Tube care and feeding ?

Tech Square

Technical and speculative discussion of amps, cables and other topics.

I'm new to tube amplifcation a close friend gave me a great deal on a DIY 45 SET amp while I was skeptical about the 1.5 watts
being enough to drive my recently built (TQWT Fostex Fe 208 e sigma
wideband driver and Fostex 17 H super Tweeter) 97db loudspeakers.
Not only is the 1.5 watts more than loud enough, but the sound is
seductive and musical (compared to my SS gear) and even a bit psychedelic to the extent I blow off taking calls, letting the dogs out, or even procrastinate taking a leak at times.
At any rate the 45 output tubes are anything but matched, different manufacture and vintage, same with the preamp tubes
one has a broken base pin etc, so I set out to have a full set of spares so if a tube goes south I wouldn't be out of action for a
week or two, the more I researched tubes the more I found myself appreciating the differences in quality and ended up getting a number of NOS tubes of each type, Mil. Spec. Mullard GZ 37 rectifier tube and Mil spec variation of the 6n7gt input tubes and a couple of pairs of NOS 45's and I can't wait to see how the sonics are effected with the better tubes, I read in the FAQ here and elsewhere that turning the bias all the way down and then slowly increasing it over 10 to 15 min. to break in the new tubes, however my amp is a fixed bias variety with hum pots, I read somewhere that in that event you should employ a Variac to do the same thing, I have a friend who has a variac he'd lend me. Is breaking in the new tubes thing worthwhile or necessary ? or just some really anal thing of dubious theoretical value or perhaps even counter productive ?
I also ran across Pearl tube coolers on audiogon that supposedly reduce or eliminate microphonics but extend tube life at least 2x
any opinions greatly appreciated ?

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Topic - Tube care and feeding ? - Fred J 01:02:33 06/02/04 (3)

Re: Tube care and feeding ? - Curtis L 19:16:42 09/29/04 (0)

not bias... - Bill Way 16:00:41 06/06/04 (1)

Re: not bias... - Fred J 22:30:13 06/06/04 (0)

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