Thought I'd post up this cool little circuit I've been trying, partly to ensure I don't lose the diagram
This is kind of stolen from Stellartone (makers of the excellent ToneStyler), with a bass cut knob added. It's not too far removed from the EQ controls on G&L's Comanche and S500 guitars.
The circuit uses a tandem vol/tone pot sold by Stellartone to roll off treble as the volume is rolled down. The pot is a 1 Meg volume and 250k tone on the same shaft. Stellartone use it to roll in their ToneStyler as the volume decreases, but this circuit just uses a standard tone capacitor (.022uF or whatever you like). The bass cut is a standard 500k pot and .010uF (10nF) cap. The 30k resistor effects how quickly the treble rolls off as the pot is turned down. A lower resistor value will make the treble roll off sooner, higher resistance rolls it off later.
So far I'm really liking this combined volume and tone control for cleaning up a distorted sound. I tend to use my volume as a gain control to go from high gain to clean instead of switching amp channels, but the side effect is a tendency for the cleaned up tone to be a little too bright (especially on the bridge pickup). This solves that issue. The bass cut pulls out the 100Hz and below region, tightening things up, which is handy on 7 and 8 strings.
Here's the drawing and schematic. In case it's not clear on the layout - the middle and last lug of the bass cut pot are bridged.
This seems like a pretty cool way to get a lot of tonal control over your guitar without too many knobs on it.