Supra Cat 8 Ethernet cable

@ram18 ex-Supra Cat8 user here too; no brightness issues; shielded Cat6a from router to ethernet to fibre optic/fibre optic to ethernet converters. - Supra Cat8 to Node. Agree with others, let it play on loop for a good number of hours. 

No, I don't use a streamer, just a computer. My ear is sensitive to all kinds of digital wrongs so I would've heard it. I don't quite remember about breaking it in, it was alright from the beginning and I bought it new.

In my case, signal goes from computer to a not too bad Burson Dac via Wywires Silver USB cable. Wywires Silver power cord on the Dac. Grado RS1 headphones.

I am running the Supra Cat 8b cable with  my streamer left on playing a bunch of music with my amps off.  Will have it running a day or two. Hope this helps. Thanks for your suggestions.

I ran my Supra Cat 8 in for a fortnight. No noticeable brightness.

Replacing with TWL Freedom, and will use it to my TV for movies.

I choose Supra Cat8 for its build quality, at 50 bucks per meter, I thought it was a reasonable upgrade. At the time I was using a Node2i with a ARC dac, can’t say for certain if there was definitive improvement over the stock Cat5, at best there was a better sense of clarity? I did recently play with Monoprice Cat8 from Amazon Prime, which is a really well made cable (heavier gauge than Supra). I didn’t detect a difference between the Supra and Monoprice. admittedly, I suck at picking out micro nuances so ymmv.
Nevertheless at $30 for 25ft run it’s a no-brainer for anyone who wants to upgrade or compare against “audiophile” ethernet cables costing hundreds per foot.