To reduce the power loss of output stage parts and to reduce the size and weight of power supply parts by applying DC voltage respectively from specific 1st and 2nd power supply voltage applying parts to driving stage parts and the output stage parts.

The 1st power supply voltage impressing part including a power supply transformer part 23 for applying AC power supply voltage AC as primary side voltage and rectifying parts 24 to 32 for rectifying secondary side voltage obtained from the transformer part 23 and obtaining DC power supply voltage applies DC power supply voltage to driving stage parts 13, 14. On the other hand, the 2nd power supply voltage applying part consisting of rectifying parts 35 of 39 for directly rectifying the AC power supply voltage AC and obtaining rectified voltage and switching power supply parts 40, 41 for switching the rectified voltage applies DC power supply voltage to output stage parts 15, 16. The switching power supply parts 40, 41 respectively execute switching processing for rectified voltage outputted from the rectifying parts 35 to 39 and generate variable power supply voltage capable of maintaining a state that its absolute value is larger than the peak values of positive or negative polarity parts of output signals from the output stage parts 15, 16 by a prescribed value.