| br>I made a board up to add multiple modes (a la Obie Xpander) to my Roland GR-300. The GR-300 uses the IR3109 chip, same as the SH-101 and MC-202. The board uses DG408 for the switching and has buffers for each filter stage so can be connected directly to the caps or to internal buffers of the filter chip. It's possible that this could work with other cascaded OTA filters like those made with LM13700, but each stage needs to be inverting to work with this board.
The modes are organized as 2 banks of 8. Bank select is manual by switch, 1-8 in each bank is selected by a 3-bit DAC so a simple pot can be used to change mode.
It has some surface mount parts but they're 1206 and SOIC so not too tough.
DM me if interested. If there are enough interests I could have a batch made. Could probably get them for under $5 for bare boards.
I did a video describing it's function in the GR-300:
[video]https://www.youtube.com/watch?v=xF9t6gT6g1w[/video] br> br>