Korg Poly800/EX800 Users

On Mon, 17 Mar 2008, korgpolyex800 wrote:

> Is the only reason you replaced VR2 with a pot so that you could control 
> VCF cutoff via a knob instead of via the VCF cutoff parameter?
===============

that seems to be a fair assessment.


> Because it appears to me that providing cut off control via the existing 
> circuitry will work just fine. The goal is to provide a knob to control 
> control cut off.
================

yeah, that should work, although it would have limited resolution. at 
higher resonance settings it become a zipper effect.


> Then, you replaced VR5 so that you could really push the resonance into 
> self oscillation. That will definitely need a digital potentiometer put 
> in its place. However, I am wondering why you use a log pot. I would 
> have thought that the resonance response on the filter chip would have 
> been linear.
===================

i used log because it produces a better response than linear. try it both 
ways, and see which one sounds/feels better.

that one, and the linear taper pot for the FM-800 mod, surprised me.


> And you ground one side which is completely different to the way the 
> trimmer is set up. Why?
===================

i can't say, without having the schematics in front of me, but it works!


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