Plural variable gain amplifiers amplify audio signals of plural channels for each channel. An interface receives, from outside, plural gain control data individually designating gain of each channel. Plural gain controllers respectively switch the gain of the plural variable gain amplifiers, based on the plural gain control data. The plural gain controllers arrange timing to change gain of a variable gain amplifier corresponding to gain control data received in a predetermined data entry period, among the plural gain control data that are inputted at different timing.