I see, I see. It sounds to me like you’re getting audio glitching due to bad sample rate management and tb incompatibility, not audio line interference. Here’s what I think, and what I’ve found.
With this mobo (Z390 designare) and the way the Thunderbolt has never been updated or ‘fixed’ - I get the Apollos in any Tb card configuration (except for the UA tb1 card on this mobo in any OS) working when in windows 10, or on a real Mac - no issues at all. On a real Mac, any UA tb 1,2 or 3 card and any tb 1,2 or 3 Mac will work just fine.
When in Hackintosh mode, I get an Apollo x8 with a tb3 card working perfectly, but when I put a tb3 card in my silver face Apollo, it also glitches a lot when on the Hackintosh, but not when on a real Mac or in windows. It has taken me months to figure this out As I was blaming everything else in my computer or OS first.
I think there is some sort of incompatibility with the silver face Apollos maybe, as they were produced during the tb1 era and this mobo has no compatibility with tb1 devices at all. So the solution is to put a tb2 or tb3 card in it to make it work right? Well, it sort of works but sort of doesn’t for me, so I’m guessing there’s still something behind the UA tb2 or tb3 card in the silver face Apollo that is not being controlled properly by this Thunderbolt controller.
I’m sure you’ve seen others have flashed their Thunderbolt controllers on this Z390 designare motherboard and had success in their tb devices working much better, including uad gear, but still have a little strangeness. Seems like a huge pain overall with this motherboard.
im going to try a UA tb2 card in my silver face and see if anything changes. If not, then I’m going to switch motherboards and Thunderbolt controllers or get a new Apollo. I haven’t got much choice at this point as I’ve been on the uad platform for 15+ years now.