No it’s an @HAGIWO project with Arduino
all infos are here 
he made 3 or 4 differents VCO with Arduino and the same circuit, only the code change (FM VCO, Additive VCO, Chord VCO…)
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Looking into this more, is there a finalized version of this schematic? One with all of the stuff with the op amps and voltage dividers sorted out? A “master”? I’d like to throw this on a board…
Cool! But this is not easy to be tuned (change frequency with a pot) right?
Probably I need a state variable filter for this… but then I would need a dual gang pot…
I am looking at the mutant hi hat as a kind of blueprint and they have only single gang pots on their BOM. There is a single LM13700, but this is used for the envelope, I guess:
Lo-fidelity original VCAs replaced by OTA-based modern VCAs
I am wondering what they are doing there…
@jaradical thanks for the link, the website is VERY nice! good explanations and a lot of stuff!
I am reading through the filter article now, to see if I can find what I need 
ElectroSmash - Vox V847 Analysis The electro smash website is also very good about analyzing circuits. From my understanding of how filters work, you’re not going to get high resonance, and certainly not a controllable resonance, without a feedback stage in the circuit. At least that’s how it is in my mind.
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I used this schem just used a TL071 with +12/-12 power with his 2 caps of 100nf
Wow, took me a few days to catch up with this topic.
Awesome work everyone 
Very nice to see all different building styles
Here’s what i’ve been working on yesterday, the safety valve vca. I build tube amplifiers so i do a lot of point to point wiring. I have like 60 of the little op amp pcb’s for 2 euros. They are peak indicators from a velleman diy audio mixers. Swapping out some components make them very handy opamp pcb’s.
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I’m curious what circuit you used for the baby8 particularly if it’s cd4017 based?
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Yes it’s with CD4017, base on Baby 10 old schematic + some add
here’s the thread about it
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Decided to try unsoldering a couple potentiometers using a hot air station. It was easier than I expected.
Next I’ll attempt dual gangs.
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I made up a simple passive attenuator module today. It also converts 3.5mm into 6mm. I havent made it look pretty yet…But it works.
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Just finished up the noise/clock/sample and hold! Have been troubleshooting it the last couple days, everything worked except the sample and hold circuit. Spend way too much time on it before I realized the issue… read online that I could substitute the obsolete BF245 with a J113… Well, turns out you can, but the pinout is reversed. Desoldered it, popped a new one in the other way and it works!
One issue is sticking around though, even with the signal attenuator pot I am getting attenuation. Not a problem for random stuff, but no good for grabbing notes out of a sequence. Going to play with it as a random source for a little bit then get back into problem solving after the weekend. Panel should be done early next week, and I also need to find a very small head screw for one side of the standoff, or find where the hell my nylon screws went so I can chop it down a bit and fit beside the pot there.
Now moving onto to finishing up the new VCOs.
Edit: bonus, a pic of my work area. Who’s got suggestions for component organization? My “toss everything in a bag and pull them all out one by one to search” method is getting to be not so good as my stock grows
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Finished up everything I could on the two VCOs, now back to waiting. Need to buy pots, jacks, 3340s and a couple transistors.
edit: Ahh found my transistors. Knew I had them somewhere. Still, definitely need the rest of the stuff
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“I’ve got the power” 
1rst test with my power supply just arrived
searched the phase to make it like my other power cases
test with multimeter and all is good
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Life is a rollercoaster ride. There’s the high point of finishing a Kosmo module, then the low point of waiting for the next one to drop.
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hm not sure if I want to post this here or in another spot, but I think it works as its related to my latest builds.
Got a panel for the sample and hold last night, so now I’ve got it racked and am ready to start figuring out how the hell to use it! I think I mentioned but I’m having problems with it attenuating the signal input even when the pot is wide open. Spent some time trying to track that down this weekend but mainly was focused on playing with it. I actually kind of like the way it sounds when being given an input for pitch, it has a very specific wounded duck sound that is not something you can use for everything, or what I wanted to use it for, but is kinda fun.
But its definitely more usable as a random source. So heres a quick patch that I really liked this morning as I’m learning to use the module.
Main riff is all Bassline being fed melody from the Turing Machine (which is being clocked from the sample and hold module). I was more or less trying to dial in a super fuzzed out guitar-ish sound - something synthy that reminds me of a Robin Finck NIN tone. Then the randomy resonancey stuff is square out of the bassline into clockdivider to go a couple octaves down, into the Polivoks, quiet so you cant really hear it but its a bit of girth, then resonance CV being modulated by a reverse ramp LFO into the sample and hold. Then the wavy windy sound is pink noise from the S&H into Ripples, modulated by a few envelopes but also manually manipulating cutoff at the same time, being triggered from a gate by pressing my keyboard.
I’ve never played with noise before so the wavy sound was an attempt to see if I can make noise sound useful to me.
So, at the end of the day - even if I cant get the S&H working like I want it to for melodies, if thats just the way it is or something, being that it also has four noise outputs, is a clock source, and can be used as a S&H for other uses that don’t require solid pitch, I think I’ll still end up getting lots of use out of this module.
Full patch picture (new S&H is top right)
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OH…that is good to know about the BF245. I have a circuit that I am replacing one with a J112. I did notice that the symbol in kicad was the other way around on the J112. I’ll keep your story in mind when I go to build and test this.
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