If you really want to get into DIY analog video synthesis at a level beyond what you can do with a CHA/V, I’d go for the LZX Cadet series of modules. They’re not sold anymore (though there may be a few synth DIY places selling some of the last of the PCBs) but their schematics have always been open source. And after they were discontinued, the company also all the gerbers and diptrace files and art files for them, so people could just straight up make the exact same boards for personal use, if they didn’t know how to (or want to bother to) adapt the schematics into their own designs. The schematics and BOMs are here: GitHub - lzxindustries/lzxdocs: LZX Industries Product Documentation (in the “Cadet …” folders and the gerbers/diptrace/art is here: GitHub - lzxindustries/lzxcadet: LZX Cadet Series EuroRack Video Synthesizer DIY Modules
These modules are excellent simple building blocks of video synthesis. An oscillator is one module, a fader is another module, a video input is another module, and so on. With them you get to really understand the signals and how to process them to make neat effects. And there’s meager but enthusiastic and friendly community using them (lots of people often willing to help debug issues you might have on the LZX forums, for example, including Lars at LZX). I didn’t really understand video synthesis until I started with the Cadet modules, and now I love it and am working on several designs myself.
Plus there are some other people/companies who’ve made their own compatible modules to provide even more functionality and are similarly sharing the schematics and selling PCBs (and sometimes kits), such as Syntonie, Visible Signals, and Foxing Hour.
There are some downsides of this approach, when compared to CHA/V (and CHA/V was created in part to address some of these concerns). First, it’s a lot more expensive than CHA/V. The “H” in CHA/V stands for “hacky” because it doesn’t really do things “properly”. There’s no electronic protection involved, there’s no impedance consideration or buffering. There’s no blanking of the incoming signal during blanking periods. Most of this stuff isn’t a big concern for the CHA/V for various reason, but when LZX designed their Cadet modules, they tried to do things as correctly as possible within reason to both make it safer (for the larger eurorack ecosystem) and because it’s a lot more complex than CHA/V and you need to have things like buffered signals in a larger more complex system. So this means there are lot more parts involved and some of those parts (like the op amps) are kind of expensive when compared to things like resistors and capacitors, and even when compared to the op amps used for audio circuits (since video deals with higher frequencies than audio). Another drawback (in some respects) is that you need a eurorack-format case for the modules, since they’re not standalone like a CHA/V. And you also need a power supply, and the power supply needs to be at least a bit better than your average wall wart, since noise in the power can add noise and other issues to your video output. You don’t need to necessarily get a super low noise (aka “clean”) eurorack power supply like some modular video people get (many ones designed for audio will work great or at least OK for video), but there are definitely a few eurorack power supplies that work fine for audio synths but really poorly for video. Another drawback for the Cadet modules is that one specific part on the Cadet 1 (which is one of the modules you need to have for a Cadet system) is effectively no longer available. There are some workarounds some people have figured out that you can read about in the LZX forums if you want. But it might be easier to build a Syntonie VU007B since that’s a module that can replace a Cadet 1 and Cadet 2 in a lot of cases (though I think it only has RCA sync out, which means some Cadets, like Cadet 4 and Cadet 9 won’t work with it, though there are workarounds). I’m not trying to scare you away from this, but in general it’s a lot more expensive and complex than CHA/V, even though it’s still DIY (again, hence why CHA/V was created – the “C” stands for “cheap”).
I’m not sure what you mean by “the commercial kits” but that could encompass what I’ve recommended. Ignoring these things just doesn’t make sense to me. They’re all such incredible resources. You could use just the schematics and make everything 100% DIY if you don’t want to pay the people who are selling the PCBs and you know how to design PCBs yourself if you really want.
