Features:1. The adjustment potentiometer is made of fully sealed type, and the input and output ends are made of pure copper terminals. The wiring is very convenient.2. The IC holder can be soldered at any time to feel the effect of different op amps and enhance the playability.3. Designed with LED indicators to monitor power state in real time.4. The board is simple and beautiful in design, and the wiring is reasonable, which makes the board have a very high signal to noise ratio.5. This board has strong anti-interference ability. There is almost no noise near the horn when there is no signal input. Specification:Condition: Brand newFrequency Range: 22Hz-300HzAudio Input: Mono or dual channelAudio Output: MonoPrinted Circuit Board Standard: Approx. 78 x 32mm / 3.1 x 1.3in, Thickness: 1.6mmPrinted Circuit Board Material: Super hardness FR-4 fiberglass boardPlate Fixing Hole Center Spacing: 70x24mm, Hole Diameter: 3.2mmPotentiometer Shaft Center Distance: 32.5mmWeight: Approx. 32g / 1.1ozPackage List:1 x Filter Board2 x Screw2 x Gasket2 x Knob CapNote:This board is a heavy bass preamp board. It will not sound when directly connected 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 shock level of individual needs. The higher the power of the pure final stage amplifier, the more shocking the bass effect will be. 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..