Wow, I suddenly feel really old. I used to build all sorts of electronic projects using CMOS chips but now that you mention it, yes, that was a long time ago!
I also remember building an 8-bit successive approximation audio AD/DA converter for the ZX Spectrum (a whopping 48K RAM!) using discrete components. It was super noisy but worked more or less.
This is just a 4029B up/down counter a 4051B multiplexer and some voltage dividers. It couldn't get any simpler but considering I'm very new to anything like this it's just educational.