I answered that very specifically. If you don't like the answer, that's not my problem, but once again:
You reach the pointless-as-magic-cables level when you buy a tube amp. After that you're into "I'm concerned that my voodoo practioner may not be following FDA guidelines" territory.
That's not to say that you shouldn't practice voodoo - or tubedoo. But you've already gone outside scientific criteria when you do. (Basically, the spiel for tube amps is supposed to be that the distortions they produce make music sound better... To which to the scientific reply is "That's not what blind test's show" and the common sense one is "I want to hear what the musician played.")
Yes, certain tubes are less bad than others. No one ever said any differently. That you weren't able to understand the other more important points I and other people made is not our problem.
Edited by scuttle - 2/7/13 at 10:17am