Amp - unwanted brittle noise

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by 900, Jul 27, 2006.

  1. 900

    900 Member

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    My Vibrolux is suddenly making some strange kind of brittle distortion when set clean. I've exchanged the power tubes, but that didn't cure it.

    The problem is that to date, the brittle sound only happened twice in one specific rehearsal room, and even there, for a couple of minutes it sounds like on the clip, then suddenly the brittle distortion disappears and for the next four hours etc. it's not possible to reproduce it. :puh

    Now I took it home and played the amp for 3 hours in my garage - everything sounds perfect as always.:confused:

    The clip is here :

    http://www.soundclick.com/bands/pagemusic.cfm?bandID=495316


    Any clue/idea? Do you think the problem could be guitar or guitar-cable related.
     
  2. Blue Strat

    Blue Strat Member

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    I'd love to hear your sound sample, but have no intentions of joining that website to hear it. Sorry.
     
  3. Hacksaw

    Hacksaw Time Warped Gold Supporting Member

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    ya sounds like a loose connection somewhere. you ahvent anything to loose by changing cables or trying another guitar!

    but if it does it cold, and does it go away when its warmed up ??

    may have something inside like a broken solder joint or who knows. time to start isolating. could even be a pot... so many things!

    you do that smack test on the amp while its doing it? just a light smack on the amp case would be enough. ( I do this on crate amps when they crackle, small light smack, and they stop, then take apart and fix).

    Blue strat, its a free non signup thing. I just listened.. and I didnt join.
     
  4. Blue Strat

    Blue Strat Member

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    Funny, when you hit MP3 this form pops up. When you hit hi fi, it skips the form.

    Anyway, it does sound pretty bad. Definitely swap in a different guitar and cable, you've got to start with the easy stuff before wasting time on more difficult stuff.

    Likely, someone will have to "go in" to check things out. Easy things you can do first are clean all the tube pins and sockets (check the FAQ on my website under Resources). Does this happen on both channels?

    Checking the bias on the power tubes can be very informative. It can alert you to incorrect bias, blown or worn out power tubes, power supply problems, etc...all without pulling the chassis. You do need a bias probe, however.
     
  5. Hacksaw

    Hacksaw Time Warped Gold Supporting Member

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    Thats intersting! I didnt try the mp3 version.. but, I had a ad pop up, and I couldnt play the hi-fi until I closed the ad.

    Glad you got around it! :)
     
  6. 900

    900 Member

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    Just to your information and to give a feedback - the cause was one specific busbar in that rehearsal room!!! :BITCH
     
  7. Reeek

    Reeek Member

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    MP3's are for download is why . . . The Hi Fi is for play back then and there . . .
     
  8. Blue Strat

    Blue Strat Member

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    Damn! That's interesting. Do other amps act wierd in that busbar?
     
  9. 900

    900 Member

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    It seems that it has happened to another guitarist, but I couldn't speak to him personally.
    The hint with the busbar came from my amp-tech, since he'd tested and tried to reproduce the problem for almost a week (using a soundgenerator etc) with absolutely no results (as myself in my garage and some other places).
    Anyway, they replaced the questionable busbar with a better quality one and it hasn't happened again since then.
     

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