Voltage Controlled Filter (VCF)
The VCF is an analog four-pole resonant lowpass filter. The cutoff
frequency control spans the entire audio spectrum. The res (resonance)
amount control can range from none to self oscillation. The character
of the filter reacts to the amount of drive. When the filter is in self
oscillation the drive can be used to balance the input signal with the
oscillation of the filter. It can be fun to try playing a duet with
the drone of the filter while it is self oscillating.
note on resonance: You may hear a slight drop in volume as the
resonance is increased. This is expected because the filter is
emphasizing the cutoff frequency, causing all other frequencies to
drop in volume. The output level can be used to makeup for the volume
drop.
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