The graphic equalizer shown here is based on the IC LA3600 from Sanyo Semiconductors. LA 3600 is a single integrated single Op-amp, 5 band graphic equalizer IC which is very suitable for applications like portable stereo, radio sets, home theater systems, car audio systems etc. The LA3600 can be operated from anything between 5 to 15V DC and is extremely stable to capacitive loads.
In the circuit capacitors C1, C3, C5, C7 and C9 are used to fix the resonance frequency of the corresponding bands. Capacitors C2, C4, C6, C8, C10 and C15 are the input capacitors and increasing the value of these capacitors will increase the low frequency response. Capacitor C13 is a decoupling capacitor and C14 is a power supply filter circuit. C12 is the output capacitor and resistor R6 limits the supply current. Gain of each band can be adjusted by using the corresponding potentiometers R1 to R5.
- Assemble the circuit on a good quality PCB.
- I used 9V DC for powering the circuit.
- The power supply must be well regulated and noise free.