Hi Noystoise,
I found that running all 4 CV lines together through a pot interfered with each individual CV envelope for the VCA unit on the keyboard in use - the Casio SK sampler. It was ok if you say, played a chord and each note was struck together, but if they were played like an arpeggiator, the CV lines combined never allowed any one line to decay to zero. So they all need to be independently adjusted, because each CV line enters a separate filter module to produce the 4-note polyphony of the filter.
Hi Gordon:
Don't forget that digital pots are noisy as hell when adjusted.....There are loads of VCF designs out there that you can rip off.
You mean like step noise as you adjust it?
Unfortunately all of the other VCF designs out there weren't independently polyphonic, weren't 9V battery powered and weren't small enough to fit into the casing of an SK-8. Hence my joy in finding this one. As well, any VCF unit cluster that would be driven off the CV lines of the SK would have the same issue.
Cheers, graham