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Whenever I tap anywhere on the amp it comes thru the speakers

Discussion in 'Amps and Cabs [BG]' started by robd, Mar 10, 2013.

  1. robd

    robd Supporting Member

    Traynor Yba-200-2

    I moved a pedal on top of my amp last nite, and I heard it thru the speakers. Thought, gee, that's weird. So I tapped the top with my finger and heard it through the speakers. Whenever I tap anywhere on the amp it comes thru the speakers. The taps are very light.

    So I figured a microphonic preamp tube.

    Changed all the preamp tubes - still there.

    Had a friend who builds and fixes amps give it a quick listen. He tapped all over and heard the noise but said he never heard anything like it before. He can't get around to looking at it in earnest for a few days but I would like to if anyone hear has any ideas?

  2. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    Someone secretly planted a mic inside the amp? Seriously, that's odd though. I can't wait to read what the problem is/was.
  3. Sid Fang

    Sid Fang Reformed Fusion Player Supporting Member

    Jun 12, 2008
    A better description of the noise would be helpful. Sometimes it's a microphonic tube, sometimes it's a dirty or damaged socket, sometimes it's a dirty or damaged jack...
  4. Microphonic power tube?
  5. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Yes it could be a microphonic power tube. Or it could be that one of your replacement tubes is also microphonic. At least these are the easiest things to check out.
  6. christw

    christw Get low!

    May 11, 2008
    Dayton OH
    I want to be Tesla (tinkerer at Dayton Amp Co)
    If you think you have a microphonic tube use a single known good tube and go through and swap them one by one. Interesting issue though...
  7. Sid Fang

    Sid Fang Reformed Fusion Player Supporting Member

    Jun 12, 2008
    That's a 4-tube power stage, so in principle one could rotate through the power tubes running with only one on either phase to isolate a microphonic one. But have you cleaned all your sockets?
  8. phtee


    Oct 29, 2006
    I had a ampeg amp that use to do that, it turn out to be a cold solder joint.
    A faulty joint in electric wiring which results from the application of insufficient heat at the joint; the solder merely covers the joint and is not physically united with it.
  9. Does it do that with the bass guitar unplugged?
  10. will33


    May 22, 2006
    With it fired up, go through and tap on each tube with the eraser end of a pencil. All may make a very slight noise, any that are louder than the rest are suspect.
  11. remainthesame


    Sep 24, 2008
    did you try NOT tapping it?
  12. That's about as funny as the clap.
  13. dincz


    Sep 25, 2010
    Czech Republic
    Microphonic tube, bad/dirty jack or connector, bad solder joint. If you're careful and/or experienced with poking around in amps, you could try gently tapping components with something INSULATED (so NOT a pencil!) to identify the sensitive area or component.
  14. SirMjac28

    SirMjac28 Patiently Waiting For The Next British Invasion

    Aug 25, 2010
    The Great Midwest
    +10000 don't kill yourself tube amps can be very dangerous even unplugged take it to a tech let them get your amp in top shape.
  15. Pencils made from wood will work. Wood is a terrible material for conducting electricity.
    So don't use metal pencils. :D
  16. greencow


    Feb 7, 2008
    When working with tube amps, you must discharge the power suply caps before poking around in there. If you don't know how to do that, then take it to a tech.
    A wooden pencil may have a conducting core and is not something I can recommend using for said activity.
  17. dincz


    Sep 25, 2010
    Czech Republic
    If you can find a pencil with the graphite core also made of wood :)
  18. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I always used the butt end of a wooden spoon. Chopsticks work well, too. I'd say almost certain it's a microphonic tube. Solder joint might be possible but the tube is most likely IMHO.
  19. Use a CHOPSTICK!

    Wood or bamboo; not plastic, nor metal.

    Maybe even wear a rubber glove to hold the chopstick...

    Hey, stop that! Just 'cause I'm paranoid doesn't mean you have to laugh at me.

  20. A chopstick recently dipped in chop suey could conduct 500V quite well....

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