[sdiy] Minimoog clone

[David Griffith]

On Sun, 11 Jul 2010, David G. Dixon wrote:

> Hey David,
>
> I built (a slightly modified version of) Ray Wilson's matrix scanning
> circuit for some matrix keyboards I ripped out of an old organ:
>
> http://www.musicfromouterspace.com/analogsynth/KEYENCODERPCB/KBDMATRIX022005
> .html
>
> This circuit is low-note-priority and generates 1V/oct CV, gates and
> triggers (although the 12V gate and trigger circuits shown in the third
> schematic are unworkable -- just keep them at 5V and you won't go wrong).
> It works very well, and I've never experienced "ghosting".  In fact, until
> you mentioned it, I'd never heard of it.  The circuit latches onto the last
> low note played, and doesn't scan higher until that note is released, so I
> don't see how things could go terribly wrong.
>
> Of course, perhaps you want a buss keyboard just for the authenticity of it,
> but at 1000 scans per second, you can play as fast as humanly possible and
> you will never hear any glitches.

You probably haven't experienced ghosting because Fatar probably worked 
out how many notes are usually held at any one time and designed the 
matrix such that ghosting would require more keys to be held.  You might 
get it to ghost by holding down a lot of keys, but then how can you tell 
ghosting from a lot of notes sounding at once?

I'm starting to move closer to a Fatar movement with a decoder circuit. 
Do you think this circuit can be made to do high-note or latest-note?  Not 
having any significant exposure to a low-note keyboard, I've come to 
depend on latest-note behaviour.  For instance, keeping a low note held 
while I play a melody on the right.  The result resembles what Chuck 
Mangione commonly produces with his horn.

-- 
David Griffith
dgriffi at cs.csubak.edu