Orban 424A Manuale utente

422A/424AGated Gompressoi/

Limrtei/De-Esser

OPERATING MANUAL

orbon

adivision of AKG Acoustics, Inc.

422A/424AGated Gompressoi/

Limiter/De-Esser

OPERATING MANUAL

95028-000-05

erbon

adivision of AKG Acoustics, Inc.

645 Bryant St., San Francisco, California 94107 USA

Phone (415) 957-1067 Telex 17-1480 FAX (415) 957-1070

GAIN REDUCTION:

Reads the gain of the VCA,

from 0to -25dB. Shows

the effect of any control

but OUTPUT TRIM and DE-

ESSER. v

INPUT ATTEN.:

Adjusts drive to compres-

sor/limiter, determining

amount of G/R.

ATTACK TIME:

Adjusts speed of response

to input level increase.

Fast: peak limiter &

compressor

Slow: compressor only

*•UN *’*

0-SHO>«-fO-?3

0»-«0-l9-tO-?S

GATE THRESH.:

Determines the input level

that causes “gating"; VCA

gain moves slowly to IDLE

GAIN control setting.

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INPUT ATTfN. COMM RATfO ATTACK TUMI Ml SHAPE REL. IIMI OATfO

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DATED COMPREBBOR/LIMITER

OUTPUT TRIM:

Adjusts VCA gain to control

or prevent clipping; its ef-

fect is seen on VCA LEVEL

meter; not an output at-

tenuator (Output Attenuator

located on rear).

DE-ESSER OPERATE/

DEFEAT:

Activates or defeats de-

esser control circuitry.

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Couples Aand Bgain and

gating circuits for stereo

tracking.

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PIODBL 4B4A

COMPR. RATIO:

Adjusts compression from

“looser’’ (2:1) to

“tighter" (°°:1).

REL. SHAPE: Lin: com-

pressor releases at cons-

tant rate

Exp: release starts slower,

then speeds up

REL. TIME:

Adjusts speed of gain in-

VCA LEVEL:

Reads peak operating level

crease when output level is of VCA. Clipping occurs

below threshold of com-

pression.

above approximately

“+2”.

IDLE GAIN:

Determines VCA gain when

unit is gated (OPERATE

mode) or anytime unit is

DEFEATED.

OPERATE/DEFEAT:

Activates or defeats comp/

lim control circuitry. Does

not bypass any circuitry.

DE-ESSER SENSITIVITY:

Adjusts threshold of de-

essing.

CAUTION

OPELECTRICAL SHOCK

DO NOT PEWOVn COVER. NO USER

SERVICEABLE PARTS INSIDE

REFER SERVICING TO QUALIFIED

SERVICE PERSONNEL Hi

^WARNING

TO REDUCE THE RISK Of FIRE

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EXPOSE THIS APPLIANCE TO

BAIN OR MOISTURE

-OR CONTINUED

PROTECTION AG»'N«,t

FtWE HAZARD RfPlACf

ONLY WITH SAME TYPE

FUSE SAC, S/S

FOR 115V MAINS I/4A

FOR JJOV MAINS I/I A

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MODEL 424A SHOWN

Table of Contents

About This Manual

Registration Card

Warranty

ICondensed Operating Instructions

5Part A: Introduction

5Performance Highlights

6Front-Panel Description

6Rear-Panel Description

7Part B: Installation

Mechanical Installation

7Electrical Installation

AC Power

Control Loop Bass Rolloff

Audio

Output

Preferred Wiring

Table I: General Input/Output Connection Rules

Wiring The 424A With Single-Conductor Shielded

Cable

1 1 Part C: Operating Instructions

II Description and Function of Front-Panel Features

Using The Compressor/Limiter

Using The De-Esser

Adjusting The OUTPUT ATTEN Control

19 Some Specific Applications

Adjusting The 424A To Provide Peak Overload

Protection

Stereo And Multichannel Operation

Speech-Activated Ducking Of Music

21 Part D: Maintenance

21 Introduction

21 ALIGNMENT AND PERFORMANCE VERIFICATION

General

Power Supply

Signal Processing Circuitry

27 MAINTENANCE AND SERVICE

Preventive Maintenance

Corrective Maintenance

Service Access

Lamp Replacement

Component Replacement

Replacement Parts

Replacement Of Components On Printed Circuit

Boards

Removal

Installation

Troubleshooting 1C Opamps

Factory Service

Shipping Instructions

31 CIRCUIT DESCRIPTION

General

Input Buffer

Voltage-Controlled Amplifier (VCA) Operation

Current-Controlled Gain

Exponential Converter

Compressor/Limiter Circuitry

General

Rectifier With Threshold

Timing Module

Threshold-Setting Circuitry and RATIO Control

Gating Circuitry

Gain Reduction Meter

De-Esser Control Circuitry

VCA LEVEL Meter

Power Supply

40 APPENDIX A: INTERCONNECTIONS AND GROUNDING

43 APPENDIX B: SPECIFICATIONS

44 PARTS LIST

53 SCHEMATIC

54 PARTS LOCATOR

ABOUT

THIS MANUAL

REGISTRATION

CARD

WARRANTY

Except for the first few sections, the information contained in this manual is

primarily for reference and to aid maintenance. The unit has been designed to be

straightforward and intuitive to use, and most experienced compressor/limiter users

will be able to use it easily without instruction.

However, anumber of subtle features have been included. Full understanding of

these will enable anyone —beginner or pro —to get the most of the unit. Time

spent with the manual will often yield substantial rewards.

The original purchaser should have received apostpaid Registration Card packed

with this manual.

Registration is of benefit to you because it enables us to tell you of new

applications, possible performance improvements, service aids, etc., which may be

developed over the life of the product. It also provides us with the date of sale so

that we may more promptly respond to possible claims under Warranty in the

future (without having to request acopy of your Bill of Sale or other proof of

purchase).

Please fill in the Registration Card and return it to us.

If the Registration Card has become lost or you have purchased the unit used,

please photocopy the image of the card reproduced below and send it to us in an

envelope. Use the address shown on the title page.

Model #Serial #

Name or Title

Organization

Street

City/State/Country

Zip or Mail Code

Purchased from City Date of Purchase

Nature of your application

How did you hear about it?

Comments:

Fig. A- 1:REGISTRATION CARD

The Warranty, which applies only to the first end-user of record, is stated on the

Warranty Certificate on aseparate sheet packed with this manual. Save it for

future reference.

Details on obtaining factory service are provided in Part D.

Condensed Operating Instructions

These instructions are primarily designed to help you get started using your

422A/424A. (The later parts of your OPERATING MANUAL contain much more

detail, and will help you get the most from your 422A/424A after you have

become familiar with the basics.)

Operationally, the 422A/424A can be considered to be abasic compressor/li miter

with enhancements. If you are just beginning to learn about it, or if you only need

basic compressor functions, you needn't worry about these enhancements.

Most of the enhancements are associated with the Gating function. If the GATE

THRESHold control is turned OFF (fully counterclockwise), these enhancements are

not operative and need not concern you now.

To Use The Compressor/Limiter: Preset the following controls:

REL SHAPE

GATE THRESH

OUTPUT TRIM

IDLE GAIN

COMP/LIMITER OPERATE/DEFEAT

DE-ESSER OPERATE/DEFEAT

LIN

OFF

0(at the detent)

OPERATE

DEFEAT

You then need to deal with only four familiar controls: INPUT ATTENuator,

RATIO, ATTACK TIME, and RELEASE TIME. These controls are always adjusted by

ear to obtain the desired sound. If you have used any common professional

compressor or limiter before, these controls should operate intuitively:

I) Adjust the INPUT ATTENuator control until the GAIN REDUCTION (G/R)

meter indicates the desired amount of G/R. Don't let the G/R meter enter the

red section of the scale.

Adjust the RATIO control to determine if compression will be "tight" or

"loose". "Tight" means that alarge increase in input level will produce asmall

increase in output level. As the ratio becomes "looser", the output level will

change more and more for agiven change in input level. 2:1 is the "loosest"

ratio; infinity: Iis the "tightest". "Looser" ratios tend to give more natural,

dynamic sound at the expense of lower loudness and less consistent levels.

(Adjusting the RATIO control to "looser" settings automatically lowers the

compression threshold to prevent peak overload of the 422A/424A circuitry or

of the device being driven by the 422A/424A when high amounts of gain

reduction are used.)

Adjust the ATTACK TIME control to determine how quickly the 422A/424A

responds to an input level increase. Fast attack times produce the most

consistent control of peak levels (and therefore produce highest loudness).

However, their effect tends to be more audible than that of slow attack times.

Slow attack times permit transient material to pass through the 422A/424A

unaffected, so that transient definition is retained.

(To prevent transient overshoots permitted by slow attack times from

overloading either the 422A/424A circuitry or devices being driven by the

422A/424A, the threshold of compression is reduced as the attack time is made

slower. This way, the peak level at the output remains approximately constant

as the ATTACK TIME control is adjusted.)

The ATTACK TIME control is calibrated with an arbitrary scale because the

attack time is automatically varied according to the nature of the program

material. This minimizes audible compression-induced side-effects.

Because the range of the ATTACK TIME control has purposely been made very

wide, certain sounds can cause the 422A/424A to produce distortion when

operated with fast attack times. Such sounds include certain male voices,

Hammond organ, and some types of bass (particularly synthesizer-produced). Such

distortion can be totally eliminated by operating with slower attack times —

usually between "5" and "SLOW" on the dial.

4) Adjust the RELEASE TIME control to determine how fast the 422A/424A gain

recovers toward maximum during those times when its output level is below the

threshold of compression.

Fast release times produce the greatest "density" and most consistent output

levels. However, they also create the greatest risk of audible side-effects. They

are most useful in recording studios or production situations where the program

material being processed is asingle track and is to be mixed with other

material.

Slower release times generally produce amore natural sound on mixed program

material. Accordingly, they are more useful in such applications as broadcast

production or cassette duplication.

The RELEASE TIME control is calibrated with an arbitrary scale because the

release time is automatically varied according to the nature of the program

material. This minimizes audible compression-induced side-effects.

(The RELease SHAPE switch determines if the release proceeds at aconstant

number of dB per second (LINear), or if it starts more slowly and then speeds

up as it progresses (EXPonential). LINear usually sounds most natural, but

EXPonential can be useful if you want to create the "open" sound associated

with slow release times, yet gain-ride quickly during pauses or low-level program

material. Like the other controls, it should be adjusted "by ear" to your taste.)

5) It is important to note that the OUTPUT TRIM control should not be treated

like afamiliar "output attenuator" control: It is ordinarily left at "0". Its

purpose is to permit you to operate the Voltage-Controlled Amplifier (VCA) in

the optimum part of its range for your application. You can use the OUTPUT

TRIM control to create controlled clipping in the VCA, to prevent VCA clipping,

or to optimize the signal-to-noise ratio. Refer to the OF*ERATING MANUAL for

further details.)

Astandard OUTPUT ATTENuator control is located on the rear panel.

Compressor/Limiter Enhancements: The IDLE GAIN control determines the gain of

the Compressor/Limiter when the COMP/LIM OPERATE/DEFEAT switch is in

DEFEAT. If the IDLE GAIN control is set close to the average amount of gain

reduction, the Compressor/Limiter can be defeated and reactivated in the middle

of program material without obvious side-effects such as sudden gain changes. (The

control also has asecond function which will be explained below.)

The gating features permit the 422A/424A to handle noise or low-level program

material differently than it handles high-level program material. The gating feature

is not the same as aconventional "noise gate": It is not intended to reduce noise

or other undesired sounds below the level at which they exist in the original

program. Its purpose is to prevent compression from unnaturally exaggerating such

material. If needed, aconventional noise gate can be used before the 422A/424A.

The gating feature is activated whenever the GATED lamp is on. This lamp will

turn on whenever the input level drops below athreshold set with the GATE

THRESHold control. (In its OFF postion, this control totally defeats the gating

feature.)

When the GATED lamp is on, the gain of the Compressor/Limiter moves slowly to

apoint set by the IDLE GAIN control. This gain change is indicated on the GAIN

REDUCTION meter. If the IDLE GAIN control is set at apoint equal to the

average amount of gain reduction occurring, then gain will neither increase nor

decrease during low-level program materal or pauses. In particular, noise will not

be "pumped up" as in aconventional compressor. For example, if you are

compressing aparticular track in amultitrack mixdown, tape hiss or low-level

material below the gating threshold will not be increased in level at the beginning

of the mix (before high-level program material first appears on the track), or

during pauses in the track.

If the IDLE GAIN control is set lower than the average gain reduction, then it

can leave a"hole" when high-level program material reappears and turns the

GATED lamp off. This is because the Compressor/Limiter must recover to ahigher

gain to produce full loudness, and this cannot happen instantaneously: The time

necessary for recovery is determined by the RELEASE TIME control.

To Use The De-esser: To use the De-esser, switch the DE-ESSER

OPERATE/DEFEAT switch to OPERATE and adjust the De-esser SENSITIVITY

control until "esses" sound naturally balanced with the rest of the voice.

The threshold of de-essing is fixed by the SENSITIVITY control, and does not track

the average vocal level (as in the Orban dedicated de-essers). For consistent de-

essing, it is important that the level presented to the De-esser be relatively

constant. This is ordinarily achieved by compressing the voice with the

Compressor/Limiter, which is functionally ahead of the De-esser.

It is sometimes possible to de-ess vocals which have been mixed with other

material. Each case must be evaluated by ear. The DE-ESSER OPERATE/DEFEAT

switch does not introduce clicks, pops, or discontinuities into the program, so the

De-esser can be keyed in or out in the middle of program material as required.

This may be the best way to handle afew problem "esses" in mixed program

material.

PERFORMANCE

HIGHLIGHTS

Part A: Introduction

The Orban Model 422A/424A Compressor/Limiter/De-Esser is an integrated AGC

device of highest professional quality. It can perform compression, peak limiting,

and vocal de-essing functions simultaneously with unusual freedom from side-effects.

It can thus serve either as ageneral-purpose no-compromise compressor/limiter, or

as acomplete dynamic processor for conditioning vocals. However, it is not

optimized for over modulation protection of broadcast transmitters, and the Orban

OPTIMOD-AM, -FM, or -TV should be used in such applications.

The flexibility and natural sound of the 422A/424A make it applicable in other

areas of professional audio as well: recording studios, sound reinforcement, public

address, motion picture sound, etc.

The product is available in both single- (422A) and dual- (424A) channel versions.

(For clarity, only the 424A will be referenced in this manual.) The dual-channel

version is equipped with acoupling switch which forces the gain of both channels

to be equal, tracking the channel demanding the greatest amount of gain reduction.

This preserves correct imaging in stereo applications. However, the stereo coupling

switch does not couple the operating controls, and these are ordinarily set

identically in stereo operation.

Attack and release times are both program-controlled, but can be scaled faster or

slower by means of front-panel controls. This results in maximum flexibility, plus

extremely natural sound over awide range of control settings.

The 424A Compressor is equipped with electronically-balanced inputs and outputs

and is compatible with the levels and impedances found in both professional and

semi-professional applications. RF suppression applied to the input, output, and

power leads enables use in relatively high RFI fields such as those common in

broadcasting.

The controls and features of the 424A Compressor are fully described in this

manual. It will familiarize you with the unit's potential and enable you to

imaginatively use the 424A for your specific installation and application.

Because the front-panel controls are marked in afamiliar way, you may be

tempted to jump right in without reading the manual. However, if you take the

time to review the Description And Function Of Front-Panel Controls and

Operating Instructions in Part C, you will find that there is "more than meets the

eye" inside the 424A, and that the time you take reading the manual will be well-

rewarded by agreater understanding of the unit's potential.

Production AGC function using circuitry adapted from industry-standard

OPTIMOD-FM Model 8I00A broadcast signal processor

De-esser characteristics similar to highly-accepted Orban dedicated de-essers

Independent compressor/limiter and de-esser control loops with optimized,

program-controlled parameters for each

Unbeatable ability to increase average loudness of program material or

individual tracks without introducing unnatural sound quality or artifacts

Defeatable gain-freezing gate with user-adjustable threshold to prevent

pumping and breathing during pauses

Wide-range attack time,release time,and ratio controls permit device to

sound extremely natural or to create special effects

Extremely easy to use because attack and release time controls interact and

also change the compression threshold, assuring consistent peak output levels

and minimizing need for manual readjustment of the output attenuator

Operation is intuitive and natural -- you don't need achart or an advanced

degree to figure out what's happening

Low-distortion operation teams clean class-A VCA with all-important dynamic

distortion reduction in the control circuitry

—25dB gain reduction range with constant 90dB (typical) clip-to-noise ratio

regardless of amount of gain reduction

Better than 25dB de-ess gain reduction available in addition to the 25db

compressor/limiter gain reduction

—True peak-reading output level meter allows operator to positively prevent

VCA clipping —or to use acontrolled amount of clipping to limit peak levels

—True peak-reading gain reduction meter

—Choice of general-purpose linear or special-purpose exponential release

characteristics

—Strong all-metal 19" rack mount package for ruggedness, roadworthiness, RFI

shielding, and ease of mounting

—Lighted meters with long-life lamps

Input, output, and AC power RFI suppression make the unit ideal for difficult

environments like broadcast stations, areas near mobile communications

transmitters, etc.

—Balanced inputs and outputs

—II5/230V 50/60Hz power supply standard

—Industrial-grade parts and construction

—Highly cost-effective

FRONT PANEL The Front-Panel Photograph at the beginning of this Manual shows the various

DESCRIPTION operating controls. These controls and their operation are fully described in

Description and Function of Front Panel Features in Part C(Operating

Instructions) below.

REAR PANEL The FUSE used in both the 422A and the 424A is aI/4A (115 volt operation) or

DESCRIPTION I/8A (230 volt operation) 3AG 250V SLO-BLO type. Replace with the same type

only.

The OUTPUT ATTENUATOR is fully described in Description and Function of

Front Panel Features in Part C(Operating Instructions) below.

The INPUT and OUTPUT connectors provided allow connection via barrier strip (#5

screw). Holes are provided for installation of "XLR"-type connectors, and aretrofit

kit is available from your dealer.

Please refer to the Electrical Installation section for connection instructions.

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