Features: Dual channel input, subwoofer output, then the output amplifier,can not directly connected to the speaker The multi-stage filter, better bass effect Specifications: Phase Adjustment: 0; 180 Power supply voltage: DC 9V-32V DC single power supply The phase adjustable Potentiometer from left to right: frequency adjustment, bass volume control The cut-off frequency: 22HZ-240HZ Potentiometer shaft center to center spacing: 3cm Special note: This board is a preamp board, and is not designed to be directly connected to the speaker. It must be connected to the subsequent stage of an amplifier board for this pre-amp to work. The so-called low-pass filter to filter out the human voice board is more than treble part, retain the low frequency part is amplified to improve the bass reproduction efforts, people will not hear the sound of musical instruments and high-frequency sound during playback. The buyer must understand knowledge of this area. PCB size: 6.1*2.6cm/2.40*1.02inch No Retail Packages Quantity: 1Set Note: Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you Package include: 1 * Module 1 * Cable