PURPOSE: To avoid unnecessary attenuation of audio when audio is present at the center of microphone left and right, by avoiding the audio matrix when the level of difference signal is less than a given value.

CONSTITUTION: The signal from the output terminals 10R and 10L of the stereo demodulation circuit 10 is respectively fed to the speakers 15R and 16L via the addition circuits 14R and 14L and a part of the signal from the output terminals 10R and 10L is fed to the addition circuits 14L and 14R via the switch circuits 19R and 19L. Further, the level of the difference signal from the detection circuit 9 is detected with the level detector 20, and when this is less than a given value, 0 is outputted from the threshold circuit 21, the switch circuits 19L and 19R are OFF and audio matrix is not made.