Z2040 LP-VCF

A 24 dB four-pole low-pass filter, a discrete design with a core like the SSM2040 of the Prophet-5 Rev 2 and its brother the SSM2044. Four modulation inputs take control voltages or audio: VC-GAIN, VC-RES to modulate and even clip the sine the resonance makes, FM for filter sweeps, and VC-FM to modulate the FM depth itself. With the resonance fully up the filter becomes a pure sine oscillator. An audio VCA, its level set by GAIN, can act on the input or the output of the filter.