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Modern EL34 reliability?

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  • Except for New Zealand and Australia, when you drop tubes there, they fall up.
    Education is what you're left with after you have forgotten what you have learned.

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    • Originally posted by Enzo View Post
      Diablo, you are probably correct, but insofar as you quoted me, I have to point out I didn't mention g1. My surmise - and it was only that - involved g2 and g3.
      They add that the G2 and G3 are not exactly aligned.
      I can't find this remark about G2 and G3. Rather this:

      "Plate power dissipation of EL34-B can reach 30W, whereas EL34A is 25W. EL34-B belongs to tetrode
      tube compared to pentode tude of EL34A. g1 and g2 of EL34-B is not exactly aligned opposite to each
      other and it is used in linear power amplification."
      - Own Opinions Only -

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      • Perhaps then I misread it, I'm not going to look it up again. If I erred, then I erred.

        Seemed to me when I read it, regardless of which grids it was, they were implying that the misalignment of the grids was why they had to consider this pentode as a tetrode. At least that is what went through my mind.
        Education is what you're left with after you have forgotten what you have learned.

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        • Originally posted by Helmholtz View Post
          If the EL34B actually was a tetrode and behaves like a KT77, why not call it a KT77?
          (IMO, the KT77 is the more advanced design.)
          But to which degree can the REALLY be used as EL34 replacements? The old datasheets state a few significant differences:

          a) smaller grid leak resistances for tubes under full load (=> replace the 220k in a Dynacord Eminent by 180k).
          b) larger bias voltages. Or does that hold for 6CA7s
          c) a maximum of 300V on G2 unless the KT77 is run in UL mode.

          Did anyone try one of those?

          During the last years there still was a source of NOS Svetlana Winged C and even old RFT tubes in Germany - but they seem to be mostly sold out. Which is a pity because my G-2000 urgently needs new tubes.

          And the RFTs - despite being of good quality - may also have their problems. I am just confronted with one that become a little bit gassy (the getter can still compensate, at least nearly) but still works just fine under 750V.

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          • For me, its JJ's. I buy them from CE distribution. When I do use them, I always make sure the screens are 2k2 5W, and add 3000V flyback diodes to the plates.
            Never had an issue!

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            • I was having A LOT of EL34 woes a year or more ago... until I switched to Watford Valve tubes... their 'Harma' brand retros specifically - which I think are Tung Sol EL34xxxx (B-STR? or something like that). They apparently put them through a process for testing and matching - but ever since using tubes from their supply I have had ZERO issues.

              Then again, I seem to have had issues with more specific suppliers... One of the suppliers I buy from I end up getting a fair share of noisy 12ax7's and have had lots of EL34 failures... Never an issue yet with using Watford's branded Harma valves... 12ax7 (balanced and unbalanced), EL34, and 5881. I have them in no less than 5 of my amps currently.

              A bit more expensive, but so far worth every cent.
              "'He who first proclaims to have golden ears is the only one in the argument who can truly have golden ears.' The opponent, therefore, must, by the rules, have tin ears, since there can only be one golden-eared person per argument." - Randall Aiken

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