[jamesfmilne]

If you are experiencing digital noise in the output, like buzzing or clicking that correlates either activity on your computer, try installing a ground loop isolator in between your computer and speakers.

This is essentially a mini transformer that physically isolates speaker/amp from the computer to isolate any power related noise.

They are dead cheap on Amazon these days.

Other than that, a USB DAC might help. You don't need an expensive one, which are mainly expensive due to inputs & microphone preamps. The main benefit will be a reduced noise floor/less background hiss, although that can also come from the amp driving your speakers.