Usage Tips:Features: 1. Mini HiFi headphone amplifier, It is delicate, compact, lightweight, and portable that it can be carry conveniently. 2. 3.5mm AUX input and output, make it possibility to output not just louder sound, but a sharper and more real stereo sound without distortion. 3. Two-stage gain switch enhances the signal input into the amp circuit for optimal performance of the headphones. 4. Rechargeable lithium battery, it adopts a rechargeable lithium battery with 1000mAH capacity, which allows it to stay working more than 8 Hours. 5. Universal compatibility, it can remarkably compatible with a various of digital devices, such as MP3 MP4 mobile phone computer. Specifications: Product name: Headphone amplifier Product color: Black Input/output port: 3.5mm audio port Distortion: 0.004% Signal-to-noise ratio: ≥120dB Load impedance: 160-300Ω Frequency response: 20Hz-20KHz (±3dB) Lithium Battery Capacity: 1000mAH Amp Using Time: More Than 8 Hours Size: 9.5 x 6 x 1.5cm(L x W x H) Package included 1 x Headphone Amplifier 1 x USB Power Cable 1 x Audio Cable 1 x User's Manual