New Tubes for my VOX AC15H1TV

Discussion in 'Amps and Cabs' started by dave s, Mar 5, 2008.

  1. dave s

    dave s Member

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    ...hearing some noises coming from the amp that scares me. Nice tube rattle when a clean chord is stuck. After having an AC30CC2x break down a couple of times on the job, I'm a little gunshy even with the HW combo.

    So, I ordered a full complement of better quality tubes and plan to pull the chassis and install said new tubes probably Saturday.

    Will the amp require a bias adjustment for the new power tubes? Anything else I should be aware of before replacing ALL tubes?

    Thanks in advance.

    dave
     
  2. hamfist

    hamfist Member

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    No biasing necessary. Everything will be fine so long as you replace like with like, and don't try any weird substitutions. What tubes ya puttin in ?
     
  3. 57paf

    57paf Member

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    Dave:
    Your biggest improvement will be heard from upgrading the EF86 and the 1st 12AX7 (next to EF86) to NOS--much more articulate, less blurry. NOS EL84s sound slightly less gritty.
    EF86s are particularly prone to microphonics, which is why the stock Sovtek EF86 is wrapped with heat shrink. Some people will buy special tube stabilizer rings, which are heat-resistent silicone O-rings.
    I made my own tube stabilizer. I bought a 3/4" copper cap, which I drilled a hole in the center to prevent damaging the glass spike on the top of the tube, then crimped it slightly (don't do this while it is on your tube) to fit snugly. Note that a 3/4" copper cap or sleeve works with standard sized EF86s, not the oversized Sovteks that come from the factory.
     
  4. dave s

    dave s Member

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    Decided to give the new Mullard EL84s a try. Preamp tubes are JJs. Rectifier JJ as well and the EF86 was a different brand.

    Think I did ok? Will replace all tubes with the correct equiv shipped in the set.

    dave
     
  5. dave s

    dave s Member

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    Thanks a bunch for this info. I'll be really careful to have this info available when I do the tube swaps.

    And I used to have a bunch of really old, never used RCA 12ax7s that have been misplaced during a move. I'm going to look into every box in the basement and try to locate a couple of them. They are from the late 50s - mid-60s.

    Thanks again for your thoughtful response.

    dave
     
  6. hamfist

    hamfist Member

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    I'll admit I like NOS tubes, for longevity as well as tone. But, for current production tubes, those should be pretty good.

    My advice, however, would be to seriously have a look at getting an RFT or Dario Miniwatt EF86 from www.kcanostubes.com if you can stretch for a few more dollars. The tone you get will bring a smile to your face ! Should also last a lot longer than any of the current production EF86's too.
    If you could also find the RCA 12ax7's you have mislaid, they would also be excellent.
     
  7. dave s

    dave s Member

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    RFT EF86 on order! And yes, it was rather pricey. Thanks for your responese.

    dave
     
  8. hamfist

    hamfist Member

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    Nice one Dave ! I'll be interested to hear what you think of it, compared to the EH tube they come with.
     

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