Blues Junior: an annoying high-pitch sizzle on notes. Tubes?

Discussion in 'Amp Input - Normal or Bright' started by Mikeylefty, Jul 22, 2021.

  1. Mikeylefty

    Mikeylefty Be Kind Silver Member

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    Just picked up a used Blues Junior IV. Not familiar with these amps but picked notes seem to have a high pitched overtone in the background. I'm comparing it to my Princeton reverb with settings as close as I can match them. Could this be a tube problem? Reading up on microphonic tubes described as a high ringing sound. That's sound similar. Need to decide whether to keep or send it back.

    I should mention that the metallic sound is staying with the notes, not ringing on afterwards.
     
    Last edited: Jul 22, 2021
  2. Black59

    Black59 Strat-Talker

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    I'm definitely not an amp expert, but I'm also curious about this. Just turned on my Tweed BJ IV and I'm not noticing anything like that. I'm pretty sensitive to high-pitch stuff as well.

    @Mikeylefty Is it a standard BJ IV or one of the limited edition ones? Also, since you got it used, were any mods done to it?
     
  3. Handsome McClane

    Handsome McClane Senior Stratmaster

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    My AC15C1 had a "fizz" sound on note decay when I first got it. New tubes took care of it. Not saying that's what it is, but that's the first thing that popped into my head too.
     
  4. Dave Harmon

    Dave Harmon Strat-Talker

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    Might be a voice coil rub inside the speaker....or a small particle down inside the coil.
    I have had both.
    I would try a different set of speaker(s) to see if the trouble is still there.
    If it is....probably tubes.

    Also....if you flick the tubes with a finger usually a microphonic tube will have a slight 'twang' or metallic sound...no need to pick a string.
     
  5. Mikeylefty

    Mikeylefty Be Kind Silver Member

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    Got it used online from a music store. It's a IV limited edition. Don't know if any mods done to it, but was strange that one of the screws that hold the chassis was about to fall out. [​IMG]
     
  6. henderman

    henderman Dr. Stratster

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    tube amp owners should have spare tubes on hand that are known to be good.

    the only way to know for sure is to buy tubes from someone that can test them to verify specs.

    reputable vendors can do this for a few bux a tube.

    every low dollar but tested and verified to be in the top of it's class tube i have ever bought was pure excellence.

    armed with known to be good tubes you can substitute them 1 at a time and only 1 at a time so you do not mix them up, which allows you to diagnose a tube situation easy.
     
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  7. Proliferant

    Proliferant Strat-Talk Member

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    This. Best get a few tubes and swap then out. You might be an inexpensive step from a great amp.
     
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  8. TheWorldsAStage

    TheWorldsAStage Strat-Talker

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    You may have already done this but try a different guitar just to rule that out. Something with the guitar could potentially be adding that overtone but this amp's frequency response is allowing it to be heard.
     
  9. Dave Harmon

    Dave Harmon Strat-Talker

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    I like JJ Tubes....worked great for me for years.
     
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  10. myredstrat

    myredstrat Senior Stratmaster

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    one thing I have found with my jr. is the tubes come loose and weirdness occurs.
    turn it off, wait until cool, and reinsert the tubes (carefully)
     
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  11. Mikeylefty

    Mikeylefty Be Kind Silver Member

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    Yes, would be good to have a variety of tubes on hand. But I just bought this amp so may return it rather than buy and test tubes.
     
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  12. henderman

    henderman Dr. Stratster

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    i agree the amp is to be good from the start and you should not have to buy tubes to test a new or new to you amp...but when you settle on one i stand by the tube thing as it will save you a lot of future aggravation.
     
  13. Morf2540

    Morf2540 Senior Stratmaster

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    I had a couple different BJs over the years and they all had this or similar problem to some degree. It was never a bad tube. I found that tube dampers (those rubber rings) solved it pretty well. Also tighten the screws on the chassis if you have not done so already. There is a lot crammed into that little box and I think it just causes a lot of vibrations you don't see on other amps.
     
  14. DeMelo

    DeMelo Senior Stratmaster

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    The amp was bought used. So we can’t know what previous owners have done to it or how worn it is.

    My advice would be takin it to a tech and having it checked.