Built-in high capacity battery Support charging over voltage protection Support high and low impedance earphone switch Support 16-600 Ω impedance earphone Support output volume adjustment and bass adjustment Introduction: This is built-in battery portable HIFI headphone amplifier,which support charging and adjusting volume and bass.Using 3.5mm cable connect it to your PC,smartphone and game console, etc.It can connect to Bluetooth devices. It used to improve the volume and sound quality of headphones. Support one 3.5mm headphone port and one 3.5mm input port Support Bluetooth connection Type-c port for charging Specifications: Input port:3.5mm(TRS) Headphone port:3.5mm(TRS) Charging port:Type-c Bluetooth-Compatible Version:BT 5.0 Built-in battery:3.7V/1400mA Charging voltage:5V/500mA Standby power:38mA Maximum working current:250mA Duration: equal 6 hours 16Ω heaphone power:110 mW 32Ω heaphone power:105 mW 150Ω heaphone power:6 5mW 300Ω heaphone power:35 mW 600Ω heaphone 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 Color:Black Material:Metal Package Contents: 1 * Earphone Audio Amplifier 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.