Well, this surprises me. I thought there would be at least a few people rolling tubes in their C-30.
16 responses Add your response
ONE day and you're surprised?
I had a pair of M60s, and I've had other poweramps that use 6SN7GTs in their frontends. In my and MANY others' opinions, there in no overall-finer-sounding 'N7 than the Tung-Sol Roundplate. They seem to be worth around $100 now, with just-found NEW ones well over $200. (They stopped making them in the early 1950s, I believe.)
One other note--even those that test low in various tubetesters still sound great in poweramps.
E-mail Ralph at Atma-Sphere to ask about the most-audible tube positions.
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.
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.
I just received this message from an Internet friend. I just emailed him for an explanation. For someone like me who is not technically advanced, can anyone comment in simple English so that I can understand what is going on here?
"DO NOT PUT THE RPs IN ANY LOCATION EXCEPT THE FRONT 2 TUBES !!! This is VERY important because the drive tubes are GTBs which have a rating of 450V - which is way beyond what the RPs can handle."
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.
In the S-30, the rear tube has a little more voltage on it. If you are using NOS tubes, a -GTA or -GTB is recommended. A GT will also work but will not last as long- it is running right at its limits. So save your expensive KenRads or whatever for the front two positions.
Modern 6SN7s are marked 'GT', like the Chinese 6SN7; they work fine (that is what we use of course) in any driver tube location.