A switching audio amplifier and method of operation. The switching audio amplifier comprises a voltage supply selector coupling a power supply input to a first power supply voltage; a switching circuit generating a drive signal for a loudspeaker by modulating the power supply input based on a modulation signal; a pulse generator receiving an audio input signal and outputting the modulation signal based on the audio input signal and the voltage of the power supply input; and a supply voltage monitor. The supply voltage monitor is configured to increase the voltage of the power supply input by causing the voltage supply selector to couple the power supply input to a second power supply voltage responsive to the modulation signal exceeding the first threshold, and the supply voltage monitor preventing the voltage supply selector from reducing the voltage of the power supply input for a first time period.