Cables to settle brightness

WOW!  Great thread.  I am in the OP's boat too, but it's not my DAC, which is a Denafrips Pontus II.  I actually think it's elsewhere in the digital chain.  Also have no issues with vinyl playback.  I upgraded to a Small Green Computer Sonic Orbiter i5 about a year ago.  Most cables in the digital chain are from Morrow Audio.  I have a Sonore UltraDigital and UltraRendu, using the I2S over HDMI to connect to DAC.  On some material it sounds really good, but my previous digital chain made everything sound liquid and musical, and I miss it.  I will look into some of the suggestions made in this thread.  Thanks!

@duckworp I doubt it's the Denafrips.  It's the fifth DAC I tried and best sounding of all except maybe my old DAC, which wasn't as good sounding in other ways, much more homogeneous sounding, making everything sound warm and smooth with reasonable detail.  I am pretty sure it's the fact that I went from WiFi using coax cable to Ethernet using both USB and I2S over HDMI.  Lots of variables, no time to try and identify exactly what the problem is, and I have blown my hifi budget for at least this year.  Whaddya gonna do?

@fittebd my old DAC was a highly modified Beresford, maxed out at 96/24 and lacked USB.  I still have it, so if I had some time, I could go from the UltraDigital to the Beresford with a coax cable.  I have enough inputs on my pre to hook both DACs up at once.  I would need a pair of decent ICs, though.  I know I really should do this, as it would tell me if it's the DAC or all the other stuff preceding it.  Yes, I have an inexpensive network switch, and no, I have not upgraded its power supply.

@earthtones I am considering the Sonore optical converter boxes.  Reasonably priced, and returnable if it doesn't do the trick.  My digital chain is already kind of a Rube Goldberg contraption, and this would make it moreso.  But if it works, who cares?  As soon as I have the budget for it, I will try it and report back.