Here is a simple 3 input mic mixer circuit using the popular uA 741 ICs. Four 741s are used here.IC1, IC2, IC3 are used as preamplifiers. They produce a gain of around 40 decibel to the individual input signals. The IC4 is wired as a summing amplifier to add the signals from three preamplifiers.IC4 also gives a gain of around 5decibel to the final output signal. Total gain of the system is around 45decibel.
- Assemble the circuit on a good quality PCB.
- A +15/-15 V DC dual power supply is needed for powering the circuit.
- All inputs and output must be connected with respect to the ground.
- ICs must be mounted on holders.
- Electrolytic capacitors C1, C2 and C3 must be rated 10V and other capacitors must be 30V.