Voltage-controlled low-pass resonant vactrol filter PCB (4HP)
A VCF finally hits the line-up
Filters don't need to be massively complex to sound good, and it's amazing the sort of noises you can get out of an op-amp and a bunch of passive components.
There's an input and output, of course, plus a CV input with an attached attenuator which feeds into a pair of vactrols, which is where the magic happens. With a bit of care, you can get everything from nice filter sweeps all the way up to squonky acid-bass and beyond.
This is a 100% through-hole build - you don't even have to use 'proper' vactrols; as long as whatever you use fits into the LDR footprint then you're good.
The BOM and design files can be found here: https://bitbucket.org/yorkmodular/vcsk/src/master/
You can hear a quick and dirty sample of the finished article right here: https://soundcloud.com/yorkmodular/vcsk-sallenkey-low-pass-vcf-sample