ETHERNET CABLES

Assuming that digital send/receive protocols work as explained by the many network people on this site, then one thing that could cause Ethernet cables to sound differently from each other would be the effect of noise and shielding as discussed here.  Another review article I found stated:

The main culprit, as with all of HiFi, seems to be of RFI/EMI noise. Some Ethernet cables have filter blocks, proprietary shielding designs, higher quality conductors, and connectors. All of these design decisions seem to shape the RFI noise that ends up in the analog section of your components. There’s no way to completely eliminate noise – but manufacturers are finding ways to mitigate it.

It seems the higher CAT rated cables offer different and/or improved shielding.  Also, based on what I have seen, many of the expensive "audiophile" CAT cables being sold are of the higher CAT 7 or CAT 8 variety.  I have read about the Supra CAT8 Ethernet Cable being a particularly good bargain but other CAT8 cables may sound just as good, assuming the shielding results in the differences. 

I have used CAT 7 and CAT 8 and fiber for a 45 foot run from my router to my server and all three options sounded fine - I simply did not hear differences.  I simplified by removing the fiber and currently use just a single 45-foot CAT8 cable into a Network Acoustics ENO then into my server.

@dpcoffey
It’s not just 1s and 0s, the data rides in an analog signal which can pick up noise from various sources. This noise is clearly audible in a resolving audiophile system

I'll summarize my experience as accurately as I can.  This is over a 15 month period.  I am using an Ayon Stealth DAC and Transport.  Together they sound killer.  They create a large expansive soundstage with more detail and resolution in CDs than I ever thought possible.  I could have almost thrown out my turntable.  Well, not really but you get my point.  Then I added a ROON based music server.  I ripped all of my CDs to FLAC files.  Once I got a better USB cable I could not hear the difference between my Server/FLAC files and the CD playing on my transport.  My transport upsamples to DSD128 via I2S to my DAC.  My music server is USB to my DAC.

I started streaming with an ethernet (CAT7) cable from my router direct to my music server.  44.1/16 files streaming had some smearing, less detail/resolution than the CD and I found the highs somewhat harsh and grainy- worse in the middle of the day.  I'd say that I had to stream a 96/24 file to get the equivalent sound of my CD player or FLAC files.  Next I added a network bridge powered by a linear power supply.  Things improved some but it was clear that 44.1/16 files streaming were still lacking.  

Then I added the Fiber Media Converters just to try it out.  I have a 15 foot long optical cord.  I didn't even try the FMC's with their wall warts.  I went to linear power supplies straight on.  This is the way to go.  For me, 44.1/16 files streaming are very close to CD now.  Streaming Hi Res sounds fantastic and very close if not indistinguishable to downloaded hi res files.  

Nightime listening is still a bit better sounding than during the middle of the day but the difference is smaller now.  But that can be true for vinyl as well.

i tried to buy the sonore optical module last winter but after waiting 4 months I gave up on it.  I'm happy with my set up now and have no further plans to change things.

Here you go. HTH:

CAT8 is 22awg - the thickest wire of the CATs and therefore arguably the best durability.  It also has optimum shielding and twists but maybe not much if any different from CAT7.  It is by far the fastest but that speed is not needed in a home environment so the only reasons to pay more are for the extra copper and the shielding.