The rated working voltage 2.5-5V, limit operating voltage 5.5V. Excellent noise suppression. in the absence of contact input audio, you will not hear any noise even put your ear close to the speaker The two-channel stereo, 5V power supply can output 5W + 5W power, directly drive 4, 8 speakers, output power, full of energy, good sound quality, with left and right channel volume adjustment. unique non-LC filter Class-D digital power board, it can be used directly for the USB-powered from computers. Volume: 23 * 24MM