[sdiy] CC-Modular

[Seb Francis]

Hi Hans,

xmurz at gmx.de wrote:

> I woulnd't start doing all LFO's and EG's in a pic, this would make little sense to me,
> but you could stick a couple LFO's and EG's in the Pic aditionally to some analog ones
> if you got some processing power left.

My reason for this would not be because I don't want to use analog modules for this .. it's just some way to try and reduce the amount of inputs and outputs which must be patched together.  A 32x32 switch matrix requires 64 16-1 Analog Mux chips, whereas a 64x64 switch matrix needs 256.  Plus every CV which needs to be controlled by a "pot" needs a D/A.

Moving 2 LFOs and 2 env gens to the digitial domain could save approx 20 inputs and 12 outputs needing patching, and save approx 20 D/A channels.

I wonder whether anyone can really hear the difference between an analog and digital LFO or env when using 12bit DACs?  Also maybe there are interesting possibilities in the digital domain such as different shaped envelope ramps, and exotic LFO shapes...

>
> Anyways, that's the way I'd do it.
> The PCI idea is also very slick. Though that would mean you'd have to write drivers for
> different operating systems and the card would have to be well shielded. (or only for one
> operating system if you want once and only for you..)

Since I would only write the "patching" software for one OS anyway, multiple OS support isn't really a consideration.  And it is important that all control can be done via MIDI in order to record any realtime parameter control in my normal sequencer (Cubase).

>
> As you need so many ins and outs you will end up with an external box anyways.
> OR you could do a custom PC chasis with additional linear PSU and stick all stuff
> in one PC  custom chasis and have the posts on the front panel of the PC.
> You can do that with a 19" 4U chasis that you build youself.
> A small pentium would be sufficient, so you could do without a fan (->no noise)
> and a zip drive to boot (which goes quet after transfer).
> You would have to shield the analog circuitry pretty good, too.
>

Nice idea to use a cheap PC for all the digital synthesis and control (rather than a PIC or similar board).  After all my Mackie mixing desk has a PC at it's core.  Would have to use some better OS than windows though - I don't fancy all the overhead of a GUI OS.  There's some "realtime" Linux kernel extensions which might be useful for this kind of thing - a synth which you can SSH/telnet into :-)

I would need to be careful with shielding and power supply separation though.

Seb