[Mini hifi headphone amplifier] exquisite, compact, , portable and easy to carry [3.5mm aux input and output] 3.5mm aux input and output, signal-to-noise ratio 120 dB and + n 0.0003%, not only output louder, more realistic stereo, without distortion. [aluminum matte ] the fashionable design provides you with a comfortable hand-held feeling, and the aluminum matte makes it [wide and small] it can be significantly compatible with a variety of digital devices, such as MP3, MP4, mobile phone and computer (Note: it is not recommended to use when charging, because current interference occur during charging, which may lead to noise) Type: Headphone amplifier color:Black Material:Aluminum alloy size:11.2 x 6.2 x 1.1cm Package Contents: 1 x host 1 x 3.5mm audio cable 1 x USB cable Only the above package content, other products are not included. Note: Light reflection 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.