Current = Asus Rog Maximus Z790 Hero / 13900k / MSI 4090 / TP-Link 10gbe Network Card
Topping D90SE -> Topping A90D -> 64 Audio U4S/U12T/Trio/Fourte Blanc (ALL dead silent, same with all my over ear)
Schiit BiFrost2 (with both OG and 2/64 card) -> iFi Pro Icann Signature -> Same IEMs, as well as above.
Previous = Asus Pro Art Creator X570 WiFi (10gbe built in) / AMD 5950x / MSI 4090 (as well as EVGA 3090 TI, Nvidia Founders Edition 3090 TI and Founders Edition 3090)
I had both DAC's and had 0 issue with internal ports
Shop PC = Gigabyte X570 Aorus Master / AMD 3950X / Nvidia 3090 Founders
Hifiman EF400 -> All quiet with IEMs
iFi Zen Dac 2 and also tested my iFi xDSD Gryphon -> All quiet with IEMs
Using my Lian Li o11 Dynamic XL cases ports that are plugged into my motherboards USB3 out, I have had one where I could hear a VERY slight humm. I figured it was just the crappy cable they use internally. Data transfer isn't effected so thats about the only thing those ports get used for.
I have almost every USB Port taken on the motherboard (I dont use wireless keyboard/mouse), but I keep my 2 DAC's on their own internal USB hubs so nothing shares. Although they are the "cheaper" compared to some, but I also have shielded 3ft USB A to B cables to both DAC's.
I do not have any of the USB power pass through changed (so it's whatever the default is), but on my laptop I do have passthrough power turned off on 1 port. I have never tested to see if it made a difference though when using either port.