Adding voltage controlled resonance to Ken's Steiner filter.

[reve]

Heeey gang.

So my favorite filter in my rig is the CGS35 Steiner tribute. I'm just now starting building the infrastructure for (matched) polyphony, and man, I would love to have eight of these suckers under full voltage control.

The trick is, to do this with eight units I really need to bring the resonance under voltage control as well. I saw the Charlie Lamm mods page that included partial VC res, but I would need the full range to avoid having eight separate resonance pots....

I'm not real bright. I can add vc resonance by cutting and pasting a linear VCA into the feedback path, but since I don't really know what I'm doing, that's about the limit of my skillz. Looking at Ken's schematic, it appears that this project would entail more than that. Anyone do it successfully, or have any other clever hints? Other than buying Cynthia tribute units at $400 a voice, of course.

Thanks!

[Mongo1]

It sounds like an interesting experiment to try -
One other route you could take is a Vactrol - The problem I see with that is that the resistance range you're trying to hit is pretty low. I was just looking at vactrol data sheets and it looks like the resistance on a VTL5C2 (for example) goes from 200 to 1M ohm. That's probably not going to be very helpful for you.

I'm surprised more people don't make a filter with VC resonance. I think the Ray Wilson SVF is the only one I've seen.

Gary

[inlifeindeath]

check out scott bernardi's VC delay schem. He uses an OTA VCA to make the feedback parameter voltage controlled. it's pretty simple too. the schem uses a 3080 but i made one using half a 13600

[inlifeindeath]

also i don't know how effective it would be, but you could try the FET or NPN method of a "variable resistor" tie the base/gate to your incoming voltage and the other two pins to each side of the rez pot

[reve]