Patches

[Tony Clark]

Skipping a few items...

> C) the third (and quite exciting) approach of the patch problem I've
> been thinking of
> is a software solution, the idea being to get rid of all plugs and
> chords.

   Watch out for Nord's "Modular" for something along these lines.

> * if the project features a large number of modules, complexity of
> analog multi-plexing will grow exponentially (or so) with the system.

   This is a MAJOR problem.  When you have people like Hans Zimmer who 
tend to build massive modulars, you have to take this into account.  This 
can be solved by having one main box that can handle a certain number of 
modules and then expander boxes that help out the main box.

> * therefore, the first idea that comes in mind is to A/D all ins, and
> let the software (burned in the ROM of the controller) redistributed 
> signals to
> the relevant outs (via D/A) according to the MIDI data received from the
> computer.

   You almost have a great idea on your hands!  There is a better way to 
do this.  By using analog switching circuitry, you can bypass the need 
for A/D D/A conversion!  Why do you need to transform the data to digital 
anyway?  The only thing you really need are a few D/A converters to allow 
you to send MIDI continuous controller data to the modular.

> * but then, a new difficulty concerns the amount of incoming signals
> to
> be sampled, and the ideal sampling frequency.
> * at first, it seems that CV signals and audio signals must be
> considered
> from different points of view : 100 or 200 Hz looks like an acceptable
> sampling frequency for CV signals (keyboard CV, ADSR, etc.), but audio
> ins/outs (when used as control signals) require a much faster sampling
> frequency (44.1 KHz actually), which is almost impossible to handle
> on most uControllers (run at 12MHz or so) and for a large number of
> signals (more than 5 or 6).

  Um, only 6?!  If you properly code a CPU of that speed, you should get 
WAY more than 6 channels!  In this kind of a synth I'd want two CPU's.  
One that is handling only A/D D/A conversion.  And the other CPU to 
handle everything else.

> The soft side of this last approach is exciting, for it allows full
> re-use of each configuration. It can also be programmed (patch
> configuration changing under certain predifined conditions).
> But the problems of the hardware side of thate idea aren't so easy
> to overcome.

  Yep, and most of the synths that tried to do this ended up costing a 
small fortune and never went into production!

> So, I'm wondering if anyone already worked on something like this.
> Or may be, for obvious reasons that I don't clearly see (mainly
> because it's quite late here), the whole thing goes straight to a dead
> end.

   I've brainstormed on this idea and I think that it is indeed 
possible!  It's one heck of a project, to say the least!  But until I 
finish up some of my other modular projects, I'm not going to tackle this 
one!

   Tony

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I can't drive (my Moog) 55!
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Tony Clark -- clark at andrews.edu 
http://www.andrews.edu/~clark
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