EHX Doctor Q filter modes

[Fancy Lime]

Hi all,

I have been tinkering with a variety of envelope controlled filters lately and have analyzed most of the common ones. Wow, soooo many ways to skin that particular weasel. Haven't have the time yet to build a 2-pole moog-ladder yet, but that looks fun. Anyway, when staring at the different EHX circuits, I realized that the Bassballs uses the same filter topology as one of the modes of the Doctor Q, namely a bridged-T in an op-amp feedback loop. However, I had never thought about which of the modes of the Doctor Q was the "Bass" mode, the bridged-T or the multiple feedback bandpass. Am I correct in assuming that the bridged-T would be "Bass"? Seems to make more sense when looking at the frequency response, although still somewhat unusual for bass use.

I am also wondering if there are any designs using capacitance multipliers as voltage controlled capacitors in State Variable Filters. If I am not mistaken the resistors in the multiplier should not see a lot of signal in this application, which would make them an ideal place for a JFET as a voltage controlled resistor, thus controlling the overall capacitance. Seems like something that should exist but I could not find an example. Might be more complicated than necessary for most applications but that doesn't seem to stop people, as far as I can tell.

Thanks,
Andy

P.S. Mistyped "bridged-T" as "bridget-T" and thought: hey "Bridget T.", good name for a Wah... Anyone(s significant other) around here named Bridget?