SF Deluxe Reverb - amp tone changing or is it me?

[Chippsta]

I've got a mid - 70's Deluxe Reverb (with pull-boost) that i bought 7 years ago. I put a Celestion Speaker in it because i got a good deal on it and the existing speaker was blown. I've recently had it re-tubed and biase'd with JJ Teslas. My problem with it is ... at the beginning of the night it sounds fantastic ... big complex, and sweet. By the end of the night it starts sounding very thin and 'crashy'. I'm running it between 3 and 5 on the volume. A friend has told me that the amp isn't changing, my ears are tired after 4 hours. Problem is, my Peavy Classic 30 doesn't seem to have this problem. I'm running stereo. Does my amp need help, maybe new speaker, or do i just need to place it so it's not killing me ?

[Tasman]

Hi
if you`re sure that the tubes are OK , it`s possibly problem with power-caps and other electrolytics. If you hadn`t do recap, you probabily should do it...
Keep the originals, (by the way).

[stokes]

Time for a re-cap.Electrolytics are only good for about 10 years.