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INTRODUCTION

The dbx

160

and 161 are single-channe

compressor/

limiters combining sophisticated technology and user-

oriented features in a compact package. Unique circuit

designs, such as true rms level-detection and feed-forward

gain reduction, place the 160 and 161 in a completely

different class from conventional compressor/limiters.

addition to increasing the stability and the available

range of compression, dbx's feed-forward approach makes

possible for the attack and release times to "track"

the

signal envelope. In conventiona

compressor/limiters,

the

attack and release times depend on feedback loop gain,

which means they constant ly must be readjusted for

optimum results at different compression ratios. Since the

attack and release t imes of dbx units vary automatically

with the rate of

level

change in the program materia

(the

envelope shape), operation is simplified; no manual attack/

release adjustments are required

At the same time, the

"naturalness"

of any given sound

better preserved.

The

dbx tec hnique of true rms level-detection gives you

audible benefits. Most compressor/limiters

use some form

of peak detection, with fast response characteristics that

can have a disturbing effect on program material. True rms

level detection closely simulates the response of the human

ear. Even at high compression ratios, the gain changing

action of the 160 Series is

highly

listenable and natural

sounding

Because of the unique feed-forward approach, dbx 160

and 161

imiters can achieve infinite compression with

comp lete stability and

inaudible

distortion. The dbx

approach is quite un

ike gain reduction in a conventional

compressor/limiter

Traditional

gain reduction is accom-

plished by sensing

signal

level at the device's output and

applying a correction signal, via a feedback loop. At

progressively higher compression ratios, the feedback

loop's

gain increases, distortion

increases,

and eventua lly instabi

or oscil lation occurs. To avoid this problem, many con-

vent ional units

restrict

the maximum amount of feedback,

thus

restricting

the maximum compression ratio to some

lower

ratio,

such as 10:1 or 20:1. The dbx

160

and 161 are

free of the instability

of excessive

loop

gain, and can

provide infinite compression (approximate ly

120:

1 ).

GENERAL

INFORMATION

Models

The Model

160

is a fully professional compressor/limiter

with a balanced differentia

input, with an automatic

ground-loop compensated output (hum resulting from any

ground loop at the output

automatical ly sensed and

attenuated at least 40dB), and with a special protection

circuit that blocks

power

turn-on and turn-off

transients

from the output.

The Mode

161 is nearly the same as the

160,

but

priced for the smaller studio, or the semi-pro

user.

It has

the same advanced rms detection and feed-forward

circuitry as Mode

160, but it lacks turn-on/turn-off

transient

protection,

and ground-loop compensation. The

161

input

and output are unbalanced and terminated in

RCA-type phono jacks

Both models have adjustable thresho ld, and a pair of

LED's that

indicate

when the

input

level is above or below

the threshold. An il luminated meter displays a fu ll 60dB

range and

switchable to read input level, output level, or

gain

change.

The

meter's sensitivity is continuously

variable, so

"zero

VU" can be adjusted to equal your

system's nominal operating level, anywhere from +10 to

-1

OdB.

Output l ine level

also adjustable, ±20dB. Maximum

output on the 160 is

+26dB

( 1 5. 5 V)

into

a high impedance,

+24dBm

(12.3V) into 600 ohms. Maximum output on

the Model

161 is

+18dB (6.14V) into a

high

impedance, or

16dBm (4.89V) into 600 ohms.

Attractive ly styled and

functionally

designed, either

model can stand alone or can be mounted in a standard 19"

rack. Two

units

can be mounted side-by-side in

just 3½"

of panel space with the optional dbx RM-150-C rack mount

kit; the R M-150-D is for

rack

mounting of a sing le unit.

Applications

dbx noise reduction systems now make it possible to

process programs with 100dB, or greater, dynamic range.

Unfortunately,

some applications it

necessary to

restrict dynamic range. While dbx noise reduction systems

are used

the studio, for record production,

to maintain

wide dynamic

range,

th is range must often be restricted to

optimize the sound for broadcast and home playback. The

restriction of dynamic range is usually done with a com-

pressor, in the final stages of recording (or record master-

ing). In the broadcast field, where many stations compete

for an audience, a

high

average audio level can make a big

difference to radio station ratings. Compression is used to

attain

high

average

levels.

However, unless a high

quality compressor/limiter

is uti

ized, distortion

and

unwanted audible side-effects may degrade the sound

so badly that the advantages of high average level are

overcome, and audience interest can be lost. The 160

and 161 do a great job

both recording and broadcast

applications.

The

dynamic range of a

ve musical performance can be

even greater than 100dB. A high-quality compressor/

miter,

used judicious ly, can restrict the dynamic range, raise the

average

level,

help the operator avoid clipping distortion,

and improve the overall sound quality. Because the 160 and

161

sound so

natural,

they won't displease performers,

making them especially wel

suited to sound reinforcement

applications.

Compressor/ limiters can be useful in other applications

too.

The

160 and

161

are

ideal

for use as a high quality line

amplifier because of their low noise and distortion and high

output drive.

The

160 and

161

have the added advantage of

allowing you to conveniently dial

compression at any

time. In any application requiring

high-quality

compression