The invention provides a component selection control system comprising signal output components 2 to 5, signal input components 4, 5, and an amplifier unit 1 having these components 2 to 5 connected thereto. The signal output components 2 to 5 have respective on-off switches 23, 33, 44, 54 provided on signal output lines 73 to 76 for delivering audio signals to the amplifier unit 1 therethrough, and the amplifier unit 1 has a common input terminal g. The signal output lines 73 to 76 of the output components 2 to 5 are connected to one another at a point connected to a common signal line 71, which is connected to the common input terminal g of the amplifier unit 1. This arrangement greatly reduces the numbers of signal lines and terminals required for connecting the components 2 to 5 to the amplifier unit 1.