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 sound experience The boards all come with onboard antennas, and the normal distance is 10-15 meters. An external antenna will only be used if it is installed in a metal casing (which will block the signal) or increases the Bluetooth distance (20-30 meters). (You need to weld the antenna base yourself) 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, 4; 55W@30V, 8. Subwoofer-208W@30V, 2; 105W@30V, 4. 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. Product size: 121x100x25mm Note: The delivery does not include power supply and audio cable. Colour:Black Material:PCB Package Contents: 1 x Amplifier board 1 x Antenna((You need to weld the antenna base yourself) 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.