[sdiy] Minimoog clone

[MTG]

If you have diode per key, you won't have ghosting.

GB
www.musictechnologiesgroup.com


----- Original Message ----- 
From: "David Griffith" <dgriffi at cs.csubak.edu>
To: "David G. Dixon" <dixon at interchange.ubc.ca>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, July 11, 2010 2:44 PM
Subject: Re: [sdiy] Minimoog clone


> 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
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