Fiber or Eithenet

@testrun good decision. I would also recommend trying a passive filter like the iFi LAN iSilencer between your Ethernet cable and streamer. Depending on the Ethernet implementation in your components and the length of the Ethernet cable, it is possible to get an improvement. If you buy from Amazon and it doesn’t make any difference, return it. 

Don't understand why anyone would convert to fiber at end of chain, converting to fiber should be done at beginning of chain. Cheap fiber converters certainly not optimal, and transceivers do make a difference, industrial grade Finisar 1475 was my choice after trying others. Corning optical cable top level, I use After Dark version. If your going to do fiber conversion cheaping out will result in second class performance.

What comes prior to fiber conversion matters greatly, fiber can't bring back what's lost prior to the conversion. Where ethernet remains, isolation and quality ethernet cable a must, entire chain must be optimized.

Fiber when ever possible. It usually has higher bandwidth, is less affected by noise, magnetism, and other interference. Also it has less drop over distance vs wire. 

As a word of caution, most cables that say they are Cat8 usually do not test out that way. It's very important that they use cat8 ends, and install them correctly. 

@mswale Some decent streamers are designed to successfully decouple/isolate the above mentioned making the upstream ethernet/fiber infrastructure tweaks a bit pointless. Some don't and benefit from the same.

This thread is a few months old but I’m chiming in because I also have a 50’ run of ethernet (Audioquest Cinnamon) between my router and Bricasti M1 DAC/streamer. I use a IFI LAN IPURIFIER PRO between the long ethernet run and my DAC/streamer. It breaks the electrical connection by converting to optical and back to ethernet internally. It also reclocks. I’ve been pretty happy with this setup, particularly for the $300 cost of the purifier. I’m playing around with a short run of high end ethernet coming off the purifier, and a better power supply for it, so it will be probably 3X the cost of the device, but I listen to a lot of streamed music and think it’s worth it.

The cable run from my network equipment to my main system room is about 40 feet. I have CAT8 Ethernet and fiber optic lines (both) permanently installed. I have A/B compared them multiple times and never heard a reliably meaningful difference between them into Antipodes, Mojo Audio, and now Sonore server/streamers. After installing the Sonore (streamer only) I now have my server (sonicTransporter i9) in the same room with the network equipment with just the Sonore streamer in my system room. Since the Sonore inputs fiber optic directly, with no conversion, the decision to use 15M of fiber optic cable from my server in the network room to my streamer in the system room was an easy one.

In summary, use what works best for your set up and if you hear something bad, check the equipment, nearby cables and power supplies, connections, and other factors before assuming it is related to the type of line.