Note: 1. This board is a subwoofer preamp board. No sound is produced when directly connected to speakers. It must be connected to a pure final amplifier board to make an active subwoofer. The power of the pure power amplifier board is shocking according to individual needs. The degree of selection, the higher the power of the pure final amplifier, the more shocking the bass effect. The so called low pass filter board filters out the high pitched part above the human voice, retains the low frequency part and amplifies the bass playback strength, and cannot hear the human voice and high frequency musical instruments during the playback process. Buyers must be aware of this and avoid using it without knowing how to use it._x000D_2. Components may vary slightly from batch to batch, but functional performance remains the same. Specification: Item Type: Preamp Board_x000D_Material: PCB_x000D_Input: DC12V_x000D_Frequency Range: 22Hz-300Hz_x000D_Sound Input: Mono or Binaural_x000D_Sound Output: Mono Features: 1Op Amp Replacement: The IC mount of the preamp board can be welded and replaced at any time to improve the effect of different op amps. 2LED Indicators: Subwoofer preamplifier board is designed with LED indicators to facilitate real time monitoring of the power status. 3Anti Interference: PCB pre amplifier board, so that the board has a very high signal to noise ratio and strong anti interference ability. 4Low Noise: Professional subwoofer low pass filter board, when there is no signal input, there is almost no noise near the speaker. 5Easy To Use: The design of the subwoofer pre board is simple and beautiful, the wiring is reasonable, and it can be used after wiring. PackageList: 1 x_x000D__x000D_PreampBoard 2 x Nut 2 x Gasket 2 x Knob Cover