Atma-Sphere MA-1 tube rolling

always nice to hear advice from the actual maker of nice gear... 

@atmasphere:
Thank you for your detailed response!  
Have your customers mentioned to you what changing out the stock 6AS7G tubes for either the Russian 6H13C or the Chinese (I assume ShuGuang) tubes do differently, for better or worse? 
Would you suggest just rolling the 6SN7 driver tubes for more adjustability?  
Thanks.

I've had my MP-1 and M60s for 20 years now. Follow Ralph's advice and stick with the Russian provenance 6AS7Gs or, alternatively, the 6H13C. I had a brief fling with the Chinese variant and found they had a high failure rate/short life span.

IME, it was problematic to roll the 6AS7 output tubes in my M-60.
I have always been a fan of NOS,
I got a set of 6AS7Gs from Brent Jesse.
They we’re not matched and were three different brands as Brent said.
As Ralph said, the failure rate of NOS is high compared to the stock Russian. 3 of the 16 failed. However, when I got good ones in, the power output went up about 20% and the tone was much better.
I would highly recommend going with NOS as long as you are aware of the failure rate,

Have your customers mentioned to you what changing out the stock 6AS7G tubes for either the Russian 6H13C or the Chinese (I assume ShuGuang) tubes do differently, for better or worse?

Actually the stock tubes **are** either the Russian or Chinese tube (which seem to sound the same; the difference is in how they fail).

Would you suggest just rolling the 6SN7 driver tubes for more adjustability? 

People roll the 6SN7s all the time with nice results. We've found that that Sophia tubes while sounding great at first, seem to have a short life of maybe only 6 months, whereas a regular NOS tube in the same spot can go for years. The one tricky bit is the driver tube which in the MA-1 will be in a different location depending on when the MA-1 was built. If you have a version with reflected left and right hand chassis the driver tube is on the corner facing the power tubes; if a newer chassis the driver tube is the one in the front. This particular tube must have a -GTA or -GTB suffix if you're using an NOS type. Modern 6SN7s like the Shugang 6SN7 or Sovtek are marked 'GT' but are actually GTBs.


If you are forced to use Russian made 6SN7s (which conversely and confusingly from the Russian power tubes are usually a poor choice), they should be screened on a tube tester to show no leakage at all on the leakage test, otherwise you may encounter a buzz. The lifespan of these tubes is also really variable going anywhere from 2 weeks (in which case send it back to where you got it and get it replaced; most tube sellers have a 90 day warranty) to maybe 2 years.