But how do they change the sound?
Has anybody some before/after review or something?
I mean, why are they so great?
Best all around: GE 5963 (I have about a dozen of these - it's no fluke)
Best highs: GE 6680
Pretty d*mn good: Raytheon CK5814A, TungSol 5814A<snip>
From someone named "zandru" on another forum (don't blame me for the grammar and punctuation):
In simplest terms, it's swapping out one type of tube for another that may sound better - or the journey in trying to find a tube that sounds the best could be termed "tube rolling." It's analogous to swapping out opamps in solid-state circuitry, but with tubes - even different brands of the same tube type may sound different, much less different tube types. As with opamps, there are some tube types that may work in your amp, but others that won't. There are databases on line that give functional equivalent lists of tube types.