[linux-audio-dev] Using Jack for "Control Volt" signals?

[Steve Harris]

On Sat, Nov 08, 2003 at 08:30:13 -0800, Thomas Webb wrote:
> in JACK, everything is a float between -1.0 and 1.0.
> So you can't just have arbitrary datatypes. Here's the
> way I abstract control voltages with JACK (This is
> based on the voltage levels I am familiar with in
> modular synths, a la synthesizers.com):

The range of the floats is immeterial, the [-1,1] range is only
significiant for signals that are to be sent to integer outputs. For
internal stuff it doesnt matter. In getting stuff out of the DA converters
you will have to beat the DC block filter. I've done this is done by
modulating the CV signal with a high freq sine wave, and using an envelope
follower on the receiver, but I've heard that you could (in theory) hack a
soundcard to be DC coupled.
 
Convention in software modulars is something like

logic/gate  signals
0.0 - false/closed
1.0 - true/open

pitch (osc and filter)
1.0 per octave

envelope/vca
[0,1]

NB I think SSM can send CV signals over JACK allready, AMS and pd should
be able to as well.

- Steve