FULL KIT: Voltage-controlled low-pass resonant vactrol filter (4HP)
1 in stock.
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.
The board is laid out based on the assumption that VTL5C3 vactrols (or similar) will be used. Whilst there's no technical reason why DIY vactrols can't be used, it may be necessary to mess around with component values - should you go down this route, I recommend socketing the vactrol limiting resistors (R4, R5) and the filter capacitor (C3) and fiddling with values until you find a combination that you like.
I have provided 'sensible' values for the limiting resistors (470k) and filter capacitor (330pF) - the values aren't set in stone; it's quite possible to leave R4 and R5 out altogether, although C3 could be considered rather essential. Lower values will give a 'sharper' sounding resonant peak. Alternatively, use a larger value to mellow things out.
You can hear a quick and dirty sample of the finished article right here: https://soundcloud.com/yorkmodular/vcsk-sallenkey-low-pass-vcf-sample