EEVblog is very specific to EE, Mike's Electric Stuff is electronics as well, but tends much more toward tear downs/obscure components/reverse engineering and Ben's channel is just a delectable collection of DIY everything. Ben became famous for building his own (and probably first DIY ever) electron scanning microscope, but has videos where he builds all sorts of amazing things in his home shop.
I mean, simple ones are easily explained, but they sound awful, so to get a usable one it takes lots of theory.
Unlike speakers, which you can build at home and can sound OK.
That said, wikipedia is a surprisingly good source on this. Also, this circuit simulator (http://www.falstad.com/circuit/) comes with some DAC/ADC circuits builtin, and you can watch them live.