TB303 filter

[Jeroen Proveniers]

Hello,

recently I've made the TB303 filter just to try it out, but I have a
problem. 
When I turn up the resonance I also get a 'basscut' effect, the sound gets
quite thin. I only used feedback to the filter, e.g only a single
potentiometer, not a dual type, and I only use the filter out (the upper
side of the resonance pot). I used the Oakley TB3030 schematic. (I will
build my own TB3030 very soon).
The TB303 uses some form of Q compensation. Without, will I get the result I
have?
So probably I must include a summing amplifier to sum filter out and
resonance?

Anyway, I'm going to throw away this experimental board, and I'm planning to
build the Oakley VCF with a MIDI interface, but I just wanna know if I'm
right...

JJ
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