How can different CAT5/6 cables affect sound.

My point is actually stronger than TCP being error free, it is that the submission of the buffered data to the DAC chips is totally isolated from the nature of the patch cords.  The data is stored in a RAM buffer and is fed to the DAC circuits by a clock in the DAC, so I am a loss as to what is causing people to hear sonic differences.

I just did an experiment, I started PRESTO streaming through my entry level Bluesound device which is wired to my LAN.  After playing the stream for a few minutes  - I pulled the LAN cable from the Bluesound node.  The music continued for perhaps 20 seconds.  The streamer is buffering about 20 seconds worth of bits, I tested that it is the streamer by repeating the exercise but pulled the TOSLink, there was an almost immediate cessation of music.  

OOPS.  Thanks Richard brand.  Streamers usually use UDP which does not have error correction, so a really bad patch cord could cause data errors.

If noise, picked up by non-shielded Cat5 cables is the problem, and from responses it seems that is might well be the issue, would that argue that a Wi-Fi (and thus decoupled) connection would work best?

I cannot personally comment on this as I rarely listen to streaming sources on my big rig (I hate to say reference system) and it does not support Wi-Fi anyway, and my 2nd system has only Wi-Fi capability.

My wife is a wonderful supporter of my high end journey (she supported my upgrade from a K-01xs to the xd) but would probably be critical of a 30 foot cable draped around the room from my WAP/Switch to the Bluesound node - but I might try it one day when she is out at the gym as I have a Cat5 cable building kit. 

The actual transfer of the bits seems unlikely to be the issue as the highest bit rate for streaming would appear to be 18.423 Mbps  (2*192k*24*2) (two channels*sample rate*bit depth*2 for the TCP and other overhead) and the Cat5 standard is for 100Mbps.

A question for people who do hear a difference between cables.

Is your streamer integrated with the DAC or is there a link to an external DAC?

The answer to this might provide insights regarding the induced noise theory.

Another test for those who run a long cable from the switch to the streamer, though this will cost about $25.  Try running the long cable to a Netgear MiniSwitch located as close as possible to the streamer, with the shortest possible (shielded?) cable from the MiniSwitch to the streamer, minimizing any RFI pickup, and hopefully, the MiniSwitch will isolate the output from any noise on the input.

My big rig's network connections are implemented by a Wi-Fi to ethernet adapter connected to a MiniSwitch and then very short cables to the Aurender server and the Bluesound Vault that I use for ripping and streaming.  (The Aurender does not support Presto). 

I could have been really contentious and asked if anyone has heard sonic differences between T568A and T568A wiring standards.

OOPS.  That should have been:

I could have been really contentious and asked if anyone has heard sonic differences between T568A and T568B wiring standards.

I think that the consensus is that the sonic differences are caused, not by digital issues, but by RFI or other noise induced in the patch cord leaking through into the analog circuitry.

Perhaps I am lucky (or hard of hearing) but yesterday I listened back to back to the Weilerstein Elgar from my Aurender SSD, USB connected to the Esoteric K-01XD SE and the same work streamed from Presto through the Bluesound Vault, TOSlinked to the DAC and detected no differences.  I live in the country, and my system is located far from any in-home electrical or electronic devices.  Also, the Esoteric unit is engineered to separate analog and digital processing.

My streaming is limited by drop-out in my internet connection.