Working Voltage:DC 3V-5V The SSM2167 chip is a low-voltage, low-noise mono microphone preamplifier. This preamplifier includes a built-in compression and noise gate. The dynamic range of the compressed microphone signal reduces the peak signal level and adds additional gain to the low level signal. The noise gate attenuates the signal level below a certain threshold, in order to amplify only the desired signal, such as speech, and reduce the noise in the output signal. These features will help improve the clarity of the voice signal received by the microphone. ========= For electret Mic: Add a 2.7K ohm resistor between the mic input and the 5VDC for biasing the electret and put a 10K ohms potentiometer in the output to adjust the power level to the mic preamp stage.