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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

Showing 1 response by johnsonwu

johnsonwu
469 posts
 
Only seen this with mismatched power tubes where no matter how you bias, if one tube doesnt match the gain characteristics of the rest it will cause hum.

So, I highly suspected that your 6SN7s are matched at all.

Never had this problem on my Phi70 monos no matter I use NOS, Sovtek, EH, or the orig red plastic base VAC Chinese tubes.
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