[sdiy] Korg MS20 Pitch to Voltage

[harrybissell at wowway.com]

The MS-20 is a "tachometer" circuit. It generates a fixed pulse width
(in time) for each incoming cycle. 

It is ~more~ clever than most, if the incoming frequency gets too high
(so the pulses would overlap) it starts to drop pulses. Its really brilliant !

However... it uses a four gang potentiometer, three gangs set a low-pass
filter so that you can adjust the time constant to the expected input
frequency range. The last adjusts the integration time so that the ripple is
the best case for in the chosen input frequency.

It will always take a (large) number of cycles to get to a stable voltage.

There are better ways to do P/V, all of them much more complex than the MS-20.

Again, what instrument do you want to track. I'm familiar with just about
every P/V ever made :^P

(anybody need a P/V expert on their payroll ??? :^)

H^) harry




On Sun, 11 Jan 2009 22:23:10 +0100, Andre Majorel wrote
> On 2009-01-11 15:16 -0000, George Hearn wrote:
> 
> > Hi.  I know the Korg MS20 had a pitch-to-voltage input.  Can
> > anyone point me in the direction of some schematics for the ms20
> > or anyone information on this part of the system?
> 
> http://www.korganalogue.net/korgms/images/service/ms20/circ2.gif
> 
> It outputs a Hz/V CV so you'll need a log amplifier to drive a
> 1 V/oct VCO.
> 
> Also, the output is not very stable, even with a clean sine. Tried
> playing a DX-7 into my MS-20's external signal processor and it
> wasn't at all the same as playing the MS-20 from the keyboard. It
> felt sort of wobbly and laggy. Wonderful for experimental noise
> but not for more conventional music.
> 
> > Was it a PLL linked to the main oscillators?
> 
> I wouldn't know. :-)
> 
> -- 
> André Majorel <URL:http://www.teaser.fr/~amajorel/>
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Harry Bissell & Nora Abdullah 4eva