Classic Tone Control Circuit with Low Noise Transistor

Tone control is a type of equalization used to make specific pitches or “frequencies” in an audio signal softer or louder. A tone control circuit is an electronic circuit that consists of a network of filters which modify the signal before it is fed to speakers, headphones or recording devices by way of an amplifier.

Tone control allows listeners to adjust sound to their liking. It also enables them to compensate for recording deficiencies, hearing impairments, room acoustics or shortcomings with playback equipment. For example, older people with hearing problems may want to increase the loudness of high pitch sounds they have difficulty hearing.

Tone control is also used to adjust an audio signal during recording. For instance, if the acoustics of the recording site cause it to absorb some frequencies more than others, tone control can be used to amplify or “boost” the frequencies the room dampens.


This classic tone control circuit uses a low noise transistor model which is interesting. The transistor makes the adjustment more suitable for the person to hear. The variable resistor also plays an important role in controlling the output. In the simulation it was transformed into a voltage divider theory having 50% resistance each. Notice the blue color waveform is the control output while the black is the input. For further simulation please see Project Link.

Project Link:


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  • NK

    picked up the local radio station with the circuit built on a breadboard and with input on a guitar; seems to be a formidable problem with these types of circuits. NK

  • NK

    hey, does this get rfi with all of the rc components; I built a tone control circuit from an app note for a low noise op amp and it worked ok, but picked up am radio pretty well too. I then used shielding and wrapped parts of the circuit in grounded foil which seemed to reduce the problem. The problem was also part of the input source (guitar). I think I may build this to see if it works better. Thanks for the circuit, chaps.

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