Patch Storage (was Re: [sdiy] Monosynth features poll)

[Tom Wiltshire]

On 29 Jan 2010, at 16:17, Dave Kendall wrote:

> P.S. FWIW, a DIY synth Patch storage solution for mere mortals like  
> me without coding experience, has long been a unrealised dream... ;-)

It's not an easy thing to pull off, although it isn't complicated  
either. Assuming we're not going entirely digital, it implies certain  
things about the circuit which is having its settings programmed;

1) All variable parameters must be controlled by CVs. You can't put  
any pots directly in the circuit.
2) All switches must be replaced by analogue switch ICs or something  
similar and controlled by digital logic signals.

These are the basic rules for programmable synth voices, and examples  
are numerous (any programmable synth from the Prophet5 onwards  
through the 80s).
If these two rules were adhered to, and better still if some standard  
were adopted (0-5V CVs and +5V logic say), it would be fairly  
straightforward to build a system that could read X pots producing  
0-5V CVs and Y switches giving either 0 or 5Vs and then output those  
signals via a multichannel DAC (or equivalent) and some output  
latches. This scheme has the advantage that it ought to be possible  
to make it "invisible" - e.g. unplug it and plug the control panel  
straight into the synth electronics and use the synth without the  
memory feature.
Obviously the memory PCB would have to have a microprocessor on it,  
but if there was one such project in the world, everyone who wanted  
to could get the PCB and start adding memories to their stuff without  
having to actually learn any coding or mess about with uPs beyond  
putting one in a socket on the PCB.

This was the scheme I originally had in mind for my monosynth  
project, but I've gone all digital since then, so the panel talks to  
the guts via a serial link now.

T.