Audiophile LAN Cable: Where does it matter?

[Zuman]

I wasn't sure whether to post this in the Cables forum or here, but I think that my question has as much to do with a larger process understanding so I'm starting here.
I run Roon via ROCK on a NUC connected to an eero mesh router via a generic ethernet cable. Also connected to the eero via a generic ethernet cable is my NAD M50.2 player/vault (which has my music library loaded onto its internal HDDs).
This past weekend, at the Capital Audiofest, I listened to two demonstrations of the M101 Nova LAN cable in which the owner/designer/inventor, Dr. Lubomir Dostal, compared it with a standard off-the-shelf LAN cable. When the M101 Nova was in use, the musical presentation was tonally compelling with excellent front-to-back and lateral imaging. When the generic cable was in use, the overall sound was harsher with more glare and the front-to-back separation collapsed.
Now I'm a long-time audio guy who cares about this sort of stuff, but my brother was with me, and he's not. His idea of good sound is a sound bar and Sonos speakers, and as we visited the various rooms at CAF, he was as impressed by most of the "good" systems as he was by the really great and well-integrated gear. But when Dr. Dostal switched from his Nova cable to the basic cable, my brother immediately said to me "that's a big difference - it's not as good." When Dostal switched back to the Nova, my brother said, "Ok, now it sounds really good again." I felt the same way, but could articulate the differences more specifically.
Dr. Dostal advised me to replace my generic ethernet cable between my eero router and my M50.2 player/vault with his cable. He did not suggest replacing the cable between the router and my Roon ROCK NUC.
I don't really understand why inserting a high-end LAN cable between my M50.2 and my router would make a difference. My "music" never "leaves" my M50.2, right, except via my very nice Hapa Aero S/Pdif cable that connects it to my DAC, so why would I need an audiophile LAN cable?
Am I misunderstanding how Roon works? I'd love to implement the improvements that I heard in the M101 room at CAF in my own system, but I don't want to spend over $1k on an ethernet cable that won't have the impact I'm looking for.
Thanks for any wisdom and clarity you can provide!

 

[divertiti]

Not quite sure what your exact signal chain is, if your M50.2 is a local file storage player that directly feeds your dac, why do you have a Roon Rock? what function is it serving

 

[Zuman]

Not quite sure what your exact signal chain is, if your M50.2 is a local file storage player that directly feeds your dac, why do you have a Roon Rock? what function is it serving

My NAD M50.2 is a music player and server. It includes two hard drives in a RAID array that store my music library as FLAC files. It runs the BluOS operating system, and I can access the drives wirelessly as a mapped drive on my home network. It is directly connected to my DAC with S/PDIF and AES/EBU cables, and outputs digital music files to the DAC.
Roon, as music management software, can retrieve information about music, organize my library, process it, and direct its playback. However, Roon cannot be installed directly to the M50.2. It can be installed to a computer (such as my laptop), or exist in a small and efficient single-purpose "appliance" installation in a device such as an Intel NUC, which is what I implemented earlier this year. My Roon NUC is quiet, fast, auto-updates, and is "invisible" to me as a user. It functions as Roon's brain, processing music files on my M50.2 and playing it according to commands sent to it from the Roon app on my phone or tablet.
What I don't understand is where Roon processing takes place. Roon says that the Roon Core (on my NUC) "manages your music library and handles signal processing and audio playback." I recognize that my understanding is limited here, but I assume that means there must be bi-directional data sharing via the LAN cables between my M50.2 and my NUC. The NUC (or your PC, Mac, etc.) would need to receive a signal from an app that says, for example, "Play Flamenco Sketches from Kind of Blue and drop the frequency response by 2dB with a curve centered on 200Hz." It would then need to carry out that command, and instruct the M50.2 to send the appropriate digital signal to my DAC. But I don't know what actually happens inside the NUC and what happens inside the M50.2.
The M50.2 and the NUC are not connected except that each has an ethernet cable running to the same eero mesh router, one of several eeros in my home. I'm trying to understand what is actually passed through those cables and whether replacing one or both of them with high-end LAN cables will improve my final sound. And finally - to muddy the waters further - before I switched to the NUC, I ran Roon from a regular Lenovo laptop computer, which wasn't connected by ANY cable (just wirelessly, to my home network)!
Sorry for the long reply...I'm trying to be as clear as I can!

 

[harsheel_dbs]

In my experience, each cable at every (ethernet) connection makes a difference. How great of a difference for better or worse depends on your configuration. I don't have an explanation as to why but let your ears be the judge.

 

[divertiti]

My NAD M50.2 is a music player and server. It includes two hard drives in a RAID array that store my music library as FLAC files. It runs the BluOS operating system, and I can access the drives wirelessly as a mapped drive on my home network. It is directly connected to my DAC with S/PDIF and AES/EBU cables, and outputs digital music files to the DAC.
Roon, as music management software, can retrieve information about music, organize my library, process it, and direct its playback. However, Roon cannot be installed directly to the M50.2. It can be installed to a computer (such as my laptop), or exist in a small and efficient single-purpose "appliance" installation in a device such as an Intel NUC, which is what I implemented earlier this year. My Roon NUC is quiet, fast, auto-updates, and is "invisible" to me as a user. It functions as Roon's brain, processing music files on my M50.2 and playing it according to commands sent to it from the Roon app on my phone or tablet.
What I don't understand is where Roon processing takes place. Roon says that the Roon Core (on my NUC) "manages your music library and handles signal processing and audio playback." I recognize that my understanding is limited here, but I assume that means there must be bi-directional data sharing via the LAN cables between my M50.2 and my NUC. The NUC (or your PC, Mac, etc.) would need to receive a signal from an app that says, for example, "Play Flamenco Sketches from Kind of Blue and drop the frequency response by 2dB with a curve centered on 200Hz." It would then need to carry out that command, and instruct the M50.2 to send the appropriate digital signal to my DAC. But I don't know what actually happens inside the NUC and what happens inside the M50.2.
The M50.2 and the NUC are not connected except that each has an ethernet cable running to the same eero mesh router, one of several eeros in my home. I'm trying to understand what is actually passed through those cables and whether replacing one or both of them with high-end LAN cables will improve my final sound. And finally - to muddy the waters further - before I switched to the NUC, I ran Roon from a regular Lenovo laptop computer, which wasn't connected by ANY cable (just wirelessly, to my home network)!
Sorry for the long reply...I'm trying to be as clear as I can!

That's much clearer, thank you. If your Roon Core is doing any type of processing, then your audio content is going from the M50.2 to your router and to your Roon Core then back. Everything in that chain impacts sound quality, your router, the power supply feeding the router, and yes the ethernet cables. As to your original question of which one matters more, usually the cable closer to the component that uses that signal has bigger impact than the ones that are more upstream, in this case the one closest to your M50.2.