PURPOSE: To control the input signals an audio output amplifier circuit with a set signal and to switch the audio output signals by enabling a user to select and set the speaker output mode of a receiver.

CONSTITUTION: When a user selects an external speaker mode in a speaker output mode selection state of a receiver, an input signal switching circuit 6 selects the left and right audio channel signals 1 and 2 as they are through a control circuit 10. These signals 1 and 2 are inputted to an audio output amplifier circuit 8. An output signal switching circuit 11 outputs the output signals of the circuit 8 to the terminals 14 and 15 through the circuit 10. Thus the right and left speakers connected to the outside are driven, Meanwhile an audio output amplifier 9 applies a shoot through the circuit 10. Thus it is possible to switch the frequency characteristic of the audio output signal which automatically detects the speaker output mode of the receiver and drives the speaker.