Mapman; I have a b&k 747 tube tester and check tubes every 6 months. I think visual and audible changes are a indication as well to check tubes.
Also I kept a bias adjustment log when I had amps with manual bias adjustments; When bias starting to drift I would pay closer attention to that output tube.
I know many people will think this is extra work but I have several $$$ invested in my amps and pre amp and just want to keep them running at their very best;much like a person who maintains their car.
Also I kept a bias adjustment log when I had amps with manual bias adjustments; When bias starting to drift I would pay closer attention to that output tube.
I know many people will think this is extra work but I have several $$$ invested in my amps and pre amp and just want to keep them running at their very best;much like a person who maintains their car.