HiFi Headphone Amplifier - It supports most headphones of high impedance 16-300, 3.5mm AUX Input and Output, signal-to-noise ratio> 100Db, THD + N = 0.0003%, fully filter noise, enjoy high-quality audio Two-stage Gain Switch- This Headphone Amp enhances the signal input into the amp circuit for the optimal performance of the headphones. Make it Possibility to output not only louder sound but a sharper and more Real stereo sound without distortion Rechargable Lithium Battery- It adopts a rechargeable lithium battery with 2000mAH capacity, which allows the headphone amp to stay working more than 12-15h. Plus, there is a volume control knob for volume adjustment Portable and Lightweight - This headphone amp is designed to enhance your music listening experience wherever life takes you; A sleek, sturdy shell and chassis allow for a robust use Broad Compatibility- This amplifier is remarkably compatible with a variety of digital devices, such as MP3, MP4,