Archive of the former Yahoo!Groups mailing list: MOTM

Spent some time on a new filter idea. Not finished yet, but tested
enough to know that it will work:

I wanted a HPF for my "Moog-style" JH-5. I thought a 4pole
HPF with built-in filter coupler would be right after the
904A-style filter. But variable slope and resonance should
be added. In the end I had both features combined:

One Slope / Resonance pot:
ccw end is 6dB/Oct, 12 o'clock position is 24dB/Oct, with
practically linear action in between. Turning the knob further
clockwise will keep the 24dB/Oct slope, but also adds resonance.
There are two additional "correction paths" built in:
Variable slope would change the cutoff point, too. This is corrected
with a CV sidechain. With a trimmer I can choose a certain
attenuation (like -6dB or -3dB) to be at an almost constant frequency
when the slope is changed.
2nd, pass band gain is corrected to approx. unity for increasing
resonance.

Slope / Resonance is voltage controlled, with (-6dB/Oct)/Volt
sensitivity in the slope range.

Not finished yet, but it looks promising.

JH.