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 panora-
ma 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 160S, this is accomplished by means of the
Stereo Couple
switch. When
activated, the 160S permits the RMS detectors of both channels to “talk” to one another. The SLAVE chan-
nel (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 volt-
age 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 160S, only the MASTER channel controls need to be adjust-
ed. The
Threshold
LEDs,
Auto
LED, and
PeakStop (Plus)
LED will not light on the “slave” channel
when the 160S 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.
The
Auto
switch sets the 160S for automatic or manual operation. When the
Auto
switch is IN (A
UTO
mode), the LED indicator lights and the 160S automatically adjusts its attack rate and release time to suit
the program envelope. (This A
UTO
mode sets the 160S 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.
The 160S offers a choice of automatic or user-adjustable attack and release characteristics. In A
UTO
mode,
the 160S utilizes the patented dbx RMS level detector with its program-dependent attack/release charac-
teristics to obtain natural-sounding compression or limiting. For special effects and certain signal situa-
tions, however, it is often desirable to set fixed attack and release characteristics. M
ANUAL
mode affords
this capability. The A
UTO
mode is recommended for vocals as well as instruments. Because the A
UTO
mode has a variable attack rate, the 160S may compress or limit some program material smoother than
in the
MANUAL
mode which has a fixed attack characteristic. 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
Setting The Attack And Release Controls
Using The Auto Switch
Using The Stereo Couple Switch
20
160S
notes
Operating
