How can different CAT5/6 cables affect sound.

Per usual arguments (from the above link), theory and measurements vs subjective listening. I've tried many ethernet cables and lengths over the years and I hear differences with certain cables. So am I to believe the science or trust my senses. The measurement crowd will say my senses are not to be trusted, expectation bias clouding my senses. Usual retort is sometimes science hasn't yet formulated the right questions to ask, in other words fails to devise measurement protocol to account for what we hear. And then we go around and around ad nauseam. 

In the end, on this one I go with trusting my senses.  As for sound differences, I've only experienced issues with tonal balance (highs attenuated), this probably has to do with improper or excessive shielding. The only other change has to do with resolution/transparency, I've found silver content to be important for digital cables, the higher the silver content the better. Anyone reporting changes in something like timbre is imagining things.

In the final analysis, both sides free to present their arguments, up to the individual to choose who to believe. 

This is curious, optical reportedly superior to LAN cable, this my experience as well. So some will say this imagination, others will trust their senses. And then we have reports the transceivers in these optical devices don't all sound alike. Now we also have reports managed audiophile switches provide superior sound via decreasing network traffic. This all very curious, networks have impact on sound quality, networks have no impact on sound quality, take your pick. I suspect this thread could carry on and on with no conclusive evidence on either side, this thread will not provide the final word.

On the issue of networks and their impact on sound quality. Those approaching this from the science perspective, prima facie argument precludes yielding any validity to those reporting networks do indeed impact sound quality. Ignoring this and reverting to prima facie arguments is not good science. Quality scientific inquiry requires addressing  this counter argument through development of more rigorous research into the possible causes for this variability. Simply writing off this evidence as some derangement syndrome, based on emotions and/or distrust of human senses doesn't pass muster. 

Instead of retreating to the same old refrains, try to find explanations for why individuals hear differences with a multitude of audio streaming devices. Another option is to actually experience these devices in your own streaming chain.

Galvanic isolation in quality streaming components is virtually a given these days, certainly there are generic streaming components lacking this, and I do agree this needs to be addressed.

@herman My first post on this thread mentioned the endless repetition of the same old tired refrains on this subject, and then I get involved yet again. I will try to remember this and simply tune out next time.