Could be the speakers themselves.
Since you ruled the amp and preamp. Maybe the tweeters are somehow damaged. You would not expect Revels of that level to be the problem but again it’s possible.
Help, my system seem to have slowly gotten " bright"
I have all all of the same stuff for several years and it has always sounded awesome. Lately thought it has gotten where some of the higher frequencys have like a shrill to them. It kinda breaks up at louder volumns but is noticable at lower ones too. I have swapped amps out, preamps too but no change.
Really the only thing left is the player which is a 7 year old sony hapzeis. the only thing i have is a cheap cd player that is like 25 years old to compare. This player has a hard drive with all lossless music on it. It has an onboard DAC too.
Has anyone expierenced anything like this where a source or a dac degraded like this instead of just quitting altogather ?