Twin-T Wah - constant Q addon?

[KarenColumbo]

Just bb'd the Twin T circuit on R.G.'s "Technology of Wah Pedals " page (http://www.geofex.com/article_folders/wahpedl/wahped.htm, first image after "Twin-T Circuits" subhead).
It works very fine (after fiddling with the capacitors a bit), but I have the gut-feeling that the Q factor could use a bit sharpening in the toe positions.
Now in this schematic Q can be controlled by the "Q" potentiometer (1k) from the first transistor's emitter to ground.

Now I'm wondering (which happens as soon as I have some hours to spare that aren't messed up with deadlines) how I could make this 1k resistance dependable on the Wah pot (which happens to be 100k, I just spliced in the Pot from a non-functioning Cry Baby).

Like ... hrm ... "Scaled-down one- way interdependent resistance pair" I'd call it. LED/LDR can't work (don't know of no LDR with light/dark resistance between 0 and 1k). A JFET as a variable resistor is playing in rather high resistance leagues, too, I guess. OTAs are too nebulous for me, yet.

Is it doable at all? And I mean: with a single 100k pot

[iainpunk]

what about mounting a dual pot on the gear? and then changing the wafer from one of the layers.

you can also look in to the filter's values, here's a nice calculator (might wanna bookmark it)
keep in mind that the graph is upside down to what the output of the wah is. (negative feedback flips frequency graphs upside down)

cheers

[KarenColumbo]

I'd like to try and do this with a single pot. There's probably no chance in hell to succeed, but I like to keep meself occupied Maybe learn something on the way, too

[Kipper4]

Have you a schematic for what's on the breadboard.
If you go with the dual pot you could //R on both wafers independently.
Maybe you could upscale/downscales the jellybean biasing. Implement with op amp?
Happy Saturday folks.
Not deadlines today

[11-90-an]

maybe try experimenting with the 1M resistor on the collector and base of the first transistor... or connect lug 3 of the "Q" pot to first trannie's emmiter, lug 2 to a 22u cap to ground, and lug 1 straight to ground... maybe that can give you a different "feel" of the Q pot...

[KarenColumbo]

Very cool ideas, thanks! Sunday is BB day.