Mark Smart smart at
Mon Nov 15 18:43:06 CET 1999

I recently got out my old PAIA MCVI and Mux Master cards (this is the older
MIDI to CV converter card set PAIA had before they came out with the
MIDI2CV8 they have now) and installed it into my ARP Axxe. I am having some
problems with it and could use advice from someone who has built these
cards before. The cards were dying pretty regularly until I got rid of the
cheesy on-board regulators to turn +15V into %v for the logic supply. Once
I hooked things up to a real 5V power supply, it stopped dying. The problem
I'm having now is that the 6522 VIA chip on the Mux Master board dies and
makes the Trigger output stay high all the time. Resetting the boards makes
it work ok for a while, then it dies again. When I first hooked the card up
to the Axxe, I didn't put any interface circuitry between the TTL trigger
outputs on the card and the Gate input on the Axxe, which expects 15 volts.
I'm thinking I might have toasted the 6522 in the process of doing this, so
I ordered replacements from PAIA. I also assembled these boards a long time
ago before I knew about water-soluble-flux solder, so maybe the flux
residue on the boards is messing things up. My next thing to try is washing
the flux off with isopropyl alcohol. 

Other than this problem, the boards work great now. I have been using it to
play the Axxe from my Yamaha WX-7 wind controller. I added patch point to
the Axxe so you can use your breath to control the VCF cutoff and VCA gain.
What an expressive instrument!! I'm amazed at what realistic wind
instrument sounds you can get out of this very primitive one-oscillator
synth just by controlling it with a wind controller. WOW. 

Anyway, if anyone has built an MCVI setup and has had similar problems, I
would appreciate their advice. Thanks!

*     Mark Smart                               *
*     Electronics Engineer                     *
*     And Musician                             *
*     smart at                      *

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