The invention relates to a power device applied to an audio system and the audio system, wherein, the device is a power device which is applicable to improving electricity use efficiency of an audio device. The power device of the audio device provided by the invention comprises a first rectifying-voltage stabilizing device which generates first DC voltage from AC voltage, a main switch device used for controlling the first DC voltage, a second rectifying-voltage stabilizing device which generate second DC voltage provided for the audio device by rectifying and stabilizing the voltage controlled by the switch, an volume regulating switch used for regulating the volume, a reference voltage generating module used for generating the reference voltage, an error voltage detecting device which provides a difference between the second current voltage and the reference voltage to the main switch device, and a controlling device used for responding to the volume regulating switch to change thelevel of the reference voltage generated on a reference voltage generating part. The invention can enhance the efficiency in utilizing electricity.