PURPOSE: To offer a loudness switching device especially enabling the switching of a loudness control operation even by a remote controller concerning an audio amplifier.

CONSTITUTION: A high output is applied from a microcomputer 11 to the base of the second transistor 6, the transistor 6 is interrupted, and a loudness control terminal 2 is connected to a reference voltage terminal 3. At this time, a loudness boosting amount is made minimum. The low output of the microcomputer 11 releases the operational striction of a selective circuit by a diode 10, the potential of a volume terminal 1 is applied through transistor 5 and 6 to a loudness control terminal 2, and loudness boost can be obtained corresponding to the potential of the volume control terminal 1.