The circuit was designed to illustrate the use of tone control circuit by which the audio signals are adjusted before being carried out to any output devices such as headphones, speakers, or recording devices through the use of an amplifier.
Equalizers have been used in several industries such as in multitrack recording and sound reinforcement systems, in live events where microphones and speakers operate simultaneously, in all audio records or vinyls where equalization is applied to the sound waveform, in early telephone systems where it was used to correct for the reduced level of high frequencies in long cables, in picturephone circuits, in modern digital telephone systems, and in individual channels of a mixing board and the sound of electric instruments where it was used to manipulate the timber of musical instruments and sounds
Using a single op-amp this easy to make equalizer offers three ranges, low frequency,mid frequency,and high. With component values shown there is approximately +/-20dB of boost or cut at frequencies of 50Hz, 1kHz and 10kHz. Supply voltage may be anything from 6 to 30 Volts. Maximum boost 20dB is only realized with maximum supply voltage of 18 Volt.
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