Symetrix 601 - Compressor Parameter Block; AGC Block

4-7
Rev 2.2, 10/31/94
THRESHOLD Switch Sets the THRESHold for start of expansion. Signals
below this level are reduced in level by an amount
dependent on the setting of the expansion gain
RATIO , and the difference between the threshold
setting and the actual signal level.
4.5.4 Compressor Parameter Block
The compressor reduces its gain for any signal level above the threshold setting. The
COMPRESSOR switch’s LED indicates that the compressor is active. When editing, the
compressor switch LED flashes, otherwise it reflects the state of the compressor (in or out).
Whenever editing the compressor or AGC parameters, the output LED display changes to read
gain-reduction. The compressor block and the AGC block are mutually exclusive; you can only
use one of them at a time.
There is no output gain control; the 601 computes the correct amount of makeup gain based on
the threshold and ratio settings (although the auto-makeup gain feature can be defeated and
the amount of makeup gain can be set manually). The shape of the knee of the gain-reduction
curve can be adjusted via MIDI or the realtime editor (see Appendix A).
ATTACK Switch Adjusts the ATTACK time (milliseconds) of the
compressor (time required for an above-
THRESHold
signal to cause gain reduction).
RELEASE Switch Adjusts the release time (time, in milliseconds),
required for the gain to return to the
below-threshold value.
RATIO Switch Controls the compression gain ratio (compression
ratio). The range is from 1:1 (out) to 10:1. A 10:1
ratio means that a 10 dB input change results in a
1 dB output change (provided that the level of the
entire change was above the threshold setting).
The compressor's makup gain may be set manually
by pressing the
RATIO switch until the display
reads
gAIn . Set the makeup gain using the Wheel.
THRESHOLD Switch Sets threshold for the start of compression. Signals
above this level are reduced in level by an amount
dependent on the setting of the compression ratio
and the difference between the threshold setting
and the actual signal level.
4.5.5 AGC Block
The AGC is a variation on a compressor that operates over a wide range of signal levels while
trying to keep its output level constant. The
AGC switch LED indicates that the AGC is active.
When editing, the AGC switch LED flashes, otherwise it reflects the state of the AGC (in or out).
Whenever editing the AGC parameters, the output LED display changes to read gain-reduction.
The AGC block and the compressor block are mutually exclusive; you can only use one of them
at a time.
There is no output gain control; the 601 computes the correct amount of makeup gain based on
the threshold and ratio settings (although the auto-makeup gain feature can be defeated and
the amount of makeup gain can be set manually). The shape of the knee of the gain-reduction
curve can be adjusted via MIDI or the realtime editor (see Appendix A).