[sdiy] pre Uprocessor schematics with ADC/DAC?

[JH.]

>> all the synths i have looked at that have ADC/DAC setups have a
>> programmed brain of some kind controlling them (prophet 5, etc)

The Korg PS-3200 didn't.
And my PolyKorg doesn't use a controller either:

DAC, ADC and EEPROM: http://www.jhaible.de/polykorg/jh_3200_digital_3.pdf

State Machine and Adress Counter: 
http://www.jhaible.de/polykorg/jh_3200_digital_2.pdf

User Interface: http://www.jhaible.de/polykorg/jh_3200_digital_1.gif

JH.