Hey! This may or may not be helpful 2+ yrs > the OP, but the most versatile fuzz out there today, imho, (and with no affiliation,) is Baltimore Sonic Research Institute's (BSRI) TFZ ("The Ultimate Fuzz")... currently being made by them as "Impossible Colors". This after trying a zillion great...
Thank you for the reminder to post on on diystompboxes.com!
I think I found my answer in Mark Hammer's article: "The Technology of Auto-Wahs / Envelope-Controlled Filter". His section labelled "The Envelope follower and Inverter" pinpoints the details I'm looking for.
Can anyone provide an ehx Riddle Q-balls *schematic*? This may be a super-simple matter, but I'd love aion's Spectron to have the capability to specify the sweep frequency range with just a little more precision. I haven't seen this on other envelope filters, but the ehx Riddle Q-Balls "START"...