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strange tube thang...

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by prof2915, Oct 3, 2005.

  1. prof2915

    prof2915 Guest

    After putting TAD EL84 (Z) in my combo-amp I started having problems with strange noices etc, and to make a rather long story short they eventually fried...

    After some research my tech found that they reacted to magnet of my speaker!!??

    Although great sounding, these tubes obviously "only" works in amp heads.

  2. Wakarusa

    Wakarusa Member

    May 7, 2004
    Indianapolis, IN
    That's a new one. If they don't like the field from the speaker magnet, what's to keep them from suffering in the electromagnetic field of the transformers in a head?

    I suspect that there's something else going on here. In order for the speaker to disturb the electron flow in the tube to the point of failure you've got to have one hell of a speaker magnet, the tube operating way out of spec, or a bad tube to start.
  3. Reeek

    Reeek Member

    Feb 1, 2005
    Reno, NV
    Right or wrong, I've had several vintage combos that after I installed a new speaker, one of the tubes would almost rest against the speaker magnet and I never had any issue with bad tone or noise or frying tubes . . .
  4. prof2915

    prof2915 Guest

    I would guess you´re right.
  5. TheAmpNerd

    TheAmpNerd Member

    Sep 23, 2004
    I think they
    all react in subtle ways. However in your case
    I'm just not sure the speaker caused the failure.

    If the innards were magnatized and the tubes
    weren't built correctly to begin with that would
    cause problems indeed.

    If you just got the tubes, send em back.
    Also, put your old tubes back for a double check.


    What else did your tech find?
  6. prof2915

    prof2915 Guest

    My tech examined the amp and changed the tubes to Russian TAD EL84(M) without charging me anyting :D

    He had recommended me the Jugoslavian ones (Z) and felt "guilty" for the failure. (He´s really a wonderful guy!!!)

    He´ll get in touch with the TAD and inform the of this strange tube behaviour, and we´ll see what will happen.

    He did not find any other strange things going on, and he was VERY puzzled by it all...

    My amp - though only beeing played for a short while - now sounds better than ever!
  7. TheAmpNerd

    TheAmpNerd Member

    Sep 23, 2004
    Keep in mind
    the bathtub curve regarding failures.

    If something is to fail it typically is at the beginning
    or the end of the product/item/cap/tube/resistor/(insert
    name here) life cycle.

    In my studio days, we just turned everything on
    and never (rarely) turned it off. If anything failed
    it was typically in the first 30 days.


    As your new amp breaks in, it will start sounding better and better. Which amp did you acquire by the way?

  8. prof2915

    prof2915 Guest

    My amp is a Laney VC30.
    No Bootheek stuff, but rather nice.
    I have a Celestion Vintage 30 in it and use another 1x12 cab (Vintage 30) as well.

    Nice tube tones at "not TOO loud" levels.

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