Ironstone are often asked for advice or recommendations on the values and options for guitar tone controls. There is plenty of very detailed information on the web, so this article is intended to be a primer for the interested guitarist / hobbyist. While there are differences in how they are applied for different guitar and pickup constructions, the electrical principles of capacitor and resistor tone controls are of course common. But as a start point, the Stratocaster tone control example will be used,
(see later for Humbucker and telecaster derivatives).
The diagram shows an electronic representation of the components that make up a Strat tone circuit. Often referred to as a 'Tone Stack' in amplifier or pedal circuits, it is no more than a simple capacitor plus resistor low pass circuit, meaning it has the ability to pass lower frequencies (to the output) and 'bleed' higher frequencies away to the signal ground. Turning the tone knobs alters the potentiometer (pot) value and thus alters the amount of treble signal 'lost' from the output.
For completeness in the diagram, both the Neck and Middle pups are shown with an individual pot (Rn & Rm) and capacitor (Cn & Cm), and the Bridge has no tone control connected. In practise, most Strats are configured without a Bridge tone control, but have just one capacitor shared (i.e. both pots connect to one side of one capacitor) between the Middle and Neck controls.
Some History;Of course these changes were not in isolation, with pickup design / winding levels varying too!
For such a simple circuit, there have been a few changes along the way;
Reference; 'The Fender Stratocaster' by A.R. Duchossoir ISBN 0-7935-4735-0 (a fantastic Strat reference guide!)