[2] Tone controls work by using adjustable band-pass filters to raise or lower the perceived volume of sounds in a specific range of frequencies (or band).
A Bass control is a low-pass filter that produces the same effect over lower pitched sounds.
The simplest control is a single Tone knob that can be turned from Bass at one extreme to Treble at the other.
Dubbed the 5F6-A from the Fender model number of the amp which first used it, this tone stack offered the performer the ability to control the amplifier's low, mid, and high frequency response independently.
[3]The simplest tone stacks are derived from a bridged T network[dubious – discuss][citation needed] implemented with resistors in place of inductors, creating a notch filter.