What tubes can be used in place of EL34s?

Discussion in 'Gear & Equipment' started by Bearitone, Mar 29, 2021.

  1. Bearitone

    Bearitone SS.org Regular

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    I have an Orange Dual Dark with EL34s. One of my first tube amps in years and I’m kicking around the idea of trying some different tubes for shits.
    Can i throw KT66s or KT77s in there without rebiasing?
     
  2. DudeManBrother

    DudeManBrother Hey...how did everybody get in my room?

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    Even swapping new EL34’s could need a rebias; but in general you can swap E34L’s and KT77’s without issue.
     
  3. diagrammatiks

    diagrammatiks SS.org Regular

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    E34l, kt77. Kt88 if the bias range allows for it.
    Really depends on the bias range of the amp.
     
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  4. narad

    narad Progressive metal and politics

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  5. Kyle Jordan

    Kyle Jordan Ace of Knaves

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    I always liked 6CA7s over EL34s. Adds a bit of 6L6 flavor to the mix.

    As for bias, it’s a good idea to make sure the bias is at least checked with any new tubes. It’s been years since I had to consider buying new power tubes, but so any of the current vendors offer tubes that they’ve tested and know the bias of? If you know what the current bias of the amp is, you might be able to order a set already in the range your amp is at.
     
  6. TheWarAgainstTime

    TheWarAgainstTime "TWAT" for short

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    I've used 6CA7's in place of the stock EL-34's in my 50/CL and they're an interesting change of pace. They land somewhere in the middle between EL-34 and 6L6 voice-wise amd were an easy swap :yesway:
     
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  7. steinmetzify

    steinmetzify CHUG & SLUDGE

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    If you go KT77s let me know what you think, would you? I’ve thought about it and have a set of Gold Lions sitting here that are extras for my Herbert, thought about it but don’t wanna fuck with perfection lol
     
  8. Emperoff

    Emperoff Not using 5150s Contributor

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    Even if the amp has a "bias switch" or "autobias", etc. Truth is you should always rebias when you change power tubes. If you replace them for the exact brand and model you can get away with it.
     
  9. Bearitone

    Bearitone SS.org Regular

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    Going to go with KT-88s if possible, KT-77s if not. I have a tech looking at it now and I’ll keep y’all posted
     
  10. budda

    budda Do not criticize as this Contributor

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    So long as they physically fit, you should be ok. KT88/6550 vs EL34 is a surprising difference when you see it lol.
     
  11. Bearitone

    Bearitone SS.org Regular

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    Lmao! I just actually looked at the bottle size and they are fat boys for sure. Fingers crossed they fit
     
  12. budda

    budda Do not criticize as this Contributor

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    Hopefully your sockets are spaced far enough apart :yesway:
     
  13. wakjob

    wakjob SS.org Regular

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    An EL34 in a PENTODE ...
    The KT88 is a BEAM TETRODE

    Different family of tube that will require some mods.
    Just like converting a 6550 Marshall back to EL34 needs screen grid resistor change, new biasing network, ect...
     
  14. diagrammatiks

    diagrammatiks SS.org Regular

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    heh ok dude.

    it depends on the amp. the original bias supply, and the tolerance on the screen grid resistors.

    Oh what the hell am I saying. you got me all turned around with your BIG CAPS DUDE.

    Going from el34 to kt88 is absolutely fine because you're putting the kt88s into the operating range of the el34s. el34s operate at a lower plate range which is well within the safe operating range of kt88s. Screen resistor value and all.

    The only thing is that the bias supply has to be able to supply the range.

    Going the other way definitely requires some mods IF IT CAN BE DONE AT ALL. see I can type big too.

    Especially since the plate voltage of kt88s can greatly exceed the safe operating plate voltage of el34s.
     
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  15. diagrammatiks

    diagrammatiks SS.org Regular

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    Just keep in mind that since you'll be running the kt88s so far out of spec it might not make the different you think it will.

    You won't magically get 25 more watts of headroom or anything.
     
  16. Bearitone

    Bearitone SS.org Regular

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    Maybe not. I just saw a guy on YouTube try a bunch of different tubes in his Rockerverb (I know not the same) and the KT88s sounded the best to me.

    If the amp needs anything more than a bias adjustment I won’t go through with it.

    Not expecting to get anything crazy out of it but, in a looooottt of comparisons I listen to (even for other non-Orange amps) EL34s are usually my least favorite so I figure anything is an “upgrade”.
     
  17. diagrammatiks

    diagrammatiks SS.org Regular

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    It will absolute sound different. but it won't be running an amp actually built for kt88s.
     
  18. wakjob

    wakjob SS.org Regular

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    Yep, sometimes one can get lucky and just pop them in and do a quick bias...
    Just trying to give a heads up on a possible curve ball.
     
  19. Bearitone

    Bearitone SS.org Regular

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    I see. You’re saying if the bias range isn’t big enough, I won’t be getting the most out the KT88s so it would be better to have hot/medium bias KT77s than cold KT88s?
     

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