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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
c1ferrari
464 posts
 
As shall I :-)
I'm pre-conditioning 6H13C's at the moment.
Best of luck with your RCA's!
o_holter OP
541 posts
 
Thanks Rushton & Clferrari. I am sure people have tried this before me but there is not much info on the web, since most of the focus has been on the driver tubes. It will be interesting.
o_holter OP
541 posts
 
After 60 hours of preconditioning I could not stand the silence anymore, and decided to give the RCA 6AS7G tube set a try. So I put the MA-1 amps from Standby (yellow) to On (red light). No misbehaviour or arcing so far, having played for three hours. Sound? Short version: not looking back, these tubes stay, my Russian/Chinese (Atma-sphere stock tubes) have now become extras. Tested with some favorite LPs, Can: Future days, Cohen: Ten new songs, Stranglers: Feline, Alan Parsons Project: Eye in the sky - all very good indeed. It is a bit of give and take though. The Russian may measure better, more top and bottom frequency, more upfront sound, but to my ears they are also fatiguing and hard. The RCAs may be more rounded off, but the musical illusion is better. Like my wife said, "they are more silent so you can hear more detail". Only trouble so far - some noise from 1-2 tubes in the right channel, off and on, seems to go away when I rap them, may need replacement.
o_holter OP
541 posts
 
I listened some more. If these 28 RCA tubes hold up there is no doubt, this is what I prefer. I am willing to foresake the strong points of the stock Russia/China tubes. Three main reasons. First, better musical illusion, in the midrange especially. Second, more musical drama. Even boring tracks sound less boring now. Third, more than with the stock tubes, the amps become chameleons. They shift according to the sound, the production of each track - a big plus in my book. So my main reaction is "I never knew this LP was that good". Like Elton John: Tumbleweed connection, things I've not played much. This is a good sign. I checked with some of the more "wool" sounding record I have, did they sound too closed in now, like one might suspect. Including Carlos Jobim: Wave (on Speakers Corner). But no, they sound good. Another plus in my book. I read somewhere that the RCAs would increase the output compared to the stock, but that is not the case for me. The only thing I miss is a bit more output and volume, "slam factor".
rushton's avatar
rushton
2,430 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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