[sdiy] Korg X911 guitar synth

[René Schmitz]

Hi Motohiko, Alwyn and all,

> It's almost same as CA6080. I try to arrange Rene Schmitz method to
> LM13600. His original page is here
> http://www.uni-bonn.de/~uzs159/ms20.html
> 
> and this is my trial one.
> http://www.aleph.co.jp/~takeda/radio/MS20clone.html

This is alomst the original again, with the most prominent difference
being the use of a LED instead of the chain of diodes.

> I made frequency response graphs for VCF that I had made.
> 
> http://www.aleph.co.jp/~takeda/radio/farmVCF2.html
> It's also Japanese only page, but you can check some graphs there.

Oh, very nice!

> "MS-20 VCF Clone" is LM13700 based on MS20 and "MS20 VCF Clone2" is
> based on Korg35.
> Korg35 based VCF has 2 peaks. I think that it should be caused by
> selection of parts or something. but their curve is almost same. And 
> their sound is so alike. I can't point out which is which, if I try to
> check in blind for myself. 

Such things could happen due to inductive properties of the caps. A
"wound" cap does have a resonance on its own.

> In a glance, their schematics looks so different. But if you check
> them in the point of view of registors,then you can find that they 
> are almost alike as same as their sounds.

Right, I think the circuit configuration is really what counts here.
And also in a mix the differences between the filters aren't as 
prominent as if you listen to it stand alone.

> the biggest difference is the feelings of operation. LM13600 based one 
> is more smooth, I think.

There should be less distortion.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159