Wah-wah pedals can sound so cool, but they are SO heavy, and not well suited for tabletop operation. I took the PC board out of an old Cry Baby and mounted it inside a chocolate tin. The knob on the side replaces the foot-treadle, for finger control. A toggle switch (the one with the black handle) selects between this wheel and the little photocell peaking out like a cat's eye near the box's edge -- wiggling your hand or elbow over the box sweeps the filter. I can plug in any volume pedal (into the jack with the black nut) if I want to get back foot control (I�ve got an old plastic Boss pedal that weighs a fraction of the wah-wah's original cast aluminum housing).

I added a "Super Switch" to switch in and out of circuit a larger capacitor that lowers the frequency range of the wah into the bass region. A second Super Switch switches the wah-wah in and out of bypass -- sometimes I like the sound of the resonant filter but don't want to hear the sweep; by tapping the momentary switch I can momentarily punch the filter out while changing frequency. There's a power switch in the upper right corner, so I can leave the circuit patched without draining the battery. I couldn't find a box exactly the width of the pedal, so I added a second jack for output (lower left corner in photo of the circuit's interior.)

Great information on wah-wah theory and mods can be found here.

(Scroll down for all three photos.)