Stereo tone controller with transistors

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The tone controller is a circuit inserted before an audio power amplifier. Its purpose is to allow the user to adjust the gain of specific frequencies of the audio spectrum. Tone controllers range from simple bass boost circuits to complex equalizers. The circuit presented here is a simple one, with a potentiometer which alters the lower third of the audio spectrum (for bass adjustment) and another one which alters the upper third of the audio spectrum (for treble adjustment).

The schematic does not contain a volume adjustment potentiometer, but that can be added before the controller input. The signal input level should not exceed 1 Vp-p. When both potentiometers are turned up to the middle (flat), the relative gain of the circuit is -1 to -2 dB. Therefore, with an input signal of 1 Vp-p, you get no less than 0.8 Vp-p at the output.

Stereo tone controller with transistors

Built prototype of the stereo tone controller