To miniaturize electronic equipment and to reduce its costs by varying an output voltage to a headphone between a positive and a negative without using a capacitor for DC cut.

By generating the intermediate voltage of a power supply voltage to be used for amplifying the voice signals of first signal lines OUTL and OUTR and by applying the intermediate voltage to a second signal line COM as a voltage for a reference signal, the amplifier can be operated just like the output voltage is varied from -VCC/2 to VCC/2 in the view from headphones 12 and 13. Thus, even without providing the capacitor for DC cut on the first signal lines OUTL and OUTR to be supplied with voice signals, the output voltage to the headphones 12 and 13 can be varied between the positive and the negative without fail.