[sdiy] Patch Routing Idea...

[Paul Maddox]

Bud,

> Well, I've been thinking about this for about a week now,
> an "easy" non-complicated way of patching an analogue
> synth without wires. How about a "digital patchboard"?!
> Hear me out...

been down this road...

> Take a matrix of tri-colour LED's. Lets say 10 by 10. (Expensive
> already).

pah, wuss, I was going for 24by 24 :-)

> The benefit of having a matrix like this would be no cables, the ability
> to store "patches" (but not knob or switch settings), and a visually
> stunning user interface. Another feature could be a "random" button.
> Changing patches would also be a rather extreme means of changing
> the characteristics of the sound, instantly!

agreed it would be nice...
Ok no the problems..

What you need is a CV summing matrix, now you cant use one of the commonly
available
cross poinbt switch chips as they only allow one input to one output.
The other complication, you now need a micro processor...
Also you could cheat, if you muxd the LEDs from the micro you wouldnt need a
hefty PSU
(anyone care to workout 24by24*20mA of current?)
Now for the CV part you need a micro controlled switch matrix..
Best I could find is MAXIM who do a SPI chip with 8 SPST switchs on..
now to get 24 by 24 you need 24*3 of these (is this getting to pricey yet?)
You also need 24 summing opamps, oh and btw this whole lot needs to be
matched so as to avoid
DC offset problems.

It IS possible, but its a lot of work..

I wanted to do this polyphonically, but I scared the pants off myself when I
thought about 576 of these maxim
chips (for 8 note poly) in a synth, let alone the circuitry for them!

Paul Maddox
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