Up to dual SSI2140-based multimode filter (vcf/vca) expansion board, under Ksolotian control, inside Gills??
Working title: "Gamuts"
I always felt that an Axoloti/Ksoloti controlling an analog filter-vca board, similar to the Shruthi-1 concept, would be really fun.
Here's what the design has so far:
- Power via +/-12V from the CV expander
- SSI2140 in pole mixing configuration: LP4, LP2, BP4, BP2, HP4, HP2, NOTCH2, NOTCH1, digitally selectable. 0.1% resistors, 1% caps. You could derive your own pole mixing config from test points.
- Full bypass using analog switch IC. Pretend your filter doesn't exist at all!
- Control using 4 digital pins on Ksoloti (or any fast enough MCU) addressing shift registers on the filter board, on-board "retro" discrete 10-bit R2R DAC gives 4 CV signals: cutoff, resonance, vca, "aux vca"
- Two linear VCAs based on SSI2164, one for amplitude after the filter, one routable (via solder pads) but normalized to control "filter drive". Thinking of e.g. routing the output of filter one to the input of filter two.
- One single board has single filter and 2 VCAs. Two of these boards are stackable so each of the two outputs from Ksoloti can be processed individually. Filter config and control is completely independent (cutoff, reso, vca, drive, mode, bypass)
All in all I am being a bit naive so far. My first analog filter design. So I can't make any promises so far if this design will work out and perform well (there be unknown challenges ahead such as CV generation, digital noise from Ksoloti, efficiency of digital control etc.).
Really not happy with the physical board dimensions and weird placement. Screwing the boards above and under the Core using M3 nuts as placeholders...
I might make it the same size as a Ksoloti Core so it could be stacked under it and used just with the Core alone (without Gills or any other device but you do need to supply your own +/-12V).
Any thoughts, anyone?? We have some great filter experts here on Modwiggler, don't hesitate to critique!
Statistics: Posted by Sebastian — Sat Nov 02, 2024 12:48 am