An audio processing circuit is provided, receiving a microphone signal from a microphone to output a differential signal. A preamplifier receives the microphone signal to output a first preamplified voltage and a second preamplified voltage. A gain stage receives the first preamplified voltage and the second preamplified voltage to output the differential signal comprising a first differential output and a second differential output. In the preamplifier, a first operational amplifier is provided. A first voltage controlled current source is controlled by the output end of the first operational amplifier to provide a first current. A first transistor has a gate coupled to a ground voltage supply, a source coupled to the first voltage controlled current source for receiving the first current, and a drain coupled to a voltage ground. Likewise, a second voltage controlled current source and a second transistor are presented symmetrically to render the differential output.