¨My¨ Modified Bassballs

[chemosis]

how do i do the resonance knob. i  want a pot for each filter even though it might not be that usefull. do i replace r17 and r12 with 5m pots ?? thanks alot mark hammer i really really appriciate all the help so damn much.

[Mark Hammer]

I'll suggest that if you want to install a variable resonance control (which would be replacing the 470k feedback resistor in a filter section), you do the upper filter only, and leave the lower filter alone.  The reason is that when you dicker with the gain of the filter stage, to vary the resonance, it changes the center frequency range.  More gain will move the filter sweep lower, and less gain will move it higher.  This is why some autowah pedals that use a similar kind of filter, and include variable resonance, will often label it "Range", because that's what you tend to notice most.

You want the lower filter to provide a solid, dependable thickness to the overall sound, and use the upper filter to provide the variation and nuance; the "re-voicing" if you will.  So a variable gain pot on the upper filter will yield lots more interesting tones without getting too complicated.

Note that increasing the gain will also monkey with the level balance between the two filters, so you'll likely want to install a  mix control.  I show how to do it in this video:  https://www.youtube.com/watch?v=eoAIKHFGOcQ

A 5-knobber, with controls for overall sensitivity, decay-time, upper filter tuning and resonance, and a mix control, will give lots of options and still fit in a reasonable-sized package.

And, if it were me, I'd start out with a 330k fixed resistor in series with a 500k or maybe 1M pot for the feedback resistance (resonance).  That's not a huge range but my gut says that it will provide more or less sufficient variation.  Going up as high as 5M will likely result in stability issues.