In hindsight, this design might not be properly called a DCO, since a DCO is an analog oscillator controlled by a digital signal, whereas this is a digital signal generator controlled by a digital input (MIDI)… Whatever. Since this is the only original circuit I designed for “My Scintillator” (the official name of the the modular synth I built earlier this year), I’m sharing the schematic here. Note that there are several TBD (to be determined) values. If you really want, you can contact me and I can try and track down exactly what I ended up using, however, I think it’d be best to experiment and see what you like. They’re all involved with the mixing and filtering of the output. Here is a thread discussing the design including another guy’s input on how to improve the it:
NOTE: Supply used was actually +/-15V not +/-12V as notated in this schematic. And while I did print a PCB from this schematic and it worked, be on the lookout for mistakes!