The board can mainly filter out the high-pitched part of the power amplifier, thereby retaining the low-frequency part for amplification to improve the bass reproduction strength. When the user connects the board to a pure power amplifier, it can change the pure power amplifier board to a subwoofer. The board itself has both low frequency and volume adjustment, and additionally provides high-level interfaces for audiophiles, which is convenient for audiophiles and audio hobbies DIY various power amplifier boards.