Digisound 80 - VCF modification
This Digisound 80-6 VCF module has been built to work in Low Pass mode. According to the documentation it should self oscillate with the Resonance pot turned all the way up. Unfortunately mine didn't, so I soldered a 47K trim-pot in parallel with resistor R6 - this allows the self-oscillation point and max amount of self-oscillation to be set.
The photo's not from a very clear angle as the module was already racked and wired up when I took it..