Non 3340 oscillators

Do you have any DIY VCOs that are not 3340 based? What are they, and what do you think of them?

I’ve been looking at the MFOS and YuSynth ones. And the Haraldswerk trapezoidal quadrature VCO looks… interesting… maybe someday.

Other good ones? Or not so good?


My dad made a 555-based VCO that seems pretty fun, I think he had some issues with temperature and octave tracking though, though that probably wasn’t the chip’s fault.

Here’s a slightly beefier variant:


I haven’t built any, so this is just a listing of maybes…

From Ian Fritz :

Some “almost circuit bendings” from Thomas Henry:


Long ago I built a multi 555 (16) vco as an exponential FM operator. Don’t! It’s a very twitchy ringing fart box :slight_smile:


Something I’m slowly working on is Kosmo version of the serge DUSG (forerunner of ‘maths’). It’s a big module, would probably be 20cm in kosmo. The upside is it can do a lot of stuff including behaving like a VCO:

I also really want to rig up a SID chip module but I’m not ready to try to figure that out yet haha


I know @devicex has an mfos vco or three


Looks interesting, but not very precise on the 1V/oct. I mean, it’s not intended primarily as an oscillator, so the fact it can be used as even a rough 1V/oct osc is good, but that’s not really what it’s for, is it?


The Erica Synths Oscillator sounds really great, tracks great, and it could do with some generous Kosmo panel space.

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Though it uses a Russian transistor array (KR198NT1A) which is not exactly common. I see someone on AliExpress claims to have them. Or apparently you can substitute other transistor arrays but they’re not pin compatible so you have to whip up an adapter… (or redesign the PCB of course)

But it’s relatively cheap from Erica directly and their shipping is fast. Worth it, I think.

The kit’s out of stock at Erica. Or you mean the chip? I don’t see it.

Well that’ll put a damper on it

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Actually, it looks like it’s just on their rare components page

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Wow, brings new meaning to “hard to find”. Took me a while to figure out how to navigate to that page.

Between that and the open source Gerbers, should be very do-able. Lots of vertical resistors crowded on that board! 94 of them. I suppose you could do SMD instead if that’s your preference.

Indeed you can:

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Wait, you did it with boards CTorp ordered? Where’d you get the chip… Erica?

Looks like those main board headers barely reach the control board sockets! Any issues there?

Thank you for asking this - I genuinely want something other than a 3340… lol
I’ve been so happy with the weird ciat-lonbarde oscillators because they sound nothing like 3340’s lololol.

Maybe I should take a crack at converting some of that shit - buffering the hell out of EVERYTHING and making some ciat inspired KOSMO modules… lol


Yeah I ordered from Erica

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No issues with the headers, but they do look a little far apart.

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I would not mind this. (and maybe dogscratch, too)

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