i'm thinking about building a big muff with the diodes on switches and figured it would be nice to bypass the tone stack also, but somehow i tend to get confused when it comes to this stuff while i'm staring at a vero layout. can anyone point me in the right direction?
(http://i144.photobucket.com/albums/r170/cautionarycloud/Electro-HarmonixBigMuffTriangleKnob.gif)
One possible bypass approach is that of wiring up a SPST switch that makes or breaks the ground connections for the cap and resistor to ground in the tone circuit.
It's not a "true" tone bypass, but will result in a substantial increase in volume, and elimination of the midscoop. Since you'd still have the 39k resistor and .004 (.0039) cap tied to the outside lugs of the 100k tone pot, the tone pot would provide modest adjustment of treble, but the overall impact of the stock tone control would generally be eliminated.
Here's how it was done on the transistor Big Muffs:
http://www.generalguitargadgets.com/pdf/ggg_bmp_tbp_sc.pdf
(R27, and SW2a/b)
Here's how it was done on the opamp big muffs:
http://cabbages.orconhosting.net.nz/graphics/joes_rubbish/fx/BMP/BMP.pdf
(C9, R13, R14, and SW1)
The question still needs asking: what do you want the tone bypass for?
Do you want it for getting a volume boost (the tone circuit produces passive loss)?
Do you want it for a different sound without due consideration of what the resulting tone is?
Do you want it for a specific preset?
etc., etc.
The optimal bypass arrangement will depend on the answer to that. The circuit options Discovlad graciously linked to will provide approximately the same volume with no tonal adjustment.