Most Important, Unloved Cable...

azbrd, as I and grannyring have said many times in the past and now once again, we are well aware of the theoretical inability of such cables to influence the sound, however, obviously theory is insufficient to explain the obvious differences. 

Are those differences obvious? Well... so far only one Ethernet cable in five has been obviously, wildly different. I can't blame people who have tried a few and found there to be no difference. If I had not come up with the "right" one I would have made the same conclusion. 

As far a s the DAC is concerned, sorry Azbrd, but the results are consistent regardless of which DAC is used. It's not a "DAC quality" question.  :) 

As an electrical engineer having extensive experience designing high speed digital, analog, A/D converter, and D/A converter circuits (not for audio), I don’t find the reported differences to be either surprising or mysterious. And I consider them to be well within the bounds of established science and engineering.

Most likely what is happening is that differences in the characteristics of the cables, such as bandwidth, shielding, and even how the pairs of conductors that carry the differential signals are twisted, are affecting the amplitude and spectral characteristics of electrical noise and/or RFI that finds its way via unintended pathways to unintended circuit points "downstream" of the ethernet interface in the receiving device. "Unintended circuit points" may include the D/A circuit itself, resulting in jitter, and/or analog circuit points further downstream in the component or system, where audible frequencies may be affected by noise that is at RF frequencies via effects such as intermodulation or AM demodulation.

"Unintended pathways" may include, among other possibilities, grounds within the receiving device, parasitic capacitances, coupling that may occur into AC power wiring, and the air.

What can be expected regarding such effects, however, is that they will be highly system dependent, and will not have a great deal of predictability.

Regards,
-- Al

Thanks Al. I should say I replaced an old unshielded Cat 5 cable going through several junction points and terminations with a straight run of the double shielded Cat 7.  No mystery I hear better sound quality on my streamed audio based on your post. 

First let me say that all of you are welcome to spend money on what ever makes you feel good, however, the science does not add up.  

What does an ethernet cable do? It caries TCP & UDP packets (which are 1s & 0s) from source to destination, these packets are built with headers & payload/data which is more 1s & 0s.  If packets dont make it to destination TCP handles retrys, if this did not work all of us would have problems with our connections to our network providers.

In a typical TCP/IP stack, error control is performed at multiple levels: Each Ethernet frame carries a CRC-32 checksum. Frames received with incorrect checksums are discarded by the receiver hardware. ... Packets with mismatching checksums are dropped within the network or at the receiver.

So if there are real network issues you get packet loss which in audio is a gap in sound because the DAC runs out of bits to process into sound.  Changing a ethernet cable COULD reduce packet loss, so could a better switch (or current firmware on the switch) but it will NOT change the 1s & 0s (which are what a DAC uses to create audio) to better 1s & 0s.  It also does not matter if the payload is audio or video so the same side effects occur, loss of packets ie 1s & 0s if a cable is bad or not the correct cable for the task.  How many of you stream Netflix or video via Apple TV, this is built on the same tech, for that matter everything on the internet is built on the same thing, TCP and 1s & 0s.  There is no such thing as a better 1 or 0 (a "better" cable) that enables a DAC to create a better sounding audio sound.  

I build & trouble shoot network and data storage issues for a living, if I use the proper cable rated for the bandwidth, ie 1g, 10g or 40g, I do the same for my home network where Stream digital 100% of the time, I build & test my own cables using CAT 5e because CAT 6 wires are so stiff and hard to work with and I only have a 1gb wired network.

The shielding alone will help in noise reduction. I think this is one area of improvement in my particular case. Best $15 I ever spent is all I know without a doubt!