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 to the appropriate setting to listen to the appropriate volumes. Colour:Black Material:plastic+metal Package Contents: 1x 3.5mm Headphone Amplifier 1x XLAConnecor 1x English 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.