The Reference 6J5 Thread (L63, 6C5, 12J5, 6P5, etc.)
Aug 28, 2022 at 8:36 PM Post #2,418 of 3,886
And they are 'Demonstrably better'! Not just good or better...
But where do I find my N.U. distributor...?
And if you do, can you use…?
Aug 28, 2022 at 9:38 PM Post #2,419 of 3,886
Aug 28, 2022 at 10:37 PM Post #2,421 of 3,886
NU went out of business around 1953 and was bought by Sylvania. The Lansdale,PA factory used to be NU.
And S&H stamps are just collectors items today.
PS…Long-plate Lansdale 12AU7 s are fantastic tubes !
Aug 31, 2022 at 1:11 AM Post #2,427 of 3,886
Here is a Sylvania 6SN7GTB tube:
But what is this?
Another Sylvania 6SN7GTB? No, as pointed out by Triod750, this is a single and not dual triode - it is a Sylvania 6J5WGT with extra (disconnected) hardware inside.
I am curious how this came about. You would expect a single triode to have just one plate:
4pm Friday came before the ‘hardware’ could be connected…?🤪
Aug 31, 2022 at 1:56 AM Post #2,429 of 3,886
It looks like it was deliberate because the tube is labeled and functions as a single triode.
I have a pair of these as well and was mega-confused when inspecting the tube for the first time. I stumbled on a bit of info half-way down this page on why they might have done this:

“If you look closely, cathode and grid are only assembled inside one of the plates. It is better visible when the tube is lit up

Obviously the same tooling and internal structure as for the 6SN7 was used, they kept the second plate inside for mechanical stability, but left the cathode and grid out.”

If I had to hazard a guess I would think it could also be related supply chain efficiency, with less unique parts to manufacture, stock, and assemble. Interesting tube but too bad they don’t sound very good…
Aug 31, 2022 at 2:06 AM Post #2,430 of 3,886
too bad they don’t sound very good…
I used to have a pair of Sylvania 6j5s that sounded phenomenal, except for a pretty strong buzz. I tried to re flow the solder, but ended up killing the tubes instead.
In my attempt to get another "magic" pair of Sylvanias, I mustve bought 8-10 pairs of 6 and 12j5s....all of them sounded pretty bad.
To this day I have no idea what made that one pair sound so good and the rest were not. Oh well....

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