A classic wah-wah effects pedal with a coil

A wah-wah is a guitar effect device that is very popular with many guitarists today again. It consists essentially of a filter that can be affected in its transfer curve. A foot pedal to be operated by the player is mechanically connected to the potentiometer. The name came from the fact that the guitar play using this effect, with suitable operation can sounds like "Wah-Wah". Circuits with a coil, such as those shown here, were very common in the first devices of this type.