Combined microcontroller VCO + vactrol VCF module (v1.5 - 6HP)
Hear it here: https://soundcloud.com/yorkmodular/badtrip-vcovcf-sample
VCO + Vactrol LPF = Bad Trip ... ... which is pretty much what it is.
Combines a switchable square/saw VCO with a vactrol-based resonant low-pass filter for generalised acidic wonkiness. As well as the usual front-panel controls, there are a bunch of trimpots on the back-side of the board to allow you to alter the response of the filter vactrols - depending on the settings you choose, hilarity may well ensue.
⚠️ IMPORTANT NOTE ⚠️ - since the VCO part of the module is microcontroller-based there are limits on the range of CVs that can be handled. Basically, a negative CV will be 'rejected' (ie. treated as 0V) and anything over 5V will be clipped to 5V, thus limiting the range to 5 octaves - there are ways around this, but they're pretty hacky.
This is v1.5 of the module, which now has a fine-tune pot on the rear of the board - people asked for it, so here it is.
If you're having problems with range (or lack of it) then make sure that the CV pot is turned fully clockwise _and_ that your CVs fall within the appropriate range - some MIDI-to-CV modules work on a -5 to +5V range, meaning you're only likely to get a response in the upper octaves - a range of 0-5V is what you need.
The firmware for the VCO can be found at https://bitbucket.org/yorkmodular/badtrip-vco/src/master/ - it is available under a permissive license so feel free to hack on it.
Completed modules will have a panel fabricated from 1.6mm FR4 (aka PCB material) and will be supplied with M3x6 machine screws for mounting.