This Demonstration shows the frequency response of a tone circuit typical of a number of Fender vacuum-tube guitar amplifiers. Sliders simulate the treble, midrange, and bass potentiometers. Setter bar controls allow you to experiment with different (common) capacitor and resistor values. (The default values are those used in the Fender Twin-Reverb model AB763.)
The vacuum-tube amplifiers produced by Fender Electric Instruments in the 1950s are some of the most legendary of all electric guitar/bass amplifiers. The "tone stack" modeled in this Demonstration is typical of several Fender models, as well as Fender-inspired designs from such manufacturers as Marshall and Vox.
Schematics of most vintage Fender amplifiers may be found at www.schematicheaven.com/fender.htm. Photos of various models can be found through Google Images. (Original specimens of certain models from the 1950s and early 1960s can fetch as much as $10,000 today.)
The frequency response function used in this Demonstration was derived with Mathematica, using Kirchhoff's laws and the Laplace transform.