Features: Brand new and high quality The board can mainly filter out the high-frequency part of the power amplifier, so as to retain the low-frequency part and enlarge it to improve the bass playback strength. When the user connects the board to the pure power amplifier, it can change the pure power amplifier board to a subwoofer. The board itself has low frequency and volume adjustment, and provides an additional high-level interface for audiophiles, which is convenient for audiophiles and audio hobbies. Dual potentiometer: low frequency strength adjustment, volume adjustment. DIY various power amplifier boards. Specifications: Working voltage: DC-12V Audio output: mono Audio input: mono or dual Op amp chip: JAC4558x2 Frequency range: 22Hz-300Hz Note: Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package includes: 1PC x Subwoofer Amplifier Board