PURPOSE: To eliminate noise at input switching, by operating selectively an electronic switch circuit performing the muting operation for a prescribed time with a control signal outputted from a touch switch circuit and impressing a power supply voltage to an input device to be selected.

CONSTITUTION: The analog electronic switch circuit 1 selects the input of an amplifiers and gives the result to the post stages and has a function performing the muting for a prescribed time until an output is generated. The touch switch circuit 2 outputs a signal for the operation of the circuit 1 with the operation of a touch switch 6 connected to the circuit 2. A switching circuit 3 supplies a DC voltage extracted from an amplifier power supply circuit 4 via a terminal 5 to an external device at the input signal side corresponding to the selective operation of the circuit 2. Thus, the operation of a power switch is not required for the external device and the generation of unpleasant noise in switching the device at the input side is prevented.