[sdiy] Polymoog, etc.

[The Old Crow]

On Wed, 25 Jul 2001, Gene Stopp wrote:

> Yes - very nice CS-80 site! Maybe someday I'll try to conquer one of
> those too... it's a disease I think...

  Of course, then there is the CS-50 that lost a bout with UPS:

http://www.oldcrows.net/~oldcrow/synth/yamaha/cs50/

> Well now the CS series is slightly digital, since there's a
> logic-driven voice assignment engine in there. I was thinking of
> purely analog in the sense that there's no flow-chart based stuff
> going on. The polymoog does have a keypad encoder and some 1-of-8
> selection, and the dividers and latches are technically digital, but
> there's no clock-driven state machine functions. So is it not purely
> analog?

  The CS-50/60/80 all use a two-chip key key-assigner logic+DAC circuit
that I am currently developing a PIC-based replacement for.  It (the KAS
board, as it is called) and the polyphonic aftertouch mapping circuit
(called the TKC board) are the only logic circuits per se in the machine.
Now, the interesting thing about the CS machines are the analog PROM
matrices built out of resistors and diodes to preselect control voltages
for parameters.  Everything else is direct-wired, as opposed to the
'fly-by-wire' approach taken in the Prophet-5, et al. (Panel controls are
not digitized in a CS instrument, hence the 4 sets of miniature "memory"
controls to set user patches on the CS-80).

  My current project is making this thing work:

http://www.oldcrows.net/~oldcrow/synth/yamaha/gs1/

  The parameter RAM is blank and I don't have the voice cards.  Avery
Burdette of Yamaha is willing to loan a voice book to me, however, so
things are looking up.  I'll archive the voice data to disk files, then
devise a widget to emulate the card reader, thus liberating the GS1 and
GS2 from depending on the cards.  I think this is one of the instruments
Toto used on tour.  It has an add-on RAM card that provided 96 memories
for presets.

Crow

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