Description: 100% brand new and high quality! This board is a heavy bass preamp board. It will not sound when connected directly to the horn. It must be connected to a pure final stage power amplifier board to make an active subwoofer. The power of the pure final stage power amplifier board is selected according to the degree of shock of the individual needs. The higher the power of the pure final stage power amplifier, the more shocking the bass effect is. The so-called low-pass filter board filters out the high-pitched parts above the human voice, and retains the low-frequency part to zoom in to improve the bass playback strength, and does not hear human voices and high-frequency instrument sounds during playback. The input and output terminals are made of pure copper terminals, and the wiring is very convenient. Soldering the IC holder can change the op amps at any time, and feel the effect brought by different op amps to improve the playability. Designed with LED indicators to monitor power conditions in real time. Simple and beautiful, the wiring is reasonable, which makes the board have a very high signal-to-noise ratio and strong anti-interference ability. There is almost no noise near the horn when there is no signal input. Specifications: Item type: Preamp Board Material: FR-4 fiberglass board Power supply voltage: DC10-24V single power supply DC Frequency range: 22Hz-300Hz Audio input: mono or dual channel Audio output: mono Size: 78x32mm thickness: 1.6mm Plate fixing hole center spacing: 70x24mm Hole diameter: 3.2mm Potentiometer shaft center spacing: 32.5mm Package includes: 1 x Low-Pass Filter Plate Subwoofer Preamp Board Notes:  Transition: 1cm=10mm=0.39inch  1. Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you!  2. Please allow 1-3cm measuring deviation due to manual measurement.