Product Features: Built-in high capacity battery Support charging overvoltage protection Support high and low impedance earphone switch Support 16~600 Ω impedance earphone Support output volume adjustment and bass adjustment Support one 3.5mm headphone port and one 3.5mm input port Support Bluetooth connection Type-c port for charging Aluminum alloy material, full of texture Product Specifications: Input port: 3.5mm(TRS) Headphone port: 3.5mm(TRS) Charging port: Type-c Bluetooth Version: BT 5.0 Built-in battery: 3.7V/1400mA Charging voltage: 5V/500mA Standby power: 38mA Maximum working current: 250mA Duration: ≥6 hours 16Ωheaphone power: 110 mW 32Ωheaphone power: 105 mW 150Ωheaphone power: 6 5mW 300Ωheaphone power: 35 mW 600Ωheaphone power: 20 mW Maximum output -p: 9.9Vp-p +N: 0.02% Signal to noise ratio: 100db Frequency response: 20hz~20Khz talk: 100db Sound balance: 0.3db Working environment temperature: -20 to +60℃ Material: Metal colour: Black Package Contents: 1 x HIFI Headphone Amplifier 1 x 3.5mm Audio Cable 1 x Charging Cable 1 x English User Manual Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.