Feature: 1. Op 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. 2. LED Indicators: Subwoofer preamplifier board is designed with LED indicators to facilitate real time monitoring of the power status. 3. Anti Interference: PCB pre amplifier board, so that the board has a very high signal to noise ratio and strong anti interference ability. 4. Low Noise: Professional subwoofer low pass filter board, when there is no signal input, there is almost no noise near the speaker. 5. Easy To Use: The design of the subwoofer pre board is simple and beautiful, the wiring is reasonable, and it can be used after wiring. Specification: Item Type: Preamp Board Material: PCB Input: DC12V Frequency Range: 22Hz-300Hz Sound Input: Mono or Binaural Sound Output: Mono. Package List: 1 x Preamp Board2 x Nut2 x Gasket2 x Knob Cover 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.2. Components may vary slightly from batch to batch, but functional performance remains the same.