PURPOSE: To prevent the unbalancing of the distortion factor between output signals from being caused by applying an output of a parallel negative feedback amplifier to the 1st and 2nd negative feedback power amplifiers so as to give an output of both power amplifiers to a load.

CONSTITUTION: An input signal fed from a signal source SG is outputted to its output terminal 2 via the parallel negative feedback amplifier A and fed to an input terminal of the negative power amplifiers AMP1, AMP2. Further, each output signal of the AMP1, AMP2 is outputted as a synthesis signal among a fundamental signal from a signal source SG, a distortion component generated by the parallel feedback amplifier A and a distortion component generated from the AMP1, AMP2. Since the distortion generated in the AMP1, AMP2 is nearly equal, no unbalance of the distortion factor is produced between the output signals of the AMP1, AMP2. Further, the input impedance of the amplifier A is sufficiently large and the decrease in the input impedance viewed from the input terminal is not produced.