This is a personal in-ear monitor headphone amplifier that can be used or in the studio, to provide performers and recording artists with a flexible, convenient personal monitoring solution.The dual XLR inputs allow 2-channel, mono or stereo operation with a convenient mix function which allows you to run two sources into it. High-powered headphone output with limiter protects your ears; loud enough for drummers Level and Balance/Mix controlsTwo simple controls,Level and Balance, help you achieve the perfect mix in an instant. Intended for drummers and other performers, the unit features a high-power headphone output that helps to that as the band gets louder, you'll still be to hear your performance.The unit runs up to 12 hours on a 9V battery (not included) or can be powered by 9V DC power supply( -PIN +RING).Personal In-Ear Monitor Headphone Amplifier for: Drummers Keyboardist Guitar player Vocalist Bass player Every Musicians that is not moving around the stage can use it. Specification: Model Number: S1 Recommended Headphone Color: Black Material: Plastic Maximum Impedance: 32-50 Ohm Built-in Battery: No Output Type: Balanced Out Input Type: XLR Power Switch: Switches the unit on and off XLR INPUTS (L) and (R): Dual XLR balanced jacks connect to the input signal source 9V DC Socket: Please use the included 9V 300mA adapter. Battery control with dual LED indicators Controls for Level and Balance Operates with 9V Battery or included AC/DC adapter Plug Type:EU Plug,it applies to Indonesia, Germany, France, Spain, Italy and so on Voltage: AC 220V Package Contents: 1* Headphone Amplifier 1* Power Adapter 1* 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.