The voltage ripple on the negative rail (PVSS) is characteristic to this part and will have minimal impact on the output signal quality. The THD+N was measured to be 0.51% on the MAX98307EVKIT for an output power of 2.95W at a 1kHz tone. PVDD was set to 5V and the load consisted of a series inductor (68uH) and resistor (8Ω). The output THD+N was measured across the 8Ω load resistor using differential scope probes.