2.0, 3.5mm Aux in, USB powered,Class D amplifier, 50% higher power efficiency,Max 2W / Ch,Volume control, ... sound. The speakers make use of the high efficiency of class D amplifiers to present excellent sound quality.Specification:Power output: RMS ... class D amplifiers to present excellent sound quality. Specifications Drivers: 1.5", 4ΩInput impedance: 10 kΩAudio input: Stereo 3.5 mm audio ...