PURPOSE: To attain reproduction with high fidelity by making a current flowing through a drive coil of a speaker correspondent to an input electric signal so as to obtain an accurate output sound pressure level in response to the input electric signal.

CONSTITUTION: A current flowing to drive coils 11, 12 of a speaker 1 is detected by 1st and 2nd current detection means, outputs are added and given to integration circuits 31, 31a and subtracted from an input electric signal. Thus, a duty signal from comparator circuits 32, 32a varied in response to the output from the integration circuits 31, 31a makes the current flowing to the drive coils 11,12 of the speaker 1 correspondent to the input electric signal. Thus, even with the dispersion in the drive coils 11,12, or heating or fluctuation of the voltage of a power supply 27 occurred therein, an accurate output sound pressure level corresponding to the input electric signal is obtained from the speaker 1 and reproduction with high fidelity is attained.