Real NOS tubes last longer than the current Russian or Chinese production. If you want current production, maybe you could buy Sophia Electric KT88 big bottle. They are better sounding than any KT120.
Audio Research - should I replace the valves?
I have a AR Ref 110 power amp and AR Ref 3 preamp. Both have done about 3,800 hours. They both work but I wonder if should be replacing the valves.
How can you tell if they’ve had it? Does the sound quality deteriorate & what happens if you don’t replace them?
i don’t think they sounds as good as they did but no pops or whistles or any other strange noises etc - just a bit flat sounding. But perhaps this is just my ears?
pp