KNACRO DC 10V-24V Low-Pass Filter NE5532 Bass Tone Subwoofer Pre-Amplifier Preamp Board Adjust the potentiometer selected Hermetically, inputs and outputs use pure copper terminals, wiring is very convenient. Selected NE5532, welded IC holder can always replace the amplifier, experience different effects to enhance playability. Design of the LED Real-time monitoring the power supply situation. PCB board design simple and beautiful, reasonable wiring, making the board has a very high signal to noise ratio, strong anti-interference ability. when no signal input close to the speaker almost hear the noise.