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How to safely run 6v6 tubes in place on 6l6's?

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  • How to safely run 6v6 tubes in place on 6l6's?

    I have a Bugera 6262 that I use to test my ideas on. The amp is a Peavey 5150 II copy. The amp actually has pretty decent tone. Being 100 watts is a bit excessive for me. I pulled two tubes and still too much volume to hit sweet spot. I had a couple of 6v6's around plugged them in for a minute or so. They amp seemed to be ok. Bugera will not release any schematics so no help there. The amp has a bias test point. What do it need to do to ensure that I don't fry anything?

  • #2
    Those voltages are to high for 6V6's if they are over 380 volts which the 5150 runs at about 500 volts on the plates. You will eventually fry them and burn them up quickly causing possible damage if the fuse doesn't blow and the tube shorts from grid to Cathode or other shorts.
    KB

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    • #3
      Yeah... I'd say that putting 6v6s into any 100 watt amp is sketchy...
      "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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      • #4
        the JJ 6V6s will do 450v on the plates - if the Bugera is around the 450v mark, you'll probably be alright.

        (5 mins later)... ok, a google search reveals this page... Properly Biasing Bugera Amps - BeerChurch's Blogs | Ultimate-Guitar.Com It states that the Bugera 6262 has a plate voltage of 480v - probably a little too high for hard gigging, but they'll probably be ok for home use.

        you could always cut the B+ down by 50v with some zener diodes between the PT's CT and ground. with around 400v B+ you'll be fine to run JJ 6V6s.
        HTH - Heavier Than Hell

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        • #5
          Originally posted by HTH View Post
          the JJ 6V6s will do 450v on the plates - if the Bugera is around the 450v mark, you'll probably be alright.

          (5 mins later)... ok, a google search reveals this page... Properly Biasing Bugera Amps - BeerChurch's Blogs | Ultimate-Guitar.Com It states that the Bugera 6262 has a plate voltage of 480v - probably a little too high for hard gigging, but they'll probably be ok for home use.

          you could always cut the B+ down by 50v with some zener diodes between the PT's CT and ground. with around 400v B+ you'll be fine to run JJ 6V6s.
          +1 Actually the JJ6V6 is rated at 500 volts ! Its really not a true 6V6 by design specs at least. More like a 6VL6! It can handle the Bug's higher plate voltages. Ran them at 470 volts in my Supersonic no problem. Read of guys running them even higher.Plus they will tolerate dissapating way more watts than any 6V6 has the right to.

          There may be impedance matching issues though. In my Rivera I run them in place of EL34's but rum a 16 ohm speaker with a 8 ohm amp output to match. Not sure what pulling two 6L6's then using two 6V6's will need.Bob
          Last edited by rockon1; 04-12-2010, 12:31 AM.
          "Reality is an illusion albeit a very persistant one " Albert Einstein

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          • #6
            doesn't running a "not a true" 6v6 that takes higher plate volts and dissapates more watts sort of defeat the postes intent of power reduction?

            I agree with dropping the B+ if you want to use 6v6's. But keep in mind that a pair of 6v6's will need a significantly higher OT primary impedance than a quad of big bottles so you'll need to make adjustments at the impedance switch or speaker load (or maybe both) to get a pair of 6v6's into their ideal load in that amp.

            Or you could just use four 6l6's and invest in a good attenuator.

            Chuck
            "Take two placebos, works twice as well." Enzo

            "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

            "If you're not interested in opinions and the experience of others, why even start a thread?
            You can't just expect consent." Helmholtz

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            • #7
              Originally posted by Chuck H View Post
              doesn't running a "not a true" 6v6 that takes higher plate volts and dissapates more watts sort of defeat the postes intent of power reduction?


              Chuck
              Perhaps but I bias them (as stated on thier spec sheet) as a 14 watt tube so the power reduction is still 1/2. I woulf be more concerned with the impedance issue's of running two 6V6's in place of four 6L6's. Bob
              "Reality is an illusion albeit a very persistant one " Albert Einstein

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              • #8
                If anything, running them into a too-low impedance might be where you get the real output drop.

                The right solution would be to acquire an amp that isn't so damn big!

                - Scott

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                • #9
                  What did Jim Kelley know that is not being illuminated here?

                  Impedance will still be an issue, unless you have multiple ohmage taps on the secondary of the amp's output transformer.

                  Bob M.

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                  • #10
                    Originally posted by Bob M. View Post
                    What did Jim Kelley know that is not being illuminated here?
                    That certain brands of NOS 6V6s could take up to 500V or so without self-destructing. Not good engineering practice IMO, but it seemed to work as long as the players kept the right tubes in there.

                    - Scott

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