Two new modules in one day! Well, one of them hardly counts. Still.
Back to Kosmo format. Here’s the Sallen-Key VCF from Barton Musical Circuits.
The board was designed with Eurorack in mind. It’s small, and rather densely packed. Still, no problems assembling it and it went together quickly. As designed the pots are all board mounted, on 1″ centers. Too close together for my taste, especially for Kosmo. So I moved the CV level pot from the middle position to the bottom, panel mounted. That was the only change I made. The panel is one I designed and had fabbed on FR4.
This thing does some crazy stuff with the resonance turned up past about midway. Not sure if that’s the intended behavior but I don’t really want to change it. If I want a clean and boring resonance I can use another filter. Maybe I might change a resistor to make the onset a little later, though.
Added later: I did make that change. As built with the specified values, I was getting self oscillation with the resonance pot only about halfway up. I reduced the 3.3kΩ resistor to 1k and now it self oscillates at around 3/4 maximum.
The other module, a real quickie: Three passive attenuators.
These are the first two modules for Kosmodrome.