In the meantime I have something else to play with:
This is a kit for a Ken Stone / CGS 57 Bi-N-Tic switched-capacitor filter. The kit is from the wonderful folks at Bridechamber and includes all parts. A close-up of the circuit board:
And the panel:
The kit incorporates nearly all of the mods and hot rodding that Ken calls out as options in his notes on this module. (The control that Ken labels "DAMPER" in his notes is called "RESONANCE" on this panel.) Switched-capacitor filters are very unusual in the synth world. I'm not quite sure why that is; they have a reputation for being noisy, but I think that rep might be the result of some early designs of the switched-capacitor concept that used mechanical commutators and crummy caps. I'm curious to build this and see how it sounds. I am going to add one mod: a switch to take the most significant bit of the digital count that goes into the multiplexor which selects one of the eight caps, and move it from the 4-bit to the 8-bit of the counter. That will have the effect of dividing the eight caps into two banks; instead of scanning all eight caps in order, it will scan over a bank of four caps twice, then switch to the other bank. I'm not quite sure what this will actually do; I think it will give the filter two resonance peaks. Anyway, it will be interesting to find out.