Why do old tubes sound better than current tubes?


just wondering, is there something in the design, materials, or fabrication that makes old tubes sound better than those being currently produced?

it seems nearly universally held that old tubes are superior sounding to those made today - is there something specific about the old tubes that make then sound better?

-Scott
srosenberg
Al, I have tested a lot of pulls from Tek scopes, which tend to only use half of the dual triodes, mostly 7308/6922/6DJ8. It is very common to find the two sections do not match in this instance. Another pitfall for those buying used vintage tubes. I have no idea however, how well matched the sections are in current production tubes.
I have great things about the new gold lion 12ax7 also, I am going to try them soon.