Q&D VCF scratchy cv input

[zhx]

I finally finished debugging my Q&D VCF (Tim Escobed's circuit), and got it working fine.

However, it reacts oddly to both cv and volume pot. When I either turn the guitar volume or en external volume pedal (controlling the cv input) a terrible scratching sound comes out. As if having a worn out wah pot or something. I'm not sure, but the noise could also be RF interference, when these pots are in a certain position. Nothing like this comes out from using the VCF's own cv pot, that basically does the same thing as the ext. control.

Any ideas?

[zhx]

Anything?
Anyone?

[trevize]

the cv input is control voltage input. which voltage are you sending to the circuit?

[zhx]

9 V.
The "frequency" pot in the circuit feeds the same voltage to the circuit. The only difference is, that using the pot there's no noise, but using an external controller the noise is there.