MIDI-CV converters (was: Building my first synth...)

gstopp at fibermux.com gstopp at fibermux.com
Tue Feb 6 17:07:17 CET 1996


     Good job Colin, this is exactly the kind of mass-CV controller I'm 
     thinking of. What I want to do is to see if I can make one out of an 
     old PC and bypass the EPROM burning.
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Re: MIDI-CV converters (was: Building my first synth...)
Author:  "Colin Fraser" <colinf at easter.euro.csg.mot.com> at ccrelayout
Date:    2/6/96 6:12 AM
     
I built my own CV convertor originally as an add-on for a BBC Micro - a 6502 
based eighties home computer. The software was written using the assembler 
functions of BBC BASIC.
After the code was fully developed I built a separate processor board and blew 
an eprom with the code slightly modified to suit its new home, then fitted the 
whole thing into a 3u rack mount case.
     
It has 32 CV outputs, which can be configured as note, velocity, controller and 
gate outputs, and also to control a stereo VCA - there is an eight channel 
mixer hardwired to 16 outputs (as the two channel volumes are calculated by 
computer from the midi volume and pan controls, its easy to make the panning 
follow a true sine/cosine function).
     
The outputs are demuxed from a single 8 bit dac, thru' 4 4051's. Gate signals 
are output from the same outputs as cv's to allow soft gate voltages (5 or 
15v). 4 channels also have 303 type portamento circuits, switchable between 
off, on and auto. There is also a din sync output that drives my 303 and 606.
     
I'm currently trying to get the source software from 40 track, 100K, 5.25" disc 
onto a slightly more modern machine, so I can mail it to another list member. 
If anyone else is interested in this, send me a mail.
I was going to produce schematics for it a while back, but never found a 
package that made it easy enough...
     




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