An introduction to computer audio
USB audio is very popular.
One of the reasons is that USB audio is part of the USB standard and as a consequence native mode drivers are available for all the popular OS (Win, OSX and Linux).
Connecting a USB audio device is a matter of plug&play.
Every PC has a USB port
Most amplifiers do not have an USB port.
You need to convert the USB to something your amp understands.
If the amp has a digital input (SPDIF) an USB to SPDIF converter will do the job.
If the amp has only analog inputs, you need a USB DAC.
Today many USB DACs are combined with volume control and headphone out.
In fact a pre-amp with USB input.
The audio is routed to the USB audio device.
This is a matter of choosing the USB audio device in your media player.
The onboard sound card is bypassed; in fact you don’t need a sound card at all.
The USB audio device is your (outboard) sound card.
USB audio is explained in detail in the USB Audio section.