MIDI->CV and controller

[Chris Stecker]

I think we've discussed this before, but a (relatively) easy approach is this:

1) use one CV signal you want to send to modulate the amplitude of a
pure-tone carrier signal.  (say, 1000 Hz).

2) use another CV to modulate a different carrier (2000 Hz)

3) ... etc.

4) mix all of those AM tones together, and send that out of the PC

5) build a box or patch that does the following:
        a) pass a signal through a bank of bandpass filters, each tuned to
           accept one of your carrier signals and reject the rest.
        b) pass the filtered signal through an envelope follower

6) run the PC signal into box(5)'s input

7) The output of the envelope followers should match your CV signals.


Of course, this approach is not perfect.  The more channels of CV you try
to cram on to one signal line, the sharper you have to make your filters,
and
the less temporal resolution you can achieve.  If you want to do audio-rate
CV, you will need very wide filters (in the limit, one channel with no
filter imposed at all; this makes the patch pretty simple: PC->EF->  )

This approach was used by Don Buchla and Morton Subotnick in the 1960's to
store control voltages on tape.  It was also used by Disney in the 1930's
to save surround-panning automation (!) for Fantasia.  Neat, eh?

-Chris Stecker
ovenguard music (www.ovenguard.com)

>What I would love to see is an eight channel DAC for my PC. Then, if
>I want MIDI->CV I can code it myself. Or if I just want to skip
>MIDI I can do things like LFOs without having to quantitize them
>into CC messages. I could also use channels to implement software
>ADSRs or n-stage envelope generators.
>
>Does anyone know of anything like this? Could I possibly use cheap
>soundcards for two channels. Will they go down to DC?
>
>Thomas