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VAC 30/30 & Sophia 6SN7's

I recently purchased a VAC Ren 30/30 amp that is an incredable little amp and the best so far in my system. I decided to try some tube rolling in the front 4, 6SN7's and purchased a matched pair of the highly reguarded, Sophia 6SN7's to try out. When I install them in the inside (splitter positions) and then power up, a very loud hum is generated to the extent that I am afraid I will damage something so I shut it down. If I install them in the outside (driver) positions everything is fine and the sound is great. My question is: Has anyone experienced this? Are my tubes bad?
I do have an email in to VAC but thought I'd seek out any experiences that other, more knowledgeable audiophiles might have.
Thanks
Markus
markus1299
markus1299 OP
252 posts
 
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
swampwalker's avatar
swampwalker
5,138 posts
 
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?
almarg's avatar
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almarg
9,670 posts
 
Highly recommended, as long as your health insurance covers disk surgery ;-)
Michael, you should try lifting (actually, you SHOULDN'T try lifting) the 70/70!! :-)

Best regards,
-- Al
markus1299 OP
252 posts
 
Update- Kevin Hayes of VAC emailed me about my experience with the Sophia's and would like me to send him the tubes so that he can test them and sort out the problem I am seeing. How many manufacturer's are willing to do that for you? Anyway, I'll probably take them over to him (I don't live to far away) and I'll let everyone know what his results are. Should be interesting.

Thanks

Markus
almarg's avatar
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almarg
9,670 posts
 
Wow! As always, Kevin is terrific.

FWIW, my speculation is that a little bit of 60 Hz and/or 120 Hz ripple is present on the DC that is supplied to the filaments of the tubes. Perhaps its magnitude is a bit greater than when the amps were new, due to aging of the filter capacitors. The excessive heater-to-cathode leakage of the tubes, in turn, couples some of that ripple to the cathodes of the tubes, thereby causing it to enter the signal path.

Thanks for the update!

Best regards,
-- Al
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