Feature:1. [Two Stage Gain Switch] Headphone amplifier with high and low gain switch for premium headphone performance. Plug and play, easy and fast to use.2. [3.5mm AUX Input And Output] Load impedance 16 to 600. Not only for larger sound, but also for clearer, more lifelike stereo sound without distortion.3. [Aluminum Alloy Material] Stylish design of the headphone amplifier provides a comfortable handheld feel, while the brushed aluminum surface makes it durable.4. [Rechargeable] The headset amplifier is powered by a rechargeable lithium battery with a capacity of 1080mAh, giving it a working time of over 8 hours.5. [Compatible] This headset amplifier is perfectly compatible with a wide range of digital devices such as MP3, MP4, mobile phones and computers.Specification:Item Type: Headphone AmplifierMaterial: Aluminum AlloyColor: BlackBattery Type: Built in 1080mAh Lithium Battery (Included)Input: 3.5mm/0.1inOutput: 3.5mm/0.1inHeadphone Impedance: 16-600SNR: -120dBDistortion: 0.00022%Applicable Devices: Perfectly Compatible with MP3, MP4, Mobile Phones, Computers and Many Other Digital Devices.Package List:1 x Headphone Amplifier1 x Sound Cable1 x Data CableNote:It is not recommended to use it while charging, as charging will produce current interference and may generate noise.