I find bass pots incredibly useful on overdrives. I switch from Strat to Gibson and they often like greatly varying amounts of low end. So with the help of some nice people at FSB and here I came up with this: a Z Vex '59 Sound with a bass control. I also added some mids because for me it needs it. The Strat especially likes the extra mid-bump - the Z Vex '59 Sound and the Box of Rock are quite light-on for mids IMHO. You can swap the 3n3 cap in the middle for the original 470pF if you like. I have tried 4n7 - almost honky, cocked-wah tones (Fab!) and 2n2 - a little flatter than the 3n3.
I also used 2N7000s in this as it seems to me to smooth out the quite harsh top end ever so slightly. That may just be my imagination though.
I based this layout on IVIark's layout. I change things around because I prefer to have the red caps cover 2-3 rows. That's my little quirk - we all have some. :-)
Well I have been playing this circuit more and more with my Strat through a tweed amp and I like it more and more. :-) I compared with one I built with BS170s and a 4n7 mids cap and I like the 2N7000 version as above more. It's clearer, smoother and all-round chunky and fat with a rather wimpy Strat bridge pickup. It possibly sounds a little more '68 50W plexi than '59 Bassman but that's all good for me. It almost makes my Strat sound like it has P90s now.
It always amazes me how a couple of pretty simple mods can make the difference between "meh" and brilliant. The bass pot idea was IVIark's and the mid cap idea might have been Nocentelli's. Together these two simple mods have made this pedal a cracker for me. Big thanks to those two fellas.