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  • Modern EL34 reliability?

    What are people using for reliable but economic replacements for EL34s running 500 plate volts?

    JJ EL34 are money wasters.

    The new 'Svetlanas' seem a bit hit and miss. Sometimes the bias won't hold/settle, even though the g1 voltage stays more or less constant - even with the g1 voltage at a steady -40, the cathode current just keeps gradually creeping up through the 30s and 40s and when it gets into the 50mA decade it starts to zoom further upward.

    I'm tired of having to replace new duds.
    Last edited by tubeswell; 07-07-2017, 11:25 AM.
    Building a better world (one tube amp at a time)

    "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

  • #2
    Originally posted by tubeswell View Post
    The new 'Svetlanas' seem a bit hit and miss. Sometimes the bias won't hold/settle, even though the g1 voltage stays more or less constant - even with the g1 voltage at a steady -40, the cathode current just keeps gradually creeping up through the 30s and 40s and when it gets into the 50mA decade it starts to zoom further upward.

    I'm tired of having to replace new duds.
    "NEW" Svetlana? These must be the tubes labeled "Svetlana" by New Sensor. Settlement of a marketing dispute about 15 years ago gave New Sensor (owner of labels Sovtek, Electroharmonix, Mullard, TungSol, GEC Genalex Gold Lion but all manufactured in their Saratov Russia tube factories) rights to sell tubes labeled "Svetlana" while the real Svetlana, now out of the consumer tube manufacturing business since @ 2011, sold theirs in the USA under flying C, =C= brand. Confusing isn't it? And perhaps someone who knows more about it can help clear it up more for us. AFAIK there's no advantage to the New Sensor "Svetlana", and they don't have whatever special qualities of tone or toughness that were attributed to the real =C=, made in St. Petersburg, Svetlana output tubes. As far as I can tell, tubes made presently and distributed with Svetlana labels are same as EH & Sovtek, differing only in the paint design on the glass. But of course I could be wrong...

    AND I'd like to know about any currently available EL34 that will hold up in hi voltage amps. It seems all we can do at the moment is 1) replace screen grid resistors with larger value ones. Trouble with this is you go beyond 2K2 and that starts to seriously interfere with the tone & feel of the amp. Or B: build a separate screen grid supply, at a voltage that's half to 2/3 of the amp's B+, then bias EL34's appropriately to 30-35 milliamps. What a big pain in the rear end! But I'm about to do it to an old Laney "Klipp" because I can't find any other solution.
    This isn't the future I signed up for.

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    • #3
      I've used shuguang el34s in an amp with 500 on the plates and they were fine. They market a version (BHT? I forget) which have been tested to work at higher voltages too and I think TAD resell these.

      EDIT:

      Ruby resell them:
      http://www.dougstubes.com/ruby-el34-bht.html

      maybe try and find them from someone else though!

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      • #4
        EH seem to work fine for me.

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        • #5
          Agree with the RUby, I had great success with their EL34B Chinese tubes. Never got a bad one, they worked/sounded good, and were reliable.
          Education is what you're left with after you have forgotten what you have learned.

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          • #6
            +1 on the Ruby rebranded Shuguang EL34B. The only tubes to survive the 'balls to the wall' test at 475Vp in a recent build. And all three pair did it. All three were microphonic though. to the point of being questionable for use in a combo amp. And I bought two pair from one vendor and one from another. ALL were microphonic like this. Sounded great otherwise. Better than the JJ's (the same amp blew up two pair). I tried the JJ E34L (some kind of different el34 that requires more bias voltage). Those survived, but sounded nothing like a proper EL34. I didn't like them.
            "Take two placebos, works twice as well." Enzo

            "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

            "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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            • #7
              I think those E34Ls were for 6L6-amps, so you could use them without reworking the bias supply... Well, maybe they were just "off-tubes" that they "found a use for," like, "hey, these'll plug right in a Fender, all you gotta do is add a single tiny jumper wire..."

              Why the craptoaster can't they make an EL34 like those Sovtek 5881WXTs?

              Justin
              Justin
              "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
              "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
              "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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              • #8
                I suspect because the EL34 is a true pentode, while the 6L6 is a beam power tube.
                Education is what you're left with after you have forgotten what you have learned.

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                • #9
                  What do you guys think about the jjs at lower plate voltages? Would you feel ok about installing them for someone in 300-350Vp amp?

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                  • #10
                    I never think of plate voltage as the killer, drop your screen voltage or screen current instead. What really kills power tubes is dissipation, not voltage. Those frail little grids in the EL34 can melt.
                    Education is what you're left with after you have forgotten what you have learned.

                    Comment


                    • #11
                      I understand and I kind of mean if those parameters are configured conservatively. It's cathoded biased to somewhat less then rated dissapation (I think I shot for ~11W), and I believe I used 2k2 screen resistors, although I didn't mearsure the screen current. Vp is about 305. Soooo.... can I give it to someone with JJs with reasonable confidence that it won't blow up? I didn't realize they had a bad rep....

                      EDIT: I guess the common sense answer is check the screen current.

                      Comment


                      • #12
                        Originally posted by Zozobra View Post
                        I've used shuguang el34s in an amp with 500 on the plates and they were fine. They market a version (BHT? I forget) which have been tested to work at higher voltages too and I think Ruby (as per edit) resell these.
                        That's great too. And I mentioned that they worked for me. Trouble is "higher voltages" shouldn't need to be tested for in a properly made EL34. If you look at the vintage spec sheets they are exampled at voltages and current that would roast new examples. Granted, none of those sheets indicate whether the tubes would fail if you clipped them under such working conditions. But asking 500Vp for an amp that will be clipping from a tube that's SUPPOSED to be rated for 800Vp seems reasonable. Especially when you consider that in other guitar amps the humble 6V6, rated for only 350Vp is often operated at over 400Vp and survives clipping without much trouble. I guess I just double take when I read that current EL34's need to be selected to survive "higher voltages" so they won't roast in amps using 60% of their RATED Vp.

                        WRT newer tubes I think EL34's have been a weakening offering since twenty years ago. If what's available now was sold by any vendor twenty five years ago they'd have been tarred, feathered and run to the edge of town by torch light. Now, today we just want new tubes we don't have to throw away.?.
                        "Take two placebos, works twice as well." Enzo

                        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                        "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

                        Comment


                        • #13
                          Originally posted by Chuck H View Post
                          I tried the JJ E34L (some kind of different el34 that requires more bias voltage). Those survived, but sounded nothing like a proper EL34. I didn't like them.
                          JJ E34L are more powerful and clean than EL34. THey are good for some things if that's what you want. I put them In my sound city 120 and liked it less because it had less distortion when cranked. It was cleaner, fuller, and louder sounding, and that amp is already loud as hell.

                          I have been running 6CA7 for months on end full volume with 580V on the plates and similar on screen . My screen supply has a 1K dropping resistor in series with 1K screen grid resistors though so the screen supply sags to about 390V at full tilt. If they eventually explode I will report back.

                          I have used KT77 in replacement of KT88 on a sunn model t style amp (the 70s one, ultralinear with 530-540V plates and screens) and they seem to stand up fine. Has more distortion and only puts out about 110W at clipping instead of 130W but sounds great. I prefer it over KT88 in the amp.

                          Why use EL34 when there is KT77 and 6CA7?

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                          • #14
                            Also as an aside and an anomoly I ran JJ 6CA7 for about a month full volume with full screen supply (580V with no 1K dropping resistor in series with individual 1K screen grid resistors) and the tubes did not die. They did however drop from 150W output to 120W in that time. When I measured the screen dissipation at full volume it was something like 17.5W. Over double the maximum screen dissipation on the datasheet, 8W. I must have done 20-30 hours of playing like this

                            maybe Im getting lucky but I find JJs to be pretty rugged.

                            Even all the 6L6s that stand up to the 530-540V plate/screen supply in Ampeg V4s

                            Comment


                            • #15
                              Valve Queen will match and burn in tubes for 72 hours at 350, 400 or 500v. She has Ruby (6 month warranty) as well as several other lines. VALVE QUEEN vacuum tubes

                              I put a set of Rubys in a Marshall Jubilee that was running at 525v. I also then put it on a bucking transformer to bring things down a bit. AFAIK it is still running.
                              It's weird, because it WAS working fine.....

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