Overview This earphone phone amplifier is made of aluminum alloy casing, which is comfortable to handle and has good heat dissipation performance. The appearance is compact and easy to carry, with a 3.5mm input and output interface, suitable for connecting all kinds of smartphone computer equipment. Features: Using aluminum alloy shell, feel comfortable, good heat dissipation. The appearance is small and atmospheric, easy to carry. There is an independent gain control switch. The operational amplifier is suitable for both positive and negative power supplies. With 3.5mm input and output interface, suitable for connection of various types of smartphone computer equipment. Built-in 600mAh rechargeable lithium battery, low power consumption, working time is about 8 hours. Specifications: Input / Output Port: 3.5mm Studio input Lithium Battery Capacity: 600mAh Amplifier Usage Time: 8 hours Working Voltage: DC3.7-4.2V Charge Voltage: DC5V SNR: more than 116db Distortion: 0.001% Output power: 32 Ohm 130mW Load Impedance: 16-300 Ohm Frequency Range: 20Hz-20kHz(+/-3db) Item Size: 10*6.2*1.5cm / 3.94*2.44*0.59in Package Size: 13*8*4cm / 5.12*3.15*1.57in Package Weight: 132g / 4.66oz Package List 1 * Headset Amplifier 1 * USB Power Cable 1 * User Manual Notes: There is a battery inside the machine, please do not open it privately. Please do not use the machine at a high temperature and humidity environment.