Can you do anything to make power tubes last longer ?

mulveling,

Could you suggest particular Amperex EL34 that I might want to try later ?

Perhaps, I should also try Sylvania 12AU7 black plates from 50s as well. What difference would they make compared to RCA black plates from 50s, I wonder ?

Mke sure there all biased correctly.enjoy the tube sound.

Found them ! Matched quad of Mullards EL34 XF2 is coming this way. It's a little risky because they are not new and the exact number of hours on them is unknown, though supposed to be low enough. Test as strong NOS, as the seller with excellent feedback says. It's always a gamble with tubes to a degree, I feel fine about it.

Found them ! Matched quad of Mullards EL34 XF2 is coming this way. It’s a little risky because they are not new and the exact number of hours on them is unknown, though supposed to be low enough. Test as strong NOS, as the seller with excellent feedback says. It’s always a gamble with tubes to a degree, I feel fine about it.

Nice! Enjoy - great tubes. Don’t worry about the exact hours on ’em. A meaningless metric, now. "They don’t make ’em like they used too" applies, etc and yada yada...

For Amperex / Hollands I’ve only used the xf4 and xf5 models, both with the brown/red-base. They both sound equally great - I’ve even mixed them in quads (matched pairs), with no problem. The older metal base Philips / Holland version is supposed to be extra special - I’ve almost pulled the trigger on these in the past, but never did.

Perhaps, I should also try Sylvania 12AU7 black plates from 50s as well. What difference would they make compared to RCA black plates from 50s, I wonder ?

Why not? I expect 1950s black plate Sylvanias should be very good. I generally prefer these over any RCAs, though I haven’t tried the 12AU7’s. You can do 5814, 6189 and 5963 subs too. The 5963 tend to be microphonic, so those should be relegated to amp driver slots only (NOT the preamp or phono slots).

RCA black-plate 5963 was the favorite 12AU7 sub for early 2000s-era VAC power amps.

@inna I wouldn't say that I recommend choosing an amp that is easy on tubes so much as I recommend against an amp that is hard on tubes.  How do you know which is which?  

I'd say avoid an amp that gets more power than normally attributed to that tube--unless I needed that power and was willing to buy tubes.   And I'm fine with that. Personally I don't think tubes are expensive compared to the rest of the audio equipment we all have to purchase.  I buy tubes when I don't need them.  A nice pair of Hytron 801As showed up yesterday. 

There is a trend now to make higher power tube amps to drive lower sensitivity speakers.  I like higher sensitivity speakers but if you're married to your 92-95dB speakers and want to drive them with a tube amp, you need more power.  So they are making more push pull, parallel SET, and High power SETs with the higher output tubes.   if you buy some of these, recognize you'll have to replace tubes more often.  (not saying push pull amps are hard on tubes, unless designed that way).

If I'm looking at a 300B SET and the OEM says 8 wpc, and 300b's generally do 6 wpc, I'm going to wonder about tube life.  (or else the marketing talk is exaggerating and it really is a 6 wpc amp).

I've found that if you go with an amp builder with a lot of experience and knowledge, they are likely to design their amps conservatively.  And if you call Aric or Apollo and order and amp, if you tell them to use conservative parameters to promote long tube life, I'm sure they can do that.

jerry