About this item: 【Mini HiFi Headphone Amplifier】It's A Cost-effective Gadget to Improve Sound Quality. It is Delicate, Compact, Lightweight, and Portable that it can be Carry Conveniently【3.5mm AUX Input and Output】3.5mm AUX Input and Output, SNR>100Db and THD+N 0.0003%, Make it Possibility to Output not just Louder Sound, but a Sharper and More Real Stereo Sound without Distortion【Aluminum Matte Surface】Fashion Design Provides You a Comfortable Handheld Feeling While the Aluminum Matte Surface Makes it Durable【Rechargable Lithium Battery】It Adopts a Rechargable Lithium Battery with 2000mAH Capacity, Which Allows it to Stay Working More than 8 Hours【Universal Compacity】It can Remarkably Compatible with a Various of Digital Devices, Such as MP3 MP4 Mobile Phone Computer Overview:This HiFi Headphone Amplifier supports impedance 16-150 Ω, Delicate, Compact and Portable, Which Make it Convenient to Carry, Can Output Remarkable Sound without Distortion. 3.5mm AUX Input and OutputHigh Quality Audio, Suitable for your Mobile Phone MP3 MP4 Laptop PCNoise Reduction Function, and Distortion with Enhanced Dynamics, Perfect Pure Stereo Effect, HD Voice Music Sound Quality OptimizationAluminum Matte Surface, Fashion and Compact DesignNot only suit for music enthusiast, also could be a ideal gift for those who has trouble hearing. Troubleshooting Q: Why there is an buzzing/hissing sound? A: Please don't use it while charging because current disturbance will occur when in charging. That's why there is noise. When fully charged, please disconnect the power supply, and then use the headphone amplifier. Q: This amp doesn't amp high enough for my bigger headphones, and why? A: This headphone amp supports headphones with 16-150 ohm impedance. Please check the impedance of your headphone. Charged by Micro USB Cable Tips: come with a USB Power Cable, adapter is NOT included. You could use 5V 1A adapter of your mobile phone or tablet to connect USB cable. Two-stage gain switch: L/H Enhances the signal input into the amp circuit for optimal performance of the headphones. 16Ω L: 90mw H: 105mw 32Ω L: 74mw H: 80mw 64Ω L: 45mw H: 50mw 150Ω L: 26mw H: 32mw Technical Specifications: Input/Output Port: 3.5mm Audio Port Distortion: 0.004% SNR: ≥120dB Load impedance: 16-150Ω Max. Power output: 250mW in Impedance 16Ω Amp Internal Voltage: ±4V Charging voltage: DC 5V Frequency response: 20Hz-20kHz(±3dB) Lithium-Battery capacity: 1500mAh Amp Using Time: about 8 Hours Dimension: 3.8 x 2.4 x 0.6inch Net weight: 102g Q&A: Q:Can this amp be used with a microphone? A:Please check item do not support microphones. Q&A:Q:Simple instructions for use A:Please check whether the audio cable is connected well to the amp interface,and fully charged the Q:Can this item work my Television set? A:Sorry it can not. Package List: 1 x USB Power Cable 1 x 3.5mm Headphone Amplifier 1 x Audio Cable 1 x User Manual