My tube amp sounds darker now.


I'm using Siemens CCAs, and after putting around 100 hours on the tubes, they are almost too dark sounding now. When I first got them, after about 20 hours of use I thought the sound was a hair too bright, so I bought warm cables to offset that, and everything was perfect for awhile. But now I think the sound is too dark, and I'm about to try some different cables again.
I noticed this just after I accidently left my amp on overnight (for 12 hours). This didn't damage the tube / amp did it? Ugh, what gives?
nemesis1218
If your Siemen CCAs are dark, then they are PROBABLY FAKE!

From my experience, they are the most open, dynamic ... compare to my stash of Amperex, Tele, Siemen ... 7308/6922/e88cc.
My tube amp sounds best after it has been on for several hours. Aural memory is very unreliable- listen further and see if your ears adjust before making changes. I've listened to systems I thought incredible, and on later re-asessment I found them bright or forward or rolled off. I only change things when a I notice a pattern or tendency that spans several sessions.
Knghifi has a valid point. Real Siemens are very open and detailed. Can u try different tubes as a test?
You might also want to test the tubes. If they are weak (especially driver tubes), that can easily contribute to darkness in the amp.