Your story is very similar to many others who dares to experiment and try.
One thing I can recommend is to at the very least buy a Cat 8 or 8.1 cable, they are very cheap compared to HiFi cables, but still has so high spec that they are naturally very good. And if you want to spend a few $ more, try the one from Supra which is like 30-40$ for a couple of meters (its Cat 8).
When I first read about this kind of stuff I would think itās crazy talk. But I can say that disconnecting the Ethernet cable and just using WIFi with my Stack Audio Link II, makes a noticeable improvement going into my Mscaler/Dave setup. Even leaving WiFi on but it plugging the Ethernet cable back in changed it for the worst.
My cable is just an Amazon cat 8 coming out of an at&t wifi extender. I believe itās the cheap extender thatās causing loss in sound quality due to cheap power adapter.
So luckily have option to just use wifi instead of Ethernet but can get drop outs with some hires audio.
To me being a techie, that just tells me to absolutely avoid this DAC combo as I believe a good DAC device (and especially an expensive one) should be able to adequately reject reasonably expected externally induced noise. Maybe even these days there is no such thing as a DAC that can reject adequately?
Out of interest, what is your DAC ā pre-amp/amp setup?
This is just a headphone setup
So itās.
Nuc core
Stack Audio Link II endpoint (wifi or Ethernet)
Mscaler connected from usb (powered by Poweradd battery)
Dave connected from dual bnc
Focal Utopia direct into Dave headphone out
Instead of saying thereās an issue it could be system is so transparent I can hear micro changes easier. But Iām open to the idea thereās actually an issue.
OK, the reason I was asking is because I have wondered if some people reporting these kind of differences with different cables, lack of cable, players or whatever other change might have their gain staging from DAC (via DSP volume control in the DAC, so any noise level will not be attenuated) to amp such that the normally expected low and generally inaudible noise floor of a decent DAC is being elevated by the full gain of the amp (headphone in this case) above the threshold of hearing.
Just a thought and was curious.
I still maintain that it is down to DACs and streamers to sort this out once and for all and with some they seem to have done so and so you dont have to care what you plug it into - minimal hifi endpoint or direct into a high power DAW PC running a heavy workload and a big stack of HDs being thrashed or whatever - it still audibly outputs the same 
Likewise in studios I believe audio over ethernet is very commonly used now in high end high channel count setups.
Yeah, I wish it worked out that way. I mean my setup sounded great with the Ethernet in place but without it, itās best Iāve heard. Itās kind of hard to say what the actual differences are other than more natural sound and better flow. I only tried WiFi connection because it came up in another thread and assumed I wouldnāt hear anything. Not like I had any expectations and didnāt spend a dime for this experiment. Think someone joked that best Ethernet cable is no cable at all.
Well - if in doubt about the sensitivity of equipment, then total isolation would seem logical (at least in so far as wireless radio comms isolates with an antenna on the board). If nothing else, then regardless of truths or untruths that may be floating around, at least then you dont worry about it any more 
Use an unshielded CAT-6.
Iāll try it but why would that help?
Iāll report back if it sounds as good.
You donāt need shielded cables unless your in an environment polluted by RF like factories and industry not homes. They are also designed to be grounded at one end and if your router doesnāt you can cause more harm than good. Some of the audio ones only have the ground connected at one end essentially creating a floating shield but most generic ones wonāt.
Thatās a clear indication of a grounding problem. Fix your grouding scheme, thatās step one. When fixed you probably wonāt hear a difference anymore or is at least neglectable. Improper grounding scheme is what causes most of the perceived difference.
You donāt need shielded for the data transmission to work, but at least for me shielded cables, especially cat 8, gives an improvement over for example unshielded cat 6. And if you get ground problem with shielded ethernet, remove the metallic contact-cover on the streamer/DAC side.
I run my streamer and DAC on LiFePo4 cells (2 for streamer, 4 for DAC), completely isolated (fiber from switch into opticalMopule then ethernet adapter then streamer then DAC), so I canāt get ground problem cause I got no ground. And yes, pin1 on XLR is cut so not grounded through amplifier
Possible ground loop due to shielded cable.
So swapping out the cable worked. I canāt tell any difference with it plugged or not. Exactly the same.
Funny I thought upgrading the cable might have some benefit but actually made things worse.
Now I get best sound without having to deal with any drop outs.
Yep, consistent with what others have already noted, Iāve seen many reports over the last few years about audio problems caused by improper use of shielded ethernet cables. All unshielded CAT6 cables at my house. 
Thanks everyone for the good advice. Love it when the fix is absolutely free.
If you use a shielded cable but want to cut ground, remove the metallic cover on the RJ45 contact that goes into the streamer. That way, RFI that gets caught by the shield can go out throughs switch ground, but your streamer is still not affected by ground issues.
A shield doesnāt do very much, if anything at all, when connected to one side only. Currents only flow in closed loops. If you want to connect it to one side only you can run a seperate wire outside the cable that is connected to both ends of your shield. Now your shield at least does something. The difference in your cable has nothing to do with shielding, since you donāt use the shield, but with a higher leakage capacitance to ground.
If current only flowed in closed loops than the whole concept of grounding would be null and invalid.
For ethernet, shielding does 2 things:
If you want 1 but not 2 you can remove the metallic cover on the streamer/DAC side.
Thatās what I was taught tooā¦