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

[Tom Wiltshire]

Now, a minimoog clone with motorised pots on the front panel and  
patch storage...that *is* cool! But...ow...the cost! Still, I guess I  
could spare the yacht in the Carribean and only overwinter in the Med.

I suppose you could use some of the many digital potentiometer chips  
that are around, but then you're back to digital control again. And  
ironically the cheapest way to interface between a genuine pot and a  
digital potentiometer IC would be a microprocessor (again). Groan.

T.

PS: On a separate note, Antti is right - the code is not the  
complicated part. The code is simple. Dealing with the many CVs is  
more of a pain, and (as he says) making the synth circuit  
programmable in the first place.
It just goes to show that "Easy" and "Hard" are all relative to where  
you're standing and what your previous experience is, ultimately.

On 29 Jan 2010, at 19:17, Joe Rounceville wrote:

> I've actually been contemplating patch storage for my mini clone,  
> and ran into the situations Tom mentions in #1 and #2.  I have pots  
> inline with the sound path just like the original mini.   
> Technically there _is_ a way to do this and preserve the pots, but  
> I'm sure it's not very cost effective.  You could used motorized  
> dual ganged pots, with the second tier being used with an ADC for  
> your microprocessor.  So your motorized pots could be  
> microprocessor controlled and use a kind of feedback routine to get  
> the pots set where they belong.
>
> Obviously that would be pretty expensive (also doesn't deal with  
> issue #2, but that one's easier to solve), and who wants to spend  
> that kind of money just to say you're using discrete components  
> everywhere?  I mean, sure, it would be kind of cool, but you're  
> only going to impress your synth nerd buddies.   :-)
>
> --jr
>
>
>
>
> > From: tom at electricdruid.net
> > Subject: Patch Storage (was Re: [sdiy] Monosynth features poll)
> > Date: Fri, 29 Jan 2010 17:21:47 +0000
> > To: davekendall at ntlworld.com
> > CC: synth-diy at dropmix.xs4all.nl
> >
> >
> > 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.
> >
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