Built-in active amplifier. USB bus-powered capability, no adapter required. Conveniently powered via with USB cable. Easily control volume with VOC on the back.

Specifications
Power output: 2 Speakers: 3W each (6W total) RMS
Speaker:4 Omh 3W.
Input sensitivity: 400mV
Distortion: 0.2 %( 1W 1KHZ)
Frequency response: 150Hz-20KHZ
Separation:78dB
S/N Ratio: 80dB
3.5mm audio output jack
Power Voltage: USB/DC 5V
Optional external power supply (DC5V-1.2A)
Accessories: USB cable, audio cable