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. Model: HA400 Input Channels: 1 Input Output Channels: 4 Output Analog Inputs: 1 x Stereo Analog Outputs: 4 x Controls per Channel: Volume Form Factor: Desktop Dimension (W x D x H): 10.5x5.8x3.3cm Voltage: AC110V Colour:black+white Material:Metal Package Contents: 1 x Amplifier 1 x Adapter Only the above package content, other are not included. Note: Light reflection and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.