I have crazy amounts of interference on my desktop and one of my laptops(HP Envy Beats audio edition that's been advertised to have lowered grounding noise), so I bought a USB DAC, specifically the iBasso D2+ BOA. I get the same interference via USB.
I have another laptop that doesn't have this interference issue, and I don't get it with the iBasso either on that laptop.
I'm thinking it's possibly a line in or CD analog in volume that I need to mute. This has happened to me before and once I muted that, the noise went away. But Windows 7 sometimes doesn't give the option in the volume mixer/properties to mute that.
Any idea how to fix this interference issue?