[sdiy] Looking for keyboard circuits

[David G. Dixon]

As part of my research into keyboard matrix scanning circuits for my
salvaged Farfisa organ keyboards, I've thoroughly reviewed the schematics of
two circuits: Ray Wilson's circuit from MFOS, and the Digisound 80 circuit.

It would appear that the MFOS circuit is clearly superior to the Digisound
80 circuit.  This is because when the Digisound 80 circuit finds a key
pressed, it stops scanning until the key is released.  When Ray's circuit
finds a key pressed, it immediately resumes scanning from the bottom.  Both
circuits give low-note priority (because they both scan from the bottom up),
but Ray's circuit is re-triggered but not re-gated when a lower key is
pressed and released while a higher one is held.  With the Digisound 80
circuit, all keys must be released before another note can be played, and
re-gating therefore occurs with every note played (like an old Moog
keyboard).  Also, the Digisound 80 keyboard doesn't generate triggers at
all; if you want a trigger, you have to touch some metal doodad on the side.
With Ray's circuit, if you want repeat triggers, you just bounce up and down
on one key.  This also means that you can play legato or staccato on Ray's
keyboard, but you can only play staccato on the Digisound 80 keyboard.
Finally, the Digisound 80 involves significantly more logic circuitry, and
Ray's circuit should be much easier to adapt to my keyboards which require a
12-by-4 matrix.

Geoff, I understand you have built the Digisound 80.  Is my assessment of
the situation correct?

Would anyone else like to weigh in before I commit to the MFOS circuit?

Also, I'm aware of the IKC project, but I'm not interested in anything that
complex just yet.


> -----Original Message-----
> From: Geoff Prince [mailto:geoffprince at f2s.com]
> Sent: Wednesday, June 17, 2009 8:25 AM
> To: David G. Dixon
> Cc: geoffprince at f2s.com
> Subject: Re: [sdiy] Looking for keyboard circuits
> 
> David,
> 
> The Digisound keyboard controller can be found here..
> 
> http://www.digisound80.co.uk/digisound/modules/80-15/80-15.htm
> 
> I've built this and it works fine.
> 
> regards
> 
> Geoff Prince
> 
> 
> 
> ----- Original Message -----
> From: "David G. Dixon" <dixon at interchange.ubc.ca>
> To: "'SDIY'" <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, June 17, 2009 8:41 AM
> Subject: [sdiy] Looking for keyboard circuits
> 
> 
> > I'm in the market for a keyboard circuit, preferably of the matrix
> > scanning
> > variety.  I've got two keyboards from an old organ I gutted recently,
> and
> > I
> > want to adapt them for use with my modular.  They are configured for a
> > 12-row matrix (i.e., by the octave) instead of the usual 8, but I think
> I
> > can work around this.
> >
> > I've looked at Ray Wilson's circuit on MFOS quite closely, and I think I
> > can
> > adapt this to my needs.  However, I haven't found anything else, and I'm
> > mostly just looking for other options to compare and get ideas from.
> >
> > _______________________________________________
> > Synth-diy mailing list
> > Synth-diy at dropmix.xs4all.nl
> > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> >
> 
> 
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