Rolling Tubes in the Atma-Sphere C-30 amp

I also own the S-30 amp. As for the power tubes I only use the stock tubes as supplied by Atma-Sphere. This is based on my conversation with Ralph as to the reliability of NOS 6AS7 tubes. Also, the version of the tube that is the slender bottle is not necessarily suitable for the amp according to Ralph. I recall trying a set of these and immediately the tubes glowed intensely orange and the amp hummed. As for the driver tubes Ralph mentioned tube rolling the front row of tubes would probably yield the most noticeable results. In my case I chose Raytheon VT-231 tubes. I use the stock Chinese tubes in the other positions.

Sabai, the row closest to the listener for the driver tubes.

The problem with NOS 6SN7 tubes these days is the fact the desirable brands like the Tungsol Round Plates, Sylvania GTs, Raytheons, Ken Rads, RCA red base are becoming scarce. What you see on eBay is a crap shoot. Most of these tubes are not being measured thoroughly and will most likely be unacceptably microphonic. There are a few trustworthy tube dealers out there that have a nice stash but you will pay for them. FWIW I have heard from Ralph based on feedback he has received from customers that the new production Psvane 6SN7 is quite good. I intend to try a set in my custom MP-3 when I receive it.

The use of GTB's in the last two rows was also mentioned to me by one of the Atma-Sphere resources. My guess is this may be due to the variants of 6SN7 (GT, GTA, GTB, WGT, etc.) tubes having different voltage specifications, but I am not certain.

Personally I have used NOS Sylvania GTB tubes in the last row, but went back to the stock tubes.