This is the simple IC TL081 based 4 microphones mixer Circuit
Diagram. A TL081 op amp is used as a high impedance to low. converter
and a signal mixer. The input impedance is about 1 megohm and the output
impedance is about 1 kohm. Two 9 volt batteries are used as power
source. Battery must be several hundreds of hours with alkaline
batteries.
IC TL081 based 4 microphones mixer Circuit Diagram
