Finally posting the end result of my VCF build!
This is a Moritz Klein inspired dual VCF. Each filter has essentially two cutoff knobs: the smaller one on the side and the center one, which is a dual-gang potentiometer. This way I can bias each side’s cutoff frequency and control both at the same time with the big knob at the center.
I also added voltage control to Drive and Resonance via internal diff-amp VCAs.
There is a switch to link both filters to Filter A cutoff CV, and another switch that does the same to the Drive and Resonance CV. There’s also a cutoff CV input normalled to the V/Oct CV trace on the power bus.
All Filter B input jacks are normalled to their Filter A equivalents, and all CV inputs have attenuverters (except for the V/Oct one, which can be attenuated to x0, x1/2 or x1/1 V/Oct wtih another switch on the front panel).
I’m pretty happy with the sound, visuals and ergonomics.
The KiCad project can be found here: GitHub - DeMarco/DMH-Dual-VCF-Diode-Ladder-Mk2: Version 2 of my dual Diode Ladder VCF module
Here’s a demo and some more pictures:
Next challenge: Dual Voltage Controlled Envelope Generator, so that I don’t need to use the one from my Moog Grandmother anymore 
