Features: Simple and compact design, but practical and powerful. The all aluminum body has been carefully designed and processed, making it compact and classical. precisions volume knob, easy to use. It has a switchs for adjusting gains and another switchs for fine tuningS the bass level. Meet the needs of bass enthusiasts. The low-pass filter on the lineS output is processed by the OPT1656 chip. Good fideliies stereo headphone amplifier and 3.5mm input/outputjacks for streaming good fidelities music to the stereo system. Improved performances headphone driver and circuit protections. 2200mAh internal battery power supply, can be used for up to 12 hours. Load impedance: 16-300. Output excellent sound without distortion. Suitable for people who love music, such as students, office workers, traveler, etc. Can be used for home entertainment, office learning, travel and leisure scenarios, etc. Specifications: Material: aluminum alloy Size: approx 90x50x12mm/3.5x2x0.5inch Input : blue teeth/AUX Output: 3.5mm earphone Chip: OPT1656 Note: Please allow 1 to 3cm error due to manual measurement, please make sure you do not mind before you bid, Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 1xHeadphone Amplifier