Specifications
DigiRack Plug-Ins Guide42
Compressor Controls
Phase Invert Inverts the phase (polarity) of the
input signal to change frequency response char-
acteristics between multi-miked sources or to
correct for miswired microphone cables.
Gain Provides overall output gain adjustment
for compensating for heavily compressed sig-
nals.
Input Meter Indicates the level of the unproc-
essed input signal to the Compressor.
Output Meter Indicates the output level of the
Compressor, including any gain compensation
added with the Gain control.
Reduction Indicates the amount of gain reduc-
tion in dB.
Threshold Sets the threshold level. Signals that
exceed this level will be compressed. Signals
that are below it will be unaffected. A level set-
ting of 0 dB is equivalent to no compression.
Unlike scales on analog compressors, metering
scales on a digital device reflect a 0 dB value that
indicates full scale (fs)—the full-code signal
level. There is no headroom above 0 dB.
Ratio Sets the compression ratio. The range is
based on decibels above the threshold. For ex-
ample, if this is set to 2:1, it will compress
changes in signals above the threshold by one
half.
Attack Sets the Compressor’s attack time. The
smaller the value, the faster the attack. The
faster the attack, the more rapidly the Compres-
sor applies attenuation to the signal. If you use
fast attack times and heavy limiting, you should
generally use a proportionally longer release
time, particularly with material that contains
many peaks in close proximity.
Release Controls how long it takes for the Com-
pressor to be fully deactivated after the input
signal drops below the threshold level. In gen-
eral, if you use heavy compression, you should
use proportionally longer release times in order
to avoid pumping that may occur when the
Compressor is forced to jump back and forth be-
tween compressed and uncompressed signal
levels. Lengthening the release time will help
smooth these changes in level by introducing a
lag in the ramp-up/down time of attenuation.
Use shorter release times on material with fewer
peaks that do not occur in close proximity to
each other.
Knee Sets the rate at which the compressor
reaches full compression once the threshold has
been exceeded. This control ranges from 0
(hardest response) to 200 (softest response).
Graph Displays the response curve set by the
Compressor’s Threshold, Ratio, and Knee set-
tings. As you adjust these controls, refer to the
graph to see how the shape of this curve change.
LFE Enable Enables plug-in processing of the
LFE (low frequency effects) channel on a multi-
channel track formatted for 5.1, 6.1, or 7.1 sur-
round formats on some plug-ins. To disable LFE
processing, deselect this button. For more infor-
mation on the LFE channel, refer to the Pro Tools
Reference Guide.
External Key Enables and disables side-chain
processing. Side-chain processing uses the vary-
ing amplitude of a separate reference track to
trigger compression. See “Using a Key Input for
Side-Chain Processing” on page 16.
Phase Invert