Under the control of a controller, a DSP supplies audio signals received from a switch circuit to a main zone DAC, subjects the audio signals received from the aforementioned switch circuit (i.e., audio signals for main zone use) to down-mixing processing so that the number of channels matches the number of output terminals assigned to each zone, and respectively supplies the audio signals subjected to down-mixing processing to the respective switch circuits of each zone. Each of the aforementioned switch circuits supplies the audio signals received from the subzone DAC to the respective volume adjustor of each zone.