Crybaby Wah with True Bypass

I modified my Dunlop Crybaby Wah pedal with a "true bypass."

Loosing some tone when your wah pedal is turned off, or bypassed, is a common problem on pedals built from older designs like the Vox and the Crybaby. This problem can be fixed by replacing the single pole double throw (SPDT) footswitch with a double pole doule throw (DPDT) switch.

The SPDT switch is much cheaper, so manufactuerers use it instead. This switch controls what is fed to the pedal OUTPUT: the wah signal or the bypass signal. The input is always connected to both the bypass wire AND the wah circuitry, even when the pedal is bypassed. In this situation, the wah circuitry acts as a capacitor, soaking up charge and bleeding off your tone. I had this problem with my crybaby.


The DPDT switch can be wired to switch both the input and the output from wah to bypass at the same time. In this scheme, the wah circuity is disconnected at the input and the output. Craig Anderton's book "Electronic Projects for Musicians" discusses these two switches and how they can switch effects.

You will have to find a DPDT footswitch somewhere - they are not common. Stewart MacDonald on Ohio sells them for about $15. Using a voltmeter I was able to dig into my crybaby and figure out where to wire the switch in. However, don't destroy your pedal unless you're sure you know what you're doing.

The improvement, by the way, was fantastic - super crisp high gain even with the pedal bypassed.

Details on the Mod

Click here for a text file describing the mod.

Dunlop Schematic

Here is a schematic from Dunlop, kindly scanned and provided by Joel Nice [joelnice@diva.EECS.Berkeley.EDU]. They use a slightly different strategy in order to perform a functionally equivalent modification. The only difference is that the input to the pedal circuitry in the Dunlop mod is connected to ground when the pedal is bypassed. This is probably designed to eliminate charge buildup there while the pedal is bypassed; such buildup would make a popping sound when the pedal is switched back on. I have not had any problems with popping on my pedal modded following my simpler strategy.



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scott andrews
sha3u@his.com