is EL84 the only 9-pin tube?

Discussion in 'Amps and Cabs' started by -kk-, Mar 7, 2006.


  1. -kk-

    -kk- Member

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    Specifically, for use in tube amps?
     
  2. Blue Strat

    Blue Strat Member

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    I'm guessing that you mean "the only 9 pin power tube"?

    The 7868, found most often in Ampegs, had 9 pin but a larger footprint so it wouldn't even fit in the same socket.

    A few '50s amps, Magnatones were some, used 6973s.
     
  3. amper

    amper Member

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    There's the SV83, which is a close relative of the EL84, but not a direct replacement. And of course, 12A-7 types have been successfully used as power tubes in a few small amps.
     
  4. drbob1

    drbob1 Silver Supporting Member

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    How about the 6AQ5, used in a few Gibson amps (and much cheaper than the 6BQ5). Also the 50C5 used in the "death trap" amps that don't have a power transformer (they use mains and have 3 or 4 tubes that add up close to 110v-50C5, 35X4 and a 12AX7 or two).
     
  5. -kk-

    -kk- Member

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    here's the root of my question.

    in single ended amps, you can sub all types of 8-pin tubes in the power amp slot, but EL84 seems to be the only candidate for the 9-pin variant. So im wondering what else can one sub in there to get more flavor?

    (stupid question alert)

    so can you put a 12A-7 type tube and run it as a power amp tube?
     
  6. thintele

    thintele Member

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    6BQ5 and 7189A are equivelents of the EL84. 7189A being a sturdier industrial version. There are plenty of other 9 pin power tubes in the NOS world as far as guitar amps EL84 is the only one used in current production amps.
     
  7. drbob1

    drbob1 Silver Supporting Member

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    Ah, I see what you're thinking. No, I don't believe that you can use any other tubes besides the variations of the El84 in there, because the pinouts are different. As an example, you'd have to rewire the socket to use a 6AQ5 in a 6BQ5 socket, even though they're similar power tubes.
     
  8. dogg

    dogg Member

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    6Pi1Pi - noval-equivalent 6AQ5/EL90 tube.
    I try it - small cross beetween CG/Vox AC
    an sound fantastic :)

    V.
     
  9. Blue Strat

    Blue Strat Member

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    As I recall, the specs are different enough on these that you'd probably kill a 6AQ5 in a rewired 6BQ5 socket.
     
  10. Roccaforte Amps

    Roccaforte Amps Member

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    +1,
     
  11. Roccaforte Amps

    Roccaforte Amps Member

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    +1, the 6aq5 will burn.
     
  12. drbob1

    drbob1 Silver Supporting Member

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    Yup, but the point was that you can't just pop a 6AQ5 into the socket and have it work. There just aren't a lot of choices like there are with octal power tubes.
     
  13. amper

    amper Member

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    Absolutely NOT. The 12A-7 types are dual triode tubes, while the EL84/6BQ5 is a power pentode. Completely different beast. The circuit would have to be specially designed to run dual triodes in the power stage.

    There's some good ideas in the AX84 Firefly project to start with. The Firefly uses a 12AU7 in the output section, but I'm thinking of doing something with the 12AT7 instead (maybe, I have to look over the spec sheets again).

    The AT/AU variants are probably better candidates for output tubes than the AX/AY variants, because they're designed for higher current output. I believe the AU is rated for a 3W max dissipation (or maybe that was the AT?), which would be nice for a low-ish volume amp.
     

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