12AX7 testing

[Kage]

From what I've been able to figure out, it appears that the Sovtek 12ax7WC is the same tube labeled as the GT-12ax7-R3, the Electro-Harmonix 12ax7, the New Tung-Sol label and the Mesa/Boogie 12ax7. I know both Groove Tubes and Mesa do testing on them before putting their own name on them, my question is does anyone know to what extent each place does their testing?

[tubby]

At least the Tung-Sol reissue and the Sovtek 12ax7WC look different:





The most distinct differences on the Sovteks are the the triple mica and the shield between the two systems.

The GT looks similar to the Tung-Sol. Couldn't find any large pics on the Mesa's....

[Kage]

Interesting, I didn't have one to compare but I'd heard the TS was the same. That looks completely different from the Mesa/EH tubes I have. Looking at the pictures on the Sovtek site they actually look more similar to the LP or LPS than the WC. Which I believe would make them the GT R2 not the R3. Anybody have an definitive info on which tubes are rebranded as what? And whose come out more consistent?

[Enzo]

Good idea is to stop listening to the conspiracy theorists about tubes.

Some people figure that since New Sensor owns SOvet, EH, etc and has the tubes all made in the same factory, then they must just be the same tubes. But they are not.

Then ther are companies like Groove Tube and Ruby Tube and Mesa that don;t make the tubes, they just sell them under their labels. THAT confuses people.

I'd say if we were trying to figure out just which tube Groove is selling under a stock name, then why not just buy the original tube in the first place, and save some money? Why pay the GT markup? You don;t seriously think GT tests every 12AX7 they sell. Buy tubes from a reliable tube vender, and they will back up the tubes they send you. I don't worry about getting a bad tube, my vendors support what they sell.

[Kage]

I guess that's what I was trying to find out, to what extent any testing is done before relabeling. It would be the only reason to pay the extra for the barrel rather than just going to the tree.

[Kage]

So, on further examination I believe that the EH is actually the Sovtek 12ax7LP, which is also the R2 from Groove Tubes. I have some Mesa's that are the same inside but also a couple of Mesa's that appear to have originally been JJ's.

I know that the LPS from Sovtek has to do with a spiral filiment, but what would be the differences in characteristics between the LP and the LPS?

[defaced]

Mesa has changed their tube source since when I owned my Triple Rec (06? maybe). They were using "Russian II's" (whatever that means, Solvteks I think) and now everything I've read says they're using JJs.

[Kage]

Yeah, the pictures on the Mesa Boogie site appear to be JJ tubes.

Dumb question, am I supposed to feel something vibrate when I tap a JJ with my hand? And does it seem to anyone else that the flashing on the JJ's disappears really quickly?

[defaced]

I have 3 JJs on hand, 81, 82, and 83s, all with different run times on them, and they're flash is all the same, and they all vibrate when I tap them with my finger while holding them. Looking at the getter, it only supported by one piece of very thin metal, so that's probably what's vibrating. I have some other tubes, an old RCA and a Chinese 12AX7, that are both constructed the same way and both vibrate like the JJs. Conversely, I have an old Mullard 84 and GE AU7 that have their getters suspended differently and don't vibrate.

[Kage]

Do the JJ's all have the flashing pretty far up towards the top? Maybe they were always there and I just didn't notice and that's why it seemed they were disappearing.

[defaced]

See attached image. If you'd like any others just let me know.

[Kage]

Aw, thanks, you didn't have to do that. But yeah, that's what they look like. I'll have to give them another tryout, I was suspicious they were going south. Maybe not.

[defaced]

I'm one of those people who uses a picture to describe something whenever I can. And with the beauty of digital cameras, that took less time to do than to type up a description.

[jrfrond]

No matter how you slice it, the end user is the final QC tester for all tubes. And you can bet that there WILL be occasional bad tubes.

As far as which 12AX7 is better than the other is all in the ears of the beholder. Each design sounds different.

I purchase all of my tubes in bulk from New Sensor, and they have been very good to us with bad tubes, etc. I can tell you, like Enzo said, that their Tung-Sol tubes are NOT the same as Sovtek or E-H just because they all come from the Reflektor factory.

Having said that, I avoid Chinese tubes like the plague, and have seen more JJ's go south than any other brand.

[Rhodesplyr]

Having said that, I avoid Chinese tubes like the plague, and have seen more JJ's go south than any other brand.[/QUOTE]

I distrusted Chinese tubes for a long time, but the latest ("Generation 9") Shuguang 12AX7s are pretty good, though I prefer the reissue Tung-Sol.

JJ has unfortunately become notorious for quality control problems, though it seems to be tube-type specific. To my ears, the small-plate JJ 12AX7s don't sound very good in musical instrument amps, though they can work in Hi-Fi equipment. The long-plate version seems to sound better in guitar amps, etc...

David