Abstract: A playback device including a processor that executes program instructions such that the playback device is configured to receive first audio data representing audio content, generate and output second audio data based on the first audio data, and at least in part while generating and outputting the second audio data, generate and output a control signal associated with the second audio data to vary a supply voltage for an audio amplifier. The playback device also includes a switch-mode power supply (SMPS) that varies the supply voltage for the audio amplifier based on the control signal. The playback device also includes an amplifier circuitry comprising the audio amplifier powered by the supply voltage from the SMPS. The amplifier circuitry is configured to receive the second audio data and generate an analog audio signal to drive a speaker based on the second audio data.