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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.
o_holter
ozzy's avatar
ozzy
3,650 posts
 
For my M-60 3.3,  I have been using the Sophia or Full Music 6SN7 tubes and I think they are better than any NOS RCA or whatever. But, I may try the Shuguang sometime though. 

On the power Tubes I purchased (36) 6AS7G 1970 vintage new from Russia. Took about a month to get them. They have been problem free during the last 3 months that I have owned them.

ozzy


o_holter OP
541 posts
 
A little update:The RCA 6AS7Gs have worked fine for the last two years - very stable - nice sound - happy with this set (although I had some failures in the beginning, despite preconditioning them).
Driver tubes: I have the four tube (long chassis) MA1 v3.2. Now trying RCA 6SN7GTA in V1, RCA 6SN7GTB in V2, RCA 6SN7GTB in V3, and Sylvania in V4. 
o_holter OP
541 posts
 
In other words, the RCA 6AS7G tube has worked excellently over four years now. I have associated it with a plus in the overall sound of the MA-1 amps. Set and forget.

Ordering a large quantity of these (28 in my case, from Brent Jessee) is a risk, of course. You may get a few problem tubes (even from reputed dealers), but these are easily spotted, showing up quite soon (arcing, strange bias behavior). You can spot them also if you have a tube tester.

In my case, the RCA failure rate is 10 percent, no worse than with Russian NOS like Winged C. Stock tubes from Atma-sphere have also failed now and then (not frequent - 5 percent maybe). It is part of the tube scenario.

By the way, a few of the RCAs are replaced by Winged Cs in my amps, working well together ;-)

The improvement from stock output tubes to NOS is maybe not so obvious, then and there, compared to driver tube changes.  It is more long term.

I am not sure of the lifetime of the RCA 6AS7G tube. The RCAs have been running "hot" for maybe 2000 hours in my system over the last four years, plus some "standby" hours that don't affect the lifetime.

I end up by thinking - no wonder users buy NOS tubes for these marvellous amps.
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