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Atma-sphere amps best power tubes

This question has been debated before on A-gon but without a clear onclusion. I wonder, is it worth it, to upgrade from stock Russian or China output tubes (6as7g), to American NOS tubes?

It seems that everyone agrees that upgrading the Atma-sphere driver tubes from stock Russian/Chinese to NOS is well worth it. This is my experience also.

I am wondering about changing the output / power tubes too. I wonder if a change to NOS is well worth it also in the output case.

It seems likely, judging from my other equipment testing.

My Audiotailor Jade OTL headphone amp uses 1 6asg7 and 1 12ax7. No surprise - it sounds better with a good NOS 12ax7 compared to Russian/Chinese stock 12ax7.

More surprisingly, it also sounds clearly better with a NOS 6as7g output tube (General Electric US NOS). The improvement is largest with the driver tube but not so much behind with the output tube. Almost 50 50.

A lot of output tubes are involved - 28 tubes in my MA-1 amps. Changing them all is costly, and so I would like to know some user experience before I go into this.
Ag insider logo xs@2xo_holter

Showing 5 responses by rushton

rushton's avatar
rushton
2,445 posts
 
O_holter, Ralph has always commented that he used the Soviet 6AS7 tubes, and now the Chinese, because he could never find US made 6AS7 tubes that were as reliable or long-lasting in his circuit. With the changes he made a few years back, his opinion may have changed. Have you called him?
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rushton's avatar
rushton
2,445 posts
 
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!
rushton's avatar
rushton
2,445 posts
 
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!
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rushton's avatar
rushton
2,445 posts
 
Will be very interested to hear you assessment of the sound quality, O_holter.
rushton's avatar
rushton
2,445 posts
 
Good report, O_holter. Hopefully the RCAs will also prove themselves to be reliable over the longer term, which will then provide a great alternative!
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