[sdiy] Linux Synth ?

[john mahoney]

Linium wrote:

> As far as i am concerned instead of using a proprietary DSP processor, i
would
> go for hybridation, use the PC as a super CV generator and keep the other
> parts analog.

The idea has merit, going back to the old Paia stuff, among others. This is
a tried and true concept. I would even like to do something slightly similar
to go with the OB-X voice modules I'm making. But...

One limitation with your scheme is that your analog signals can't easily be
used to affect the CVs coming from the PC. This is fine for some uses but is
not ideal for modular synth uses. To handle that you'd need some kind of
card with DC-coupled inputs, plus custom software to use it in your system.

A bigger problem is that sound cards generate audio signals, not DC control
voltages. You will have to use a MIDI-to-CV convertor (or perhaps some kind
of industrial controller) to generate DC signals. Don't forget, the CVs have
to be able to go negative, too.

A sound card may be alright for producing some modulation CVs, or will it?
First, LFOs are often producing sub-audio frequencies, and sound cards can't
go that low. Second, the signal levels are all wrong -- they are much too
weak compared to analog synth voltages. Less than 1V peak-to-peak instead of
the needed -5 to +5 V. I guess you can use amps on all the signals, maybe
built into your mux. The mux also needs to have a CV sample & hold
capability. But the sub-audio LFO problem is not easy to get around (with a
sound card).


> The anti-aliased oscillators (you can find some free as LADSPA
> plugins) are not so great to my taste :)

Are you really judging all software synths by the quality of free plug-ins?


> And i like much analog filters :)

Mmmm, analog! :-)


Well, have fun! It's not a bad idea, but a PC sound card is not the
appropriate hardware for this use.
--
john