Let's talk about the Vacuum t0ob family tree .......

Discussion in 'Amps and Cabs' started by Dr. Tweedbucket, Feb 21, 2008.

  1. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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    Sooo, we have the EL34 which is a nice crunchy tube ........... and it's cousin is the KT77 which is a very nice tube that stays somewhat clean, but gets down and dirty when asked. Does the 6550 hang out with the EL34s or is it more of a 6L6 type of tube?

    Speaking of the 6L6, it's a nice clean to crunchy USA sounding tube, but I'm not quite sure who is related to it....... [​IMG] .... maybe the KT88? And as far as I know, the 5881 is just the beefed up cousin of the 6L6.

    So really, I guess it's just the 6550 and KT88 that I'm not quite sure about.


    Then, let's look at the kids ..... the EL84 is like a mini EL34 and the 6V6 is like a mini 6L6 ? Would that be a fair statement? [​IMG]


    That's all the tubes I am familar with, for guitar amps anyway. I would be happy if someone could clear this up. :mad:
     
  2. HeeHaw

    HeeHaw Member

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    It's all giving me a headache.
     
  3. SatelliteAmps

    SatelliteAmps Member

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    Here's a lot of very generalized issues here. The EL34 and the KT77 (and 6CA7) are essentially the same tube. The 6L6 family does include the 5881, KT66, 6L6GC, KT88, and 6550. They have slightly different ratings, and generally speaking they distort and compress differently. Most people think of the 5881 and KT66 as the lower power, slightly warmer ones. The KT88 and 6550 are usually considered higher power, tighter sounding tubes.

    The EL84 is not a mini EL34, and a 6V6 is not a mini 6L6. They are lower wattage tubes, and tend to be in some similar amps, but they aren't really mini versions.

    A lot of this is very generalized info.
     
  4. rooster

    rooster Member

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    And, we haven't even gotten to the orphan of the group, the 7591A.

    rooster.
     
  5. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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    So ,the 6550 and KT66 and KT88 are on the 6L6 side of things? I thought the 6550 was more on the EL34 side of things as far as being able to take higher plate voltage.

    Also, I understood the 5881 to be a military grade 6L6 with basically the same tone as the 6L6. :confused:
     
  6. zoooombiex

    zoooombiex Member

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    perhaps you are thinking of the 7581A?
     
  7. redtoploader

    redtoploader Member

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    So ,the 6550 and KT66 and KT88 are on the 6L6 side of things?

    Yes...they are all from a family called 'beam power tubes'...they have whats called a beam plate in them(6v6s too). El34's and El84s dont have this.

    Also, I understood the 5881 to be a military grade 6L6 with basically the same tone as the 6L6.

    You are correct. The 6l6gc, 6l6, and 5881 are in the same family but have different max ratings. They sound a bit different from each other though...IMO.
     
  8. redtoploader

    redtoploader Member

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    no, he's right. The 5881 improved upon the early 6l6. I think some people confuse the 6l6 with the high voltage-rated 6l6GC.
     
  9. zoooombiex

    zoooombiex Member

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    true - based on the questions, i assumed he was referring to the 6l6gc
     
  10. uberpict

    uberpict Member

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    There are construction and operation differences between the EL34 and the KT77, one is a pentode and the other is a beam forming kinkless tetrode. Seems the 6CA7 is different still but I can't remember what that is besides the bigger bottle, maybe it's a beam forming "kinked" tetrode like the 6L6. For all intents and purposes they're interchangeable.
     
  11. jbird

    jbird Member

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    And some, not all, are interchangeable, correct? Such as with a Mesa, having a bias select switch for 6L6's/EL34's. And my amp, able to run either KT88's/6550's! I've never seen/heard of interchanging say... KT88's/6550's w/6L6's/EL34's though?
     
  12. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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    The 6550 and KT88s take a lot more current than the 6L6GC .... as I understand it. Mesa being a fixed bias amp has a prob with that. I would think you could run the 6550 or KT88 in an adjustable bias amp.
     
  13. DGDGBD

    DGDGBD Member

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    6550 and KT88 draw a lot more filament current, so you risk frying the power transformer if you use them in amps desigend for 6L6GC.
     
  14. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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    That's good to know! Thanks. I think then on a Mesa that can run either 6L6 or EL34, it should be ok.


    Let me ask this, On a Marshall JTM45 ( running KT66s ) can you run EL34s in it if you have decent screen grid resistors and re bias the current draw for the tube? ...... or will it stress the OT?
     
  15. Caddie

    Caddie Supporting Member

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    hmmm....seems that we need a physicist, electrical engineer and a tube amp "cork sniffer" on this case.

    Wasn't there an article on this very topic in the monthly mag of the IEEE Assoc about 10-12 years ago?
     
  16. Caddie

    Caddie Supporting Member

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  17. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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  18. SatelliteAmps

    SatelliteAmps Member

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    The 6L6 takes .9a, EL34 is 1.5a, and the 6550/KT88 takes 1.6a of filament current. USUALLY if an amp can run EL34s, it can run 6550 or KT88s.

    Spec-wise the EL34/6CA7/KT77 are all fairly identical on paper, and are close enough to be grouped together. (the KT77 is a beam tetrode, where the EL34/6CA7 is a power pentode. Different, but in our purposes essentially interchangeable with similar input and output ratings as the EL34)
     
  19. µ¿ z3®ø™

    µ¿ z3®ø™ Member

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    where's john phillips when U need him?
     
  20. DGDGBD

    DGDGBD Member

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    There are a bunch of variables to consider for the feasibility of using different power tubes in amps (ie other than was original design). Not sure if this is complete, and someone please jump to add anything here, but you have:

    -socket size
    -tube pinout
    -tube design specs (most importantly max plate voltage, heater current draw & max plate dissipation) vs. the voltages and current that the amp is set up for.
    -optimum primary:secondary impedance ratio

    Usually, tubes with radically different design specs are not compatible to interchange. However, I have an amp thats set up so I can use either EL34s and 6V6 without rebiasing (well, at least with the two pairs of tubes I'm currently using). In most amps this is not possible but the B+ voltage is this particular amp is low enough to allow the 6V6s. I just have to use double the normal speaker load when using 6V6s.
     

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