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Tube Amp problem

Discussion in 'Amps and Cabs [BG]' started by andy_p6, Apr 22, 2005.


  1. andy_p6

    andy_p6

    Apr 5, 2004
    London, UK
    Hi there

    I'm having trouble with my Sunn 300T. I was getting farting noises and I'd thought I'd blown the horn in my Eden 410XLT, so I unhooked it altogether but it has made no difference. I've changed all my leads and the cab also seems fine with my borrowed Hartke HA5000. So I think I've singled out the Sunn as the problem.

    The distortion sounds like excessive fret buzz and is most prominent from the open A up to the D (5th ft). Whats bizzare though is that last night at the gig whenever the drummer hit his kick drum (only when the large drum fill was switched on), the cab farted. Even when my bass (stingray 5) was unplugged. What the? :help:

    Does anyone have any ideas??
     
  2. You've got microphonic tubes. If they're in the power section, they could destroy your amp and cabinet.
     
  3. popinfresh

    popinfresh

    Dec 23, 2004
    Melbourne, Aus
    It's an all tube amp.. replace them?
     
  4. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    Check the power tubes and make sure they are all sitting in the sockets correctly. Also check to see if they are all glowing the same color. Sometimes if one tube is bad the color will be off from the others. If this is a power tube change it quickly. It may be one of the tubes not sitting in the socket based on what you said about the drums... start there first
     
  5. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    What you could also do is to tap the tubes lightly with a finger. Do it one by one until you find the one that makes a rattle noise through the speakers. Remember, do this LIGHTLY. It should reveal itself.
     
  6. andy_p6

    andy_p6

    Apr 5, 2004
    London, UK
    Thanks for the tips. I gently tapped the tubes and it was the one on the far end causing the problems. It was certainly a bit loose. The six tubes are set up in pairs and both the problem one and its neighbour are burning brighter than the others. Should I replace just these two (are they both now stuffed?), all the power tubes, or is the amp good to go?

    cheers for the help
     
  7. Rockinscott

    Rockinscott

    Nov 24, 2003
    It's always safer to replace ALL output tubes at the same time with matched tubes. This prevents one (or more tubes) from drwaing excessive current above the others which can cause some serious problems for your amp, not to mention less than stellar performance from it. :)
     
  8. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    +1 if possible. If not make sure that you get a matched pair and rebias (you'll need to do this anyway)
     
  9. I will further this by stating you should have a TECH replace and rebias your output tubes. While it may sound expensive, a tech can check for any other problems that the amp may have that possibly CAUSED your old tubes to fail. Tubes don't burn out lightbulbs or just quit working unless there is something WRONG. They should last for decades, even currently produced ones. If you have a solid state amp that was having problems with its output transistors, you wouldn't try to replace them yourself. It's the same with tubes. You could end up ruining your amp and an expensive set of tubes.
     
  10. Rockinscott

    Rockinscott

    Nov 24, 2003
    "Psycho" is absolutely correct. You probably spent a lot of time and energy, not to mention money on finding and obtaining the amp that is right for you. Give that same attention to getting it repaired and keeping it in good working order. ALLWAYS have a qualified Tech do the work! :D