About The Circuit
Given below is the circuit diagram of a simple three band graphic equalizer circuit. An IC called LF 351 IC is used here which is designed to operate as a wide bandwidth single operational amplifier. The IC also has a very high input impedancewhich helps the circuit to become more compatible to almost all the audio signal sources.
An input voltage between (6-30) Volts can be applicable to this circuit. It is to be noted that as the inpt voltage increases the gain will also increase. If an input voltage of 12 Volts is given for the circuit the electrolytic capacitors used in the circuit should be more than 12 Volts. The op-amp used in the circuit is wired as an inverting amplifier. The input signal is first passed on to the inverting input through the filter network. This filter network can produce a +20 to -20 dB enhancement or a cut on the frequency bands, 50Hz,1KHz and 10KHz.The gain of the se banda are adjusted using the POTs R1, R2 and R3. The circuit should be assembled on a PCB.