All about it
The ultimate multimode VCF-Dennis Colin's finest hour!
This VCF, originally designed by the person who invented the voltage-controlled multimode filter for the ARP 2500, is a great sounding multimode VCF with unique features.
Firstly, it features an equaliser-style output switchable between Notch reject and Peaking modes, to add great-sounding phaser-like musical effects under voltage control.
Secondly, it has an unusual resonance circuit. Whereas nearly all multimode filters have what is essentially a diode fuzz circuit to prevent high resonance settings from clipping, this one has an envelope detector that feeds into the resonance control circuit to essentially limit resonance feedback (and mixer overload) to levels below clipping. This gives it a unique clean, but rich, sound.
For this module, it was impossible to fit all the circuitry onto a 10HP board, so it marks our first foray into surface mounting! We have kept the schematic identical except for component value adjustments to handle the change to 12V supplies. We still use mean Mica mofos as filter caps (now surface mount, but still quality Cornell Dubilier parts). A pair of LM13700s substitute for the original's three CA3080 OTA chips, and the LM301A has had an upgrade to the industrial-grade LM201A.
+5V: Not required
Eurorack standard, 10HP width
40mm depth below mounting rails with connected power cable
Queued for expected production in early 2018
Watch this space