With high power Class-D audio amplifiers, layout is often critical for achieving maximum power and optimal performance. For this reason, a ground plane on two layers is recommended to provide a solid ground reference for the amplifier and to minimize ground voltage differentials across the die of the monolithic amplifier. However, as found with the TPA32xx family of amplifiers, referencing the analog input grounds directly to the ground plane can cause issues, especially when using single ended op-amps.
This applications report discusses the grounding recommendations for analog inputs only. It is always recommended to use a ground plane for high power and switching nodes with all Class-D amplifiers.