Atma-sphere amps best power tubes

I found some comment in earlier threads.
06-12-11: Entrope
"As the owner of Atma-sphere M60 mkII.3's I find the the RCA 6AS7 available and not to pricey. They sound much better than the stock Russian tubes. In speaking with Ralph Karsten he indicated the amps probably had a somewhat greater power output with the American tubes over the stock tubes. He indicated as much as 20%."
See thread 1307834958.
Also there was a thread on Atmasphere output tubes in October 2014, although I cannot find it now. I copied a few of the posts:
"atmasphere 6as7g output tubes.
Time to get some new tubes, I know atmasphere does not recommend nos tubes. I really have to say my amps would not sound the same without nos input tubes. I was wondering if there are any opinions regarding using nos or vintage tubes for output tubes."
Toothman (Threads | Answers | This Thread)
10-15-14
Responses (1-17 of 17)
10-16-14: Brf
"It's your amp and it's your money, therefore, as long as you are using the same tube type, knock your socks off and roll the NOS tubes."
Brf (Threads | Answers | This Thread)
10-16-14: Atmasphere
"The American 6AS7Gs can have issues, although we have found that the 6AS7GAs are the ones that are most problematic.
Here is what we know about the American tubes so far:
1) you get best results if your amplifier is a Mk3 or later.
2) If NOS, the tubes should be preconditioned for 4 days and 4 nights. This is done by placing them in the amp and putting it in Standby only for that time. If you apply B+ during that period the preconditioning process is ended.
Preconditioning can double the life of the tubes, help restore a better vacuum by activating the getter, and will also reduce the possibility of premature arcing.
BTW this process applies to all output tubes, assuming they are new/untested or NOS.
I would regard the use of American 6AS7Gs as experimental as you may run into premature arcing, but some customers have had excellent results. I think a lot depends on the tubes, if they are really NOS, that sort of thing. However- stay away from the GA varieties- they won't work."

O_holter, Great information collected from Ralph. Thanks for collecting it all into one place and sharing it. Sometime I'll have to re-tube my MA-2 amps, so you can imagine I'm likely to be even more cautious than you!

Thanks Rushton! A pleasure.

Besides buying some US tubes to try out, I am investing in a MR-1 tube tester from Helmut Beck, Germany - custom setup so it takes all the tube types in my system. I have no less than 87 tubes alltogether in the system (blush! I had not planned this).

I've had quite a large failure rate with 6as7s and this seems to be a common experience. My hope is that the tester will at least help avoid putting bad tubes into the system and that this will mean less repairs, less damage to other components etc. Hopefully the tester will also be of help getting the best sound, combined with listening.

Just be cautious about relying on the testing with the 6AS7G tubes. Again, recalling what Ralph has mentioned to me over the years, typical tube testers do not measure a 6AS7G in the same manner as is used in the Atma-Sphere circuit. Perhaps the MR-1 from Helmut Beck does so.

I keep hearing about failures in these power tubes. In 14 years running the MA-2, I've had only 4 tube failures with the Sovteks installed. Many of my tubes are still orginal with thousands of hours on them. I suppose my time is coming due. ;-)

And, I now feel absolutely free-spirited with only 84 tubes in my system!
.

84 tubes only - you are on a diet I suppose?