Baxandall Calculator

This is a Baxandall circuit calculator for an active filter design connecting to an operational amplifier circuit shown above. This works best when the op-amp package has FET inputs, as there is no current-compensating resistor between the non-inverting input and ground. This article helps compute the component values required in an active filter such as this.

Baxandall Tone Circuit Design

Usually, one starts with points ZB and ZT that are the ±3 dB corner frequencies, which is usually part of the design specification. Often the specification states a certain level of boost or cut required and this is a parameter given in ±dB format. For the bass control, we usually boost or cut all frequencies below ZB, and for the treble control, we boost or cut frequencies above ZT. However, as you can see in the graph, there are two more corners (poles) left, which this calculator will find for you.

The default values in the text boxes are for a typical Baxandall type circuit, where the ±3 dB corners are at 300 Hz (bass), and 1500 Hz (treble), with a boost/cut requirement of ±20 dB. You can change these parameters for your particular requirements.


Circuit Parameters

ZB (Hz)


ZT (Hz)


G Boost/Cut (dB)


Treble Capacitor CT(F)


Bass Capacitor CB (F)


Usually, metalized film capacitors are expensive and difficult to source, therefore I have made this calculator such that you start out by entering the values of the capacitors you may already have or can get cheaply. The capacitor for the bass (CB) is usually larger than (CT) for the treble by a factor of ten. The default values are readily available at online shops.




Calculated Parameters

PB (Hz)


PT (Hz)


RT (Ω)


Treble Variable Resistor VRT(Ω)


RB (Ω)


Bass Variable Resistor VRB (Ω)


A Baxandall circuit calculator is one of the most difficult to make, which is why nobody has one. I had to use a number of transforms to simplify the equations, which is beyond the scope of this page. Feel free to send me feedback as to how it performs for your design.