Using the Behringer HA400 is easy. First, connect your audio source to the amplifier. Then, plug in up to 4 pairs of headphones into the corresponding jacks. Each person can adjust the volume of their headphones using the Phones Level control for their channel. When using the amplifier, make sure to use the included DC 12 V adapter to power it. Avoid exposing the amplifier to extreme temperatures or moisture. To keep it in good condition, clean it regularly with a soft, dry cloth. If you encounter any problems, refer to the user manual or contact Behringer's customer support.