Suggestions For Different Tubes?

Discussion in 'Amp Central Station' started by youdevil, Oct 18, 2012.

  1. youdevil

    youdevil TDPRI Member

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    I just bought an old Oahu 8" amp. Some of the tubes sound microphonic, and if I'm going to replace them, perhaps I should consider a different complement altogether.

    Currently it has:

    one 6N7
    a pair of C9s
    one 80

    Can anyone tell me what sort of sound that arrangement is designed to deliver, AND what you'd recommend in order to maximize gritty, early breakup? I play blues rock.

    Many thanks!
     
  2. firemedic

    firemedic Tele-Meister

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    If it's an old amp it probably should be recapped. Stand by while I research the tubes & circuit if possible...
     
  3. youdevil

    youdevil TDPRI Member

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    Thanks. I looked inside the chassis and FWIW there are many new caps and wires in there, and a 3-prong plug has been swapped in.
     
  4. jmiles

    jmiles Friend of Leo's

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    My experience with my '52 Pro Amp. My tech made adapters to use 12AX7s. We put them in, fired up the amp, looked at each other and said, "Well, that was a mistake!" The amp did not sound nearly as good as it did with the octal tubes it was designed to use.
     
  5. firemedic

    firemedic Tele-Meister

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    I couldn't find the circuit for it.

    The 80 is a rectifier tube, IIRC, a mercury gas tube that glows purple? If it still works, very cool.

    I could not find data for C9s. You sure that's the correct tube type?

    The 6N7 is a twin power triode. I've never seen one but it looks like an output tube to power the speaker.

    If I had to guess I'd say you have an amp designed for a Hawaiian steel guitar. Just before tweed amps came out, in the '40s & '50s, that was what people meant by "guitar amp".

    I say leave it alone. Since the tubes are not likely in high demand (except the 80) you can probably get NOS fairly cheap, try KCANOStubes.com. If it works, the 80 is probably good anyway.

    It probably does not have cathode bypass caps. If you want a growly amp, they're easy to add for a large boost in volume and dirt.
     
  6. printer2

    printer2 Poster Extraordinaire

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  7. firemedic

    firemedic Tele-Meister

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    Where do you dig up these old links, printer? Very nice stuff!
     
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