VAC 30/30 & Sophia 6SN7's

Yes, I had similar results when I installed a matched quad of Sophia 6SN7's in my VAC Ren 70/70 MkIII, except that the hum level was not "very loud." It was acceptable for the first few months, just about inaudible at listening distance (after I put the worst tubes in the outside positions). However, eventually it worsened somewhat in one channel, and that prompted me to recently replace all four tubes with vintage 1950's Sylvania 6SN7GTB's. Quoting from my recent post in my system description thread:

Replaced the Sophia Electric 6SN7s I had been using in my VAC amplifier with 1950's Sylvania 6SN7GTBs, a matched pair of "chrome domes," and a matched pair of "chrome tops." A slight hum that had resulted from excessive heater-to-cathode leakage in two of the Sophias recently worsened, prompting the change. The Sylvanias have no measurable leakage, and do not produce any hum. Preliminary listening impressions are that the change resulted in significantly improved dimensionality and instrumental "body," while retaining the timbral accuracy of the Sophias, which I had been very pleased with.

The heater-to-cathode leakage in my Sophia's, as measured on my vintage Hickok tube tester, was as low as 3 or 4 megohms on some sections of some of the tubes, and was in the 5 to 10 megohm area on most of the others. That is very disappointing, especially for such expensive tubes. At some point in the future I'll contact Sophia to ask what they would be willing to do about that, but not immediately as I'm just at the mid-point of the one-year warranty I purchased.

FWIW, as I indicated in my system description thread I was very pleased with the sound of the Sophia's apart from the hum problem, which would not have been evident on speakers having significantly lower sensitivity (mine are 97db).

Regards,
-- Al

You need to change to a 6SN7 tube with a GTA or GTB suffix. Almarg's suggestions of going with vintage 1950's Sylvania 6SN7GTB's is a good one.

Thanks, Paul (Pdreher). I don't think that in this case, though, the lack of a suffix is the problem. The datasheet that is linked to at the Sophia site for their 6SN7 is the datasheet for the General Electric GTA and GTB tubes.

Best regards,
-- Al

Prior to insalling the Sophia's, I was running Sylvania 6SN7GTB's in outer sockets and RCA VT231's in the inner sockets. I did notice on the Sophia site that there 6SN7 spec's were the same as the GTB's so I thought I'd give them a try. They are amazing in the outer sockets and really take the sound up a notch or 2 but will not work in the inner sockets. Surprised! Guess I need to get the tube tester out per Al's suggestion about leakage. I did get the 1 year warranty so we will just have to see how this goes down. Thanks guys for your input.

Markus

an incredible little amp

You must be a power lifter, Markus. I thought that my Doshi/Lectron JH-50 was HEAVY until I got my Ren 30/30!! Highly recommended, as long as your health insurance covers disk surgery ;-)
I'll have to check out my Sylvanias but I will comment that the Shuguang Black Treasure 6SN7 equivalent (CV-181?) sounds pretty darn good. I have them in all 4 slots on my Ren 30/30. Not to hi-jack this thread, but has anyone tried the Shuguang Black Treasure 300bs in their VAC Ren?