Patent ID: 8130982

Claim:
A signal amplifying apparatus comprising: a voltage amplifier that amplifies voltage of an input audio signal, outputs the amplified audio signal and limits the maximum amplitude of the output signal based on power feed voltage; a power amplifier that amplifies power of the audio signal subjected to the voltage amplification by the voltage amplifier; a power supply that feeds power into the voltage amplifier and the power amplifier; a control signal generator that generates a voltage control signal indicating magnitude of voltage; a voltage value determination unit that determines a voltage value based on the voltage control signal generated by the control signal generator and if the voltage control signal indicates a predetermined value, determines the voltage value to be a non-drive value at which the voltage amplifier enters a non-drive state; and a voltage controller that controls the power feed voltage fed into the voltage amplifier from the power supply so as to be the voltage value determined by the voltage value determination unit by lowering the power feed voltage.