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In Reply to: RE: Tube rolling buzz with new 12AX7's posted by airtime on April 26, 2015 at 09:22:23
Hmm, the fact it is EITHER diminished or gone that complicates things a bit. But, I think it boils down to two possibilities:
-A) The TungSol has a buzz. You'd need to describe said buzz a little more, but it could be a heater, maybe? Given the intermittency of the buzz, this requires more testing; try more tubes, eliminate the TungSol completely, and see what happens.
-B) The TungSol is fine, and the socket is a little worn/dirty, making so the TungSol has poor contact (even post resto, sadly).
That said, I find there's some notable variances in newer tubes in terms of the pin widths and the 9-pin glass bases. It could be just a half millimeter compared to that RCA, but that could mean quite a bit in terms of proper contact.
Also, I find a lot of newer tubes have these really shiny pins, like polished stainless steel. I'm not metallurgist and I don't have an electron microscope to prove it, but I think a rougher-surfaced pin would sport microvalleys and edges that would effectively "dig into" the socket's contacts. With a smooth surface, you would have to depend on true and proper contact between flat surfaces. As the socket wears out, good and reliable contact may increasingly difficult to achieve with newer tubes.
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May your tubes be warm, long-lasting, and always lively. Holy be thy heater.
Follow Ups:
Again the buzz, not hum, is steady and both channels.
The tubes are good. they were tested before I got them.
Age and type - New TungSols with gold pins.
Right now I am using the RCA Blackplate in V1 and the Tungsols in V2 and V3 with no problems. However I did have to "wiggle" the RCA last night to get better contact.
I can retry the Tungsol in V1 and try "the wiggle" with the amp on. WOWWWWW do I hate doing that! But I tried all the Tungsols in that position several times and the buzz was the same. So a contact problem would change with all that motion????
charles
Try cleaning and tightening the socket tangs. Dental probe works nice with 9-pin mini sockets. Unit off, main caps drained.
How do I cinch the socket without trashing it?
charles
From the top of the socket, I insert the end of a metal Dental pick into the edges of the socket tang. Then, bend the tangs in, gently, on each side.
Power off. Be sure to discharge any residual voltage from the main PSU caps before inserting the metal dental pick.
But on a good note, the hum is now equally loud on both channels.
It's the a good loud hum. Seems it really did need a pin tightening anyway.
charles
The RCA is still quiet, in the same socket?
Yeap, so is the Bell & Howell and Zenith I switched over from the phono section. In June I'm going to try some tubes Jim recommended. I'll post any interesting findings.
thanks
charles
I actually have one of those. And no I'm not a dentist. Just a hobby - kidding!
Thanks, I'll try that tomorrow. I thought I was going to have to take the bottom off and crimp the tangs. I know Mike cleaned the HECK out of this amp. So pin dirt and corrosion wasn't high on my list.
thanks again
charles
Excellent advice from Steve! The RCA pins are likely making a bit better contact. I'd bet the hum is contact related!!
Last night I tried the thumb trick you recommended. I did get a nice nasty array of whooshing and popping sounds. Never actually got to the hum part being I was afraid of popping a speaker at one point.
I'll give it another try tonight.
When I was trying all the other tungsol/RCA combos, each time it was the same buzz. I do think it is a pin issue. but i found it curious that it didn't change with all those different trials. And it doesn't seem to be an issue in the V2/V3 sockets.
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