The subwoofer power amplifier board uses the disassembled tube and has a very high signal-to-noise ratio. No noise can be heard without plugging the input line.It also has full relay protection,such as power-on delay,DC output,horn short circuit,etc. for DIY installation,and the pre-stage low-frequency processing capability is strong. Can be used with a variety of low speakers,connected to passive speakers can be used. Product Name: TDA7377 2.1 Amplifier Board Chip Type: TDA7377*1 Input Voltage: AC 9-12V DC 12-18V Output Power: 10W*2 + 30W*1 MAX. Channels: Dual channel + 0.1 subwoofer Output Impedance: 4-8 ohms Frequency Response: 20Hz- 20kHz Speaker Recommendations: Left and right channels: 3-5 inch, 4-8 ohms, under 30W; Subwoofer: 4-6.5 inch, 4-8 ohms, under 50W. NE5532 low-frequency processing + TDA7377 amplifier chip, low noise, clear and natural treble, robust and powerful bass. Beautiful design, simple and elegant appearance, no jumpers. Left & Right Channels: Left and right channels recommended: 3-5 inch, 4-8 ohms, 15-30W full-range or high/low frequency combination speakers. Subwoofer Channel: Subwoofer recommended: 4-6.5 inch, 4-8 ohms, 10-50W (The surround should be robust, the magnet large, and the cabinet design very important). Color: As Shown Material: Metal+PCB Package Contents: 1*Amplifier Board Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.