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Thread: 12AX7 testing

  1. #1
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    12AX7 testing

    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?

  2. #2
    Member tubby's Avatar
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    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....

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    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?

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    Senior Member Enzo's Avatar
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    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.
    Education is what you're left with after you have forgotten what you have learned.

  5. #5
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    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.

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    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?

  7. #7
    Old Timer defaced's Avatar
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    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.
    -Mike

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    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?

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    Old Timer defaced's Avatar
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    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.
    -Mike

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    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.

  11. #11
    Old Timer defaced's Avatar
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    See attached image. If you'd like any others just let me know.
    Attached Thumbnails Attached Thumbnails dsc_0172-large-.jpg  
    -Mike

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    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.

  13. #13
    Old Timer defaced's Avatar
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    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.
    -Mike

  14. #14
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    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.
    John R. Frondelli
    dBm Pro Audio Services, New York, NY

    "Mediocre is the new 'Good' "

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    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

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    I like the sound of the JJ's long plates too, but not as much as the Sovtek LPS...

    What I'm about to say amounts to nothing more than my opinion, but take from it what you wish.

    Lately I'm using Sovtek LPS tubes for everything except for V1 in high gainers. My usual 12AX7 tube is the RCA gray plate. The RCA sounds as good as the Sovtek but is usually non microphonic. Where the Sovtek is almost always a little too microphonic for V1. So I use the Sovtek WA short plate tube for V1. Not as dynamic as I'd prefere. The WA sounds good but lacks some top end clarity, but when I'm cranking an amp it all evens out and the WA is dead quiet. So my tube line up for the amps I use and sell is usually a Sovtek WA followed by all Sovtek LPS. Unless NOS tubes are requested and then I like the RCA's and Mullards.

    The only way to know if you like a tube is to try it. I've tried a lot of tubes and IMHE there is no point at all in buying preselected/rebranded tubes from Ruby, Groove or Mesa. I've always done just as well or better buying the original MFG labled product.

    JM2C

    Chuck

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    So what would be the difference between the LP and LPS? I know one has a "spiral filiment" but I have no idea what that means/does.

    Further discovery indicates that the EH's I'm liking so much are a shorter plate version of the LP/S, not just the same tube with a different label.

  18. #18
    Member tubby's Avatar
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    spiral filament just means that the heater wires in the tube are twisted pretty much in the same way as it is done with heater wiring inside the amp chassis in order to minimize stray-pick up from the heaters (if operated with AC). this supposed to be quieter, could be also just a marketing thing....

    Someone ever A/B tested spiral and normal filaments?

  19. #19
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    A spiral filament will have less Cathode-to-Filament capacitance than a straight wire type. Depending on the application, you will notice a difference. The spiral is like a spring, not like two wires twisted together, as are normally run to heater connections.

  20. #20
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    Quote Originally Posted by defaced View Post
    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.
    Ah but how the "getter" is supported is relatively meaningless. Its done its job already. Its only function was to hold the material to make the actual "getter" which is generally called the flashing-the silver coating inside that absorbs unwanted gases. Bob
    "Reality is an illusion albeit a very persistant one " Albert Einstein

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