Tone stack

The network of controls inside an amplifier that sets its frequency balance, usually bass, middle and treble, often interacting with each other.

The controls are not independent equaliser bands in the way a mixing console's would be. Passive stacks, which are the commonest arrangement, cut rather than boost, and because they share components, turning one knob changes how the others behave: raising the treble also affects the midrange response, and the middle control often determines how prominent the whole sound is. That interaction is a large part of an amplifier's characteristic voice.

Example: on many amplifiers, a midrange control near halfway gives the most gain and the fullest sound, with the extremes thinning it out.

Tone stack

See also