a buzzsaw like whine in the background that goes away when I unplug or turn down the PC audio
Like that?
That’s mosquito whine caused by badly filtered USB battery (in the computer) and an interface that has no filtering, either. This usually shows up with a home USB microphone (see: Yeti Curse). We do have a pre-baked filter for it.
This is based on the idea that most USB systems work the same way. They don’t have to do that, but it’s usually cheaper to use pre-baked components in computer construction.
The solution is change the computer. We tried all sorts of patches and work-arounds and no dice.
there is an issue but it’s completely separate
What is the issue that’s completely separate and can’t possibly have anything to do with this?
Koz