[sdiy] Digital Oscillators

[Mark Smith]

Hi,

been synth DIYing for ages, but only recently joined the group - Thanks Trev.

I've spent the last year playing around and have completed yet another 303 type clone. Unlike others I have seen I have chosen to bypass the Midi - CV - VCO. The result is a single chip ( PIC )  midi to DCO. Although it has been designed to replace the original oscillator in a 303 it has many other uses.
The circuit is pretty close to the original, other than the level detect/schmitt bit is done by the micro. The exponential current source is programmable - so as to keep the amplitude constant. Thus I have a digitally controlled oscillator which includes many of the original parts, but keeps in tune. The design is entirely SMD, but for the J-FET and Caps on the oscillator. If anyone is interested I could re-lay and possibly get some boards made. Adding triangle / sine wouldn't be a problem.

pictures of my clones are at  http://www.meadowfield.freeuk.com/synth/synth2.html

mark