The wah effect moves a peak in the frequency response up and down the frequency spectrum. This movement is usually controlled by rocking a foot pedal, but there are also stomp-box effects which allow the peak to be triggered up or down by your playing intensity.
The frequency would usually be moved from around 400Hz to 2Khz. One factor that makes different pedals sound special is how the resonance changes as the frequency is moved. For example, early Morley pedals used a design that gave higher resonance as the frequency increased.
Some other controls you might see are:
- Resonance
- A switch to select of different frequency ranges
The original Vox and Cry-Baby pedals are considered something of a benchmark. These use the same circuit that has been extensively copied by other manufacturers over the years. They use a coil & capacitor combination to provide the peak, and much fuss has been made of their special coils which apparently contain magical properties.
There are some likely reasons for this, besides plain nostalgic sentiment.
- Electrical component tolerances weren’t as good 40 years ago as they are today. The variation between coils in early models caused different pedals to have slightly different frequency ranges and resonances. These differences suit some players and guitar combinations better than others.
- Marketing of new pedals heavily promotes the concept of capturing the essense of the vintage designs. Don’t believe everything you read, folks!
- There is some research that indicates that the original Fasel inductors (which we believe were just a cost effective choice at the time) were in fact flawed either from new, or with repeated use due to the circuit design. Maybe this really is the source of the magic!
