PURPOSE: To reduce the components for audio system, by combining the automatic radio having two amplifiers and left and right four speakers with the car stereo having two amplifiers, and suitably making the selective use of the aoutomatic radio and the car stereo.

CONSTITUTION: The automatic radio 1 having the speakers FL, FR located front, left and right and the speakers BL, BR located back, left and right, and having two power amplifiers 15L, 15R, and the car stereo 2 having two power amplifiers 26L, 26R are provided. At the output of the amplifiers 15L, 15R, one of the fadar control volume 16 having the variable resistors 16a, 16b is connected, the speakers FL, BL are directly connected to one end of the volume 16, and other speakers FR, BR are connected to another end of the volume 16 via the selector 17. Further, the output terminals 21R∼23b of the stereo 2 are connected to the input terminals 18R∼20b of the radio 1, and in case of stereo playing, the speakers FL, BL and FR, BR are driven with the amplifiers 15L, 15R and the amplifiers 26L, 26R of the stereo 2.