Tip: Only with sufficient audio input and sufficient power supply voltage/current can there be sufficient output power. Higher power supply voltage result in higher relative power, and speakers with different impedances have different output power. When the voltage and current are sufficient, the larger the number of ohms of the speaker, the smaller the relative sound power. Please note that Due to different batches, there may be differences in product appearance and printed text, which not affect use. 502MT: Bluetooth version: 5.0 (unobstructed 15 meters) Input method: Bluetooth input+AUX input Channel count: around 2.0 channels (stereo) Adapted power supply: DC9-24V/3A or above (cannot be connected to 24V battery pack) Adapted speaker: 15-50W | 4-8 ohm Output power: Left channel less than equal 50W Right channel less than equal 50W Protection mechanism: overcurrent, overheating, short circuit protection 502L: Bluetooth version: 5.0 (unobstructed, 15 meters) Adapted power supply voltage: 5-24V Channel count: Left and right dual channels (stereo) Adapted speaker: 30-200W, 4 ohm, 8 ohm Adapted power supply: DC15-36V (undervoltage protection below 9V, can also support 12V power supply) Power voltage: 12V-8 ohm speaker/12W9 (left channel)+12W (right channel), 4 ohm speaker/20W+20W 15V-8 ohm/18+18W, 4 ohm 30+30W 19V-8 ohm/32+32W, 4 ohm 45+45W, 24V-8 ohm/38+38W, 4 ohm 50+50W Protection system: self recovery overheating protection, self recovery short circuit protection Colour:Black Material:ABS Package Contents: 1 * Amplifier Board kit 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.