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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
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
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
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
markus1299 OP
252 posts
 
Thanks Almarg for the info. I will pass your suspicions on to Kevin for consideration. I believe, for what we paid for these tubes, we should not be seeing this trouble But, it's all a learning process in this hobby isn't it?

Markus
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