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3 band audio equalizer circuit schematic

3 Band Audio Equalizer Circuit

This 3 band equalizer circuit is an active filter network for bass, mid and high audio ranges. It is designed around the LM833 opamp from National Semiconductors.
This opamp IC has the following charactersistics: very low noise figure, wide bandwidth and a relatively high slew rate.
How does the three band audio equalizer works

The output of this 3 way graphic equalizer is designed to be DC coupled, however due to slight DC variations through the 100K potentiometers at the feedback lines of the opamp A2, a coupling capacitor might be needed.

Technical specifications for the 3 band equalizer

The cutoff frequencies:

  • bass range = 200 Hz
  • high range = 2 kHz

The midrange is a bandpass network with a center frequency of 1 kHz.
The maximum equalizer range is about 15 dB. In the middle position of potentiometer, the noise attenuation is about 90 dB with a bandwidth of 1 MHz and a gain of 0 dB. The gain can be changed through R2 using the following formula: Vu = R2/R1.

Audio Equalizer Circuit Diagram

3 band audio equalizer circuit schematic

10 Comments

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  • hector velador

    Im trying to install a pioneer eq model 720 to a mofset 50wx4 stereo

  • Rahman MR

    Please show us how to make 3 way audio amp

  • shrikant

    How to give audio input? I am not able to give audio input properly

  • Alexander

    Я собрал эту схему на TL072 [NE5532] и питал + – 15 v стабилизировал от общего питания усилителя эффект мне понравился. (I picked up this scheme to TL072 [NE5532] and fed + – 15 v stabilize the total power amplifier I liked the effect.)

  • Craig Mitchell

    It’s been a while since I’ve wielded the soldering iron so I’ve got some probable noob-ish questions :/ the texas instruments datasheet has the vcc max at 36v will it be ok to link this circuit to a dc power source of say 24v instead of 15v ? I’ve also read there’s a optional cap at the output to help smooth out the audio what size of cap and does it link to ground or run in line of the output ?

  • Ryan

    A couple questions – which components determine the frequency? Do you use 1/RC to fine the time constant?

  • RAZZITEAK

    iv’e noted that you’ve set vcc+ and vcc- to 15v on the lm833.
    Does this aplication require it to be set at 15v or is the output of the lm833 independent from the input voltage?

  • John mwangi

    Thanks for the passion and willingness that you have potraid..
    I would like to ask whether the device will amplify the audio or it will need second amplification. Thank you though!

    • kiarie

      Are you a kenyan and if not so am a pro in electronics

    • Jim Keith

      According to the text, the gain of A1 may be changed to suit. Please note that the schematic is in error –R2 and R3 designations are swapped. Av = R2 /R1

      Also, if a high input impedance is desired, A1 could be set up as a non-inverting amplifier without affecting the equalization portion of the circuit.

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