[sdiy] 4 channel polyphonic midi2cv with trigger

[The Old Crow]

On Tue, 17 Sep 2002 sbernardi at attbi.com wrote:

> I've got an EFM rxcvpro midi2cv, and a PAIA midi2cv. The rxcvpro is nice
> because it is cheap, but it does not have a separate trigger output. The
> PAIA is $99 and can do two simultaneous channels with CV, gate, trigger,
> velocity, mod wheel, and aftertouch. What I would really like is
> something that could do 4 channel polyphonic with CV, gate, trigger, and
> velocity.  That's 16 outputs - should be possible with a PIC based
> midi2cv? Does anybody know of such an animal that doesn't cost $100's?
> Lord have mercy - I'm thinking of doing a 4 voice polyphonic synth.

  I used a PIC16F877 (40 pin part) to emulate the key assigner/DAC chipset 
of the Yamaha CS-series "KAS" board.  The KAS does 4 or 8 voices, so I 
know it is certainly possible.  The only caveat regarding the KAS is that 
it is a V/Hz device as Yamaha CS VCOs are linear response.  It would be no 
big deal to make a V/Oct version, though, provided one did not mind the 
rather odd way in which the KAS assigns keys.

  The Paia 9700 could do it *if* you drill eight holes for trigger jacks
in the front panel, add a small circuit with an extra latch+output buffers
to store trigger signals to the main board, and reprogram the 8031
firmware ROM to use the new 'trigger port' for triggers and adopt the
newly-created trigger port into the existing control modes.  I wish they'd
done this in the first place as it wouldn't be that much more expense for
the kit once the initial tooling effort is done.  Maybe $5 extra.  Ah
well, maybe I'll do it myself one of these days...

Crow
/**/