[sdiy] Korg MS20 Pitch to Voltage

[ganesha]

Does anyone know a good source for those four gang potentiometers? 

regards,
K.
--- On Mon, 12/1/09, harrybissell at wowway.com <harrybissell at wowway.com> wrote:

> From: harrybissell at wowway.com <harrybissell at wowway.com>
> Subject: Re: [sdiy] Korg MS20 Pitch to Voltage
> To: "Andre Majorel" <aym-htnys at teaser.fr>, synth-diy at dropmix.xs4all.nl
> Date: Monday, 12 January, 2009, 12:28 AM
> 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/>
> > _______________________________________________
> > Synth-diy mailing list
> > Synth-diy at dropmix.xs4all.nl
> > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 
> 
> Harry Bissell & Nora Abdullah 4eva
> 
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