JJ 6V6 in a Bonneville C50?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by RobRoyMcCoy, Feb 2, 2005.


  1. RobRoyMcCoy

    RobRoyMcCoy Member

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    Auckland, New Zealand
    Hi Guys,

    I have put a pair of JJ 6V6S into my Bonneville C50 combo (rated at 50 watts rms, assuming EL34's). In pentode mode I have measured the plate voltage to be 470V (max. as per spec. is 500V). I have set the bias such that the plate current on the hottest tube is measuring 21mA or 70% of maximum dissipation. The spec for the JJ tubes says 14w max dissipation per tube.

    I have had the amp sitting with these valves in them for 10 mins with no problems, but with everything turned down. I am nervous about plugging in and playing for an extended time until I am more certain I can run these tubes without blowing them or the amp up!

    My questions is: Is there a fundamental reason why I cannot run these tubes in my amp?

    Thanks

    Rob in NZ
     
  2. BPlexico

    BPlexico Member

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    I contacted Bob at Eurotubes with a similiar question on the JJ 6V6s as I was interested in trying them in my Komet which has a plate voltage of ~475V depending on line source. According to him, they will work fine in the KOMET and should be set to ~ 20 to 22mA per tube.

    You should be fine - might want to check to make sure the plates aren't glowing red though...

    -- Barr
     
  3. TheAmpNerd

    TheAmpNerd Member

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    Well lets to the math:

    .021 mA * 475 V = 9.975 watts.

    It should be okay. Check the load for
    the tubes and the opt and see how well
    they work out.
     
  4. Wakarusa

    Wakarusa Member

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    I've personally run JJ 6V6 at over 700VDC on the plates for over 30 minutes with no failure. Of course in this territory your mileage may vary significantly.
     
  5. TheAmpNerd

    TheAmpNerd Member

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    That is pretty funny Todd.

    Did you figure out total plate current?

    Did you put it in
    A. an amp - how did it sound?
    B. test rig - did the plates glow red?

    Also, did you do any distructive testing and
    find that magic point where the tube melts down?
     
  6. Wakarusa

    Wakarusa Member

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    I'd have to go back and look at my notes. To be honest, most of my experiements were to confirm or debunk what LV had claimed these things would survive. I do seem to recall getting something like 25W static dissipation without a hint of red in the plates, though I don't recall the voltage.

    All done in a test rig capable of 1KV@200mA (amazing the mischief you can get into with a good DC power supply :D)
     

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