Specifications

DigiRack Plug-Ins Guide64
The Compressor reduces the dynamic range of
signals that exceed a selected threshold by a spe-
cific amount. The increase of input signal
needed to cause a 1 dB increase in the output
signal of the compressor is called the compres-
sion ratio. For example, with a ratio of 4:1, an
8 dB increase of input produces a 2 dB increase
in the output.
Audio material often varies in loudness, and can
be above the threshold at one moment and be-
low it the next. The Attack slider sets the com-
pressor’s response time, or attack. The Release
slider sets the amount of time that it takes for
the compressor’s gain to return to its original
level.
Using Compression Effectively
To use compression most effectively, the attack
time should be set so that signals exceed the
threshold level long enough to cause an increase
in the average level. This helps ensure that gain
reduction doesn’t decrease the overall volume.
Release times should be set long enough that if
signal levels repeatedly rise above the threshold,
they cause gain reduction only once. If the re-
lease time is too long, a loud section of the audio
material could cause gain reduction that persists
through a soft section. Of course, compression
has many creative uses that break these rules.
The Compressor has built-in metering that
shows the amount of gain reduction taking
place. The gain reduction meter usually remains
at 0 level when the input signal is below the
threshold and falls to the left to show the
amount of gain reduction in decibels when the
input signal exceeds the threshold.
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
Phase Invert