Ultra-compact stereo headphone amplifier for studio and stage application.  With 4 headphone output channels and 1 input channel.  Volume of each output channel can be controlled independently.  Provides highest audio quality for each headphone even at maximum volume.  Ultra low noise 4580 operational amplifier for outstanding audio performance.  Comes with a DC 12V power adapter.  Input Type:LINE IN (AUDIO IN)  Output Type:LINE OUT (AUDIO OUT)  Built-in Battery:No  Recommended Headphone Maximum Impedance:65-80 Ohm  Type:Mini Amplifier  Model Number:HA400  Bluetooth:No  WIFI:No  Power Adapter:EU Plug  Plug Type:EU Plug,it applies to Indonesia,Germany,France,Spain,Italy and so on.  Item Size:Approx.10.5 * 5.5 * 4.5cm/4.1 * 2.2 * 1.8 inch  Item Weight:185g/6.5oz  Package Size:22.5 * 14 * 8.5cm/8.9 * 5.5 * 3.3 inch  Package Weight:385g/13.6oz  Colour:Black   material:metal  Package Contents:  1* amplifier  1* power adapter  1* English manual  Only the above package content, other products are not included.  Note: Light shooting 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.