Techniques for providing multiple power supplies in electronic devices are disclosed. According to one aspect of the present invention, an appropriate power supply is provided only to accommodate a volume setting. In other words, there are at least two power supplies, one with a low voltage and the other with a high voltage. The high voltage power supply is only applied when there is a need to accommodate a volume setting. Thus the power consumption of the amplifiers is well controlled. As a result, the designs of the device and heat dissipation therein can be simplified and lowered in cost.