There are many tone control designs out there. Let’s take a look at those and analyze each circuit. If you are planning on designing a tone control circuit for your guitar effects, it is not actually that not hard to do. You only need to understand the basics. Please note that these are only passive type tone control meaning you will loose some signal strength when you use this circuit. To compensate for the attenuation caused by this circuit, you will need to add an amplifier circuit with a gain of at least 2.
Single tone control circuit
This circuit is found on many guitar effects such as the sonic distortion and Big Muff Pi to name a few. It only consist of a low pass and high pass filter. Basically you are just choosing between treble or bass boost. You can’t have the bass and treble boost at the same time. Setting the potentiometer at the middle will give you flat frequency response.
Schematic Diagram
The circuit is very straight forward, it is only composed of low pass and a high pass filter. Frequency is computed by:
F = 1/(2*pi*R*C)
Frequency Response
The response when the potentiometer is set at the middle is flat.
3 Band tone control
Unlike the 1 band tone control featured here, this 3 band tone control is very different as setting all the potentiometer at the middle will not give a flat response.
Frequency Response
Image from http://www.premierguitar.com/