[sdiy] Digital Oscillators

[Paul Maddox]

Mark,

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

welcome

> 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.
>

Yes!
DCO's ROCK!
ok dont flame me for this...
a well designed DCO has many many advantages over analog VCOs..
and for somethings are simply the best way of doing stuff...

> 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.
>

Shame about the PIC, but hey ;-P
(ask trevor about my comment on that)
and also SMD, no many DIY'ers brave the depths of surface mount, now I have
(Waveterm C) I shall be useing it more often, its compact, cheap and VERY
quick...

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

nice stuff!

perhaps I can ask you for help with a Scenix based project Im haveing fun
with :-)