Increasing Wah Range

[Chester]

Hey there! I'm completely new to these kinds of DIY projects, but have had some electrical engineering classes so here goes:

I have read on some other site somewhere that it is relatively easy to increase or change the tone range of a wah pedal by changing the value of some component or components. What would these be, on say a Dunlop GCB-95 or equivalent pedal?

I am currently building the beginners NPN boost project and love how the breadboarded circuit sounded! I love it!

Thanks

[ACS]

Welcome on board!

There are a bunch of websites out there with how-to's on just this kind of thing...  Google is your friend

Try http://www.google.com.au/search?hl=en&q=modding+crybaby+wah&meta= and see how you go...

Have fun!
Aidan

[John Lyons]

Try these:
Diyguitarist.com  Has some dunlop diagrams too actually
GEOFX linked above (technology of the wah)

john

[R.G.]

The center of the range is set by the value of the cap from the emitter of the second transistor to the inductor, and of course, the value of the inductor.

The range is much more difficult to change. The frequency of any LC filter is proportional to the square root of L*C. If L is fixed, like it is here, and we vary C, like we do here, then the change in frequency is proportional to the square root of the change in C.

In a standard Vox-style wah, the effective capacitance is changed by changing the gain of the first transistor. The capacitance is effectively gain times the real capacitor from the second transistor's emitter. So the range is limited to be the square root of the gain of the first stage, assuming that the lowest gain is zero.

For widest gain, you need the biggest gain out of the first transistor. If you go too far, you start having biasing problems and stability problems with the first transistor; and the payback is only the square root. If you get 4x the gain, you get only 2x the range; 10x the gain, only 3. times the range. It gets out of hand pretty quickly.