VCF is a tone-shaping module which processes the `raw' output of the
VCOs to provide a wide variety of different tone colours and amplitude
VCF has four filter functions. A low-pass filter with a rolloff of -12dB
per octave above the turnover point, a highpass filter with a rolloff
of -12dB per octave below the the turnover point, a bandpass filter
with variable Q and minimum slope of -6dB per octave on either side
of the centre frequency, and a notch filter. The turnover point - or
centre frequency in the case of the band filters - is the same for all
four filter functions, and can be varied by the application of a control
VCF 1 is a state-variable design with an exponential voltage-to-frequency
response set at 1Volt/Octave.
VCF 1 incorporates a 4-channel audio mixer for incoming audio signals and a 4-channel CV mixer for the control signals.