I have 2 Taylor 572B tubes in my SB-200 Amp. I replaced many bad components and installed 2 brand new matched 572B Taylor's in it 3 years ago. I was having no trouble until recently and I note that my power out has dropped to 200W. It was giving me 500W +/- before now.
Has anyone heard of this happening? I feel I should know this but I am just to PO'ed to think.
Thanks in advance for any help.
You have bad tubes. 572B's are notorious for short emission life. People will tell you it is something you or the amplifier can avoid or control, but that is all BS. You will have short unreliable emission life no matter how you run them. The problem comes from poor tube manufacturing, not from anything even remotely in the user's control.
The sole exception to this is if you physically melt a tube down from mistuning or severe abuse or run the filaments at 7 or 8 volts or more, or below 5 volts.