Description 1: Classic appearance, increase the high-end experience of the encoder, increase the mid-range adjustment, and fully cover the subwoofer, mid-range and 2: APP has a timer shutdown function 3: One-key on/off, no need to long press and wait to see the indicator light 4: [input ] AUX+Bluetooth+U disk+USB sound card 5: Input anti-reverse connection, overheating, overcurrent, short circuit protection [Product Name] 2.1 Channel Bluetooth Audio Power Amplifier Board Module [Product Model]-MT21S [Number of channels] 2.1 channels (left channel + right channel + subwoofer) [Input ] AUX+Bluetooth+U disk+USB sound card [Bluetooth version]5.1 [Switch mode]Mechanical switch (no need to wait for a long press) [Power supply by adapter]DC12-24V , 8A [Adapted speakers] Left and right channels 20-50W, 4-8ohm subwoofer 20-100w, 4-8ohm [Output power] Left and right channels less than 50W, subwoofer less than 100w [Protection mechanism] Input anti-reverse connection, overheating, overcurrent, short circuit protection [Product size]93x96x22mm Tip: Only when the audio signal input is enough and the power supply voltage/current is enough, will there be enough output power! The higher the power supply voltage, the greater the output power, the smaller the speaker impedance, the greater the output power! make that the power of the adapted power supply is the actual working power of the power amplifier! Colour:black Material:ABS Package Contents: 1 x Amplifier Board 1 x Screwdriver 1 x Terminal Only the above package content, other products are not included. Note: Light 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.