Fangrui Product Details No Power Required, Plug And Use:it Can Be Used Just By Connecting It To The Device Interfaces. No External Power Supply Is Required, And The Operation Is Simple. High/low Gain Switcher For Optimal Performances Of The Headphones. Thexlr Input Connection Features A Locking Mechanism To Prevent Accidental Cable Disconnection. Simply The Tab Next To The Bottom Mount Connector To Release The Cable At . Standard 3.5mm Headphone Output Port:the Metal 3.5mm Headphone Output Interfaces Can Easily Regular Earplugs Or Professional Monitoring Headphones, Giving You A Clear Music Experience. Usage: 1.please Keep The Volumes Control Of The Headset And Plaver To A Minimum Before Connecting.the Input Plug Of The Headset Volumes Controller To The Output Of The Player. 3.connect The Headphone Plug To The Output Socket Of The Headset Volumes Controller. (if You Use A Headset Other Than A 3.5mm Stereo Mini Plug,be Sure To Configure The Appropriate Adapter.) 4.adiust The Volumes Of The Player And Headset Volumes Controller T