DIY oscillator Modules

I’ve just built 8 Cadet modules from Thonk and I’m absolutely loving life! I’ve been pining after a video synth for years so it feels amazing to finally start a system.

I am however lacking oscillators as they’d sold out. I’m going to buy and build some Castle oscillator modules but these are only a square wave output and I’d like the option of multiple waveforms, at least a triangle wave. I’m wanting to stay DIY for the time being, with the apparently sudden rush of other creators putting out new DIY modules is anyone selling any oscillators?

During my undergrad I experimented with the 4046 PLL (which is what the Castle Oscillator is based around) as a video oscillator for a CHA/V project and did get good triangle and sawtooth waveforms from it so I’m tempted to resurrect that project and get some PCBs made but I’m time poor at the moment so if anyone is ahead of me and producing PCBs please let me know!

I’m aware that LZX have a new range of DIY modules planned for post-Chromagnon and I assume there will be an oscillator among them so if anyone had any idea what these will look like please share!


I don’t think there are any DIY video oscillator kits available at the moment aside from the Castle Clock VCO, I guess this must be a harder module for smaller manufacturers to get right or something. Perhaps you could transfer the Cadet Oscillator schematic to perf board? Might not be a perfect solution but it’s definitely DIY friendly and immediately available.


Check out the sandin Ip vco. This would be a decent starting point for a diy oscillator. There’s a lot of things that would need to be changed, such as the output would need to be scaled to 0-1v. I believe originally its +/-1v.


Would love to see more oscillator designs out there but you could also look at Gieskes’ 3trins. While it’s a capable video instrument by itself, you can also get 3 flexible VCOs out of it if you use the expander board to make its RGB outputs LZX compliant. You can rack it if you flip it sideways.

The expander board was out of stock for awhile but it looks like someone traced out the original and you can order them in 3x batches via OshPark. Find two other folks on the forum who want a board and you’re set!

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Wow, that uses an 8038!? Those things are unruly beasts!

I don’t find the 8038 so bad. What have you found?

I (Visible Signals - I should probably see if I can get my username changed here) am working on a VCO design based on one of Rob Scafer’s unpublished circuits that he very kindly shared with me but it’s still early days at the moment.


Tuning it to perform within an audible range was disastrous, at least for myself. I only attempted circuit examples in the datasheet but the outputs would swing from sub- to post-audible frequencies with the single turn of a relatively small pot. I wasn’t looking for video rate frequencies at the time, so maybe it is a lot more useful here. (and obviously it is, based on the legacy left by Sandin.

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I tried to get an 8038 into the high hundreds kHz for nice tight vertical lines and found the waveform shapes were horrible and getting frequency stability was challenging. I only breadboarded it though; a prototype on a PCB might do better.

If you’re looking for audio-rate 8038 oscillators then definitely check out Thomas Henry’s circuit - I have a bunch of them and they’re pretty darn good.

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