Another rung

I built another module the other day, got around to starting to test it last night. Right away there was a problem, no +12 V on the board after the protection diode. Today I touched up the diode connections and all was well.

It’s a VCF.

(And yes, I am out of large knobs for 6.35 mm pot shafts, why do you ask?)

Initially Kosmodrome was planned to have one VCF, but I changed my mind after building the Sallen-Key filter. For one thing, it was behaving strangely and I wasn’t sure I’d ever get it working right. (I did.) For another, it was clear the Sallen-Key’s sound characteristics, especially at high resonance, were ones I would not always want — I decided it’d be nice to have a choice of filters.

This one is a transistor ladder filter. (Hence the transistor matching I was doing.) My version is essentially unmodified, other than a restyled front panel and slightly different jack and pot footprints, from one by LMNC Discourse group denizen Sebastian Beyer, a Kosmo format version of a design from Kassutronics that was partly inspired by a module from YuSynth, which was a clone of the Minimoog filter. There, that’s the genealogy.

The graphic elements on the front panel are by Sebastian from his panel design. I definitely wanted a panel that more or less matched the style of my other ones, but those curves were keepers.

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