A well‑designed PCB should follow good grounding practices: separate power ground from signal ground, keep input traces short and away from output traces, and provide a solid ground plane when possible.
The STK412-530 requires a split (±) power supply. Due to its Class H architecture, it requires two pairs of supply voltages: a "low" voltage (±VCC_L) for the output stage quiescent bias and normal operation, and a "high" voltage (±VCC_H) that is switched in only when large signal peaks demand more voltage swing. stk412530 datasheet