Supports Bluetooth 5.1 connectivity Classic mechanical switch, a turn on/off without long press wait. Over-temperature and short-circuit protection against static electricity Support BT, AUX, U disk, USB sound card input With heat sink Audio Input: AUX+ Bluetooth+U disk + USB sound card Channel: 2.0 (stereo) Power Range: DC9-24V/4A above (high power recommended high voltage) Adapter Speaker: 20W-100W, 4-8 ohm Protection Mechanism: overvoltage, undervoltage, overheating, DC detection, short circuit protection PS: In the audio input is enough, the supply voltage/current is enough, there will be enough output power! The higher the supply voltage, the greater the output power. The smaller the impedance of the speaker, the greater the output power! Please that the power of the adaptor is the actual working power of the amplifier Type: Subwoofer Amplifier Board Batch differences may lead to product appearance, text, color will be different, does not affect the use of Note: Recommended with 8Q speakers, power supply 9-24VDC, not over voltage, if driving 4Q speakers, the power supply can not exceed 12V. Color: Black Material: PCB+metal Package Contents: 1 x amplifier board (need to install themselves) 1 x screwdriver 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.