Description 1. High current, low magnetic loss, small parasitic capacitance, low heat generation, use of oxygen free copper wire to improve sound quality; The magnetic shielding mechanism has strong anti electromagnetic interference EMI performance. 2. Thickened heat sink, silent and long-life fan; Solved the heat dissipation problem and better utilized the advantages of high power 3. Transparent sound, fast low-frequency response, strong mid frequency texture, high frequency smoothness, and minimal loss 4. Extremely low noise, quality, extremely low distortion, protecting your for original-sound experience 5. Protection mechanism: Input undervoltage, overheating, overcurrent, short circuit protection. No input anti reverse protection, positive and negative poles cannot be reversed! Product name:2.1 channel Bluetooth power amplifier board 100W+100W+200W Product model:-ST21 Adaptable power supply: Working voltage range 12-30VDC, recommended voltage 24V-28V, DC power supply with current 10A or above. Maximum power: left or right channel - 105W@30V, 4ohm; 55W@30V, 8ohm. Subwoofer-208W@30V, 2ohm; 105W@30V, 4ohm. In short, the higher the voltage, the smaller the resistance, and the greater the output power. Compatible speakers: The left and right channels support speakers of 3-8 ohms and within 100W; The subwoofer supports speakers with 2-8 ohms and within 200W. Bluetooth chip: 5.1, transmission distance 15 meters Input :Bluetooth + AUX + U disk + sound card Number of channels:2.1, left channel + right channel + subwoofer Power amplifier chip:two TI TPA3221 Protection mechanism:input undervoltage, input anti-reverse connection, overheating, overcurrent, short circuit protection. Note:Need to assemble by yourself ,The delivery does not include power supply and audio cable. Colour:Black Material:PCB Size:121x100x25mm Package Contents: 1 * Amplifier board(With case) 1 * 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.