I was recently made aware of a few effect pedals designed as static Wahs, and while I’ve stayed away from Wah pedals in the past because of the inhibiting cost of the hardware these effects used a regular pot to manually set the frequency. Not really a new idea, but I figured I’d make one and add an expression jack so it can still function as a normal Wah if I want to.

I didn’t have any schematics of these effects, but instead drew my own based on a basic Wah circuit and a few common modifications, as described in an article called “The Technology of Wah Pedals” by R.G.Keen over at Geofex.

Here’s a vero layout of the same Wah except I only included three different capacitors for the cap selection switch. I built this last night and it works nicely. The only thing I’m still not sure about is the orientation of the “Frequency” pot. I might have that one wired in reverse, but I’ll find that out once I try this with an expression pedal.

I’m planning on housing this in a 1590BB enclosure with regular knobs for all the pots and a TRS jack that disengages the “Frequency” pot when an expression pedal is connected. Looking forward to this…

Update (28.03.2011): Updated both schematic and vero layout. After some rewiring all pots should now work as intended.

Update (29.03.2011): Apart from labeling and adding some knobs my new Wah-in-a-box is now finished! I housed it in a regular 1590BB enclosure and added a TRS expression jack. The controls on the front should say (from left to right) “Volume”, “Q”, “Frequency”, “Gain” and “Sweep range” (this is a 3P rotary). You can disengage the “Frequency” pot by inserting a TRS cable and add an expression pedal at the other end giving you a regular Wah to play with. I really like this one!

Update (20.10.2011): Fixed dead schematic and layout links.

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7 thoughts on “Wah-in-a-box

  1. Just built! I “outsourced” frequency pot wiht my good old Yamaha FC7 (which has a 50K pot) and it sound really, really good.
    Thank you very much for this site.


  2. Hi,
    I just made the wah-in-a-box and the gain pot is making a lot of (heavy) noise. All the other pot are working fine. The overall volume is also lower than the original volume. Is it possible to by-pass the gain pot to see if the pot is broken? Or do you have other suggestions?

  3. Yes, it matters. Depending on which way you wire it you could end up with a reverse sweep that works the opposite of how a usual Wah operates.

    The frequency pot, whether it’s the expression pedal or the panel mounted one, should have lug #3 connected to ground and the other lugs connected to the vero board as indicated. Now, I don’t know about other expression pedals, but the cheap plastic one I had lying around had lug #3 connected to the TRS tip and lug #1 connected to the TRS sleeve, so I had to use an isolated TRS jack to prevent the sleeve from grounding against the metal enclosure.

    The TRS jack needs to have (I don’t know the technical term for this) an additional “normally connected” lug on each of the sleeve, ring and tip that disengage when you insert a plug. Now you wire the panel mounted frequency pot to the disengaging lugs, #1 to sleeve, #2 to ring and both #3 and the tip to common ground. Then you wire the other “permanent” lugs to the vero board. Voila!

    Hope you can make out what I’m trying to say. I’m poor at explaining things…

  4. Awesome pedal man. would love to see it in action and utilizing the use of the expression pedal as a controller. is this identical tothe layout you have published and how would i wire the TRS expression jack? does it matter as long as the wires are identical n the expression pedal side and the pot lugs ultimately match?

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