Features: This digital power amplifier board with high-fidelity and two-channel stereo sound quality; input voltage is DC9~24V, audio input supports Bluetooth-compatible, AUX , USB, it can be directly connected to mobilephone etc. If you are tired of power amplifiers with only a single volume knob, then you feel right, because you have further requirements for audio. By adjusting the high and low frequency knob of ZK-LT23, you can make the sound more layered. Safety Protection: Circuit for Protection, Over-voltage and Under-voltage for Protection. Bluetooth-compatible 5.1 version, Transmission Distance Is Farther. The Transmission Distance Can Reach 33 Feet In An Open Environment. You can directly use wireless bluetooth-compatible connection, or choose 3.5mm earphones (wire plug way) Package Includes: 1x Subwoofer Amplifier Board Specifications: Max Output Power: 2x 50W+100W Power Supply: DC9~24V Channels: 2.1 Output Impedance: 4~8ohm Working Type: Class D Audio Input: AUX / Bluetooth-compatible 5.1 Size:Approx.75x70x20mm/2.95''x2.76''x0.79'' note: Please allow 1mm errors due to manual measurement. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.