PURPOSE: To reduce a converting clock frequency, by applying the converting processing of PWM after the bit of a PCM digital signal is split.

CONSTITUTION: The bit of the PCM digital signal 1 are split into, e.g., two, and the result is converted into a PWM signal at separate PCM-PWM converters 2, 3. Thus, the clock frequency is reduced extremely in comparison with the clock frequency not split. Further, the PWM signal obtained from the said converters 2, 3 is amplified at switching amplifier sections 4, 5 with required weighting, they are applied to voice coils 7, 8 wound independently as a speaker drive signal.