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In Reply to: RE: Who makes that tube? posted by Jay Buridan on July 07, 2020 at 10:58:59
Made by PSvane. https://www.dagogo.com/audio-note-uk-4300e-output-tube/
The first picture in that article immediately actually struck my interest since the top mica support does not come in contact with the envelope. further down in the article there is a seemingly identical picture of a different tube where the top mica is in direct contact with the glass.
speculation below.... would love to see citations for or against the concept.
When early tube manufacture moved away from globe to ST shaped tubes the top mica showed up in place of a glass arbor (talking globe 50 here) This mica also was a "press fit" into the inside of the top of the tube to assure everything was visually straight. Now globe and ST 50's sound very different and the big thing you notice is when you tap the tube, the ST sounds like hitting a trash can and the globe has an almost gong like sound. When the new production globe tubes came out over a decade+ ago, the top support mica remained and tethered the top of the plate structure to the envelope. I didn't notice a major difference between globe and ST tubes of the same manufacturer. There were small differences but nothing like that of a globe vs. a ST 50. This is what made me start thinking it was not the shape of the envelope but the mechanical resonant behavior that caused the difference in sound between globe and ST tubes.
Back to the AN tube. The first picture has a screened logo and may have been a first prototype and could have used a ST mica. The second picture has what appears to be an engraved badge with serial # inside the tube and it will be interesting to see which way the final production went wrt top mica.
made in China, of course, in which the top mica does not touch the glass to secure the inards of the tube.
Good sounding tubes but microphonic as all get out.
Later, Full Music/TJ claims to have fixed this with a larger mica that held the workings in place and claimed less microphonics than the first version.
I find it hard to believe that firmly fixing the structure to the top of the envelope as well as the bottom helps isolate it from outside vibration. If anything, I would expect it to push the resonant frequency of the vibrating bits up which i would expect to be much more objectionable.
My gut feel is that the top support showed up in conjunction with the ST tube to make assembly easy and repeatable... nobody wants a tube with a plate leaning to one side or the other... all of the electrons will most certainly fall out.
Well, the ST build fixes the top to the glass with some mica. The design of this mica varied a fair bit, usually little nubs, the Tung-Sol mouse ears, and the 5881/6098-style additional pads...
The folks I talked to all said this was assembly for assembly alignment. As with all the internal features that often seem taken as hallmarks of THe Right Tube, I do have my doubts as to their intentional addition for anything else other than improving and shortening the ramp up to full specification production when it came time to execute a type run.
There have been plenty of leaner tubes through my hands, though this has mostly been base to glass. Sift a big pile of 6SN7's and see...:)
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
My thoughts exactly!
Whatever they did, and maybe they did other things as well, they claim to have fixed the microphonics in later TJ/Full Music globe tubes. I never tried them so I have to take their word for it.
Have a pair of early KR 300B (ST with very thin glass) that are also mircrophonic. Later KR had thicker glass and were supposed to be less microphonic.
Who knows. Best 300B I've had in my system is the Charlie's Kansas made WE300B which I've had for about 15 years? No getter left but they still play.
Doubt I'll live to see another WE300B from Charlie. :-(
Used pair for sale now on eBay, with picture.
Interesting... the ebay ones show the tube to have an round top mica support with another "Trimmed on the side" round support above it extending beyond to the tube glass. This looks identical to the one in the dagogo picture of the tube with the serial number inside the glass. The top picture in the Dagogo article with the screen printed label is rotated 90° but is from a low enough angle that you would still see the second layer extend to the glass beyond the mica. It almost looks as if it were trimmed in the the "support free" image but now that I look at it closer I think it is there but has a slight bend to it from the down pressure of the tube envelope making it disappear since it is perpendicular to the lens. If that is the case I would expect the back half to also be bent down an equal amount and should be visible which it is not. I can kinda make out the 5 points on the front and back but I do not see any convincing evidence one way or the other.
The tubes pictured in the Audio Note shop and Parts Connection don't look like that. They look like the one that Dave Slagle put up in his message.
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