Wiring Schematic Diagram

This is a low noise preamplifier circuit for dynamic microphones. The circuit is based on the Op-Amp UA739. The uA739 is a dual audio operational amplifier with high gain and excellent stability. Out of the two opamps available in the IC, only one is used here.

The audio signals from the microphone are coupled to the non inverting input of IC1 through the capacitor C1 and resistor R1. C1 performs input DC decoupling. The R1, C2 network bypasses the unwanted high frequency signals from the microphone. A fraction of the output is fed back to the inverting input in order to prevent oscillations and ensure better stability. The input impedance of this circuit is around 50K.This amplifier can handle signal from 20Hz to 20 KHz, which makes it excellent for audio applications.