Series, 160s, 160sl – dbx 160SL User Manual

Page 21

160S

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series

160S

controls

160S

notes

160S

Operations

160S

Operations

Inspection

Operating

Connection

Installation

Technical

Introduction

to your system

considerations

contents

concept

diagram

applications

support and factory service

160S

Specifications

160S

Manual

Design

Block

Controls

Advanced

Warranty

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series

Using The Stereo Couple Switch

Two channels of program material do not necessarily constitute a stereo program. A stereo program is one where
the two channels are recorded and/or mixed to create the illusion of a single unified panorama of sound. The
stability of the psychoacoustic image of each sound source within the stereo spectrum depends upon its ability
to maintain a specific phase and amplitude relationship from the left to the right channel.

If two independent compressors are used to process the stereo program, a loud sound occurring in one channel
will cause a gain reduction only in that channel. This gain reduction would cause the perceived image of any
sound spread between the two channels to move toward the side which had not been compressed, because the
spread signal would be momentarily softer in the compressed channel. This can be avoided by linking the two
compressors in such a way that both channels receive the same amount of compression. On the 160SL, this is
accomplished by means of the Stereo Couple switch. When activated, the 160SL permits the RMS detectors of
both channels to “talk” to one another. The SLAVE channel (right, channel 2) then sends its signal to the MASTER
channel (left, channel 1), where the RMS power of the MASTER and SLAVE signals are combined to generate a
control voltage. This control voltage is then used to compress both the MASTER and SLAVE channels equally.
This dbx process is called True RMS Power Summing

™

When compressing a stereo program with a 160SL, only the MASTER channel controls need to be adjusted. The
Threshold LEDs, Auto LED, and PeakStop (Plus) LED will not light on the “slave” channel when the 160SL
is stereo linked. The Bypass switch and LED, Sidechain switch and LED, and the Meter Mode switches and
LEDs remain channel-independent and function normally in linked mode.

Using The Auto Switch

The Auto switch sets the 160SL for automatic or manual operation. When the Auto switch is IN (Auto mode),
the LED indicator lights and the 160SL automatically adjusts its attack rate and release time to suit the program
envelope. (This Auto mode sets the 160SL for the same attack and release characteristics as dbx Models 160, 161,
162, 163, and 164 compressor/limiters, the LED indicator above it turns OFF, and the front panel Attack and
Release rate controls determine the maximum rate of gain change and the behavior of the level detector circuitry.

Setting The Attack And Release Controls

The 160SL offers a choice of automatic or user-adjustable attack and release characteristics. In Auto mode, the
160SL utilizes the patented dbx RMS level detector with its program-dependent attack/release characteristics to
obtain natural-sounding compression or limiting. For special effects and certain signal situations, however, it is
often desirable to set fixed attack and release characteristics. Manual mode affords this capability. The Auto mode
is recommended for vocals as well as instruments. Because the Auto mode has a variable attack rate, the 160SL
may compress or limit some program material smoother than in the manual mode which has a fixed attack char-
acteristic. This is especially true on vocals.

There is no

right way to set the Attack and Release controls. Generally, you want a slow enough attack to avoid

pumping or breathing sounds caused when background sounds are audibly modulated by the dominant signal energy,
yet the release must be fast enough to avoid suppression of the desired signal after a sudden transient or a loud
note has decayed. Depending on the desired effect, you might want a very slow attack so that percussive or
transient sounds are not restricted, but average volume levels are held within the desired range.

A very fast attack setting (control maximum counterclockwise) will cause the 160SL to act like a peak limiter even
though RMS detection circuitry is used. Slower attack settings cause the 160SL to act like an RMS or averaging
detecting compressor/limiter.

160SL

lue

series

160SL

controls

160SL

notes

160SL

Operations

160SL

Operations

Inspection

Operating

Connection

Installation

Technical

Introduction

to your system

considerations

contents

concept

diagram

applications

support and factory service

160SL

Specifications

160SL

Manual

Design

Block

Controls

Advanced

Warranty

lue

series