designed around a standard input sig- nal level.

The transmitter does not have op- erational input controls. Those which are provided are intended for set -up, and trimming controls. The opera- tional control of the input audio levels must be done by external audio limit- ers or similar devices.

A.M. MODULATION

The modulator in the a.m. trans- mitter requires considerably more audio signal level for full modulation than does the f.m. modulator. There will be several audio amplifier stages within the a.m. transmitter besides the modulator itself, which is an audio power amplifier. High input signal levels to the transmitter can overload these audio stages.

The most common results of overload are peak clipping and intermodulation distortion.

The audio stages may be able to handle the high input audio level with- out distortion, but it will be applied to the rf modulated stage.

With more than enough audio to fully modulate the carrier on negative going peaks. the carrier will be cut off during the peak portion of that signal. Cutting the carrier with high level audio peaks in this manner creates clipped audio negative peaks and in other distortions the recovered audio at the receiver. the severity depending upon the amount of overmodulation.

(continued)

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NEGATIVE PEAK

CUTS

OFF CARRIER

PEAK CLIPPED

OVER

MODULATED

AM CARRIER

RECOVERED AUDIO

Figure

3.

Overmodulation of the a.m. carrier on the negative peaks will cause the be audio peak in recovered audio to clipped.

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MEASUREMENT ADJUSTMENTS

During a maintenance period when measurements are being made on the a.m. transmitter, higher than usual dis- tortion figures may he indicated, in spite of the fact that the modulation and input levels are correct. The modu- lators and the modulated stage can age so that they become somewhat non

-linear. a condition which creates distortion. Balancing the modulators for minimum distortion ordinarily re- quires adjustment of the bias on each of these stages.

Changing the bias can increase the gain of the modulator so less input level to the transmitter is now required.

If

the input, for ex- ample, now requires r/2 dB less than previously for

100 per cent modula- tion, the limiter or other driving ampli- fier at the input of the transmitter must also he reduced by the sanie amount.

If

this is not done, that in- creased t/2 dB can cause

5 per cent overmodulation during programming.

Consequently, the peak will be clipped and distortion result. perhaps far more distortion than the adjustment in the was first removed by place.

POWER REDUCTION

Many a.m. stations are required by

FCC

Rules to cut back transmitter output power at sunset every day.

This reduction can be considerable. for example

5 kW day to

1 kW night.

It requires a correspondingly smaller amount lower of audio to fully modulate the rf power level.

This is usually accomplished within the transmitter by switching in an audio pad. or a trimming potentiometer for accurate balance. Any fault in this circuit could cause severe overmodulation at the lower power level.

Components will age after a time, so it is necessary to check for correct balance and then trim the audio when necessary to ac- complish this.

FM

OVERMODULATION

Most f.m. transmitters use direct modulation. A pair of solid state.

(continued)

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INPUT

AUDIO

II

HI

AM

TRANSMITTER

-

POWER

LOW

I

i

RELAY

POWER

-

TO

MODULATOR

Figure

4.

Typical arrangement to reduce the audio when the ri power is cut back in a.m. voltage variable capacitor diodes are placed across the frequency- determin- ing tuned circuit of the transmitter's master oscillator. Any change in ca- pacity in this circuit will directly change the amplitude carrier's frequency. This of the audio input signal is applied across these diodes; this change will their capacity a correspond- ing in amount. Changing the capacity, turn, changes the carrier frequency a corresponding amount. The FCC specifies

75 kHz on each side of the carrier resting position as

100 per cent modulation.

The modulator is de- signed for linear operation on standard input levels within this range.

When the audio input levels are too high, the modulator can be driven into non

-linear regions and distortion re- sults in the recovered the audio. Should diodes become non -linear in the normal range. distortion will result with normal input levels and modula- tion. More than one input can modu- late the the carrier at the same time.

If modulation was set for

100 per cent with the composite only, for ex- ample, when the SCA channel comes on, the transmitter will he overmodu- lated by

10 per cent.

Another factor is in the

75 microsecond pre -emphasis the audio input.

If

the audio has considerable high frequency energy. the boost by this pre -emphasis can severely overmodulate the transmitter or move into non -linear regions the modulator. Aside from of distortion in the modulator, a restricted band

- pass cause along the system is a common of distortion. The fully modu- lated f.m. carrier is a very wideband wave. The system should have a band

- pass of at least 200 kHz or better.

MONITORS

Besides audio and accurately adjusting the rf system for correct modu- lation levels, program modulation must be continuously monitored so the op- erator knows the station is within

FCC limits in addition to listening to

(continued)

qEOUENC"

00

5

I

I

'

`

AATC3,-I

r-

I

INPT a

%rte

.3

I

AC p>E

t..ouo

J

i"

J

From now on your store or plant needs these

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MONO

INPUT

STEREO

COMPOSITE

INPUT

SCA

INPUT

SCA INPUT

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S ac e

res

pa

v/s

4

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Figure

5.

More than one input can modulate the t.m. transmitter at the same time.

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what is on the air. Set -up adjustments and operations require some accurate standard of measurement. The moni- tor can do this, but it must be cali- brated properly if it is to indicate accurately.

An oscilloscope and tone modula- tion can be used to calibrate the a.m. monitor.

Set the peak flasher adjust- ments and the meter adjustments for accurate

100 per cent negative modu- lation.

During programming, however. use the peak flasher as the more ac- curate indication of overmodulation.

The meter circuit will not provide true peak indications on program material.

The f.m. monitor can he calibrated with a spectrum analyzer if one is available. or the method as old as f.m. can be the used: tone modulation of carrier, a communications receiver and the

Bessel

Zeroes, or nulls. With

100 per cent tone modulation of the carrier, operate the positive and nega- tive switches to note if both peaks are equal.

If they are not. there can he some non -linearity of the signal in the rf system.

THE RECEIVER

The equipment at the receiving end of the transmission system can do much to degrade the recovered audio. hut we can do nothing about it.

Poor receiver design. limited and distorted bandpass, poor design in the audio stages, the speakers, plus faulty com- ponents, mistuning, multi

-path recep- tion, antenna and so forth can all have a definite bearing on what the listener hears. Yet another factor in the design of the receiver is the lack of filtering to sort out the various signals into their own channels. This enters the picture when the f.m. sta- tion is in stereo, or mono, and in

SCA in either mode. Unless there is actual cross -talk among these various chan- nels occurring at the transmitter, they can show up whistle, etc. here as birdies.

10 kHz without proper filtering in the receiver.

RECAP

The rf transmission system can dis- tort the recovered audio signal.

We have touched on only a few of th_ areas in the rf system where dis- tortions can arise.

There are many other possibilities. From the opera- tional view, overmodulation and im- properly calibrated monitors can be a common area of distortions. Modu- lated carriers have greater bandwidth and require a comparable bandpass of all circuits through which they must pass. At the end of the system. a cheap receiver can undo just about everything we have tried to accom- plish with the audio.

Soundmixers enjoys noise with

-free

84

recording channels

of

dbx

tape

noise reduction.

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Hirsch.

President

Soundmixers,

New York City. d

Xdbx,

Incorporated

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Card www.americanradiohistory.com

PRESENTS

THE

$100

MICROPHONE

STAND

MARTIN DICKSTEIN

441

soma

With

Images

The Space Camera and Related

Subjects

4

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If you can tolerate only the best in your act, act now and call us for all the details.

Can you recall how far back the first space camera was used in a space vehicle? We're not going to tell you.

You can do your own research.

What is interesting, though, is that a new camera is being developed by under contract to the

RCA

NASA

Johnson

Space

Center. ones used

It will be similar to the in the

Apollo lunar surface adventure. Those were also developed by RCA.

This camera system contract will be up around

$10.5 million and will trans- mit live color and black and white t.v. pictures during the manned orbital

Space

Shuttle flights. The Space Shut- tle is a recoverable launch vehicle that can he reused to place multiple pay- loads into orbit.

It is launched like a rocket, orbits the earth as a satellite. and returns to the ground as an un- powered aircraft.

That portion of the

Shuttle which flies into space is called the

Orbiter.

The closed circuit system will be installed on the

Space

Shuttle for earth orbital missions starting in 1979 and subsequent

RCA flights scheduled will provide up to for

1980. fifty cameras for approximately 500 shuttle flights planned over the next ten years. Each

Space

Shuttle

Orbiter can carry up to six t.v. cameras as part of the closed circuit system.

The camera system is intended to assist the crew

Shuttle in of the performing the complex tasks of deploying. retrieving and ser- vicing spacecraft in orbit.

The system on each flight will con- sist of several t.v. cameras, a video control unit, pan and and tilt mechanisms. monitors. The system will use the standard 525 lines of the US

NTSC broadcast system. Cameras will he in- stalled in the crew the compartment. in cargo hay. and on a remote manip- ulator arm.

Within the cargo bay. camera positions will he located at the forward and aft bulkheads and in the

A space shuttle closed circuit t.v. system.

Space

Closed

Shuttle

Circuit

N

System

IATEwTE

DEPLOYED

IN

CANT

WAR

GO SAY

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Else.

The Orban 516EC Dynamic

Sibilance

Con- troller

is

the

de- essing specialist. It

inaudibly removes

excessive sibilance

from voice while retaining brilliance

and crispness. Sibilants are

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and

that transfer

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optical film or

cassette

without distortion.

Your Orban dealer

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The camera in the crew compart- ment will be portable and capable of beaming

"live" telecasts in color to earth monitoring stations. This porta- ble unit could also be used by an astro- naut in any extra- vehicular activity

(EVA).

The astronaut could leave the crew compartment with the hand -held unit and investigate areas of the vehi- cle that arc not adequately covered by the mounted cameras.

PORTABLE CAMERA

The equipped

portable

camera

will

be with its own viewfinder to enable the astronaut to focus accurately on an object in space, such as the moon any or a free -flying satellite, or on part of the vehicle. The fixed cam- eras will be black and white units with full pan and tilt movement. These cameras can be controlled remotely by either the crew or by the ground con- trol personnel at

Space

Center. These

NASA's

Johnson units will he sup- plied lenses. with multiple focal length zoom

The cameras will weigh about

14 pounds and measure

151 inches long by

5 inches high by 5' inches wide. They will contain a silicon -in- tensified- target

(SIT) vidicon tube.

This tube is relatively immune from damage by high brightness and pro- vides high sensitivity to low light level conditions. The cameras will have in- terchangeable lens assemblies for color and black and white pictures.

S.M.P.T.E. CONFERENCE

Speaking and of space video equipment delivery systems reminds me that the S.M.P.T.E.

120th will be holding its

Technical Conference in

New

York from

October

29 to

November

2. One of the subjects that will be cov- ered in the sessions relates to the space shuttle, including discussions of

Future

Developments in

Satellite Communica- tions, Transmission of

Four

Simulta- neous Television

Programs via a Sin- gle

Satellite Channel, Remote Control of Earth Systems, and more.

Other subjects to be covered at the conference are

Digital Television.

Sound Technology in two separate sessions, Video

Production, and topics related to film production, film

-to -tape and tape -to

-film transfers, and video- disc special effects, plications. editing. and ap-

In addition to the technical sessions. the conference will have an exhibition of professional motion picture and television equipment. More than

100 companies have signed up and there will be more than 200 booths.

Among the exhibitors planning to he there will be Belden, Bell &

Howell, Robert

Bosch Corp., Chyron Telesystems.

CMX

Systems, Convergence

Corp..

Marconi,

Rangertone, Sennheiser,

Tek-

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Reader Service

Card www.americanradiohistory.com

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a

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Nashvi..le Record Production,

Inc., uses

Stanton exclu- sively are throughout its

Disc Cutting Studios. Naturally, they mostly involved with Country Music, but they also get into

Pop and Rock.

John Eberle states that they use the

Stanton

681A

Calibrated

"for

cutting system calibration, including level and frequency response ",

.. and they use the

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Triple

-E in their Disc Cutting operation

...with

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Stanton's 881S.*

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STANTON!

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CA)

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N tronix, TeleMation.

Thomson -CSF, and more than a from

England. half dozen companies

Last year more than 6,000 people attended.

This year expectations are for even more.

Make it

if

you can.

VIDEO EXPO

Speaking ferences, of conventions and con-

Knowledge

Industry Publica- tions of White

Plains.

N.Y. is again running its

Video Expo. In May, they had the conference in

Chicago. The next meeting will take place in

New

York at

Madison

Square

Garden from

October

15

-17th. In December. from

Space Shuttle

Television Camera

MONROR

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Audio Sweep

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Scope Output.

Variable Chart Speed.

Now, Hard

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Audio System Performance

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Filter design.

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5th to the

7th, the shops and exhibits

VideoWork- will move, for the first time, to the Southwest. The

Hyatt

Regency

Houston in Texas will he the conference site.

Then. the whole affair moves to the West Coast.

From

Feb- ruary 20th to the 22nd. all the exhib- itors and video experts will get to- gether at the

Jack

Francisco.

Tar Hotel in San

Each of these

Expo locations will give those the involved or interested in video field to get the latest infor- mation on what's happening in hard- ware and software. The workshops and seminars phases will provide experts in all of the industry to instruct and direct hands

-on sessions. In the

New

York meeting. over

1

1

0 exhibitors have signed up for space.

The others will also have the hest in exhibit equip- ment and software, as well as related services.

First, there will be a seminar on the

Introduction to

Electronic Editing. in- tended to be a review of where we are and where we're going in editing. Then. there vtr /vcr will be a seminar on

Audio

Methods and Techniques.

This will include discussions on prac- tical approaches to choosing. using. and expanding your audio system with emphasis on microphone selection. placement. set

-ups, and niques other tech- for studio and location produc- tions. (This session is intended for those in video who want to improve the audio of their video productions.

Old hat to you guys. right

?)

Then. there'll be a session on

Basic

Lighting

Skills. another on

Learning to Read

Video (video meter, wave- form monitor, vectorscope, and other specialized devices to read and inter- pret a video signal). Other topics will include Advanced Electronic Editing.

Interactive Television Methods and

Techniques. Media Center

Set

-Up and

Management,

Hardware

/

Technology

State

-of

-the

-Art

Report. Color

VTR/

VCR Problem Analysis and Diagnosis.

Portable Video Production Techniques and Guidelines,

Evaluating Color eras and VCRs, and more.

Cam-

In the exhibit area

(which you can attend without going to even one semi- nar), you'll be able to discover what's new and coming in cameras, tape re- corders. video projectors, tape ment, cassettes, editing equip- systems, ac- cessories, etc. there

Among the exhibitors. will be

Adwar Video,

Arvin/

Echo Science Corp., BJA

Systems.

Devlin Productions,

Dynasciences,

Hi- tachi, Ikegami, Image

Transform.

Sharp, Sony, Tele

Vue Optics. Video

Components, and many, many more.

No kidding. This is one show you really should go to. East Coast, West

Coast, or

South West

.

.. no excuses.

Circle

29 on

Reader Service

Card www.americanradiohistory.com

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That's

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JBL

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As might be expected, my column matching, damping factor and such, in the July issue, brought some re- sponses. Most of them concerned theory in much the same way as the question had come

up-a

more or less

"overall" thing. But one of them in- troduced the question of load lines, and how things have changed since the days of tubes, when load lines were critical, to now, when switching devices, such as transistors, with lots of feedback, are the order of the day.

Of course, a lot has changed. But basic principles have not. Perhaps negative feedback was a bigger new thing than transistors or other solid state devices were. son,

And for that rea- perhaps it is still less understood.

Load lines are just as relevant, if less often used, with switching devices, as they were with tubes; maybe they're not as critical, but even that may be a matter of viewpoint.

The first tubes used for amplifica-

tion-

whether just with voltage am- plification to provide gain or with power amplification to provide power

-were

triodes. Choosing an operating point, by laying a load line on these characteristics, enabled the right re- sistance load and supply circuit to be provided to get maximum output. whether voltage or power. the

Because with a triode the slope of characteristics represented a lower resistance value than the load into which the voltage or power was fed. triodes had what later became known as damping factor, greater than

l-or

an internal resistance smaller than their load resistance.

TETRODE AND PENTODE

Advent of the tetrode and later, the pentode, produced a quite different family of plate characteristics. The slope of these characteristics is quite different from that of the triode and represents a high internal resistance. compared to any load that is used with them. The choice of the load line was more critical to getting maximum volt- age or power.

The spacing between the character- istic lines was also less linear for the pentode than for the triode so that. until the advent of feedback, pentode outputs, while far more efficient, en- abling bigger output from smaller power supplies, produced more distor- tion than triodes. In view of today's low distortion figures, we should put some figures in here.

Typical distortion, at maximum out- put level, for a triode was

5 per cent, mostly second harmonic. Typical dis- tortion for a pentode at maximum out- put was

10 per cent, consisting of second, third, and even higher orders of harmonic.

That was not all, these were measured into their ideal resist- ance load. As anyone knows, loud- speaker impedances spend a lot of their time being reactive, which makes an elliptical load line, increasing the contrast several fold.

FEEDBACK

Then came feedback, to "straighten things up." Unfortunately, it was more difficult to apply lots of feedback to a circuit using pentodes than to one using triodes because of their more complicated supply circuits; you had to decouple the screen voltage, and all that.

This led our old friend, Dave Hafler, to come up with something that seemed www.americanradiohistory.com

Crazy

Like

a

Fox

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Drive a drill with a

125 -watt audio amplifier?

Of course you wouldn't.

But we did...to prove a point.

Our Tech

-crafT

TCB

-125 professional amplifier drove the drill for a solid week, continuously, even though we repeatedly clamped the chuck to overload ìt. Feeding an induction motor like that is one of the toughest torture tests you can give an amplifier, yet it drove the drill through a

2x4 again and again...thanks to our current limiting circuit which protected it from harm even under adverse overload. Crazy? Not if this unusual test convinces you that at

Bogen, RELIABILITY is NUMBER ONE.

If it can handle a drill, you can be positive that a

Tech

-craft amplifier can handle any speaker load under virtually any conditions... beautifully.

The performance specs include frequency response within

±.1 db from

20 to 20,000

Hz at rated output power...and total harmonic distortion less than

1% from

25 to

22,000

Hz, also at rated power. dual channel power amplifiers, mixer -power amplifiers, graphic equalizers, a compressoriline amplifier, and a wide range of accessories.

They are designed with unsurpassed features and specifications for today's sophisticated requirements, highest reliability and total system compatibility.

We believe they offer the finest values in professional sound equipment.

Availability? Who but

Bogen delivers a line like this from stock?

One last point. The drill we drove was made by another

LSI division, National Twist Drill and Tool. They're tops in their field, too, and we mention it to emphasize the vast technological resources that stand behind us as part of a

S1 billion corporation.

ALL

BOGEN

PRODUCTS ARE G.S.A.- LISTED.

For more information, please write or phone us.

What does it take to produce a line like Tech -craft?

A company like Bogen.

The Tech

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Professional Series incorporates all the knowledge and skill we've acquired during 45 years in sound.

Yet it isn't encumbered by any earlier design concepts. We developed the entire series at the same time, using the latest state

-of- the

-art technology.

It includes active mixers and mixer -extenders, single and

Circle

16 on Reader Service

Tech-crarT

PROFESSIONAL

SOUND

by

A

BCOGEN®

DIVISION

OF LEAR SIEGLER. INC

P O

Box 500. Paramus. NJ

(2O1)343 -5700

07652

Card www.americanradiohistory.com

V

to get the best of both worlds: using a he special kind of output transformer, made a pentode tube work as some- thing in between a triode and pentode, an effect known as ultra linear.

To explain this

-any

pentode can be run as a triode by strapping its electrodes together so the screen voltage moves with the plate voltage.

That produced an operation that was no more efficient than a triode, since in effect it was a triode; connect- ing it as a pentode got much more power, but with much bigger distor- tion too. The ultra linear connection got much more

power-

almost as much as pentode connection

-with

much less distortion. It also made the application of larger lumps of feed- back easier than it was wtih pentode connection.

TRANSISTORS

Finally came transistors. The first thing that engineers noticed was the collector that current

-voltage character- istics, working grounded emitter, are very like the pentode characteristics of a tube. But the circuit is much simpler than that in a tube because the tran- sistor is a triode, not a pentode. Its load impedance, if not its internal impedance, is much lower than that of a pentode, which make larger amounts of feedback possible too.

Further, it can be operated as a grounded collector, instead of as a grounded emitter, which makes it like the cathode follower used during tube days. When complementary pairs are employed they do not even need an output transformer to get push

-pull coupling.

So the transistor eliminates a whole lot of problems that came with the pentode tube, in spite of their similarities.

When the transistor is used as a grounded collector, it functions more like a tube than in any other mode.

In the more conventional grounded emit- ter mode

-which

is the mode in which characteristics are usually taken

-the

characteristic lines represent incre- ments in input base the lines current, where for a pentode tube represent increments in input grid voltage.

But when you change to a grounded collector operation, which merely means the that the collector, instead of emitter, stays at a constant voltage. what the base needs more than a cur- rent swing is a voltage swing, just like its tube counterpart. the cathode fol- lower. It's true there is a current swing input which the tube cathode follower does not have, the but in other respects operation is identical.

In fact, the grounded collector tran- sistor amplifier makes a more perfect impedance multiplier or divider (ac- cording to which way you view it) than the tube ever did.

The voltage at the base and emitter, just like the volt- age at the grid and cathode in the case of a tube, are close to identical (much closer than for the able current tube) while avail-

-creating

the output

-is

multiplied at the emitter, as compared with the base, by the the transistor. current gain of

But getting back to transistor char- acteristics and their similarity to the pentode tube characteristics; load lines are determined in essentially the same way. Both a tube and a transistor have a maximum dissipation line, in the form of a hyperbola (shown dashed in the figures). Both have a maximum voltage which, when operated in Class

B so the unit is cut off when it gets its maximum voltage, is close to double the operating voltage.

This means age that needs to be the operating volt- about half the maxi- mum voltage in each case.

For maxi- mum current, the limitations are little different but, operationally, their ef- fect is similar.

For the tube, maximum current depends on the point where the grid voltage crosses from negative to zero, because at that point the grid

The

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It's capacity for effects seems endless while its reliability in its performance as a

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Circle

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MODEL 2710 ONE

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Fine

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Covering the

Audio

Spectrum

Gives Professional Sound Man More

Balanced

Input and

Output

Control

Highly Portable in

Studio or on

Tour

MODEL 2709

ONE

-THIRD

OCTAVE

REAL TIME

ANALYZER:

Nine

Amplitude

Display

Steps Per

Band

Internal Pink

Noise

Generator

Display Sensitivity Control

Switchable

Range

Line -in, Line -out Jacks on Rear Panel

REAL TIME ANALYZER model 2709

-

-

- - - - - -

-

-

- -

- -

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-

-

-

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-

-

-

-

-

-

-

-

- - - - - -

-

- -

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- -

-

-

-

-

- - -

-

-

-

-

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.

.

.

.

.

. . . .

.

. .

.

. . .

.

W

-

-

1

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11

MA

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SG

M1/8

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IN

f

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LM

11 s.

-

-

-

-

i

w

belongs in your next system

Just the duo you need for ultimate sound control.

Gives super fine adjustment and up

-front display capability over 27 one

-third octave bands. Professional quality and reliability at surprisingly affordable cost.

A demo from your favorite pro sound dealer will be the convincer.

Or write for our promo sheets.

For sound that makes the stars shine

..

Neptune Electronics Incorporated

934 N.E. 25th Avenue

(503) 232 -4445

Circle 39 on

Reader Service Card www.americanradiohistory.com

Portland,

Oregon 97232

N

CD

current starts, complicating things.

For the transistor, the current rating of the transistor sets the limit.

Inherently, the linearity of transis- tors and pentode tubes is not very different. The advantage of the tran- sistor is that it is easily possible to lay on enormous amounts of feedback, so its effective linearity is much better than that of the tube. Also, since it is a triode. it is possible to reduce the number of reactive coupling elements which, as well as allowing much more feedback, also makes it much more stable, against being thrown off its op- erating point, when the maximum level is accidentally exceeded.

OPERATING POINT

SHIFT

Every transformer or coupling ca- pacitor in a feedback loop introduces the possibility of the operating point shifting as the instant maximum level is reached, after which it takes the amplifier a time to return to normal. depending on the time constant of that circuit. This may happen in the case of a tube because the grid starts to conduct, upsetting the operating grid voltage.

In the case of a tran- sistor, when the base -emitter junction ceases to conduct, a similar thing can happen because base -emitter voltage is normally small and nearly constant, where when it ceases to conduct, it suddenly rises in the opposite direction.

So, while the superficialities may seem different, transistors and pent- odes have more similarities than most people realize. With both, the effect of large amounts of voltage- derived feed- back is to make the output voltage al- most independent of the load value connected, which represents a high damping factor.

McINTOSH AMPLIFIER unity coupling

-

a cathode swung equally and opposite to the plate its

-

the first to apply large amounts of was feedback. But the tubes were operat- ing as pentodes, because the screens were kept at a constant voltage differ- ence from the cathodes. In Dave

Haf- ler's ultra linear circuit, the cathodes stayed at constant voltage and the screens swung at a specified fraction of the plate voltage swing, so the tubes operated in a condition between that of triode and pentode.

Transistors are triodes, but have characteristics more like pentode tubes, bringing to bear the best potential for high output

-or

high efficiency output

-with

low distortion, yet.

The basic principles, or theory, do not change.

The practical ramifications do. sales offices

THE SOUND ENGINEERING

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York

1120 Old

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Designed for driving headphones,

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20 to 20,000 Hz. The unit includes individual and master gain controls.

Mfr: Edcor

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Complexities usually found only in studio mixers are present in Series

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2.5 kHz, and 750 Hz and

15 kHz; four independent equalizer amplifiers avoid interaction between bands. The stereo mix can be overridden on monitor headphones by an auto -solo pushbut- ton on any input or output channel, which also switches two -volume unit meters to read the solor level.

Three auxiliary mices are provided, two for prefade monitor and one for post

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CATALOG

Circle 28 on Reader Service Card

BROADCAST DELAY LINE

A maximum delay of up to

6.4 seconds is possible with BD955 broad- cast delay line, used to blip objec- tional material from live broadcasts.

When an announcer hears the ob- cenity or other unsavory noises, he presses the DUMP button. The pro- gram continues immediately in real time while the BD955 extends the safety delay margin to maximum. De- lays ranging from

6.5 milliseconds to maximum can also be used to fake

"doubling," create echo effects, and provide delay for echo chamber feed.

In t.v. applications, landline trans- mission of audio can be delayed to match satellite video signals.

The de- vice is rack mountable, has a frequency response of either

15 or 7.5 kHz; the lower frequency is suitable for "talk only" use while the

15 kHz response model can handle any program material.

Mfr: Eventide Clockworks, Inc.

Circle 83 on

Reader Service

Card www.americanradiohistory.com

Good

FM sound is good

FM business.

2

ma.,--.r_u

nniv station equipment

Dolby Laboratories Mud needed for Dolby

FM.

More and

more

FM listeners these days are sensitive to

good sound.

If you have any

doubts.

just take a

look

at the sales of

For

quality home and automotive stereo equipment.

these listeners.

signal quality could

well be a

significant factor

in

distinguishing your

station

from

the run of the mill.

Signal

quality

is what Dolby

FM is all about. The Dolby

FM

process incorporates

a

reduction

of pre-

emphasis from

75 to 25 µs. along with

B

-type Dolby you

encoding.

That gives

about

8

dB more headroom

at 10 kHz

-

just the thing

for

today's

program sources

that are rich in high

frequencies.

Limiting

can

go

back to

doing what

it was

originally designed for

- handling

the

occasional difficult

peak

rather than filtering out

the

highs most

of the time.

Listeners with receivers have the

equipped

for Dolby

FM

reception* opportunity. for

the first time. to

recover your

signal in virtually the same signal can

form

it left the studio. Your FM

sound

as

good

as the high

quality records

and tapes

your

listeners play at home.

At the

same

time. listeners with

conventional

receivers aren't penalized. because

75

its

de-

emphasis subjectively complements

the Dolby

encoded

25

ifs

signal

for compatibility.

Attracting

new listeners to

your

FM station is one thing: keeping today's another. That's

sound

sensitive listeners

happily tuned

in is

where

signal

quality and Dolby

FM

- come

in.

If you

would

like to find out

more about how

the

good sound

of Dolby

FM can be

good for your

business, please

contact

us at the

address

below.

"There are now more than 80 consumer product models equipped for Dolby FM reception, including several new car stereo systems.

DOLBY FM

'Dolby and the double -D symbol are trademarks of

Dolby Laboratories

Dolby

Laboratories

731

San

Sansome Street

Francisco

CA 94111

Telephone

(415) 392

-0300

Telex 34409

Cable Dolbylabs

Circle

25 on Reader Service Card www.americanradiohistory.com

346 Clapham Road

London SW9

Telephone

01

-720

1111

Telex 919109

Cable Dolbylabs London

STORAGE

UNIT

Sharp contemporary design, all black plexiglass and brushed matte finish aluminum, make the Audiofile

Lowboy a showoff piece. The unit has a plexiglass top and heavy casters, can handle in excess of

400 lbs. of equip- ment with a rack mount capability.

Optional shelving is available. Dimen- sions arc

42; x

26'4 x

18; inches.

Mfr:

Hammond

Industries.

Price: $399.00.

Circle

84 on

Reader Service Card

MODULAR CONSOLE

Conveniently situated barrier strip connections, on the rear of the con- sole, simplify wiring and patching from SP610 I0

-in

10

/8-out stereo console. Input modules include a

41

in. conductive plastic slide fader,

6- knob

3

-band parametric equalization.

8

TK assignment buttons, post echo sends, monitor send control,

2 cue sends, solo button which allows stereo panning when engaged, a mic

/line switch, program

/sync switch, and an attenuation switch of

-10

or

-20

dB.

Output includes cue

1 and cue

2 level controls, each of which can be soloed, and

2 echo returns. Mic input impedance is

150 ohms balanced, line input impedance

10k ohms, dB, output level vu. output level

+20

dBm.

Mfr:

Speck

Electronic

s/n

-72

+4

dBm above zero

Price: $4,120.00.

Circle 85 on Reader Service Card

AUDIO

CONNECTORS

JACKS

/PLUGS

/PATCH CORDS

Shipped from STOCK! c

Ask for Our

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PHONE (312) 827 -8388

Circle

17 on

Reader Service Card

REAL -TIME SPECTRUM

Covering the frequency range from

20 millihertz to 25.6 kHz, Model

3582A spectrum analyzer is useful for electrical and physical measurements which have significant spectral in- formation in the audio and sub

-audio range. Amplitude and phase are dis- played alphanumerically on a large crt display. Two independent meas- urements (amplitude, phase, or both, as well as coherence) can be displayed simultaneously or digitally stored and recalled later for visual comparisons.

The unit has a zoom feature (band selectable analysis) which makes it possible to locate frequency spans of

25 kHz down to

5

Hz anywhere with- in the frequency range of the instru- ment. A microprocessor executes the

Fast Fourier Transform to measure signals that have long measurement times. An exponential form of power averaging is used for measurements where the spectral information is not stable but varies slowly, continually reducing older spectra importance to prevent old data from obscuring new data. Because of it's built -in noise source, the unit can be used to pro- vide a drive signal, which functions like a tracking generator, or low -fre- quency network analyzer with real

- time measurement speed.

Mfr:

Hewlett -Packard

Price: $10,000.00.

Circle 86 on Reader Service Card

ANALYZER www.americanradiohistory.com

At TDK, we know that your test cassette is a vital element of your laboratory or service procedure.

So when we created a series of test tapes, we approached them as integral com- ponents, with both tape and housing engi- neered as precisely as your test instruments.

You'd expect that from the high bias reference the makers of TDK SA, standard for many manu- facturers' cassette decks.

TDK test cassettes don't jam and they're dropout

-

free. They're built to last under unceasing use.

If you're a store service manager, assembly line quality control inspector, or highly discerning audiophile, you need that kind of precision and reliability.

To make abso- lutely sure you get it,

ALIGNMENT

TANE

Pre- recorded

TEST TAPE

AC-34<

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&f WiTti,

AC

323

AZIMUTH

we custom quality

-control each and every one.

No matter what data you need, TDK has 'a test cassette to help you find it out: bias/EQ alignment;- playback level calibration;

Dolby calibration; head azimuth alignment; wow and flutter and tape speed and

11, five and three

-point frequency characteristics checks.

Check out the complete line of TDK test cassettes by writing, or calling

(516) 746 -0880.

When you do, find out about our bulk duplication cassettes, bulk duplication pan- cake tape, audio visual, leaderless, data and endless cassettes, too.

Yóu'll find that the same TDK reliability quality and that goes into our test tapes applies all the way down the line.

Pre

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ST TAPE FREQUENCY

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TDK Electronics Corp.. 755 Eastgate Blvd.. Garden City, NY 11530

2906

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Rosecrans Ave.. Suite 365,

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Circle

21 on Reader Service

Card www.americanradiohistory.com

www.americanradiohistory.com

AMPEX

ATR-700

10,

_

,.

+_

_

+a.^O" v

=

040

Y afir

.Q designed for

°

rnrnerc ¡al a

p

se

rvice-

package,

óadcstin9

AT:/

This

the

tough or and is

Ampex

Use en

seen

heavy sive the the

M

switch the roo for most

ATR 7O duty,

P

- audio

7Q.

for the cop n

s9

t sting that

A continuous of

The recorder reel dim, al keeps trips Nowthere's

I is a betty

-to"

le

tape erran

Work. half-track

clearlyeters

an d ationruns sty on the e4

All switches deepr,d types, moving excuse

Monaural,

la showal

witchable a

the

s than for reel the arts less from align ns

4

°rt ompact

¡cation nad even

st

ofe turn out. on the

Ampex d city. every mal

-to

-reel portab

the

field. audio portable situation i itself full rang And

18 after

ont' means

in stereo,

instant

a areas actors rigid,

Mas- hundreds the s for

pro9aesi,

most uattAmpex audio the fin and it's

City,

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9 ap63, 415

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MVO

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401 www.americanradiohistory.com

MICROPHONE SPLITTER

OPEN REEL

DECK

qv

New

Literature

®OOOOOOOUO

®®®®It3®®®IOI01

TEAC

i\

/4

12..j

19

-inch rack mountable Model

1003

10 x 3 microphone splitter is con- structed for sound reinforcement as well as recording and broadcasting.

Working from ten female XLR con- can go three ways from each input

-

direct output for phantom powering from the main console for condenser microphones or splitter outputs con- sisting of two bridged outputs with ground lift switches on each. The transformers are dual

Faraday shielded. to eliminate hum and buzz.

Mfr: Uni -Sync Inc.

Price: $840.00.

Circle 87 on Reader Service Card

audio

for

Tape

professionals

7

Three -head, three -motor, two -speed

(15 and

71/2 in

/sec.) Model A -3440 four channel open reel deck with Simul-

Sync accepts

10

-inch reels, can be monitored through monophonic head- phones, each channel switch -selectable.

Features include professional micro

- switch, manual cue level, four vu level meters, mic

/line input selectors, four front -panel mic jacks and independent output level controls for each chan- nel.

Remote control is available. Spe- cifications include 0.04 per cent wow and flutter, 65 dB

s/n

ratio, and 35 to 22.000 Hz frequency response at

15 in

/sec.

In the same series, the manufacturer is also offering two new reversing decks taking a seven -inch reel, and another

10

-inch reel model.

M/r:

TEAC Corporation

Price: $1,500.00.

Circle 88 on Reader Service

Card

VOCORDER

"By its nature, the

Vocorder is absolutely multi -para- poly -phonic" is a quote from a fascinating booklet on the

Vocorder Sound Effects device, which, among other sounds, is able to replicate human speech. Source: Senn

- heiser Electronic Corp.,

10

W. 37th

St., New York, N.Y. 10018.

AMPLIFIERS

The

Son of Ampzilla and his entire family tree of amplifiers are described in a sort of amp Roots, an

8

-page brochure. Source: The Great Ameri- can

Sound Co., 20940 Lassen St.,

Chatsworth, Ca. 91311.

OSCILLOSCOPES

Dual and single trace oscilloscopes are the subject of a full

-color catalog from

Leader Instruments. Source:

Leader Instruments Corp.,

151

Dupont

St., Plainview, N.Y. 11803.

CASSETTE WINDER

WORLD VIDEO STANDARDS

A laminated

4 x 9 in. trifold card lists 150 countries alphabetically, along with their standard plus scan fre- quencies and their line voltage and frequency rates. Source: Devlin Pro- ductions, Inc., 150 W.

55th

St.,

New

York, N.Y. 10019.

REEL TO 1 EEL

TAPE

Ampex.

3M.

All grades.

On reels or hubs.

CASSETTES,

C

-10

-C-90,

With Agfa. Ampex.

3M tape.

LEADER & SPLICING TAPE

EMPTY REELS & BOXES

All widths, sizes.

-

('O \1I'E1111VE

FROM STOCK

-

For your

) at.h

. all or write:

Vito Cappi

CJ

Recording Supply

Co.

Div. or 1233

Rand Road

Polyline

Corp

Des

Plaines.

IL

60016

Circle

51 on

Reader

Service

Card

Lightweight sette

(10 lbs.) CW

-3 cas- winder will rewind three c -60 cassettes in 55 seconds. Individual cassettes can be loaded or removed without affecting the operation of the other stations. Precision set torque evenly winds the cassettes.

M

/r:

Pentagon Industries

Price: $165.00.

Circle

89 on

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Card www.americanradiohistory.com

ELECTRONIC COMPONENTS

A

20 -page catalog lists capacitors, resistors, switches, cable assemblies, accessories, etc. Source: World

Busi- ness

Corp.,

1669

E.

Del

Amo

Blvd..

Carson,

Ca.

90746.

POTENTIOMETERS

Miniature

12 and

16 mm 300 de- gree potentiometers for consumer and commercial applications are covered in a data sheet. Source:

Murata

Cor- poration of America,

1148

Franklin

Rd., S.E.,

Marietta, Ga. 30067.

J

We're

the

still at it.

We started in

1935 as

Audio Development Company producing

jacks and jack panels

for

the broadcast and telephone industries.

Since then,

ADC

has produced such

innovations

as

Bantam

Jacks,

printed circuit board

jacks and

Wrapid terminal

blocks.

What

are we

doing for you

today?

do7

We are

introducing our

new line

of low

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Products

DIVISION

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MAGNETIC CONTROLS

ADC

Products. 4900

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Telephone:

1612)

835 -6800

TWX 910

-576 -2832

Telex 29 -0321

Sales offices in

Atlanta GA (404 i

766 -9595 Dallas.

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241

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761

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Fairfield.

CT (2031 255 -0644

Lafayette. IN (3171474-0814 Melbourne

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(305) 724 -8874 Menlo Park. CA (4151323-1386 Minneapolis. MN (6121835 -6800

Washington. DC 1202) 452 -1043 Montreal. Quebec

(5141677-2869

Circle

47 on Reader Service Card www.americanradiohistory.com

f0

CD

Editorial

IS

THE TAPE -TO

-DISC transfer session the last step in record production, or the first step in record manu- facturing? It depends on whom you ask. Some disc mastering facilities (notably abroad) are located at the pressing plant, far, far away from the influence of anxiety- ridden producers

who-if

given half a chance spend hours trying to "fix it after the mix."

-

will

Other facilities are found right at the recording studio, where the recording engineer and producer can directly supervise

Still

(or interfere with) the transfer from tape to disc. others are found at "halfway houses," specializing just in disc mastering, and usually not affiliated with a particu- lar record company or studio.

So, perhaps we should view disc mastering as a little bit of both the production and the manufacturing process.

And maybe we should also spend a little more time learn- ing something about it.

After all, how many people hear your priceless master tapes?

Iry Diehl helps us get started, with a look at Basic Groove

Geometry.

On tape, the recorded level has no influence whatever on playing time.

Not so on disc, where every extra dB means a bit less playing time.

On tape, a

101/2 in. reel will record for about thirty minutes (at

15 in.

/sec).

How long is a

12 in.

LP record?

Well, it depends. Depends on what? Check with Iry for the answers.

When was the last time you saw a new disc cutting lathe?

We saw one at the recent Audio Engineering Society con- vention, and sent Suzette Fiveash (our new Associate Ed- itor, no less) out to find out something more about it, and report back.

She did, as you'll read in her story,

Cybersonics: A New Disc Mastering Lathe.

From

Given the time vs. level constraints of disc recording, wouldn't it be nice to figure out a way to squeeze a few more dB onto your next record? The folks at the CBS

Technology Center thought so too, and have spent the past five years developing a way to do just that. Charlie

Repka reports on their progress in his feature on the

CBS

DISComputer Mastering System.

Direct

-to -disc recording has been attracting a lot of notice these days. And, whenever versation turns to "d -d,"

(or wherever) the con- you're sure to hear the name of

Bert

Whyte mentioned.

Bert has been very active in this challenging area, and in between sessions, we asked him to tell us a little something about The Logistics of Direct

- to -Disc Recording.

Never one to take the easy way out, Bert does most of his d -d work on location. And that means he's got to beg, borrow or steal a few cutting lathes for every session.

And that means talking a few disc mastering engineers into coming along, and not just for the ride. Well, since Ms.

Fiveash made the mistake of sending her Cybersonics story in early, we sent her out again

-this

time to talk to

Stan Ricker at the JVC Cutting Center, about what it's like to Bring

Direct

-to- Disc

Your

Own Lathe: The Logistics of Cutting

-on

Location!

This issue of db was really inspired by a letter from

James Shelton, president of Europadisk Plating Company.

Mr. Shelton took us gently to task for not saying much about the lesser -known aspects of audio

-such

as the rec- ord plating process. We cheerfully admit to ignoring record plating for years. And for good reason: we don't know much about it at all. And that placed the ball back in

Mr.

Shelton's court, where he quickly obliged by serving us A

Look At the Record Plating Process.

And that brings us to the end of this issue. We know a little more about disc cutting now, and promise never to take it for granted again. What about you?

J.M.W. www.americanradiohistory.com

1

fact:

1

you can choose your microphone to enhance your sound system.

Shure makes

Like microphones musical instruments, for every each imaginable different type of use.

Shure microphone has a distinctive "sound," or physical characteristic that optimizes it for particular applications, voices, or effects.

Take, for example, the Shure SM58 and SM59 microphones:

SM59

Mellow, smooth, silent...

The SM59 is a relatively new, dynamic cardioid microphone.

Yet it is already widely accepted as a standard for distinguished studio productions.

In fact, you'll often see it on TV

...

especially on mus- ical shows where perfection of sound quality is a major considera- tion. This revolutionary cardioid microphone has an exceptionally flat frequency response and neu- tral sound that reproduces exactly what it hears. It's response when miking markably designed to give good bass rugged

-

at it's a distance. built to

Re- shrug off rough handling. And, it is superb in reject- ing mechanical stand noise such as floor and desk vibrations because of a unique, patented built

-in shock mount.

It also fea- tures a special hum

-bucking coil for superior noise reduction!

Some like it essentially

flat... i

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Crisp, bright

"abuse proof"

Probably the most widely used on- stage, hand -held cardioid dynamic microphone. The

SM58 dynamic microphone is preferred for its punch in live vocal applications

...

espe- cially where close -up miking is important.

It is THE world

- standard professional stage mi- crophone with the distinctive Shure upper mid -range presence peak for an intelligible, lively sound. World

- renowned for its ability to withstand the kind of abuse that would destroy many other microphones. Designed to minimize the boominess you'd ex- pect from close miking. Rugged, effi- cient spherical windscreen eliminates pops. Lightweight (15 ounces!) hand -sized. The first choice rock, pop,

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Reader Service Card www.americanradiohistory.com

IRWIN

J.

DIEHL

Basic

Groove

Geometry

The mathematics góverning the spiral trip from the perimeter to the center

of

a recording disc.

DESPITE ALL THE RECENT

ADVANCES in all audio technology, the recorded disc remains the fav- orite mass

-market medium for music recordings.

Yet, at times disc recording appears to be a sort of step -child to the recording industry. Often misunder- stood, the disc recording art is considered by some to be a

"mystery technology."

Of course, there have been impressive advances in disc recording technology too, but, the basic principles em- ployed in cutting discs have remained unchanged for decades.

Simply stated, the disc record comprises a spiral groove, engraved or embossed on the surface of the disc.

Con- ventionally, the groove is engraved from the outside to the center of the disc, while the signal to be recorded modulates the groove. Other than for the sake of stand- ardization, there is no reason why the process could not be reversed with the record beginning near the label and then spiralling its way outwards, towards the record's outer diameter.

RECORDING PITCH

One first principle that may be obtained from this simple description is the relationship between the time it takes the groove to spiral from the outside to the center of the disc, and the duration of the program to be re- corded. The spiral rate, or pitch, depends upon the dimen- sions of the disc (7

",

10,"

12

"), and determines how many lines there will be from the start of the recording to the end. The number of lines will therefore be related to the dimensions of the disc and the program length. This relationship is expressed by the formula:

P

=

(T)

(Ve)

R

P

T

Vr

R

=

Pitch, measured in lines -per -inch

(LPI).

=

Program time.

=

Rotational velocity of the disc.

=

Dimension available for recording.

Typically, a twenty minute program, to be recorded on a

12 in.

LP record at 33.3 rpm, will begin at an outer diameter of

11.5 inches, and should end at an inner diameter of about

5.5 inches.

The outer diameter con- forms to the

Record Industry Association of America

(RIAA) standard for the Outermost Groove at Recording

Pitch. The standard also specifies a

Minimum Inside Di- ameter of

Recording, which is 43/a inches. However, if the program length is not excessive, most disc mastering engi- neers prefer to end the recording well before this minimum dimension in order to minimize inner -groove distortion.

The dimension over which the program is recorded is equal to the outer diameter minus the inner diameter, divided by two. (11.5

-

5.5)/2

=

3 inches). This is the radial distance across which the groove spirals while the program is recorded onto the disc.

Using the above for- mula, we find the required pitch to be:

(20 min.) (33.3 rpm)

P 222

LPI

3 inches

Once the recording pitch has been determined, other parameters can be ascertained.

For example, the spacing between the lines is the reciprocal of pitch.

(For our pur- poses, we are assuming the groove is spiralling inwards at a constant rate.) If the pitch is

222 lines- per -inch, then the line spacing is

1/222, or 0.0045 inches -per -line.

Typically, this dimension is expressed in mils

(thou- sandths of an inch), which in this case would be 4.5 mils. www.americanradiohistory.com

This space between lines must be apportioned between the width of the groove, the modulation displacement, and any headroom that may be required. The basic groove width is generally equal to, or greater than,

2 mils. The space remaining after subtracting the width of the groove is that available for modulation.

DISPLACEMENT AND VELOCITY

When we inspect the modulated groove under a micro- scope, one parameter observed directly is the amplitude of displacement. However, there is no direct relationship be- tween the applied electrical signal level and the resulting mechanical displacement. The quantity that is directly proportional to the applied electrical signal is stylus velocity.

As the applied signal voltage is increased to twice its origi- nal value, stylus velocity increases by the same proportion.

Displacement of the groove, on the other hand

-though

dependent on the magnitude of the applied signal

-is

in- versely proportional to the frequency of the applied signal.

As the recorded frequency decreases, displacement in- creases, and vice

- versa.

Due to the direct relationship be- tween the the applied electrical signal and the stylus velocity,

RIAA pre- emphasis and de- emphasis characteristics are tabulated in terms of velocity, as are recording levels.

(These RIAA characteristics arc analogous to the NAB pm- and post

-emphasis found in tape recorders. Ed.)

The relationship between stylus velocity and groove displace- ment is expressed as:

V,

A"

=

2TrF

A =

Amplitude of displacement.

V

=

Peak stylus velocity.

27rF

=

Angular frequency.

Given a line -to -line spacing of 4.5 mils, and assuming a groove width of

2 mils, 2.5 mils of space remains to ac- commodate modulation. A common record velocity refer- ence level used in disc recording is 7 cm.

/second (peak) at

1 kHz. Note that this reference is a peak, or maximum, velocity, thus implying that other velocities are involved as well.

Unlike an automobile travelling at a fixed speed along a winding road, on an LP record it is the

"road"

(that is, the groove) that is doing the travelling, while the

"car" (the stylus) is pushed from side -to -side by the undu- lations of the groove.

If the groove is a sine wave, at each of its amplitude peaks the stylus comes to a halt and then reverses direction, pretty much like a pendulum.

It then picks up speed, until it reaches its peak velocity

(at the zero crossing point) and then it begins slowing down again as it approaches the next amplitude peak in the sine wave.

Our

7 cm./second reference level represents the maxi- mum velocity at which the stylus travels, as it traces

(or engraves) the groove. The displacement that would result if

1 kHz was recorded at a reference velocity of

7 second is calculated below: cm./

V

7 cm.

/second

A"

2.7F

6.28(1000)

=

0.00111 cm.

=

0.439 mils peak displacement

Doubling this value gives us a peak

-to -peak displace- ment of 0.878 mils. Since the next adjacent inner and outer lines (grooves) are also modulated, the total space required between adjacent lines is equal to the peak

-to- peak displacement (A

"

).

In our example, more than ample space is available for signal modulation at

1 kHz.

On the other hand, if a frequency of

100

Hz was re- corded at the same velocity, we would find that our groove displacement is excessive, and the adjacent grooves will run into each other, causing overcut.

In this example, we have included a conversion factor, 103/2.54, to provide an an- swer directly in mils.

X

A''=

6.28(100)

= =

8.78 mils.

254

=4.39 mils

VELOCITY

AND RIAA

PRE

-EMPHASIS

Since groove displacement is inversely proportional to the frequency of the modulation signal, the standard RIAA

Recording Characteristic provides for a low frequency at- tenuation to conserve disc space (some

-13

dB at

100

Hz), as well as a high frequency boost. When referenced to

7 cm.

/second peak velocity at l kHz, the peak velocity and resultant displacement at some other frequency (after

RIAA pre -emphasis) will be;

7

V dB

=

Peak velocity as some specified frequency. cm.

/second

V

=

(10dBÌ20) 7

(taken from the

RIAA cm.

/second

=

Amount of pre -emphasis at the specified frequency standards).

=

Reference velocity at

1 kHz.

For a frequency of

100 Hz, we find that the peak velocity is

(10"13120) 7

=

(0.2239)

7

=

1.57 cm.

/second. There- fore, since earlier we found plify matters, A

.

=

V

that

/irF),

A

=

V

/27rF (or, to sim- we can now calculate the displacement of a

100

Hz input signal, with our system calibrated to a 7 cm.

/second reference at

1 kHz. Once again, we include the conversion factor for mils:

V

103

X

A

"

"

7rF

2.54

1.57

=

1.864 mils, peak -to

-peak displacement.

103

6.28(100

)

X 2.54

It is evident from the last example that if the applied electrical signal at the input to the disc recording system was constant at all frequencies, the resulting groove dis- placement would not be constant, but would increase as frequency decreases, even with the compensation provided by the RIAA standard.

We have looked at just one point in the low frequency range, namely

100

Hz. What of the displacement at say,

50 or

70 Hz?

Why not try these yourself, to get some in- sight into disc level constraints at low frequencies?

RIAA RECORDING CHARACTERISTICS

Frequency

Pre- emphasis

Frequency Pre -emphasis

15,000 Hz

14,000

13,000

12,000

11,000

10,000

9,000

8,000

7,000

6,000

5,000

+17.17 dB

4,000 Hz

16.64

15.95

3,000

2,000

15.28

14.55

13.75

12.88

11.91

10.85

9.62

+

8.23

1,000

700

400

300

200

100

70

50

30

+

6.64 dB

4.76

+ 2.61

0.0

1.23

3.81

5.53

8.22

13.11

15.31

16.96

-18.61

AN

ADDENDUM

ON

VARIABLE PITCH

Note that most modern disc cutting systems provide a variable pitch function. This automatically adjusts the pitch, as the disc is being cut, to provide the optimum spacing between grooves.

Typically, during a quiet passage. when not much space is required between lines, the pitch will be tightened. Before a very loud signal, the pitch will

"open up," to provide ample space for the increased groove dipslacement. www.americanradiohistory.com

If

this is what you are

looking for.

If you demand nothing less than true hi -fi performance, you'll understand the advantages and flexibility that resulted when

Technics separated the basic amplifier /control /tuner functions into the five units we call the Flat

Series:

The automatically switchable dual

IF band

ST-9030

FM tuner. The

SU

-9070

DC preamplifier.

The

SH

-9010 stereo para- metric

/graphic frequency equalizer.

The

SH

-9020 peak/peak-hold/average metering system.

And the

SE

-9060 stereo

/mono

DC power amplifier.

You'll also understand why the

Flat

Series challenges the performance of the most expensive professional equipment in the world. And very often

Inpu Waveform to ST9030 FM

Tuner.

11

i

r

1 surpasses it.

Look at the graphs.

The repro- duced waveform is virtually true to the original. All types of distortion

-some measurable, some not

-are

negligible.

And the linear frequency response is

Output Waveform from Technics Fiat Series.

0.1

Stereo

....._..

8f2 Both ch driven

..

.

_..

-

- extremely wide.

Were confident that the truly dis- criminating critic will recognize the magnitude

of

our achievement.

Espe- cially when that achievement is offered at prices that are unprecedented for equipment of this caliber.

And with the flexibility to incorporate one or more, or all five units into your system.

Depending on your needs or budget.

To see how

Technics achieved the incredible performance shown in the graphs; you have to see and compare the incredi-

-o o

+120 ble specifications that are typical of the

Technics Flat

Series on the facing page.

-eo

0.1 s

0.01

0001

0.1

1.0

Output power (W)

20Hz

10 low

. .

.....:

'low car off

DC-..:

(DC)

........

-_._-

!.0

--..

-'-fc11:11.

100

Frequency (Hz)

IK

100

THD vs.

Output. Power in

Stereo

SE

-9060.

10

Gain, Phase vs.

Frequency Response,

SE

-9060 A np

TECHNICS ST-9030

.

THD (stereo):

Wide-

0.08%

(1 kHz).

Narrow

-0.3%

(1

RESPONSE:

20 Hz

-18

kHz°

+0.1,

-0.5 dB.

SELECTIVITY:

Wide

-25 dB.

Narrow

-90 dB.

CAPTURE RATIO:

Wide

-0.8 dB.

Narrow

-2.0 dB. IMAGE and

IF kHz).

S/N

(stereo):

73 dB. FREQ.

REJECTION, SPURIOUS RESPONSE

(98

MHz):

135 dB.

AM

SUPPRESSION

(wide):

58 dB. STEREO SEPARATION

(1 kHz):

Wide

-50 dB.

Narrow

-40 dB.

(10 kHz):

Wide

-40dB.

Narrow

-30dB.

CARRIER

LEAK:

Variable terminal

-

65 dB

(19 kHz). Fixed

-70

dB

(19 kHz, 38 kHz).

TECHNICS

SE

-9060. POWER OUT-

PUT:

70 watts per channel (stereo), 180 watts

(mono) min.

RMS into

8 ohms from

20 Hz to 20 kHz with no more than 0.02% THD. INTERMODULATION

DISTORTION

(60 Hz:

7 kHz,

4:1):

0.02 %.

FREQ. RESPONSE:

DC'ti100 kHz,

+0dB,

-1- dB. POWER BANDWIDTH:

5

Hz

-50 kHz,

-3

dB.

S

/N:

120 dB (IHF A).

RESIDUAL

HUM

& NOISE: 100

V.

INPUT

SENSITIVITY

& IMPEDANCE:

1V/471Q.

All the specifications of

Technics

Flat Series are too numerous and corn

- plex to list here. But their performance is too good to miss. So don't.

Technics

Flat

Series is now available for demon- stration at selected audio dealers. For very selective ears.

And for very selec- tive eyes there's Technics

SH

-999. A movable

19" custom rack with rosewood veneer side panels.

Technics Flat

Series.

A rare combination of audio technology. A new stand- ard of audio excellence.

IOK

100K

Technics

Professional Series

by

Panasonic

Circle

36 on

Reader Service

Card www.americanradiohistory.com

This is what

should

listen

to www.americanradiohistory.com

SUSETTE FIVEASH

From

Cybersonics:

A

New Disc-

Mastering

Lathe

Smaller size and cost -trimming simplicity might bring this lathe into the more modest studio operation.

40

The Cybersonics DM 2002 Disc Mastering

Lathe.

DEVELOPMENT of the

Cybersonics DM 2002 Disc

Mastering Lathe began about five years ago. At the time, there were all sorts of new ideas and products around. Consoles were becoming auto- mated, digital delays had made their appearance; there were parametric equalizers, new expanders and com- pressors, noise reduction systems

-the

list goes on and on.

Most of these newly -developed devices were brought about through the application of an ever -expanding variety of digital and analog integrated circuits, many using the new computer technology, which was fast becoming ac- cessible to audio design engineers. Designers had a seem- ingly endless number of options from which to choose in developing newer, smaller, more compact devices. It seemed as though everyone was improving everything.

Yet, disc mastering remained more -or

-less invisible. Im- provements in this area were known only to those few with an intimate knowledge of the medium. It occurred

Susette Fiveash is db's

West Coast associate editor. to

Cybersonics president Tom

Lippe] that here was an area of professional audio that could also benefit from some of the new technology. He noted that a very small percentage of recording studios were directly involved in disc a mastering. Possibly, the complexity and expense were deterrent, limiting the field to a comparatively few specialists

.

Thus, the newly- formed Cybersonics.

Inc. directed its

R &D towards coming up with a mastering system that would be far less formidable than those presently available.

In doing so, they hoped to make disc mastering more attractive to the small studio, by keeping the price tag down and offering a lathe that would be simple to operate and maintain.

In fact, simplicity became the primary goal. not only because it would allow a precision machine to be manufactured at a reasonable cost, but it would also permit the non -specialist user to easily gain competence in disc cutting.

EARLY RESEARCH

Cybersonics is located in

Southern California, which is not only a focal point in the recording industry, but also supports the bulk of the aerospace design companies in www.americanradiohistory.com

The head mount assembly.

Prototypes of electronics cards, accessed by sliding the front panel out on drawer slides. the USA. The accessibility of technical information from both industries was a great asset in the development of the lathe.

After reviewing the various technologies, and research- ing several methods of generating controlled linear motion, digital positioning systems, and other electro- mechanical systems, it appeared that it would be possible to design a complete mechanical system

-in

modular form

-without

using any belts, pulleys, gears, or hydraulic devices.

FIVE

YEARS

LATER

What emerged after five years of development was a self

- contained disc mastering lathe bearing little resemblance to its predecessors. When first encountering the

Cybersonics

DM

2002

Disc Mastering Lathe, one notes its compact- ness of design.

In fact, it could almost be mistaken for a large record playing device of some ultra -modern design.

Not only is it compact, but its designers seem to have paid some attention to aesthetic detail as well.

In other words. it doesn't exactly look like a traditional lathe. This may distract some, who arc accustomed to the behemoths seen in the modern tape

-to -disc transfer facility, hut there is certainly some rhyme and reason hehind the DM 2002's diminutive size, 351/2-inches wide,

271/2-inches deep and

16- inches high (including microscope).

It weighs in at about

250 pounds. and this should make it especially at- tractive for those remote direct

-to -disc sessions, where a lathe must he transported to an often -hostile environment. and set up very quickly.

THE MECHANICS

Mechanically, the concept is: simple, direct, small. The lead screw carriage, microscope drive system and turntable assembly are all mounted on a single platen, which is

'fl- inch thick. 33- inches wide and 24- inches deep. is

The platen constructed of special -grade aluminum, ground and fin- ished to a flatness within a weight

I mil tolerance. The platen's

-in

excess of

150 pounds

-offers

extreme damping. stability, and linearity to all moving mechanical functions.

The actual lead screw and head -mount carriage assem- bly consists of two end blocks

-also

precision -ground, and pinned to the underside of the platen. Between the end blocks are two stainless steel parallel rods, on which the carriage assembly glides, and these arc mounted on super

- precision low- friction linear bearings. The head -mount carriage itself is driven by a

lad

screw, captured by a half -nut follower made from a special "oil

-homogenized" plastic material.

The microscope drive system is a smaller replica of the carriage assembly, and is also fitted to the platen. as is the turntable drive system.

D.C.

TORQUE MOTORS

A good measure of design simplicity was made possible by a new d.c. torque motor, one of many components "bor- rowed" from the aerospace industry.

It is a permanent

- magnet d.c. servo motor, with enough commutator seg- ments to virtually eliminate any "togging."

The motor's speed

/torque relationship is linear, and it satisfies

Cyber- sonics' precision -design requirements for all mechanical sub -assemblies.

For its size, the motor has extremely high torque. very low inertia, and is easily controlled with rela- tively simple electronics. Consequently. Mr. Lippe! feels that its speed control is considerably superior to that of other types of motors.

Four of these torque motors are used in the

DM 2002.

The motors directly drive the lead screw. the turntable, the cutter suspension, and the microscope.

In the lead screw carriage sub- system, the motor con- trols the linear speed (lines -per -inch. or LPI) of the car- riage.

It is able to follow a complex velocity profile quite accurately, thus assuring precise control of the groove spacing on the disc's surface. Since the motor is direct

- coupled to the lead screw. all complicated systems

(such as clutches, gears, belts and pulleys) are eliminated, along with their associated problems. The motor's slow speed reduces the possibility of mechanical vibration transmis- sion, and its design simplicity reduces the necessity of many routine adjustments.

In the turntable sub -system the torque motor is used as a constant

-speed device. It has sufficient torque to accelerate the ten pound platter to 45 rpm in about one quarter of a revolution. Once up to speed, it is held constant by a crystal -controlled phase lock loop. Long term speed sta- bility is as good as the crystal, 0.001 per cent. Wow and flutter are negligible because the motor's torque is always in control. The lathe also has an automatic disc hold -down vacuum system, which utilizes a hollow drive shaft through the motor housing to the underside of the platter.

(No more forgotten vacuum chucks!)

In the microscope -drive sub- system, slow speed and easy control are the requirements, so the motor is pulse -width driven. Speed and direction are controlled from a single knob on the operator's panel. This allows the engineer to inspect the disc being cut comfortably. and therefore do a more thorough job inspecting the lacquer for groove imperfections.

(continued) www.americanradiohistory.com

The precision ground lead screw and carriage ways viewed from below.

The trol. fourth torque motor is for cutter- suspension con-

It is only rotated through a few degrees in total: while the disc is being cut, it moves through seconds of an arc. Its primary function is to control cutting stylus pressure and thereby the depth and width

Electronic damping of the groove.

-using

a feedback circuit in conjunc- tion wtih the cutter head suspension-eliminates levers. strings, knobs, cams, and hydraulic dampers.

Again, there's not much to adjust or change: therefore, not much margin for error.

The motor is also used to raise and to lower the cutter head, at the start and finish of the transfer.

FRONT PANEL CONTROLS

Deliberately, the ease front panel than been kept simple, for of operation. Microscope control knobs and switches are at the extreme left. Next, two large analog meters indicate pitch and depth information.

At the center of the panel, a recangular l.e.d. display reads out the precise diameter at which the stylus is cutting. This is accom- plished by means screw. of a shaft encoder coupled to the lead

The encoder also eliminates the need for mechanical switching relating to automatic mode functions, such as head drop, lead -in spiral, automatic tape- start, lock -out concentric groove diameter, head tract-to- rest position. lift, and automatic re-

Within the I.e.d. display area, two additional readouts indicate stylus heater current and turntable speed.

The speed indication is actually a digital strobe. and reads the precise speed at which the platter is rotating.

Motion and mode control buttons are located to the right of the front panel. Below the front panel. there is a sub

- panel with pre

-set controls for heater current, band -time switch, half

-speed selector. etc.

THE ELECTRONICS

Contemporary electronic devices arc used within the

DM

2002: random access memories, twelve -bit analog -to- digital and digital

-to- analog converters with an accruracy of one part in 4.096 (213), or ±0.025 per cent, precision sample- and

-hold circuits with f.e.t. op

-amps and low power

Schottky logic. These circuits control the pitch /depth com- puter as well as the basic lathe functions, such as turntable speed, mode control, etc.

Additional logic circuits provide safety against an accidental head

-drop when the lathe is functioning in a mode that would be dangerous.

For ex-

The

New

TCD

340

A

With

The

Exclusive

ACTILINEAR

Recording System

Tape recorders can no longer be looked upon as independent units in today's ex- tremely sophisticated sound systems, but rather as components within a total system with performance capability as advanced as all other components of that system.

Drawing upon its unequalled

30 year tradition in magnetic recording technology,

Tandberg has met this challenge by developing a completely new concept known as

ACTILINEAR Recording (Patent pending).

In conventional recording systems, the summation of record

& bias currents in the recording head is done through passive components, leading to inherent com- promise solutions. The new ACTILINEAR

System is free of these compromises, as the passive components have been re- placed with an active Transconductance amplifier developed by Tandberg. Just a couple of its benefits are: up to

20 dB more headroom over any recording system cur- rently available, and the ability to handle the new high coercivity tapes.

In fact, Tandberg's new ACTILINEAR

Recording System, when used in conjunc- tion with the soon- to -be- available metal particle tapes now under intense de- velopment in the U.S.. Japan and Ger- many, offers performance parameters approaching those of experimental Pulse

Code Modulation (PCM) technology, yet is fully compatible for playback on all existing tape recorders.

It is literally a recording system for the future, with no obsoles- cence factor, as it can be used with any tape, available now or in years to come.

Tandberg engineers have mated this advanced recording system with the finest cassette deck making their transport available new TCD 340

A a today, worthy suc- cessor to the world- famous TCD 330 cas- sette deck. When used with the better brands of recording tape currently availa- ble, the TCD 340 As ACTILINEAR Record- ing System permits an extremely linear frequency response, a significant increase in headroom, as well as a reduction of high frequency

IM distortion and the cancella- tion of Slew Rate limitations.

And when metal particle cassette tapes become available, the TCD 340 A can be adjusted to take full advantage of their increased signal capacity. At that time,

Tandberg will also sette deck offer the ultimate cas-

-the remarkable TCD 340 AM, complete with front panel switching for the new metal particle tape.

Both these remarkable cassette decks excel in more than just their circuitry. Like their famous predecessor, the TCD 340 series offers

"2 -in

-1 three separate heads (not a sandwich" head compromise) for professional recording

& monitoring, as well as

Tandberg's renowned three -motor, dua' capstan closed loop transport, coupled with complete logic- controlled solenoid operation. Plus exclusive fea- tures such as adjustable azimuth

& built

-in

10 kHz tone generator, allowing the user to select the perfect alignment for each cas- sette, as well as to spot dropouts and inferior quality tape.

And the TCD

340

A boasts a

70 dB signal

-to

-noise ratio, plus very low 0.12% WRM wow

& flutter!

And there's more: Automatic take -up of tape loops when the cassette is inserted.

Frequency -equalized, peak- reading met- ers.

Servo -controlled high speed winding.

Plus vertical or horizontal operation, op- tiona, remote control

& rack mounting.

Tandberg's TCD

330 was the deck that delivered cassette performance exceeded only by the finest reel -to -reel machines.

Now, the 340 series with

ACTILINEAR

Recording narrows the gap even more.

For your nearest dealer, write: Tandberg of

America,

Inc.,

Labriola Court, Armonk,

N.Y.

10504.

Available in Canada.

TANDBE;TO

www.americanradiohistory.com

The microscope carriage viewed from below. ample, automatic head

lift

is initiated if the operator stops or changes turntable speed, or moves the carriage in the fast

-out mode while cutting.

When the front panel is pulled out, all electronics are exposed, for easy trouble

-shooting. l.c.'s are mounted in computer -grade sockets to allow quick replacement if and when the need should arise.

COMPUTER PITCH CONTROL

All control signals are taken from the standard preview head on the tape playback system to allow the circuits to anticipate what is going to happen to the groove when it is cut. The preview signal is also stored for one revolution in the computer, where a comparison is made between what the previous groove loked like and what the uncom- ing groove will look like. This information is converted into pitch and depth control signals. is

The computer receives new capable information constantly and of up- dating pitch and depth information from two to eighteen times per turntable revolution. A program- mable delay time in the computer's logic compensates for preview head -to- playback head distances, disc speed, and tape speed, thereby eliminating the need for complicated tape paths on the master tape machine.

All control signals are formed into eight

-bit words. in order to facilitate automated disc recording, in conjunc- tion with presently available computer mixdown systems. or with future microprocessor

-based systems. The feature also makes it possible to tronically. for high link several lathes production or direct together elec-

-to -disc recording.

CONCLUSION no

Because of its small size and ease of operation, there is doubt that the Cybersonics lathe could open the door to versatility in disc mastering a bit wider. Two or three lathes might be placed in the amount of space formerly required for just one. Since the lathe is not much bigger than a typical tape recorder, it is conceivable that it could be placed in the recording studio control room. This would allow the engineer to cut a reference lacquer in the same environment in which the multi -track recording and mixdown were done.

And more important perhaps, if the Cybersonics

DM

2002 Disc Mastering Lathe lives up to its promise ducing the cost and complexity of re- of disc mastering, it should make this important aspect of recording services more accessible to the small and medium

-size studio operation.

,,.=_7.:1!.

[Dnac,iab

J

-CT

Circle

27 on Reader Service

Card www.americanradiohistory.com

o

C. P.

REPKA

CBS'

DISComputer

A micro processor based unit controls consistent production in disc

-cutting operations at

CBS' fariung installations.

CONSIDER the following problem. You are a major record company producing records on a world wide basis and you have to manufacture enough records album, along to meet the demand for your latest hit with all your normal production demands.

Solution

??

Design and build a state

-of- the

-art variable pitch and depth computer and install around the world. Now it in all your cutting lathes

if

these first two sentences don't seem related to each other, perhaps a few more facts will clear things up a bit.

The production of a million or copies of the same record requires that a large number of identical metal stampers also be produced.

And this in turn requires that a large number of identical lacquer masters be made. In a large company like

CBS, and variety of with its large staff mastering equipment, of cutting engineers the chances of the same engineer, using the same necessary lacquers equipment, cutting all the for that million dollar seller is very small indeed.

At the same time, there is an excellent chance that a tape mastered by engineer

A, using a

Neumann cutting system using a

(for example) cannot be duplicated by engineer

B

Scully

/

Westrex system, or vice versa. In addition.

if

you consider that some records

(usually classical) will remain in production for many years and that

CBS has divisions all over the world producing what are theoreti- cally identical discs, you can see that what appeared to he a relatively simple problem is in reality a very complex one.

The awareness of this problem led

CBS Records to ask

CBS Laboratories (now known as the CBS

Technology

Center) to find a way to improve lacquer mastering stand- ards. The research team began by ting system existing at the time investigating every cut- with the hope that one system could be chosen as a standard. This idea was quickly rejected when it was discovered that all the cutting systems were either inadequate wtih respect to repeatability or were too conservative in design to meet the demands of modern studio recording technique

(as well as that ever lurking nemesis, the modern record producer!).

It would also have been away all prohibitively expensive for

CBS to throw of its existing lathes and replace them with any one manufacturer's system.

It was then decided that the best approach would he to design a variable pitch and depth computer that could be interfaced with any lathe used by any division of

CBS

Records.

The result, after five years of research and devel- opment, was the CBS

DISComputer.

MICROPROCESSOR

The start of the

DISComputer is a microprocessor unit which allows the very complex pitch and depth command

A close -up of the recording lathe.

Charles Repka is a freelance

8

in Oakland, N.J. recording engineer based www.americanradiohistory.com

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The entire disc

-mastering system. signals. needed repeatable to a during the cutting of an

LP side. to be high degree of accuracy. The analog signals from the preview head are continuously examined for maximum waveform levels. The maximum level is sam- pled 200 times on each disc and then stored in the revolution, converted to computer. Next. the digital. computer uses the previous revolution's stored signal and the present sig- nal to generate proper pitch and depth control signals that not only meet the demands of the program material, but also the constraints (level, pitch and groove width) re- quired by the cutting engineer as well as several pre- programmed constraints. (The circuit details regarding the manner in which the command signals are generated within the computer are considered proprietary by

CBS and can- not be discussed until proper patent protection has been secured.)

The high sample rate (about

25 times higher than used in previous systems) allows a more efficient use of the available recording space. The pitch computer can expand the for a loud signal and then close the pitch again very quickly, while remembering to avoid those groove excur- sions on the next revolution.

Since more "decisions" are made in each cent revolution, the net result is a

20 to 40 per improvement in space utilization. This means the engineer can space either cut a record using

25 -40 per cent less than before (sometimes desirable due to distortion considerations) or use the same space and put a

2

-3 dB higher level on the disc.

The built

-in constraints control the rate at which the pitch and depth can change to keep the control signals well below the point of audibility, yet make efficient use of record space. Studies by CBS

Technology Center revealed that these changes should be smoothed to yield a well de- fined path of cutter head motion, which has virtually all of its energy resonance concentrated at frequencies below the tone arm of the playback system.

This ensures maximum utilization of record "real estate" with no disturbance to the listener. The computer also has a built

-in non

-linear function (again based on extensive studies in the lab which corrects for pre- and post -echo that can take place during cutting and plating).

The use of a microprocessor has resulted in several unique features not usually found in professional audio equipment. The ates each time the checked and. unit is turned on. 800 test points are

if

a malfunction is found, the problem area is computer has a self -test function that oper- indicated on the front panel. The test function can also be initiated at any time by the operator.

FAIL -SAFE

The computer make a will not permit the cutting engineer to

"dumb" mistake.

Say the engineer tells the com- puter to cut at 800 lines per inch with a

4 mil groove width.

The computer will ignore the

LPI command and will in- stead set

4 mil itself to 250

LPI

(the maximum allowable at a width) and indicate the proper

LPI on the readout display.

The computer can also be used by the engineer to deter- mine the optimum level

When cutting a tape for for the any given first time, program material. the engineer looks at the running time and the nature of the program material and makes an educated guess as to the proper pitch and level settings. side, the

The lacquer is then cut and at the end computer displays the amount of the of level

(in dB) that should be added or subtracted (assuming no change in the basic pitch setting) to give an optimum cut utilizing all the available space.

Or, more simply put,

if

the chosen pitch and level has not used up all the available space, the computer tells the engineer how many dB he can raise the level. using the same pitch setting, to fill the disc.

If, on the other hand, the engineer had guessed wrong and run out of space. the display would show how many dB the level must be lowered to fit the program onto the www.americanradiohistory.com

disc. a

This process can also take place lacquer by without ever cutting simply playing through the computer and observing the display at the end of the tape.

Of course. the engineer always has the option of trying a different pitch setting and going through the process again.

As part of the research for this article,

I went to the

CBS mastering facility in

NYC to observe the

DISComputer in operation.

I brought with me a tape that

I had cut on another system (no names please, but it was the best money could buy, about one year ago) with which

I had experi- enced some difficulty. The tape was of a symphony orches- tra recorded in a large reverberant hall, contained no unusual levels or dynamics and was only

23 minutes long.

However, the recording had been made using spaced omni microphones and, as a result, contained a great deal of out

-of

-phase low frequency information that cause the sys- tem

The to overexpand and run out of space on the initial cut.

DISComputer cut the same tape at the same level, with room to spare. and told us at the end additional

11/2 dB of the tape that an of level could have been used.

A second cut was then made at the higher level with no problems.

During both cuts, mastering engineer Stew Romain used a much coarser than

I had used pitch (300

(400

LPI at 2.6 mils groove width)

LPI at 2 mils). Using my pitch set- tings, several tained. additional dB of level could have been ob-

To achieve a satisfactory cut with the other system.

I had to resort to a

150

Hz mono combine network as well as a slight reduction in level.

Installation of the

DISComputer involved the removal of the existing pitch and depth computer as well as the lead screw drive mechanism and replacing them with the

CBS -designed units. Typical installations

Neumann lathe and an older Scully with system are a modern shown in the accompanying photographs. Units are currently in ser- vice in CBS cutting facilities in New and Canada. and

York City. Nashville modifications are taking place at

CBS divisions in

Australia, Mexico, Holland. Germany, and

Japan. Since installation has been completed in the

U.S..

CBS has experienced a master related significant reduction of lacquer

- quality control problems in its plating and pressing plants. to overcuts,

This means there are fewer rejections due lifts (too narrow a groove), and fewer recuts due to mastering related problems in the plating process.

EVALUATION

In summation, the new CBS

DISComputer has brought the following improvements to the recordmakers' art:

Increased the average level of a typical disc by

2

-3 dB.

Made possible longer sides improved repeatability with no sacrifice in level. for lacquer recuts.

Improved product uniformity in all CBS divisions.

Reduced costs by reducing the number of recuts caused by cutting errors.

Improved disc quality achieved by improved s/n ratio and reduced pre- and post -echo.

That's quite an impressive list and before any of you accuse me of being paid off by the CBS

Publicity depart- ment, you may be surprised to discover that CBS has no plans whatsoever to market the

DISComputer: only enough computers will be made to equip the various

CBS record divisions. CBS is not and does not want to he in the disc computer manufacturing business.

The DISComputer will pay for itself at

CBS by means of reduced manufacturing costs and hopefully. through increased sales as a result of improved product quality.

I find that to be a refreshing thought!

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The

Gramophone

If a machine talks, we are apt to regard it as almost human; if it sings, we look upon it as being artistic.

MAKING

EITHER permanent or transient records of sounds, as exemplified by Scott's phonauto- graph or Koenig's monometric flames, is no longer a novelty, but recording and repro- ducing musical sounds and speech are recent. Sound re- producing machines are no less wonderful than sound transmitting apparatus, and although the talking machine may not find as wide a field of application as the tele- phone, it is perhaps more interesting and instructive, and has the additional peculiar charm possessed by anything mechanical that faithfully reproduces any of life's actions.

If a machine talks, we are apt to regard it as almost human; if it sings, we look upon it as being artistic.

The versatility of the gramophone enables it to embrace almost any sound; military bands, instrumental solos, piano, cornet, clarionet, banjo, etc., songs, recitations. whistling, imitations. Educational features of the instrument are lessons in elocution, lessons on the correct pronuncia- tion of different languages and the memorizing of verses, songs, and music.

Some years ago we gave an account of the earlier work of the inventor, Mr. Emile Berliner, in this direction, and our present first page engraving illustrates the gramophone in its latest form. It is presented as a popular instrument for the use of everybody. It affords amusement to people of all ages and also presents a means of preserving records of various kinds.

In FIGURE

1 is shown a gramophone provided with the reproducing apparatus only, it being designed for use in connection with records made by the

Gramophone Com- pany or the dealers. The instrument is provided with a turntable mounted on a pivot, as shown in

FIGURE 8. which is revolved by frictional contact with a rubber wheel on the shaft of the fly wheel.

The latter is provided with a pulley and is driven by a belt extending around

This is a reprint of an article which appeared in the May

16,

1896 issue of Scientific American. the larger pulley on the crank shaft.

On the placed the turntable is rubber disk bearing the record. The sound box is mounted on a swinging arm, which also supports the conical tube or resonator.

FIGURE 2 represents the recording instrument operated by a simple electric motor.

The essential parts of the recording instrument are the turntable, the worm screw which guides the carriage hold- ing the recording diaphragm, and the recording diaphragm.

The action of the mechanism is to so guide the recording diaphragm, while recording the sound, as to make it trace a to continuous spiral line from the the center. outer edge of the table

The method of making a sound record is to place upon the turntable a highly polished disk of zinc, previously prepared with a film of fat, exceedingly delicate to the touch of a lightly bearing stylus, but dense enough to re- sist an etching bath.

As the machine is set in motion, a delicately pointed finger or stylus pivoted at its center transfers the wave vibrations from the diaphragm to the zinc surface. The finger moves laterally. and literally writes the sound through the thin film which covers the zinc disk.

During the operation the plate is kept soaked with alcohol from the glass reservoir seen in the cut. The object of this is to soften the film and to prevent the particles of film or dust from collecting around the point of the stylus or finger; by this recorded. method a true and exact sound wave is

The record made, the zinc disk is taken from the turn- table and the alcohol is rinsed off: the disk is then placed in an etching bath of chromic acid. The length of time consumed in the etching depends solely upon the ampli- tude of the wave vibrations. Recorded waves of small amplitude receive short etching and those of large ampli- tude long etching. When taken from the etching bath the disk is cleaned and ready for the first reproduction.

Since the first reproduction consists mainly in cleaning out the groove, the sound is at first slightly harsh and grating. Two or three reproductions make the record smooth and quick. www.americanradiohistory.com

The record is now ready to go through the duplicating process.

A copper matrix is first made by a method of careful electrotyping.

From the matrix hard rubber dupli- cates are pressed in the manner in which castings are made. in

The rubber duplicates are superior to the zinc records several ways.

They will hear rough handling and an indefinite number of reproductions, whereas the zinc would burnish and soon wear away. They are louder and smoother than the zinc. The rubber records will stand over 1,000 reproductions, the zinc from 50 to 300, according to their delicacy. A first class matrix can press out

1,000 perfect duplicates.

A peculiarity of the gramophone record is that it has almost the penetration of the original sound, although not the he broadness of tone, so that if 1,000 gramophones could worked simultaneously, it would be possible for an orator to fill a hall 1,000 times larger than his voice ordinarily would fill.

Gramophone recording agencies have been established in

Philadelphia and Washington, New

York and Boston, and similar ones will be established in every city of importance, where the voices of those dear to us may he permanently recorded.

In

FIGURE 4 is the record of a shown the cornet solo. arrangement for producing

The reproducing sound box, which is shown in

FIGURE 5, is provided with a diaphragm connected with a spring arm fixed to one side of the diaphragm cell and carrying a point like an ordinary darning needle point. This point, when the instrument is arranged as shown in FIGURE

1, rests in the groove in the record plate and follows the groove as the turntable is re- volved. in the

The engagement of the needle point with the groove record disk causes the spring arm to vibrate and produce vibrations in the diaphragm, which are the same as those of the recording instrument: as a consequence, the original sounds arc reproduced in the resonator of the gramophone with a loudness and clearness which are surprising. The reproducing sound box is provided with a curved damping spring for reducing the vibration of the spring arm when it is desired to connect the sound box with ear tubes to be held in the ear.

A cross section of the reproducing sound box is shown in FIGURE 6.

The manner of holding the sound box in the position of use is shown in FIGURE

7. In

FIGURE

9 is given a much en- larged view of a section of a record, showing the sinuous nature of the grooves. An electric motor has been applied to the gramophone, as shown in FIGURE 10, by means of which the table is rotated at a uniform speed. and in

FIGURE

11 is shown the adaptation of spring clockwork to rotate the turntable.

The type of reproducing machine which seems to find most favor is turned by hand, and as the groove in the record itself guides the sound box, thereby eliminating the necessity of a costly worm screw and intricate gear- ing, it moves so easily that with five minutes' practice a child can operate it so as to reproduce a hand selection or a song in perfect tune. Those who object to manipula- ting will the crank can have a simple motor gramophone that reproduce the selections by merely turning a switch.

The modest plant first started by the Berliner Gramo- phone Company, 1032 to 1036

Filbert Street. Philadelphia. has been increased to four times its original size.

Dupli- cates are pressed out by the thousands, showing the rapid growth of this fascinating little machine.

Overleaf, the reproduced Scientific

American cover

- that illustrates this article.

btx presents the 30.track

audio

recorder

The btx 4500 SMPTE interlocking system lets you operate any two multi -track recorders in tandem for

14,

22, 30 or

4b

-track capability.

Using standard machine, any

SMPTE time code written on one track of each two recorders may be synchronized, including video to audio. tracks,

You can even mix makes, formats, speeds, and numbers of with or without servo controlled capstan drive. The btx

4500 is a micro -processor

-based system capable of tracking within

50 secon n actual mechanical loc

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A

taiiprt

Test

Report

Keith

Monks'

Record

Cleaning Machine

The Keith Monks Record Cleaning Machine. co

F

YOU have seen one of these units at a distance, you may be believing that it is the invention of the late

Rube

Goldberg.

As it comes out of its carton it is a turntable system that clearly will not play records.

What it is, however, is a turntable that will superbly clean records.

It may seem, based on the following description, that this machine is a kind of cleaning overkill. It probably is, if you have but a few records to clean on occasion. But if you maintain a record station library, retail shop. etc., where discs flow through regularly, this unit will prove extremely effective and efficient to use.

To begin, then. The Record Cleaning Machine is a turn- table that revolves at high speed (80

-100 r.p.m.

?), washes down the grooves of the disc to be cleaned via a brush www.americanradiohistory.com

that is swung over the disc, and then proceeds to remove the wash water and dirt by use of another arm that vac- uums up the material.

Underneath the deck, there are three bottles. One is filled with a cleaning liquid of 50 per cent distilled water and 50 per cent industrial methylated spirits.

A second bottle is not to be filled; it contains merely air.

A third bottle is where the vacuumed

-up glop is deposited.

All three bottles are connected to a vacuum pump

/motor

system which serves all the action.

To use, the disc to be cleaned is placed on the platter. and an electric switch moved to

WET. The brush (adjust- able) is placed across the grooves and a front panel plunger depressed. This releases a controlled amount of cleaning fluid through the brush onto the grooves and, after a few revolutions the disc has been thoroughly cleaned, but is

The cleaning machine will not help these discs.

We thank Fred Calero for his art. Fred is chief recording engineer at the

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The vacuum head.

A nylon thread acts as a buffer between the disc and the head.

It is slowly sucked off a below -deck reel into the bottle wtih the dirty fluid.

The cleaning brush is fully adjustable.

o

co also thoroughly wet.

Now you swine the brush off the disc and throw the aforementioned front panel switch to

DRY.

This starts the vacuum action. Then if you place the vacuum arm at the center of the disc. it will slowly move outward, slurping up the liquid and dirt into its innards, to he deposited in the appropriate bottle.

Does it really work?

I took some new

CBS -100 test rec- ords, measured their response, then cleaned them several times through the cycles of the machine. and measured them again.

No change. But were they quieter sounding!

Even a new disc can be reduced) by a pass further cleaned (and thus noise through this system. It's quite effective and, once mastered, easy to use.

A cleaning machine sells for

51,492.50.

It will prove a valuable investment.

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lR

BERT WHYTE

The

Logistics

of

Direct-

to

-Disc

Recording

The a search

for

direct -to

-disc pristine sound winds through labyrinth of frightening possibilities.

T HAS

BEEN

SAID that making a direct -to- disc

-recording is an exquisitely refined form of masochism. Cer- tainly it is an exhausting, tension

-filled experience for artists and engineers alike. The direct -to -disc re- cording process is unquestionably the most demanding and unforgiving of all present recording techniques.

In spite of this, more and more d

-d recordings are helm; made: it is claimed that more than

60 companies are pro- ducing them. Needless to say. the quality of a d

-d record- ing can vary as much as it does in conventional recordings.

The mere fact that a recording has been made with the d -d process does not automatically confer on it some extra- ordinary degree of fidelity to the original sound. In point of fact, the number of d

-d recordings that fully exploit the capabilities of this medium is comparatively limited. In consideration of the difficulties in working with the d -d medium, the obvious question is, this field

?"

The answer,

"Why all the activity in of course, is that

if

the stringent requirements of the d

-d process are scrupulously observed. this system is the highest medium in use today. quality, most accurate recording

WIDE RANGE ACCURACY

Few engineers, or the audiophiles who are the principal buyers of d

-d recordings, arc aware tication or the technical capabilities of the degree of sophis- of modern disc cutting systems such as those made by

Neumann or Ortofon.

The

Neumann SX74 and heads,

Ortofon

732 are moving -coil cutter

- employing motional feedback. They differ in a number of important respects. but their overall specifica- tions are similar.

As

I happen to have the

Neumann specs at hand,

I'll describe this system. The SX74 is a remarkable device. an exceptionally linear, very low distortion trans- ducer. Its frequency response surpasses that of the very hest tape recorders, being a rather astonishing

7

Hz to

25 kHz. plus or minus

3 dB. Even more impressive is that in the critical range from

15

Hz to

16 kHz, the deviation from flatness is a miniscule plus or minus a half dB! In a

Virgil

Fox organ recording

I engineered for Crystal Clear

Bert Whyte's as career as a recording engineer is almost legendary as some of the conductors he has worked with.

11esupervised and engineered the great Stokow- ski interpretations, as well as many others, while with the original Everest Records, and earlier made some of the first stereo while with or binaural orchestral recordings

Magnecord.

Records. the particular

SX74 cutterhead in the system we used was down only

3 dB at 4

Hz! Obviously. the

16 cycle fundamental recorded of the 32 foot pedal stops could he with a cutter with such an extended low fre- quency response.

The harmonic and intermodulation dis- tortion of the cutterhead is less than one percent.

Unlike tape recorders. there is no modulation noise in this

Neu- mann disc cutting system. wow and flutter are exceptionally low, and the

So dB. dynamic range /signal -to -noise ratio is about without the use of any noise reduction systems.

This truly is

"state -of- the

-art." and permits recording of the highest known quality.

People not familiar with the d

-d recording process have commented adversely on the hack time per side. In comparatively normal tape -to -disc restricted play transfer. an

- ad- vance head on the tape playback machine is positioned a certain distance before the standard playback head on the machine. The special output of this advance head feeds into a computer on the lathe and controls a number of automated control functions. Principal among these is automatic of the pitch and depth of the record groove that is being cut. The actual pitch (lines -per -inch) cut on the lacquer disc is continuously variable. as a function of the amplitude and dynamics of the program material.

In low level passages of music, the automatic variable pitch me- chanism makes the groove width narrower, and spaces the grooves closer together. In loud passages. the combination of variable pitch and variable depth control makes the grooves wider, deeper and spaced further apart.

With this variable cutting technique, space on the record can he saved (as compared to cutting at a fixed pitch). and there- fore more recording time per side is possible.

When we record direct -to -disc, there is no tape and ob- variously no advance head, and therefore no possibility automated control of of groove pitch and depth.

Now we must depend on a really savvy cutting engineer (preferably one who can read scores, and thus to a certain degree anticipate the dynamics of the music) who must manually control the pitch and depth mechanisms. Even the most skilled cutting engineer simply cannot compete with the speed of the computer as used in the normal tape -to -disc transfer. With the limitations of manual control, and de- pending on the dynamics of the program material, the playback time per side on a d

-d recording can rarely ex- ceed 18

-19 minutes, at

331 rpm, and about

12

-13 minutes per side at 45

As www.americanradiohistory.com

rpm.

if

the restrictions of manual cutting control were not enough of a handicap in d -d recording, the really conscien- tious d -d companies who strive for maximum quality make rn

Author Bert Whyte with conductor Arthur Fiedler and the equipment used for the recently released Boston

Pops album (Crystal Clear Records). life for the cutting engineer still more difficult by eschewing the use of any kind of limiters or compressors in the re- cording chain. Some do not even use the stylus accelera- tion limiter in the Neumann electronics. m

MERCILESSLY REVEALING

As mentioned earlier, the use of the d

-d process is no guarantee of high quality. medium. which

It is a mercilessly revealing will expose the bad just as easily as the good. The

"garbage

"prime directive" of computer technology

in-

garbage out

"

-is

equally applicable to d -d

-

recording. Thus, the signal fed into the cutting head elec- tronics must be as sonically pure as possible, if the high quality of the d -d process is to be fully realized. In the

Virgil

Fox and Boston Pops recordings

I have engineered for the

Crystal Clear

Records people,

I had the advantage of using highly refined custom

-built recording equipment. especially designed to interface with the d

-d cutting elec- tronics.

Thus special attention was directed to the suppres- sion of transient intermodulation distortion in the micro- phone pre- amplifiers. Similarly, in the recording console. all input transformers were eliminated, and sophisticated discrete circuitry employed for ultra -fast transient re- sponse, the lowest noise and gain stages and all minimum tid. other

The active devices amplifiers are in character- ized by ultra

-fast rise

-times and high slew rates, resulting in little or no time -delay distortion or tid. The console is extremely simple and straightforward

-there

are no echo send or return facilities, and no equalization is available, nor is any used throughout the entire recording chain. You might he amused by the fact that the engineers who made simultaneous digital recordings along with the d -d record- ing on the

Virgil

Fox and

Boston

Pops sessions wanted to make sure that the signal coming out of this fancy console was a

"clean enough" for their digital recorder.

They were hit nonplussed when they used the highly accurate Sound www.americanradiohistory.com

Technology distortion analyzer and couldn't get because the console distortion was below the a reading residual level of the instrument!

BLANK LACQUER DISC

In d -d recording, it goes without saying that the lacquer recording blank disc is a vitally important part of the process. There are only four manufacturers of lacquer re- cording discs in the western world. and naturally, every cutting engineer is partial to a particular brand. The lacquer disc is. in every respect, a precision product. which must be made under the most tions. The carefully controlled condi- aluminum base discs must be ground and pol- ished to near -optical flatness. The lacquer coating is a mixture of cellulose nitrate in a very volatile solvent, plus plasticizers, lubricants, dyes, and various other ingredients.

Lacquer disc manufacturers have special proprietary methods of coating or "flowing" the lacquer onto the aluminum bases to ensure as flat and uniform a coating as possible.

After coating, the discs are passed through

"curing" tunnels. where the solvent is driven off at a con- trolled rate to insure minimum deformation of the coating.

In spite of this care in fabrication. the discs have minute deviations and undulations on their surfaces.

The cutter

- heads cope with this by being mounted in a special suspen- sion with a controlled amount of flexure. A top quality lacquer recording disc has a dynamic range

/signal

-to- noise ratio of about

80 dB. which is better than that of tape, even with Dolby A noise reduction.

Even though the lacquers have been

"cured" in the manufacturing process, many cutting engineers like to maintain a stock of lacquers which are

"aged" by allowing them to "out

-gas" for five or six weeks.

This is felt to he of particular inportance in d

-d recording. Cutting engineers also seem to be in general agreement that, ideally, when a lacquer has been cut, it should be put into the electro' plating tank at once. (But, sec

Stan

Ricker's opinion, in

Suzette

Fiveash's in August companion article. Ed.) Which is why of

1977, you would have found

Ed

Wodenjak. president

4 a.m., of Crystal Clear

Records, on the freeway at rushing lacquers of the

Virgil

Fox d

-d sessions from

Garden Grove, 60 miles

North to the

AFM plating plant in Los

Angeles.

RECORDING

ON

LOCATION

If

a d

-d recording session in a studio is fraught with peril (and it is), the problems

ofd

d recording "on loca- tion," can be positively nightmarish. First thing is the mat- ter of the lathe itself. Whether it is a

Neumann or a

Scully. it is at one and the same time, delicate, big, ungainly, and very, very heavy! on a solid

Among other things. it should he placed foundation, with as little vibration as possible.

Needless to say, finding such a location at the recording site can be a matter frustrating experience. There is also the of the recording console, monitor speakers, perhaps an analog or digital back -up tape machine. and other para- phernalia fitting into the same location as the lathe.

Now it is obvious that a recording lathe can cut but one lacquer disc at a time.

If

you want to

"generate" enough lacquers so as to ensure a specific number of pressings. you can have the artists repeat their performance as many times as their stamina and union recording rules will per- mit. Or you can record on more than one lathe. Or, you can do both.

If

you opt for more- than -one -lathe, you com- pound the misery of handling these beasts.

At the

Virgil

Fox sessions two lathes were used. and on the

Boston

Pops recording, there were three lathes. heaven help us!

Of course, we recorded multiple performances as well. The organ used for the

Virgil

Fox recordings was a magnificant Rufatti instrument from Italy, ensconced in

the

Garden Grove Community Church. in

Garden Grove.

California, some sixty miles south of

Los Angeles. The church is a modern structure, far removed from. traditional concepts of religious architecture. and by its nature, not suitable we for housing assorted recording equipment. Thus wound up in the immediately adjacent administration building. using a second floor room normally used as a choir dressing room.

I won't go into the harrowing details of set

-up and communications this entailed.

The sessions began at IO not to o'clock in the evening, so as interfere with church functions

-and

because

Virgil

Fox is a

"night person." Four nights produced two record- ings which have been very well received, hut oh, the prob- lems! As you can readily understand, when you are making a d

-d recording, once the recording begins, the artist must perform the particular work completely, for a duration some

16 to

IS minutes. of

If he makes an obvious mistake early in the recording. we must stop, put on a fresh lac- quer blank, and start all over again.

If the mistake is made only a few seconds before the end of the recording, it's still back to "square sanie token, one" again, with another lacquer.

By the

if

the performance is note

-perfect. but there is a technical problem, again it's back to the beginning.

Among things we had to contend with on the

Fox ses- sions was the some police breaking in people 600 feet away during a fine take because complained we were making too much noise. (How's that for an appreciation of music from the great unwashed

?) a

Another take was low

-flying helicopter. And at the conclusion of ruined a by bravura performance broke of the

Widor

Toccata, some kids outside into loud and lusty cheers before the revcrb had fully decayed. lacquers.

Maestro Fiedler was delighted with what he heard from test lacquers and digital tape playback, and joined us in a champagne toast at the conclusion of the sessions.

MICROPHONE STRATEGY

Whether it be an organ recording church, or the Pops with

Virgil

Fox in a with

Fiedler, the choice of micro- phones depends on the philosophies does of the engineer. as their placement. There is essentially but one differ- ence in mie placement between a normal tape

-to -disc re- cording session, and a direct -to

-disc session.

While one tries the to exercise his judgment to ensure the best possible balances under any recording circumstances, it is still par- tially truc in the normal tape

-to

-disc context

...

"fix it in mix," but obviously this is not possible in the d -d process.

It can be seen that many things can go wrong on a direct

-to -disc recording session, but even assuming that everything goes like superb lacquers clockwork, and you have made some

-you are not "home free" just yet.

For yet more perils are lurking in the electroplating baths.

For all their generally careful work, the plating companies can, and do, lose lacquers to a would be possible number of technical grem- lins. In most cases, this means a reduction in the number of pressings that can be produced. In an extreme case, it for all the lacquers to be ruined, and the entire recording effort a total loss.

So, direct -to -disc recording is not for the faint of heart.

The obvious question, is it commitment worth the effort, depends on the of the recording company to the production of really high quality recordings. When they arc done properly, I think the direct disc recordings are the truest reflections of the original sound.

BOSTON POPS

The Boston

Pops sessions had their own share of prob- lems.

First off, when my wife and

I arrived at

McArthur

Airport on

Long Island to fly up to

Boston on the

Friday before the sessions on

Monday, we were blithely informed that the is that flight was cancelled.

Now, out in the hoonies. that

...

there is only one flight per day.

So it was either grind back into New York, or do what we did

-which

was to drive to

Orient

Point at the tip

World War Two, of

Long

"Landing Craft, Tank,"

Island, and take which they a now call a ferry, to New London,

Conn. and thence wend our way to Boston.

Our logistics engineer,

Frank Dickinson. was already in

Boston desperately trying, late on a

Friday afternoon, to find tanks heads and of helium and nitrogen for cooling the cutter

- blowing off lacquers, respectively. In Boston we used three lathes. Symphony

Hall is a magnificent room. but it wasn't designed with direct

-to -disc recordings in mind. The the was

Ancient Instrument

Room, which to the only place we could set up the lathes was in

-you

guessed front, and the left of the second balcony.

it-

If

it hadn't been for the wonderful help and co- operation of the great Boston stagehands, the been a disaster.

The ancient recording would instrument room is have not large. and true to its name, contains glass

-fronted cases cient musical instruments, may of them three of an- or four hundred years old. Fascinating yes, the cases but the reflections from would make our monitoring just awful.

So there was

Frank, out getting

Fibreglas 703. and covering the front of every case.

In this room was crammed two Neumanns and one

Scully lathe, the recording console, two of the big new

UREI

"time aligned" monitor speakers, an

Ampex

ATR

102 and

ATR

104. and, spilling over into the adjacent lavatory, was

Dr. Tom

Stockham and his

Soundstrcam digital recording equipment. Actually, once didn't have too many problems, and a minimum set up. we of "blown"

YOUR

"FISH SCALE" WAS DESIGNED

TO

WEIGH FISH!

The Tentel tape tension gage is designed to diagnose problems in your magnetic tape equipment. Throw away your fish scales (or put them in your tackle box where they belong).

The TENTELOMETER will measure tape tension while your transport is in operation, so you can

"see" how your transport is handling your tape

. smooth, proper tension for quality recording? or oscillating high or low tensions causing pitch problems, wow and flutter?

"See" what your heads

"See" and HEAR the difference.

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SUSETTE FIVEASH

Bring Your

Own Lathe

EDENTARY RECORDING

Studio

B. engineers, who feel

FIRST STOP

-THE

INSURANCE COMPANY that re- mote than recording sessions are just more trouble they're worth, will find little cause to envy to go the disc mastering engineer who is rash enough

"on location" with his lathe. Consider the adventures of

Stan

Ricker and

Richard

Simpson. As two of the west coast's finest disc cutting engineers, one would think that by now they had picked up enough smarts not to venture out of doors with their lathes.

But not only have they done just that

-they

have transported their lathes across the country to work with

Bert Whyte (and others) on re- mote direct

-to -disc sessions.

As

Stan same

Ricker described it to me, it's not quite the thing as wheeling a tape recorder down the hall to

Still back home in Los Angeles, as the cutting system comes apart for shipping, so does the insurance policy.

For once outside the cutting room door, all bets are off.

So.

Step

#1 is to get a marine insurance policy, one that will cover about $100,000 worth of very fancy hardware.

If

you can convince the insurance company that you're really sane, it's safe to begin the disassembly and packing.

The lathe must be

(carefully!) broken down into its many component parts, and these must be packed with great care.

If

an electronic component runs afoul of the shipping company, usually a little solder will take care of things. But there's not much that can be done for a lathe carriage assembly that arrives on -site with a dent in it.

At

Bert Whyte's

Virgil

Fox session, two Neumann lathes were used. Stan and

Ricker brought along a

Richard

Simpson supplied his

VMS

70 system.

AM

32B.

Both are quite heavy, so Stan and

Richard become an assembly team. once the equipment arrives on location.

LATHE PLACEMENT

Unlike a tape recorder

-which

can probably be placed just about anywhere

-choosing the wrong spot for a lathe can be a disaster. about a

Generally,

Stan looks for a likely spot foot or so away from a wall, since the wall adds some mize wall rigidity to the floor in that area and this helps to mini- building vibration. Hopefully, it's not an outside with a super- highway on the other side, but even that's better than a arc also a lot railroad.

Subways under the of fun. Even building

if

you can't hear the roar, the lathe ing may feel the vibrations transmitted through the build- structure, and an otherwise- perfect lacquer master may be destroyed.

Once the lathes are re- assembled, the dure begins, using an alignment proce-

NAB test record. When the play- back electronics arc properly aligned, the test record is replaced with a blank lacquer, and a test cut is made.

With a reference tone applied to the drive level is adjusted while cutter head amplifier, the monitoring the playback of the test cut. In general principle, it's about the same procedure as aligning a tape recorder. However, since the playback stylus is located about three -quarters of a revo- m

Suzette Fiveash is the new associate editor of db

Magazine and is based in

Los Angeles, California. lution beyond the cutting stylus, there is a lag time than one second of more until the record level adjustments show up at the playback electronics.

As with test tapes, test records come with a variety of reference levels available.

For example, test records from the

Victor

Company of

Japan use a reference level of

3.54 cm. /second, while the

NAB standard is

7 cm./ second.

(For more on this subject, see

Irwin

Diehl's article on

Groove Geometry in this issue-Ed.)

DON'T FORGET THE REFRIGERATOR

Temperature plays a very important role in getting a quality master disc plated and pressed.

Ten minutes of direct sunlight or prolonged exposure to warm tempera- tures can virtually destroy a lacquer.

Therefore, it must be stored in a cool place. Stan keeps his in a insure their quality. After cutting, a refrigerator, to common problem is getting the lacquers being exposed quickly packaged to keep them from to heat on the way to the plating plant.

Stan packages his finished lacquers in lined styrofoam cartons, with

Saran wrap.

Aluminum is then wrapped around the styrofoam, and the cartons are placed in a crate filled with those

"plastic peanuts" that we all know and love.

BEWARE

OF THE OOZE

The lacquer that is used to cut discs has a melting point of

130 degrees Fahrenheit, but, since it is vinyl, it isn't a very well

-defined type of melting.

It oozes.

When this happens, high frequencies deteriorate. Transients suffer first, creating a loss

On one of crispness on the final product. direct

-to -disc session, several masters were cut.

These were sent to

Canada, plating plants in

Germany and Japan.

California, New York,

All were carefully packaged, but later, one set of test pressings betrayed a tell -tale loss of highs.

The only conclusion that

Stan and the pressing plant engineers could make was that somehow the lac- quers had been exposed to heat in transit. The exposure must have been long enough to cause the damage.

On playback, the effect of heat exposure sounds some- what like a medium

-thin blanket draped over the speakers.

It doesn't cut the highs completely. but rather, subdues them.

A general conception in the plating business is that a lacquer must be put in a plating bath fifteen minutes after completion of within cutting. the first

Stan feels this isn't really necessary, so long as the lacquer itself is protected against the elements. Back in Los Angeles. his cutting room is kept quite cool, and the lacquers cut beautifully. and may be stored for quite some time with- out degradation. Under such controlled conditions, the disc might be preserved indefinitely. but of course

Murphy's

Law clearly states that "On a remote session, the optimum location for a lathe will also be the hottest spot in the house, once the session gets under way."

MICROPHONES AND DISC CUTTING

Although the microphone choice and placement is left up to the recording engineer, the disc mastering engineer should check for possible phase problems with an

X/Y

oscilloscope to make sure the disc input signal going to the will present no problems later on.

Ideally, the ratio of lateral -to- vertical modulation should be about 2:1. The www.americanradiohistory.com

playback stylus doesn't really care too much modulation and

-as

Stan neatly puts it for vertical

-there

..

a lot of nasty problems associated with it." may be

With lateral modulation, the playback stylus is driven to the left and right by the groove walls.

With vertical modulation, the stylus is driven up the groove wall by a positive -going waveform, but literally falls back down through natural gravitational forces and the vertical com- pliance there of the cartridge /stylus design.

Nothing else is to drive the stylus back down, so

if

the groove falls away faster than the stylus can tact with the groove drop, the stylus loses con-

-an acute symptom on loud vertical modulation. Although it's no problem to cut such heavy vertical modulation, the difficulties during playback of will the test pressings. show up

And later the test on, press- ings don't show up until long after the session is over.

So it's best to keep a close watch on the 'scope at all times!

HARMON MUTES

AND CIRCUIT BREAKERS

On any direct

-to -disc session, the fine art of gain riding can make cussion or break the disc, particularly on brass or instruments.

One example might be that per- of a trumpet soloist using a

Harmon mute.

Although the trumpet may not seem to be very loud, the upper har- monic structure is quite intense. When this type of signal is vent the is cutter head also cooled from burning up, although the head with helium to help keep the heat away from the sent to the disc, the circuit breakers may trip to pre- drive coils. But, because of that fine line between the head doing its work well and protective

"going up in smoke," this circuitry is still required. It also means that an overly -enthusiastic musician may wind up blowing more than his own horn!

Or, one nice transient peak from the kick

drum-

although it may not pop the breakers

-can

easily overcut the previous groove and then become the overcut itself with following groove, because of the unexpected displace- ment. (Remember, there are no preview heads around on direct

-to -disc sessions to prevent such little surprises.)

This type of overcut may not be easily seen while the record is being cut, so it can get awfully sweaty

if

the disc mastering engineer guesses wrong and stops the session needlessly.

But it's just as bad to discover the trouble later on, after the recording is over.

Either way. you lose.

To keep the disaster rate within reason, and ulcers at a minimum, there must be much pre -session planning.

The recording engineer, producer, musicians and disc mastering engineer must review any musical passages piece itself. In fact, the most that may have phase correct them or level problems, and work together to without violating the musical value of the important word on any di- rect -to -disc session is organization. And on a remote ses- sion, the word is spelled with a capitol

There's a whole series

"O." of finely

-tuned decisiois

-and

then actions

-required

to create a successful direct -to -disc recording. The end result depends heavily upon coordina- tion between musicians and engineers. The cutting equip- ment must be in first class shape.

The disc mastering engineer should he able to follow the score, and act as his own

"preview head," anticipating fortissimos and pianissimos, in order to properly adjust pitch and depth controls. The musicians must be up playing a complete side to the pressure of without interruption.

There must be no airplanes, subways, door wrong notes. missed cues, and so on. slams, chair squeaks.

Aside from that, there's nothing to it!

Just ask

Stan

Ricker or Richard

Simpson. But don't tell them

I sent you.

Sound Workshop will introduce the

Audio Machinery

Shared

Access

Memory System at the

A.E.S.

Convention in

New York

City on

November 3rd,

4th, 5th, and

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It will change all your present concepts about digital delay, pitch shifting, and digital reverberation.

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bringing the technology within everyone's reach.

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JAMES

P.

SHELTON

A Look at the

Record-

Platin

g

Process

The need for controlled conditions and expertise could trigger a whole new industry.

FEW

YEARS AGO, the introduction of tape cassettes and

8

-track cartridges once again prompted pre- dictions of the imminent demise of phonograph records. Such predictions have been made num- erous times in the past, yet the record industry has pros- pered. Even now, some say the video disc is again ringing the death knell for records.

However, no other medium for sound reproduction has such wide tolerance in all phases of its manufacturing and playback technology. The records themselves cover a range from floppy Evatone discs cheap enough for mass direct mail promotions, to the latest direct

-to -disc releases costing upwards of

$12.

Record player quality spans the spectrum from a $20 children's machine to elaborate systems cost- ing thousands of dollars.

The remarkable simplicity and wide tolerance of the record medium is likely to stand it in good stead before such potential competitors as the video disc, which is a comparatively critical, high technology medium. For the foreseeable future, it appears that records will continue to be the preferred medium for the reproduction of music.

The continuing popularity of records seems to be as much a surprise to some industry leaders as to anyone else.

How else does one account for the serious lag in the devel- opment of improved technology for record plating in this country? Significant improvements have been made in master tape and disc master technology, especially with regard to dynamic range and signal -to -noise ratios. Yet the m

James

P. Shelton is the president of the Europadisk

Plating Company, of New York City.

U.S. record industry has made virtually no efforts to im- prove what is now the weakest link in the record making

process-

American plating is still largely being done with the same primitive methods and equipment employed for the past twenty years.

There is another and equally destructive problem here and that is the notion that there is some close relationship between the plating and pressing operations. The molding of vinyl under high temperature and pressure is definitely heavy industry, involving equipment such as steam boilers and hydraulic presses, the same technique used to make a vast array of plastic products from toys to plumbing pipe.

A

DELICATE PROCESS

Record plating could hardly be further removed in terms of equipment, environmental and operational considera- tions. The electroforming of record production parts is a highly complex process, demanding extremely tight control of all operational parameters as well as the maintenance of a contaminant

-free environment. Such high standards of cleanliness, control, and handling do not lend themselves to an industrial environment, but are better suited to a laboratory. The operational considerations for operating a record press are quite different from those required to oversee a complex electro- chemical operation consisting of a number of completely different processes, each requiring constant monitoring and adjustment. There is, in fact, no more correlation between plating and pressing operations than between the disc mastering and pressing operations.

Electroforming is an entirely unique part of the record making process and, as such, should he a separate industry as distant from the pressing plant as is the recording studio.

More and more these days, one reads record reviews and hears talk among record collectors of the superior quality of European pressings. When questioned closely. most people mention surface www.americanradiohistory.com

noise as the most obvious quality difference between American and European press-

ings

-those

pops, ticks, swishes. ocean roars, crackles. tearing, and ripping sounds. Perhaps the most annoying noise of all is the pre- and post -echo sound, or "ghosting."

Undoubtedly, some lems in the pressing of this noise can he traced to plant, such as contamination prob- of the vinyl material or perhaps non

-fill of the record stamper due to incorrect temperature, pressure. or timing in the press in cycle.

However, it is the conviction of many people cutting, plating, and pressing operations that the great majority of noise and echo problems are generated in the plate making process. The basis for this conviction is that this process is tolerant of a surprisingly wide range of errors while still producing a part which is deemed

"

"useable

IGNORANCE

THE

CULPRIT

Most U.S. plating is mired in mediocrity more through ignorance than conspiracy. "We've always done it this way," is the answer one receives most often when question- ing practices that invite unnecessary noise and other prob- lems. parts ters as

The nickel sulfamate plating process used to produce will tolerate a considerable latitude of such parame- boric acid concentration, plating bath temperature,

Ph levels, and nickel concentration. But experience in state

-of

-the -art operations indicate that all these parameters have to significant effects and the more closely they are kept their optimum levels, the better and more consistant are the results. One can tell by a glance at a typical matrix that things aren't wavy and looks as is the result right in the plating plant; the part is

if

it wants to curl up. This curly look of plating bath contamination with metals other than nickel which causes stress to he

"built into" the part as it is formed and results in early failure of the part by cracking or splitting. A grainy, rough finish on the back of the matrix instead of a smooth, grainless surface is further indication of a poorly controlled plating process.

The obvious consideration of cleanliness to exclude po- tential contaminants short from the plant environment gets shrift in most operations.

All it takes is a single mote of dust in the right place at the right time to produce an audible pop or plants are tick on the finished pressing.

Yet most vertible pig stys, with accumulations of dirt, spilled chemicals, dust, etc. on the floor, equipment and work surfaces.

Most make no attempt to control the clean- liness of the air; dust laden outside air flows freely over all operations. Metal part polishing stations that produce metal dust arc not sufficiently separated from critical sil- vering and plating areas.

Rough handling is another major problem in an industrial environment. There is no time at which the record making process is more vulnerable than when the lacquer master is first unpacked in the plating plant. Handling at this point and during the silvering and pre

-plating require delicacy and precision, hardly the qualities one would expect from the industrial workers found in a pressing plant. Even the metal parts, though tougher than lacquer masters, arc highly subject to damage

Coming in contact with from a rough or hard surface careless can handling. permanently imbed a particle into the groove or collapse a groove wall.

The U.S. record market is presently dominated by rock music and this has served to encourage mediocre plating.

Since much rock music has a essentially steady state level limited dynamic range, the of the program will cover vir- tually all noise and echo problems. As a result, the atti-

Talking about automation is one thing.

Showing a working system is another.

Sound Workshop will demonstrate the

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A.E.S. Show in

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We suggest you check it out.

Sound Workshop

PROFESSIONAL

AUDIO PRODUCTS

bringing the technology within everyone's reach.

Sound

1324

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rn

co tudes of many plating plants has been to allow these low quality requirements to become the standard of their work.

WIDE DYNAMIC RANGE

More mature levels of rock music, as opposed to so- called "bubble gum" rock, as well as all classical music, are characterized by a wide dynamic range.

This type of pro- gram will expose any surface noise during low level pas- sages and echo problems become percussive attacks are painfully obvious when either preceded or followed by silence. Echo is often heard on piano solo records be- cause of the percussive nature of the instrument.

These problems are typical of poor plating.

There is already a shortage of plating facilities good enough to do this critical work. and as the demand for quality plating grows. the shortage will become acute. The premise for this growth is based on the fact that the median age of the record buying public is increasing along with that of the population in general.

This increase in maturity translates into a growing market for classical and other serious music with a wide dynamic range.

The trend is already in evidence and there is a growing demand for records of the highest technical quality as exemplified by the recent interest in direct -to -disc records. which exploit the wide dynamic range capabilities of lacquer masters.

With good plating and pressing. these efforts represent the highest state of the art in the record medium. There are actually record producers, some of the direct

-to -disc people among them, taking their business to

Germany because they cannot get adequate plating and pressing quality in the

U.S.! Such evidence cannot be taken lightly. since it means that the producer is willing to pay roughly double the U.S. cost and is still able to find a market for the result.

Of course. most producers cannot afford to double their pressing costs by going to

Europe and simply have to take their lumps (pops and ticks) and live with their frustrations.

Superior playback equipment is also contributing to de- mand for better records. Even a moderately priced stereo system costing $500 to

$600 boasts a good magnetic cart- ridge and speakers capable of reproducing all the noise. just as clearly as they do the program. The really expensive equipment is a proliferation of further indication of the interest in achieving the highest quality in sound repro- duction.

Such systems have the capability of reproducing quality far beyond that offered by commercial tape for- mats.

Only state

-of- the

-art records can provide a program source consistent with such superior equipment and there arc precious few domestic records in that category.

MATRIX CLEANING

One of the most important factors in preventing the in- troduction of surface noise in the plating process is matrix cleaning. When two matrices are separated at the comple- tion of a plating step, some particles from the matrix being plated are transferred to the surface of the new plate.

Any such particles must be completely cleaned off before the next plating step, or they will be reproduced on the following matrix. This also applies to any contamination. such as airborne particles, reaching the surface of the new matrix after separation.

In order to remove the so- called horns which have been transferred from the lacquer master to the mother matrix, the mother matrix is polished, which contaminates the surface with polishing compound. This contamination must also be completely removed before the final plating step to produce the stamper.

These two cleaning steps are extremely critical in that they must be thorough and yet not damage the matrix sur- face.

At

Europadisk. we are using a new technique devel- www.americanradiohistory.com

oped at Teldec which, so far as we know, is not in use elsewhere in the U.S. The process is and is the most electrolytic in nature thorough and safe technology yet developed for this critical application. In most U.S. plants, this clean- ing is accomplished by using a stiff brush and solvents.

Perhaps even more important than equipment and tech- nique is the basic approach, the philosophy

if

you will, of the plant owner /operator.

This consists principally of a firm commitment to achieving the highest quality obtain- able in every aspect of the plating operation. In any such endeavor there are the interest constant temptations to compromise in of expediency or cost. By making a commit- ment to quality above all at the outset. the pitfalls of mediocrity that are endemic in the U.S. plating industry may be avoided. such

It must also he realized that to make high standards practical will require operating per- sonnel of the highest caliber and this will make personnel as well as equipment costs higher, relative to other U.S. plating operations.

CAREFUL PLANT LAYOUT

The layout of a high quality plating plant is such that different types of operations minimize contamination from arc physically one to the separated other. to

Packing/ unpacking is done in a room separate from silvering and plating operations to keep cardboard and paper particles out of these critical areas.

The stamper hack- polishing and mother face -polishing, which generate metal dust are in their own room.

Special consideration must he given to surfaces such as floors and walls to help minimize airborne particles. Special and electronic air treatment, including both mechanical filtration is also required.

Because of higher equipment and personnel costs. rates will be higher than at most other plating plants.

However. when this age press higher cost is amortized per pressing over aver- runs, the increase is negligible: typically, less than one cent per pressing. Certainly this small premium will not present an obstacle to quality

-conscious producers since plating costs are a very small part of overall produc- tion costs.

One

As important goal is to make record producers more aware of the importance of good plating and to encourage them to specify the plating plant to be used for their work. it is, some producers are not familiar with the vital role plating plays in the quality of the finished pressing.

This can best be accomplished in cooperation with a reli- able disc -mastering studio.

In a

The quality operation, pro- ducers generally have a close association who cuts with the engineer their masters and a healthy respect for his opinion. majority of these engineers are already aware that many defects in the finished pressing are caused in the plating process and, because task is simplified. of that professionalism. the

Of course it is in the interest of the cutting studios to have their lacquer masters receive the best plating possible, since that will mean fewer problems as well as better results for their clients.

As quality plating work becomes better known in the industry, we hope that new interest in its role will be generated.

This awareness can stimulate the growth new industry. The series of a of events that has led to the birth of disc mastering as a separate industry may prove to be a a parallel for the same sort of phenomenon in plating. Only few years ago, mastering was exclusively associated with pressing plants, operations recording studios, or were the in -house of major record companies.

With the introduc- tion of new

European cutting technology and a philosophy of excellence, a whole new industry came into being. We hope to generate a similar transformation in the plating industry and, at the same time, make a commercial success of our own

Europadisk Plating Company.

440,

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Closing date is the fifteenth of the second month preceding the date of issue.

Send copies db to: Classified Ad Dept.

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ENGINEERING MAGAZINE

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FOR SALE

THE RESONATOR is more than a reverb.

Designed for use with any console, in- cluding

Tascam. $359.00. Dyma, Box

1697, Taos, N.M. 87571.

AMPEX, SCULLY, OTARI, all major pro- fessional audio lines. Top dollar trade

- ins.

15 minutes George Washington

Bridge. Professional Audio Video Cor- poration.

342 Main

St.,

Paterson,

N.J.

07505. (201) 523 -3333.

MINI -STUDIO

$2,599, using package systems from pro- recording equipment from Revox, Otari, Lamb Labs, Trident.

Beyer.

Write for full details of offers to

Entertainment

Sound Services, Inc.,

78

N.

Franklin

Ave., Hempstead,

N.Y. 11550.

(516) 538 -2220.

USED RECORDING equipment for sale.

Professional mics, speakers, miscel- laneous gear. Dan (415) 232 -7933.

TEST RECORD for equalizing systems. Helps you sell stereo equalizers and installation services. Pink noise in

1/3 octave bands, type QR-

2011

-1

@ $20.

Used with precision sound level meter or

B

&K 2219S. B &K

5111 W.

164th

St..

44142.

Instruments, Inc..

Cleveland. Ohio

FREE CATALOG 3

®OPA

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AUDIO APPLICATIONS

CONSOLES

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MIC,

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TAPE, DISC, POWER

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AUDIO.

TAPE

BIAS

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1033 N.

LOS

1213)

SYCAMORE AVE.

ANGELES. CA.

934 3566

90031

NEW PROFESSIONAL LINE of pre -as- sembled mic and patch cables in seven colors, two thicknesses; not a me -too copy of existing cables. Further info,

Sound

Applications,

342

Lexington

Ave.,

Mt.

Kisco,

N.Y. 10549. (914) 241

-0034.

CANADIANS!

SEMI -PRO MULTITRACK RECORD-

ING

HEADQUARTERS FOR:

TEAC/

TASCAM, Soundcraft, Sennheiser,

BGW, Altec, Lexicon, dbx,

Bi

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Beyer, R.S.D., Tapco, and more.

Richard's Music

Shop Inc.

6078

Sherbrooke

W.

kg10.

Montreal,

Canada H4A

1Y1

(514) 487 -9911

FOR SALE, large

Moog synthesizer. All components,

2 keyboards, ribbon con- troller,

2 sequential controllers. Excellent condition. Scott -Textor Productions,

220

E.

54th St., New

York,

N.Y. 10022. (212)

688 -4330.

IVIE SOUND ANALYZERS, all stock. Theatre Technology, models

37 W. in

20th

St., New

York City 10011. (212)

929 -5380.

AUDIO and VIDEO

On a

Professional Level

Lebow

Labs specializes in equip- ment sales, systems and installation engineering,

-full

service and demonstration facilities in- house.

We represent over 200 manufac- turers of professional and semi- professional equipment for record- ing, broadcast, sound reinforce- ment, and

Call or pricing. for commercial sound. write for information and

LEBOW LABS,

INC.

424 Cambridge

St.

Allston

(Boston) Mass. 02134

(617)

782 .0600

((Y(I111I111P(% www.americanradiohistory.com

(O

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FOR SALE

SCULLY

8

-TRACK w

/Sync

Master, mint condition; Accurate

8 x

8 mixing con- sole; best offer over $6,000.00 takes both. Le Mans Sound. (201)

359

-5520.

HAECO

CSG -2 compatible stereo gen- erator, new condition,

$1,700. Used

Westrex 1574D cutter amps, $400 each.

Pultec

MH -4 mixer, $125. HAECO LX

-1 crossover,

$600.

Fairchild

670 stereo limiter,

$650.

Frankford /Wayne Record- ing,

134 N. 12th St.,

19107.

(215)

561

-1794.

Philadelphia,

Pa.

NAB ALUMINUM

FLANGES. We manu- facture

8

", 101/2", and

14

".

Also large flanges and special reels to order. Stock delivery of assembly screws

& nuts

& most aluminum audio, video,

& com- puter reels. For pricing, call or write

Records Reserve Corp., 56

Harvester

Ave.,

Batavia, N.Y. 14020. (716) 343 -2600.

REK -O

-KUT drive belts.

$9.95

Specify model. delivered.

QRK

Electronic

Prod- ucts, 1568

N.

93703.

Sierra Vista, Fresno,

Ca.

TASCAM Model

10, 12

-in

/4

-out, acces- sories; Sony TC8

-54 4- channel; asso- ciated equipment.

Steve Kurtz,

2421

Mapleview, Kalamazoo,

Mi. 49002. (616)

323 -9410.

CUTTERHEAD REPAIR SERVICE for all models Westrex, HAECO, Grampian.

Modifications done on

Westrex. Avoid costly down time;

3

-day turnaround upon receipt.

Send for free brochure: Interna- tional

Cutterhead Repair, 194 Kings

Ct., Teaneck, N.J.

1289.

07666. (201)

837-

AMPEX SPARE PARTS; port; technical sup- updating kits. for discontinued pro- fessional audio models; available from

VIF

International,

Box 1555,

Mountain

View,

Ca.

94042. (408) 739 -9740.

STAGE / STUDIO /

BROADCAST audio systems: AKG. Allison Research, Amber,

Amco., A.P.I., Audiotronics,

Beyer, Can- non, dbx,

E

-V,

Eventide

JBL, Lexicon, MicMix,

Clockworks,

MRL, MXR,

!vie,

Nagra,

Neotek, Neumann, Nortronics, Orban/

Parasound, Orange County, Otari, Pul- tec, Robins, Russco, Scully, Sennheiser,

Sescom,

Shure, Sony,

Soundcraft,

Speck,

Switchcraft. Spectra

Sonics,

3M,

Tas- cam,

Technics, more. For

White,

UREI rurther information plus many on these and other specialty items from our fac- tory operations contact: Midwest

Sound

Co.,

4346

W.

63rd

St.,

Chicago, Ill.

60629. (312) 767 -7272.

MODERN RECORDING TECHNIQUE. by

Robert

E.

Runstein. The only book cov- ering all aspects of multi -track pop music recording from microphones through disc cutting.

For engineers, pro- ducers, and musicians.

$10.50 prepaid.

Robert

E.

Runstein,

1105

Massachusetts

Ave.,

#4E, Cambridge,

Mass. 02138.

FOR SALE:

Westrex

3DIIH, $3,495.00;

Haeco

SC -2,

$4,800.00; Haeco

SC -1,

$1,495.00; pian

BI

Grampian

D,

$385.00; Gram-

/D,

$325.00; Westrex

2B, $525.00; all Haeco cutterheads new, other cutter

- heads reconditioned and in specs. Inter- national Cutterhead

Repair,

194

Kings

Ct.,

Teaneck,

N.J. 07666. (201) 837 -1289.

DISCOUNT PRICES on fresh name

- brand tape. Check our prices in bulk, reels, boxes, carts, and cassettes. P.B.P.,

4100 West Kennedy Blvd., Tampa,

Fla.

33609. (813) 877 -7125.

REELS AND BOXES 5" and 7" large and small hubs; heavy duty white boxes.

W

-M Sales, 1118 Dula Circle, Duncan- ville, Texas 75116. (214)

296 -2773.

RANSTEELE custom heavy duty wall/ ceiling speaker mounting brackets for

JBL, Altec,

Big Reds, etc., $160 pair.

Ransteele 200W

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Scully lathes; complete turnkey master- ing rooms. Ransteele Audio, Inc. 1697

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265 -5563. GOING OUT OF BUSINESS. Ampex

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280

-2; Audi

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18

-in

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Eventide harmonizer,

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-mics, amps, etc., all in perfect running order; most under one year old. (516)

295

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THE LIBRARY

.

.

.

Sound effects re- corded in STEREO using

Dolby through- out. Over 350

$100.00. effects on ten discs.

Write The

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P.O. Box

18145, Denver, Colo. 80218.

NAGY SHEAR -TYPE TAPE SPLICERS t

IMR1

FOR CASSETTE

Vi &

K IN. TAPES

HAND-CRAFTED

FIELD

PROVEN

FAST, ACCURATE

SELFSHARPENING

NRPD

Box

289

McLean,

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FREE

Subsonic

CATALOG

Filter is required for optimum bass response in your system.

ACE

AUDIO

CO..

532 5th

St.,

East

N'thp't.NY

11731

REVOX

MODIFICATION, variable pitch for

A -77; in

/sync for

A -77 or A -700; pro- grammer for

A -77; rack mounts, slow speed

17/s; full track; auto rewind; high speed

15 i.p.s.

A -77. for

A

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Machines available with or without mods at low cost

(A

-77 from $695). All mods professionally performed by

Revox trained technicians. Entertainment

Sound Services, Inc., 78

N.

Franklin

St..

Hempstead, N.Y. 11550. (516) 538 -2220.

ROADSHOW EQUIPMENT. Clearing wide range new

& used items including mix- ers (from $350 to $3,500), bass

& bins (w

& treble w/o speakers,

$125 up). lenses, horns, etc.: limited quantity: be first.

(516) 538 -2220.

Entertainment

Sound Services,

78 N.

Franklin

St..

Hempstead, N.Y. 11550.

FOR SALE: Ampex

MM1200 24

-track with

16

-track heads, search to cue, VSO

Excellent condition.

Take over lease or best offer. Also, Ampex

440 mono, 440

2- track, two

TEAC

1/4

-track

3300's. Lar- rabee Sound,

8811

Santa

Los Angeles,

Monica

Ca. 90069. (213) 657

Blvd.,

-6750.

TAPCO and

Electro- Voice: mixers, equal- izers, amps, mics, and raw ers. Write or call loudspeak- for low mail order prices. Sonix

Co., P.O.

Box

58.

Indian

Head, Md. 20640. (301)

753 -6432.

UPDATED OUR EQUIPMENT. Used mics by

Neumann; Sennheiser; Beyer; etc. for sale. (415) 232 -7818.

ONE -THIRD octave real time analyzer,

Hewlett- Packard Model

8050A with trav- elling case, cords, and

Altec pink noise generator. Perfect condition.

$2,400.00.

(212)

675 -1166.

SCULLY 16-

TRACK

-Model

100 com- plete with

8

-track stack and guides, spare elect.

/remote sync master; both stacks like new; $10,500. 16x16 APSI console with patch bay plus spare

1/0 module,

4

-band eq.

(4 para), bi- f.e.t. elect. Very flexible board

$5,000.

We're going

24.

Normandy Sound

401

-247 -0218.

CASSETTE LABELS

13

Colors

/2

Whites Pressure sen- sitive;

12 upon an 111/4" x 71/4" sheet; packed

100 sheets

(1200 labels) per pkg; die cut and ready to print or type.

Audico,

Ltd.,

Div. Michael

Book

Co.

219

Crossen

Elk Grove,

III. 60007

(312) 640 -1030 www.americanradiohistory.com

TEST GEAR

Amber

4400 retrofit and factory recai, perfect.

Philips

PM3232 dual beam scope, two probe sets, cables, Polaroid Scope Camera. All for

$3,100.

San

Richard Jennings,

2247

Clement,

Francisco,

Ca.

94121. (415)

752-

6209.

Copies of db

Copies of all issues of db

-The

Sound Engineering Magazine start- ing with the November

1967 issue are now available on 35 mm. micro- film.

For further information or to place your order please write di- rectly to

University Microfilm,

Inc.

300

Ann

North Zeeb Road

Arbor, Michigan 48106

BUSINESS OPPORTUNITIES

WEST COAST engineers

/producers:

Bay

Area sixteen -track; fully equipped with tube Neumanns, Schoeps, etc., EMT;

DDL's (2); acoustic chamber; Dolby A;

Spectrosonics; Scully; Ampex. Free flight for out

-of- towners. Tewksbury.

(415) 232-

7933.

24

100

CHANNEL sound reinforcement mixer foot snake, balanced input,

3 band eq,

3 submixers, monitor, echo, solo

...

includes

UREI model 527A graphic equalizer. Must sell! Asking price

$2,950.00.

B. C. & G.

Box 708,

Enterprises,

P.O.

Arvada, Colorado

80001. (303)

751 -5991 or (303) 424 -6151.

WANTED

WANTED: Karlson model

8

-U enclo- sures. State condition and price. B.

Sherrard, FSI

/P-

Mountain,

APO New

York

09023.

CUSTOM DE

MEDIO

(to

24 console,

24 x 16 with patching),

24 x 4 monitor, e.q.,

4 echo sends,

2 cue sends, many other features. Available with

24

API

550 e.q.'s. (550 not

Gray, (415)

771

-5780. sold separately.)

FOR SALE: Mavis road cases

15/4 road boards in with snakes.

SPR

Systems.

(616) 392 -2379.

REVOX A

-77

RECORDERS at low, low price

$695.

Brand new batch just re- ceived in manufacturer's sealed car- tons, manufacturer's warranty. It's a steal.

Other models available including

A

-700's at $1,350. Write for full listing or make

&

$15 checks or money order

($695 freight

& handling

A -77. N.Y. residents add appropriate sales tax) payable to Entertainment Sound

Ser- vices, Inc.,

78

N.

Franklin

Ave., Hemp- stead,

N.Y. 11550. (516) 538 -2220.

WANTED: Recording equipment of all ages and variety: Neumann mics. EMT. etc. Dan

Alexander,

602E

Bernhard, Rich- mond,

Ca. 94805. (415) 232 -7933.

MAINTENANCE

/CUTTING ENGINEER.

Large independent

East

Coast disc mas- tering facility seeks an experienced maintenance /chief engineer who is look- ing for a bright future and who is com- pletely familiar and is able to maintain

Neumann, Scully, Westrex, and Capps cutting room equipment. Other duties will include occasional cutting,

R

&D projects, and construction. Applicant must be able to work with little or no supervision and be of high calibre.

Ex- cellent company benefit programs.

Salary commensurate with qualifications.

Reply with resume to

Dept.

81, db Maga- zine, 1120 Old Country

Rd.,

Plainview,

N.Y. 11803.

EMPLOYMENT

AMPEX, OTARI

&

SCULLY recorders in and stock for immediate delivery; new rebuilt.

RCI, 7912

Georgia

Ave.,

Silver Spring, Md. 20910. Write for product list.

SPECTRA SONICS

1024 -24 recording console;

24

-in

/out. Producer's desk.

18 months old, excellent condition, $25,000.

(805) 966 -6630, 966 -1271.

PROFESSIONAL AUDIO COMPONENTS:

AKG mics; Badap

1;

Lab;

Crown; dbx; Delta

Eventide; Frazier;

Gauss; GLI;

Ivie; mann

Malatchi; MasterRoom; Nagra; Neu- mics; Orban; Otari; Pentagon;

RTR; Sennheiser mics; Switchcraft;

Tascam;

Uni

-Sync; and UREI. These products are on demo in our show- room and in stock for immediate de- livery. Our paid. shipping is insured and pre-

Barclay Recording

&

Electronics,

233

E.

Lancaster

Ave., Wynnewood,

Pa.

19096. (215) 667 -3048 or 649 -2965.

FOUR 3M -64

2

-track record

/reproduce tape machines; all machines in excel- lent condition.

$16,000.

O'Day Broad- casting, Don Winget,

1305

Third

Ave.,

Suite 400,

Seattle,

Wa. 98101. (206)

682 -2828.

CURRENT MCI console, JH528; stereo quad; 28 -in

/24 -out; operated only a few weeks; latest factory mods. Cherokee

Recording Studios.

(213) 653 -3412.

FREE PROFESSIONAL CASSETTE specs. w/

Larksong,

Box 468M,

Point Arena,

Ca. 95468.

AUDIO DESIGNS 16x8 board, separate stereo

& mono mixdown. Now in ser- vice. Mint condition.

$17,500.

Fred

Arthur Productions. (303) 832 -2664.

TWO

Phase

ALTEC

A7 speakers, $300 ea;

2

Linear

700B power amps, $500 ea;

2

Yamaha B3

V

-FET power amps.

$800 ea;

1

Westrex

3DI1 cutter head with amps, $3,000;

1

Neumann com- plete disc cutting system with

SX -68 head and JG66 amps, console, tape deck, eq., etc., $20,000;

1 x 12

Bushnell

24 console,

$15,000;

1

Dukane

30

-50 generator,

$200;

1

3M56

8

-track re- corder,

$6,000. All prices FOB

Holly- wood,

Ca.

United Recording,

6000 Sun- set Blvd.,

Hollywood,

Ca. 90028. (213)

469 -3983.

AMPEX SERVICE COMPANY: Complete factory service for Ampex equipment; professional audio; one

-inch helical scan video; video closed circuit cam- eras; video systems; instrumentation; consumer audio; professional audio motor and head assembly rebuilding.

Service available at 2201

Lunt Ave., Elk

Grove Village,

III.

60007;

500

Rodier Dr.,

Glendale,

Ca.

91201;

75

Commerce

Way,

Hackensack, N.J. 07601.

SERVICES

IMPRESS your manager. Save money on:

Technics, Ampex, Scully, Nortronics.

Stanton, Inovonics,

UREI.

Electro-

Voice,

Betar, Orban, etc. Val

-tronics,

Inc. Call collect,

(717)

655

-5937.

DISC

MASTERING ENGINEERS. The

East

Coast's largest independent disc mastering house is in need of two ex- perienced cutters, preferably with a good technical background and cus- tomer following. Excellent salary and benefits. Apply with resume to: Dept.

82, db Magazine,

1120

Old Country Rd.,

Plainview,

N.Y. 11803.

WANTED: Engineer (local) to design audio equipment. Partnership agreement possible. Ace Audio

Co., 532 5th St.,

East

Northport,

N.Y. 11731.

WANTED: Apprentice engineering posi- tion. Experienced in sound and video studios; will relocate, self starter, hard worker, and dedicated. References.

Contact: Michael Ciesinski, 5611 South

Merrill

Ave., Cudahy,

Wisconsin

53110.

LARGE

24

-TRACK recording studio,

NYC seeking experienced maintenance engi- neer, preferably familiar w /Neve, Studer,

3M. Salary requirements, references.

Dept.

101, db Magazine, 1120 Old Coun- try Rd., Plainview, N.Y. 11803. www.americanradiohistory.com

People/Places/Happenings

N

Festivities for a

Centennial of

Light, celebrating Thomas Edison's invention of the electric light, which culminated on October 21, 1879, are being planned by the

Thomas Alva

Edison

Foundation,

(P.O. Box 1310,

Greenwich. Conn. 06830.) Focus of activities will be at

Edison shrines. such as

Menlo Park, N.J. and Ft.

Myers, Fla. Because of the close con- nection between Henry Ford and

Edison. the Museums at

Dearborn,

Mich. will also participate. Educa- tional materials for science fairs and exhibits will he provided by the

Foun- dation.

The post of semi

-professional prod- ucts sales manager at dbx, Inc. of

Newton. Mass. has been filled by

Emil Handke. Mr. Handke's appoint- ment is part of an executive expan- sion sive program. Mr. Handke's exten- experience in recording and sales was

Tenn. mainly acquired in

Nashville,

Lawrence G. Jaffe has assumed the position of vice -president in charge of marketing at

Uni -Sync Inc. of West- lake Village. Ca. Mr. Jaffe joined

Uni -Sync at the time of its purchase by

BSR last year, as marketing manager.

The newly- formed Creative Audio and Music Electronics Organization

-

CAMEO, is a combination of elec- tronic manufacturers and distributors who serve musicians and production people engaged in creative and origi- nal sound. Charter members include:

AKG, Alter. ARP,

BGW, dbx, Fen- der- Rogers- Rhodes of

CBS Musical

Instruments, ITX- Aphex, JBL, KM

Records. MXR, Oberheim, Phase

Li- near, RolandCorp US, SAE, Sirius

Music, Soundcraftsman, Tangent, Tap

- co, and TEAC Tascam. Headquarters are

Suite 3501. LaSalle Plaza.

180 N.

LaSalle St.. Chicago. Ill.. 60601 (312)

332 -7400. David

Schulman is the ex- ecutive director.

New manager for antenna engineer- ing at is

RCA's Gibbshoro. N.J. facility

Bruno F. Melchionni. Mr. Melchi- onni has been with RCA since

1941 except for a period of Air

Force ser- vice

RCA. during World War

II. Also at

Edward

B.

Campbell has been appointed manager of industrial elec- tronic services marketing at the RCA

Service Company. concentrating on the company's vices operation. industrial electronic ser-

The Meadow Lands.

Pa. facility of

RCA has acquired the services of

Richard

L. Rocamora as manager of broadcast transmitter equipment engi- neering and product management. Mr.

Rocamora has been with RCA since

1952 as an electrical engineer.

Several managerial level appoint- ments have been made at Shure Bros.

Inc., Evanston,

Ill.

Patrick J. Dalton has been sales named domestic distributor manager and Ken Reichel will head the technical markets and product management department. Working with

Mr. Reichel will he

John F. Phelan. professional sound products:

Al

Groh. high fidelity products:

Jerry

Quest. manager of communications and gov- ernment products. Lee Habich has been appointed as manager of adver- tising and sales promotion.

Assisting

Mr. Habich are three section managers.

Ruth Delke, Jim Paton, and Shelly

Brown.

Here's an opportunity to win some

"esoteric" audio equipment. Just think up a brand name for the

Carver audio line.

Further details may he obtained from Mr. Bob Carver, P.O. Box 604.

Woodinville. Wa. 98072. The contest. open to residents of the continnental

U.S.. closes

November

30. 1978.

Howard Harman has been appoint- ed to the post of western regional sales manager of

Audio -Technica, of Fair- lawn, Ohio. Mr.

Harman had been previously covering the northern Cali- fornia district for Harman International. the

The promotion of Almon Clegg to position of assistant general man- ager. product engineering division at

Panasonic, of Secaucus.

N.J. has been announced.

Mr. Clegg, who has been with Panasonic since 1974, has also been associated with

General Electric and has been a professor at

Illinois

Central College.

Research and development pro- grams at

Kustom Electronics, Inc., of

Kansas

City. Mo. are now in the hands of

William Goodson. Mr. Goodson has been with the firm since 1973. in the capacities of design engineer and pro- ject engineer.

The Society of Motion Picture and

Television Engineers has organized a committee. "Working Group for Inter- face of Television Broadcast Studio

Equipment." The intent is to create an optional control interface communications scheme

-

tape recorders, film chains.

-a

digital for video character generators, still stores, audio tape decks. audio consoles, video switchers, frame synchronizers. etc. The committee is under the direction of

All,

Robert

W. Mc-

Vital Industries, Inc.,

34

Autumn

Lane, Hicksville, N.Y. 11801.

The importance of telecommunica- tions has gotten the nod at Switch

- craft, of Chicago.

Ill. with the ap- pointment of their first telecommuni- cations marekting manager.

Fred Fitz- patrick. Mr. Fitzpatrick, who comes from Amphenol, will focus on new programs to market electromechani- cal components to telecommunications customers through authorized tele- phone distributors. Another personnel item at Switchcraft is the appoint- ment of Gerald F. Olsen as vice pres- ident in charge of finance. Mr.

Olsen had previously been with the Ray- theon Company.

Sales in Europe, Africa. and the

Middle East will be the special respon- sibility of Milo L. Cermak, recently appointed vice president. international marketing at

Information Terminals

Corp., of Sunnyvale.

CA. Mr.

Cermak has served as an international advisor for a number of companies. including

RCA and

AMF.

Also at

Information

Terminals. Paul Olmstead has assumed the job of corporate controller.

After a number of months of fa- miliarization with the executive work- ings of the company.

Thomas R.

Shepherd has assumed the post of president of

GTE

Consumer Electric

Company, the television marketing or- ganization of

General Telephone

&

Electronics Corporation of Stamford,

Conn. Mr. Shepherd's activities. since

1956, vania have been mainly with the Syl- portion of the company.

Lex

Rodgers has been appointed president in charge of engineering at

Fisher -Burke Professional Audio, of

Phoenix. Arizona. Fisher -Burke spe- cializes in broadcast consulting. www.americanradiohistory.com

The

90

-16.

$100000 per track:

O

:WU nil

Now you while you

can

make money save money.

Let's really sell face

it.

What you want your to do

is

album. And the new affordable

TASCAM

Series

90

-16

can help do just that.

But you at the to can same time, pick up cash help you pay for

it

by recording other musicians' songs for them.

And here's how you save.

You

don't pay studio time.

You

don't pay for

2"

equip- ment.

And you don't pay the heavy hit

of

"outboard"

DBX

which usually cost about

$300 per chan- nel. Our retail price

of

just

$16,000' suggested includes inte- gral

DBX

interface.

If

you're an engineer, the

90 -16

Function

Select make to you.

One button operation simulta- neously switches three interrelated record, panel will a source, lot of functions: sense tape/ and

DBX

need for three arms.

If

you're playback/ decode /encode thus eliminating the this a musician, human ing factor you won't engineer- means have wait

for

the to engineer and lose the sponta- neity

of

your music in the process.

All of

which that

if

you tracks, means need you only

16

have one choice: the new

TASCAM Series

90

-16.

You'll

sively find

it

exclu- at these

TASCAM dealers.

ot

A n.e:;-.:

EAC

C<v por

DEALERS

Audio Concepts

7138

Santa

Monica

Blvd.

Hollywood,

Ca.

90046

(213) 851-7172

The Express

Co., Inc.

1833

Sound

Newport

Blvd.

Costa Mesa,

Ca.

92627

(714) 645 -8501

Sound Genesis

2001

Bryant

St.

San Francisco, Ca.

94110

(415)

285-8900

Nashville Studio Systems

16

Music Circle South

Nashville, Tenn.

32703

(615)

256 -1650

Audio

By

Zimet, Inc.

1038

Nor.hern

Blvd.

Roslyn, New

York

1157.6

(516) 621

-0138

A.M.I., Inc.,

680

Indiana

St.

Golden, Colo.

80401

(303) 279 -2500

AVC

1517

Systems

East Lake

St.

Minneapolis, Minn.

55407

(612)

729 -8305

Electronic Music

Box

2320

6th Ave.

Seattle,

Wash.

98121

(206)

622 -6984

Arnold

&

Morgan

510

South

Garland

Garland,

Tex. 75040

Rd.

(214)

494 -1378

PA

Palace

2631

Buford

Hwy.

Atlanta, Ga.

30324

(404)

636 -3044

Lebow Labs

424

Cambridge

St.

Boston,

Mass.

02134

(617)

782-0600

Ford Audio

&

Acoustics

Inc.

1815

Classen

Blvd.

Oklahoma

City,

Ok.

73106

(405) 525 -3343

TASCAM

SERIES

BY

T

E AÇ new generation

of

recording instruments

A for a new generation

of

recording artists.

'Prices subject to dealer preparation charges where applicable.

TE.AC

:: st Hoed ly

White Electronic Deve.opment Corporation.

1966` Ltd

Circle

11 on

Reader Service

Card www.americanradiohistory.com

Your ears believe won't what they're not hearing!

Feedback has plagued sound systems since the day they were invented. It's something city councils, church choirs and boardrooms have had to cope

with...

something most sound system manufacturers have learned to live with

-or ignore.

Not

Altec.

Altec never gave up their search to find a better way of controlling nagging feedback.

It wasn't an easy task, but it was the kind of challenge that Altec has been meeting for over

40 years

... applying advanced research techniques to perfecting sound system technology. That's why they're the leader.

To

Altec, being a leader also means being an

innovator

introducing the

1628A

Automatic

Microphone Mixer.

Several microphones can be used simultaneously with this newly- patented device that automatically divides the system's volume among the in -use microphones, compensating for the number of persons speaking into them

-without

affecting intelligibility or the overall volume of the system. Each person will still be heard loud and clear all the way to the back of the room.

If only one microphone is in use, it receives the maximum system attention while the others are automatically silenced.

The

1628A also automatically turns the various microphones up or down as persons speak or stop speaking into them. And, up to five

1628A's can be linked together to accommodate up to 40 microphones.

That's an innovation!

The difference with automatic microphone

mixing...

In conventional systems, multiple microphones used simultaneously have had to rely on manual techniques, or, in some cases, a less- than -adequate "voice gating" system.

Neither has been successful.

The sophisticated 1628A operates on the principle of adaptive threshold audio gating (unique to Altec), which means that its activation point is automatically adjusted. allowing the system to discriminate between various noise levels and the voice signal that activates the microphone.

Let a professional Altec sound contractor demonstrate the

1628A to you.

Your ears won't believe what they're not hearing. Write today for further information.

1515

So.

Manchester

Ave.,

Anaheim, Calif.

92803.714/774

-2900

ALTEC CORPORATION

Circle

12 on

Reader Service Card

ALTEC,

rGGesnrrod of expeìvcomx.

www.americanradiohistory.com

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