Compressor Circuit
Threshold Control
The Threshold control sets the point at which
the compressor circuit will act on the input
signal. Turning this control counterclockwise
lowers the Threshold (adding more
compression to a signal). Turning this control
clockwise raises the threshold. Setting the
Threshold control is dependent on the Preamp
Output control (or the output of the device
plugged into the compressor return insert
point). The easiest way to set the threshold
control is to start with it fully clockwise. After
setting the Preamp Output control, slowly turn
the Threshold control counter-clockwise,
(lowering the threshold) until you see the
yellow (0dB) Threshold LED light in the Gain Reduction display. Now adjust the
control (either lower or higher) until you have the amount of compression you desire.
Use the Gain Reduction LEDs as a visual guide to the amount of applied compression.
Ratio Control
The Ratio control sets the compression ratio (or slope) for the compressor circuit. At its
minimum position, the compression ratio is an active 2:1. This means that for every
2dB over the threshold the input signal rises, the compressor’s output will change by
1dB. This is a very mild and musical compression ratio, which is ideal for smoothing
all types of signals. At its maximum position, the compression ratio is greater than
10:1. This is typically called “hard limiting” as it allows only a 1dB change in signal
level for any signal reaching over 10dB of the set threshold. This setting is ideal for
applications where exceeding a certain level is not desirable (i.e., mixing, popping bass,
digital recording, etc.)
Attack Switch
The position of the Attack switch selects the attack characteristics of both the varible-
mu and optical compressor circuits. The “in” (Fast) position allows the compressor to
react quickly to fast-rising attacks. Note that the variable-mu circuit is inherently faster
responding, and can be aggressive on signals with quick transients, such as snare drums.
The “out” (slow) position can be helpful in reducing compression artifacts for signals
with very little high frequency content (piano, flute, etc.).
Release Switch
The position of the Release switch selects the release characteristics of the compressor
circuit. The “in” (Fast) position allows the compressor to recover quickly once the
signal falls below the threshold. The “out” (Auto) position allows the compressor to
adjust itself depending on the characteristics of the input signal. Use the Fast setting
when the signal has repetitive, consistent characteristics (kick drum, snare, vocals, etc.).
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