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I have a pair of Doshi Audio monoblocks that have a Hytron 12SJ7 input and two Philips 12SN7 drivers. I'm getting some noise and occasional volume drop out. I checked the SJ7s and they are weak, the SN7s are strong. I'm going to replace the 12SJ7s. How much of a difference will a different brand make? Obviously a good testing tube will sound better but is there any make that will be better than another? Thanks.
Follow Ups:
...but is there any make that will be better than another?
Better than another?
Try some WT Grant or Woolworth.
Anything other than JJ.
"I can't compete with the dead" (Buck W. 2010)
"It would take me forever. I don't think I have forever" (Byrd 2015)
When in doubt, buy RCA!
Eli D.
nt
I have mil spec 5693 (6SJ7) in a couple amps. I like the tone over consumer level 6SJ7. But, metal tubes tend to be microphonic.
Good hunting!
Thanks for that info. Would tube dampers help with the microphonics?
In my experience, very little help using damper rings with metal cased tubes. Noisy tubes just need to be replaced. Luckily, there seems to be a lot still available.
Not being able to see IS a problem. If a metal envelope tube is slightly microphonic, a silicone rubber "O" ring, where the envelope meets the wafer base, and a blob of high temperature RTV on top can be tried. For some added mass damping, embed a piece of lead, like fishing split shot, in the top RTV blob.
Eli D.
Pardon my ignorance-What is RTV?
Which one is the glass tube version?
what role does it play in the amp?
Thanks in advance for a reply.
RTV = room temperature vulcanizing. A link to a suitable Permatex product is provided below.
If you want a 12SJ7, with a glass envelope, look for 12SJ7GT.
Eli D.
nt
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