The datasheet provides a specific pin configuration (25-pin SIP). Unlike discrete transistor amps, misreading pin 1 on an STK module means instant destruction.
The shift power supply is a form of Class H operation. The IC monitors the input audio signal and switches the voltage supplied to the power transistors between two (or more) levels. When the signal is low, the supply voltage is reduced, saving power. When a high‑amplitude peak occurs, the supply is switched to a higher voltage, allowing the amplifier to deliver maximum power cleanly. This technique significantly improves efficiency without sacrificing audio quality. stk412530 datasheet
This is the most important step during installation. The datasheet provides a specific pin configuration (25-pin