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Dynamics Processing 101 - Continued
Soft-Knee / Hard-Knee
In order to prevent harsh, unnatural envelopes on compressed signals, sophisticated dynamics processors like
the C Com 16 feature an SKD (Smart Knee Detector) or automatic knee circuit. The Smart Knee Detector auto-
matically switches from Soft-Knee when the signal is less than 10 dB over threshold, to Hard-Knee when the sig-
nal is 10db above threshold. In Soft-Knee mode, there is a gradual affect on gain change, which begins as the
signal approaches the threshold level. In Hard-Knee mode, gain reduction is linear based on the threshold and
Ratio controls. Any signal that falls below the threshold level will be unprocessed.
Noise Gates
Noise gates are used to remove unwanted noise and/or bleed from recorded tracks in the studio or from open
microphones in live sound systems. Noise gates can also be used as a sound effect, most commonly to chop the
end of a reverb, let’s say on a snare drum, so that the entire snare sound ends just before the beat. The basic
principle of a noise gate is to work as an automatic mute switch. Mute off (Gate Open) when the desired signal is
present and mute on (Gate Closed) when the desired signal is not present. In order to get the gate to work pre-
dictably, it is necessary to set a threshold, or trigger level that will determine when the gate will open. If the signal
is below the trigger, the gate will remain closed. When the signal is above the trigger, the gate will trigger open
allowing the desired signal to pass and be heard. Noise gates often have other adjustable controls like attack,
hold, range and release. Many noise gates like those in the SAMSON S com, S com plus, S com 4 and S gate 4
use sophisticated circuits to control some of these parameters automatically.
Downward Expander
The purpose of a well-designed Downward Expander is to increase the perceived dynamic range of a system.
This is accomplished by decreasing the gain during the softer sections, thereby lowering the relative noise floor.
When the signal level is below the desired trigger level, the expander lowers the overall gain by the selected
amount.
Side Chain / External Key
The C Com 16 features a side-chain or external Key function. The external Key function is used to externally
process the compressor’s detector circuit. There are many useful applications for processing the detector circuit
including Equalizing for frequency dependent compression, De-Essing - the use of EQ to remove sibilance, and
externally keying off a vocal track for Ducking effects, to name a few. The Key insert jack sends the compressors
trigger signal for external processing, and then receives the processed signal, which will now control the com-
pressor’s detector.
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