3-Band Active Audio Tone Control Circuit

This topic continues the coverage of audio tone controls. The first entry started with a Passive Tone Control circuit using different RC filter configurations and introduced an active filter. The second entry showed a fully designed 2-Band Active Tone Control circuit, and now this third section covers a 3-Band Active Tone Control circuit. Compone
3-Band Active Audio Tone Control Circuit - schematic

nt values are sometimes provided as examples, but the final filter characteristics are left to the designer, although design equations are provided. Alternate configurations are possible for any of the circuit schematics, as these are all just low-pass or high-pass filters [active filters in the case of the Op Amps]. This audio tone control combines adjustments [RC filters] for a Base control a Midrange control and a treble control all in the same circuit. The design combines an operational amplifier, as the active element, with a passive filter section. The design also uses a buffer amplifier between the external input to the circuit and the actual tone control filters. As indicated this circuit contains three individual filters, or one filter with three individual controls, that adjust the low band [Base], mid band [Mid-range] and high bands [Treble] of the audio range. As with the previous active tone control design the first part of the circuit is nothing more than a buffer and its presence does not effect the operation of the filter [tone control]. If the implementation does not require a buffer, than the first TL082 amplifier does not need to be used. That includes the 10k input bias resistor, and the 5uF blocking capacitor. The 1uF capacitor at the output of the Op Amp is also a DC block and is also not part of the filter circuit, but should be used as isolation between the filter and what ever input circuit is...

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