This power amplifier is compact, easy to carry, and simple to use, dual channel stereo sound, without compromising sound quality.   Knob usage instructions: Rotation: Adjust the volumelevel. Click: Pause/Playing. Double click: NextSong. Three strikes: Switch playback mode (BT/AUX/U disk). Long press: Turn on/off.   Specifications: Color: black, red (optional) Material: aluminum alloy BT: 5.1 Output power: 2*10W@8Ω/12Volt, 2*30W@8Ω/24Volt, 2*50W@4Ω/21Volt, 2*100W@2Ω/21Volt PowerSupply: DC9-24Volt/5A above Remote battery: 1 * CR2025, 3V, 150mAh Item size: 78 * 52 * 35mm / 3.1 * 2.0 * 1.4in Item weight: 110g / 3.9ounce Package size: 150 * 90 * 70mm / 5.9 * 3.5 * 2.8in Package weight: 250g / 8.8ounce   Package List: 1 * Power Amplifier Main Board 1 * 3.5mm AUX Cable 1 * RCA to AUX Cable 1 * Remote Controller Multiple audio input methods: BT, AUX and U disk. Supports BT wireless connection. Aluminum alloy oxidation process, rust proof, lightweight and practical. It can be controlled through the mobilephone app, the knob and the Infrared remote controller(included), making the operation more convenient and quick. Comapct size for easy carrying.