Power tubes matched?

Discussion in 'The Workbench' started by Emtbreid, Aug 31, 2019.

  1. Emtbreid

    Emtbreid Well-Known Member

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    I’m not very technical. Biasing is something I’m comfortable with. Beyond that? I’m not very comfortable, and I’ll readily admit that. Sounds like matched is the safe thing to do.
     
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  2. mickeydg5

    mickeydg5 Well-Known Member

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    If you order a matched set then they are usually within a couple mA or better. Once you get to 8, 9 and 10 mA difference area there will be hum.

    I use matched tube sets for maximum benefits.
     
  3. Emtbreid

    Emtbreid Well-Known Member

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    That’s what I’ve got. 4 el84, 3 say 29, 1 says 28. Being as this is my first tube amp/first time changing these power tubes I wasn’t initially sure if this is matched or not. But I see that it is. I adjusted the bias myself last week, I’m comfortable doing it. Got some electrical contact cleaner to clean the sockets, and I’m ready to start. Wish me luck!
     
  4. mickeydg5

    mickeydg5 Well-Known Member

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    You have a matched set as others have exclaimed.
    Although when seating them in your amplifier check the idle bias for each and move them around as needed.
    Contact within the tube sockets can vary so when it comes to push-pull balance the sides as good as possible.
     
  5. Emtbreid

    Emtbreid Well-Known Member

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    Will do, thanks so much! So far so good !
     
  6. mickeydg5

    mickeydg5 Well-Known Member

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    Good deal. Let use know your findings and end result. :thumb:
     
  7. Emtbreid

    Emtbreid Well-Known Member

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    I removed all the old power tubes so far. The new ones are installed.... sprayed the pins with electrical contact cleaner and worked them in and out a bit. Letting it sit and dry 100%. Question for you.... I changed the preamp tubes 6 months ago, and just put a new preamp tube in V1 for something different (tung sol). While I have the chassis our should I take each preamp tube out and clean with the EC spray, or just leave it?
     
  8. john hammond

    john hammond Well-Known Member

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    right there around 8..thats the magic zone.
    The temptation is too much just thinking about that level of tone, time to torture the neighbors some.
     
  9. Emtbreid

    Emtbreid Well-Known Member

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    Forgot to add, those preamp valves were the originals when I changed them (14 yrs)
     
  10. mickeydg5

    mickeydg5 Well-Known Member

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    You do not have to clean them constantly. Sometimes removing them and reseating helps. If anything is questionable then clean.
     
  11. Emtbreid

    Emtbreid Well-Known Member

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    I never cleaned them when I changed them.... and they were originals. While I’ve got it out I’ll clean them up ...
     
  12. mickeydg5

    mickeydg5 Well-Known Member

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    Preamp tubes vary so much.
    I have bought new tubes that tested shittier than old vintage tubes.
    A good higher output preamp tube will do so much more in any position.
    Try to learn what you are buying and roll the tubes to see where they sound best in your amplifier.
     
  13. Emtbreid

    Emtbreid Well-Known Member

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    Well, I had all JJ in V1-V4, but it sounded a bit muffled to me. I need to start buying more tubes and rolling to find something better. I bought a new tung sol, and seems to be much better in V1. I’d like to get one for V2 and see how it improves.... I know they can’t go in V3 of my amp because that’s the cathode follower.
     
  14. mickeydg5

    mickeydg5 Well-Known Member

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    Some Russian tubes had issues in athe cathode follower postion but I would think that is ironed out now.
    From post and opinions about J/J preamp tubes, most of those are on the darker side.
    Look up the preamp tube thread with who, what, when and where or something like that. So many good tubes are discussed.
     
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  15. Emtbreid

    Emtbreid Well-Known Member

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    Will do.

    As for bias, I’m done. Biased to Marshall’s recommended specs of .550mv and let it sit for 20 mins or so, so far so good. Just cut the power, and I’m gonna let it cool, put it back together, and do the most important test there is :band:
     
  16. Emtbreid

    Emtbreid Well-Known Member

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  17. john hammond

    john hammond Well-Known Member

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    the most important element of biasing you've managed to get right.
    Now, if you consider my angle...in the future, don't panic if theyre out of whack.
    theres a lot of panic around these parts in relation to neg bias issues.
     
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  18. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    which amp?
     
  19. Emtbreid

    Emtbreid Well-Known Member

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    That makes sense. The amp sounds great gentleman. Thank you @john hammond and @mickeydg5 for all of your advice!
     
  20. Emtbreid

    Emtbreid Well-Known Member

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    Jcm2000 DSL401
     

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