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SF Vibrolux question...

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by guitarmook, Mar 15, 2005.

  1. guitarmook

    guitarmook Member

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    Can I run 5881s in this amp? Do I need a different rectifier?

    I'm not gonna just 'try it', but would like to know if it's even possible...
     
  2. Swarty

    Swarty Member

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    No problem, not sure if you mean real 5881s or the Russian thingy called a 5881 for marketting purposes. If they are real 5881s expect a bit earlier breakup and more midrange honk. If they are the Russian thingys they are a tough sounding 6L6 type sound. Either way, a bias adjustment is all that is required.
     
  3. fullerplast

    fullerplast Senior Member

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    Careful.....a real 5881 has a max plate voltage rating of 360V. Your VR is likely in the 450V range.
     
  4. guitarmook

    guitarmook Member

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    I'm planning on using 'real' 5881s...

    Fullerplast - I'm assuming that means I'll be either abusing the tubes, or worse... blowin 'em up... how much wiggle room is there? - is this a case where the tube-life will be decreased by half, or orders of magnitude?
     
  5. fullerplast

    fullerplast Senior Member

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    I wouldn't recommend a NOS 5881 in a VR, personally. The Sovteks are really 6L6GC's and can take 500V on the plates, Tungsols and others are interchangable with 6L6GB's, but not GC's. They may be able to handle it but I wouldn't put them in my VR. Under 400V on the plates, maybe. YMMV. I'm sure there's someone out there using a quad in a Twin Reverb.....:eek:

    If you want to try something along those lines, try a pair of JJ 6V6's. They will be OK (only JJ's!) and may get you where you want to go tonewise. Keep in mind that you will need to re-bias, and your tubes will want to see 8 ohms instead of 4, but it will work fine.
     
  6. Blue Strat

    Blue Strat Member

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    Yes, the max rating is 360V. The same is true of 6V6GTs which run perfectly in DRs with 430+ volts on the plate.

    VRs run closer to 430 and 5881/6L6WGBs seem to do just fine in these amps. Bias in the low 30s.
     
  7. fullerplast

    fullerplast Senior Member

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    Like I said, YMMV. I wouldn't put them in mine, that's all. A silverface runs 450V nominal with a 5U4, maybe more if your line voltage is higher. To me, that's pushing it too far. It's a risk/reward thing. :cool:
     
  8. Swarty

    Swarty Member

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    FWIW, I've run lots of Philips/Sylvania & Tungsol 5881/6L6WGBs in BF/SF Fender without incident. Heck, an original tweed Bassman called for over 450v on the plates and the Tungsol 5881 was very much a part of that sound, and they last a very long time.
     
  9. fullerplast

    fullerplast Senior Member

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    Yeah, I understand Swarty. People exceed nominal ratings on tubes all the time and get away with it. It just makes me uncomfortable to recommend it. I wanted guitarmook to be aware of the ratings so he can make an educated choice.

    I'm curious Blue Strat, and mean no offense, but since you sell tubes, do you warranty NOS 5881's run at 450V? How do you handle it from a seller's perspective?
     
  10. Blue Strat

    Blue Strat Member

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    Depends on the user and the application. If I'm confident that they'll be biased properly I'll take the chance. I usually recommend a cutoff of 440 Volts for these.

    In my experience VRs run at 440V. Mine does and so did many others that I've worked on.
     

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