This is the design diagram of 5 band graphic equaliser circuit build using operational amplifier chips, the NE5532 or LM833. The op-amp ICs is a good choice because of inexpensive and comes with fairly good quality output. Each IC contains dual op-amps circuit, so you will need 4 ICs of NE5532 or LM833 to build this 5 band graphic equaliser.
For maximum audio performance, use:
- Regulated power supply circuit (use LM78xx)
- Use MKM type of nonpolar capacitor
- Use tantalum type of bipolar capacitor (electrolytic capacitor)
- Use metalfilm type of resistor
Equaliser circuits generally divide the audio spectrum into separate frequency bands and have independent
gain control for each band. The output of each band is mixed at IC4(A) and then fed to an audio power amplifier. Proper quality factor (Q) needs to be selected to avoid overlap in adjacent bands as this introduces colouration into the audio signal.
The potensiometers (VR1 through VR5) are in the signal path and hence should be of the best quality possible. Wrap the body of the pots with bare copper wire and solder the other end of the wire to ground. Since the filters are very sensitive and for maximum performance, all resistors should be metal-film type and the capacitors should be polyester type.
5 Band Graphic Equaliser Document Reference:
More explanation about how the circuit work, download this document:
Download datasheet document: