[Product parameters]: 4 Euro 2x5W [Power interface]: Micro-5p (reserved 2.5mm welding port) [Input voltage]: 3.7V-5V [Amplifier working mode]: switchable class AB and class D [Signal to noise ratio]: 90DB [THD+N:-70DB crosstalk]:-86db Colour: Black material: plastic DNR: 91db [Output Interface]: Speaker output port x 2 groups (one group for left and right channels), it is recommended to connect 4 ohm 5W-50W power speakers to use Users can freely switch between CLASS AB or CLASS D working modes according to sound preference and power collocation. [Features]: The power switch and the volume knob are integrated. When the sound is adjusted to the minimum, turn it counterclockwise. When you hear a clicking sound, it is turned off. Turn clockwise to turn it on. Powered by Micro-5p interface, ordinary mobile phone charger 5V2A charging cable can be used. [Product Usage]: Can connect the audio signal of mobile phone, laptop and tablet to the output of stereo power amplifier through 3.5mm audio cable Package Contents: 1 x Amplifier Board 1 x USB Cable 1 x Audio Cable Only the above package content, other products are not included. Note: Light shooting 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.