About The Circut
Here is the circuit diagram of a 741 IC based 3 input mic mixer ckt. Altogether four 741 IC’s are used out of which IC1, IC2, and IC3 are used as pre-amplifiers. A 40 dB gain is produced by the op-amp on the induvidual input circuits. A summing amplfier (IC4) is also used so as to add the signals from the three pre-amplifiers. A 5 dB gain is provided by IC 4 to the final output signal. So totally 45 dB’s is produced as the gain.
The circuit should be assembled on a high quality PCB. It must be noted that the inputs and outputs are connected with respect to the ground. The power should be given from a +15/-15 V DC dual power supply. All the IC’s must be mounted on holders for their safety. Only 10 Volt rating is required for the electrolytic capacitors C1, C2, and C3, while the other capacitors must have a rating of 30 Volts. Take a look at the circuit schematic.