168 Chapter 13—Dynamics Processors
THRESHOLD—This determines the level of input signal required to trigger the com- pressor. Signals at a level below the threshold pass through the compressor unaffected. Signals at and above the threshold level are compressed by the amount specified using the Ratio parameter. The trigger signal is sourced using the KEY IN parameter.
OUT GAIN—This sets the compressor’s output signal level, and can be used to compensate for the overall level change caused by the compression process.
KNEE—This determines how compression is applied at the threshold point. When set to hard, compression at the specified ratio is applied as soon as the input signal level exceeds the specified threshold. For knee settings from 1 to 5, however, compression is applied gradually as the signal exceeds the specified threshold, creating a more natural sound. This is called soft-knee compression.
ATTACK—This determines how soon the signal is compressed once the compressor has been triggered. With a fast attack time, the signal is compressed almost immedi- ately. With a slow attack time, however, the initial transient of a sound passes through unaffected. Attack times from 1 to 5 milliseconds are a good place to start.
RELEASE—This determines how soon the compressor returns to its normal gain once the trigger signal level drops below the threshold. If the release time is too short, the gain will recover too quickly causing level pumping (i.e., noticeable gain fluctuations). If it is set too long, the compressor may not have time to recover before the next high level signal appears, and it will be compressed incorrectly. Release times from 0.1 to 0.5 seconds are a good place to start.
RATIO—This determines the amount of compression, that is, the change in output signal level relative to change in input signal level. For a 2:1 ratio, for example, a 10 dB change in input level (above the threshold) results in a 5 dB change in output level. For a 5:1 ratio, a 10 dB change in input level (above the threshold) results in a 2 dB change in output level.
GATE
A gate, or noise gate is essentially an audio switch used to mute signals below a set threshold level. It can be used to cut background noise picked up by open micro- phones, noise and hiss from guitar valve amps and effects pedals, and leakage between drum microphones. It also has many creative uses too. For example, gating a drum sound with a short decay time tightens up the sound. Also, patching a gate into a droning bass synth channel and then triggering it from the kick drum channel allows the bass synth through only when the kick drum is struck, adding extra “oomph” on the beat.
+20
+10
0
–10
–20
–30
–40
–50
–60
–70
Threshold = –10dB
Range = –30dB
Range = –70dB
–70 –60 –50 –40 –30 –20 –10 0 +10 +20
Input Level (dB)
| Parameter | Range |
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| THRESHOLD | –54 dB to 0 dB (55 steps) |
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| RANGE | –70 dB to 0 dB (71 steps) |
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| HOLD | 0.02 ms–1.96 s (fs = 48 kHz) |
| 0.02 ms–2.13 s (fs = 44.1 kHz) |
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| ATTACK | 0–120 ms (1 ms steps) |
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| DECAY | 5 ms–42.3 s (fs = 48 kHz) |
| 6 ms–46 s (fs = 44.1 kHz) |
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