Kurzweil K2661 - Band Suppression

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KDFX Reference
KDFX Algorithm Specifications
Figure 129 Band suppression
To determine how much to expand the signal, the expander must measure the signal level. Since musical
signal levels will change over time, the expansion amounts must change as well. You can control how fast
the expansion changes in response to changing signal levels with the attack and release time controls.
The attack time is defined as the time for the expansion to turn off when the signal rises above the
threshold. This time should be very short for most applications. The expander release time is the time for
the signal to expand down after the signal drops below threshold. The expander release time may be set
quite long. An expander may be used to suppress background noise in the absence of signal, thus typical
expander settings use a fast attack (to avoid losing real signal), slow release (to gradually fade out the
noise), and the threshold set just above the noise level. You can set just how far to drop the noise with the
expansion ratio.
Figure 130 Expansion transfer characteristic
The signal being expanded may be delayed relative to the side chain processing. The delay allows the
signal to stop being expanded just before an attack transient arrives. Since the side chain processing
“knows” what the input signal is going to be before the main signal path does, it can tame down an attack
transient by releasing the expander before the attack actually happens.
L Input
R Input
L Output
R Output
Filter Gain
Select L,
R, or
Max L, R
Expander
Computation
Delay
Delay
Analysis Filters
(Single or Multi Band)
L, R,
Or L & R
Out Gain
Notch Filters
(Single or Multi Band)
0 dB
Exp Channel
0 dB
Out
Amp
In Amp
Threshold