[sdiy] Exponential Keyboard (KORG MS-20)

Andre Majorel aym-htnys at teaser.fr
Sat Sep 1 13:04:52 CEST 2007

On 2007-09-01 05:42 -0400, Tony K wrote:

> I don't remember but was the KORG high note priority ?

Yes. The highest note takes precedence.

> All this leads me to scrap that part of the circuit altogether and do 
> a straight forward 1 V/OCT design [...]

Good move, IMHO. The combination of Hz/V keyboard and exponential
VCF CV inputs is why you can never get proper keyboard tracking on
the MS-20.

> Only things that concern me is the lower impedance seen by the
> exponential converter and now FM wouldn't be Hz/V changing the
> character of the machine (?).

FM from the TOTAL bus and FREQ jack is exponential already. With
either pot at 5, it's about 5 V/oct. With either pot at 10, about
0.9 V/oct.

If you're talking about FM from the "VCO 1+2 CV IN" and "VCO 2 CV
IN" sockets, yes, it's Hz/V and it would be good to have. I
sometimes use it because it's the only way to modulate the
frequency of a VCO without affecting the other (FREQ and TOTAL FM
controls are common to both VCOs).

André Majorel <URL:http://www.teaser.fr/~amajorel/>
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