An audio interface is a device that bridges the connection between your PC, microphones or guitars, and your speakers. You simply connect the USB cable to your PC and your speakers or amplifier to the audio interface through the appropriate outputs (Balanced TRS in the picture below)
Then you select your audio interface as your playback device, and you’re good to go!
Why do I need an audio interface?
If you’re using both a pair of headphones in addition to speakers at your desk, an audio interface is a great way to control everything without having to unplug anything when switching from one playback device to the other. These interfaces usually offer way better pre-amps, DACs, and headphone amplifiers than what is built-in to your PC.
What if I also have an Arendal Subwoofer?
In that case, you would simply connect the audio interface to the subwoofer first, and then connect from the output of the subwoofer to your amplifier that powers the speakers. If the interface only has TRS outputs and the sub only has RCA inputs, using two TRS to RCA adapters will be perfectly fine.
Setup?
If you want to learn more about the setup procedure, please check out this article: 2.1 Desktop setup