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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
mechans
3,048 posts
 
How many good roughly matched 6AS7G US made or other NOS tubes can you assemble. I also have a headphone amp which uses the 6080/6AS7G/421A etc. tubes. I can't recall having a large number of special 6AS7gs offered for sale. You can of course find different Soviet era tubes.
I am curious as to why you thought changing the output tube would nothave a big impact on the sound. I have been on a crusade telling any who care to use tube power amps.
My main system didn't have it's magic sound after years of switching and tweaking, until I switched to tube monoblocs.
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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o_holter OP
977 posts
 
Rushton - Yes it seems that Ralph is now more positive to using American 6as7g tubes, at least in recent amp versions (I have 3.2). In another thread he wrote about some customers reporting good results. Preconditioning is important. There will probably be failures, but that is the case with new Soviet and Chinese tubes also, in my experience.
Mechans - thanks, I agree, in general better tubes means better sound. Yet it would be interesting if anyone has actually tried a full set of China/Russia versus a full set of US output tubes in an A-S amp, and could describe the sound difference more precisely.
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