[rockadanny]

I've read that their sound quality degrades. But if proper bias is continuously maintained by the amp, is this necessarily true then? Would you be able to hear the tube's sound decline even if your amp continuously adjusts for proper and consistent bias?

[Freo-1]

I'm not sure that is entirely true.  As long as the tube is within operating specs, they should sound pretty good.  Telefunken 12AX7's are noted for sounding great even when they measure on the lower end of acceptable.

[jimdgoulding]

I, too, will read all replies with interest.  I've read someplace that tubes should be replaced at 1000 hr intervals.  Say it ain't so somebody.  I use an Audio Research line stage with Mullard tooled Matsushiba 6922's or so they were advertised with a Hagerman phono pre.  I'm tempted to try a K&K phono amp kit.  I have a friend who has one and would help me assemble.  Let's see now . . should I do that before or after I get some WyWires IC's . 

[Freo-1]

I, too, will read all replies with interest.  I've read someplace that tubes should be replaced at 1000 hr intervals.  Say it ain't so somebody.  I use an Audio Research line stage with Mullard tooled Matsushiba 6922's or so they were advertised with a Hagerman phono pre.  I'm tempted to try a K&K phono amp kit.  I have a friend who has one and would help me assemble.  Let's see now . . should I do that before or after I get some WyWires IC's .

Nope.  Small signal tubes should last from 5 to 10 thousand hours.  It does seem some of the current production Russian tubes do not have good longevity.

[jimdgoulding]

Thanks, Freo.  I should have a long ways to go then.  That's a pretty fine system you have there, ole bean.  Think I need a little "Blondie" in my room, too.