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The primary role of this project is to convert a differential input audio signal into a single-ended output signal while rejecting noise that is common to both inputs (common-mode noise).

The circuit presented here is a differential amplifier intended to receive balanced line inputs in audio applications requiring a high level of noise immunity and optimum common-mode rejection. The circuit typically achieves an extremely high common-mode rejection ratio (CMRR) of 91 dB while maintaining an ultra-low THD+N of –120 dB at 1 kHz for 22-dBu signal levels. Precision matching of on-chip resistors gives the circuit an excellent CMRR performance. Operating supply range +/-12V to +/-15V. Connection of a stereo balanced line input via 2 x female XLRs to a stereo unbalanced output on RCA connectors. The circuit includes D1 power LED, Ferrite beads L1, L2 on the supply line to provide noise immunity. Ferrite Beads at input signals to reduce the RFI/EMI noise.”

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