Breakup Decay Observation

Discussion in 'Marshall Amps' started by coyote, Sep 16, 2018.

  1. KraftyBob

    KraftyBob Well-Known Member

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    Good point about the Ultra Gain Channel. It’s probably there but you can’t hear it over the heavier distortion.

    There’s another thread that someone just started and we we’re talking about this on there as well. The discussion led to AC/DC Live Wire - if you listen closely to the beginning of the song you can hear some buzzing as the chords ring out a little. If the Young brothers have this on a recording with their equipment then who am I to complain about my little ‘Ol 40w DSL.
     
    Last edited: Sep 20, 2018
  2. karl childers

    karl childers New Member

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    I have owned 2 marshalls since 1992.Number 1 is a jcm 900 model 2100 hi gain master volume mk iii. Number 2 is not quite 2 yrs old and is already F'ing up. It is a DSL 100h and it never really had the presence or sustain from day one. If you ever played a good sounding tube amp,it "sings" and isn't a fight to have to play it.This amp has the same issues mentioned. The notes don't carry and it almost acts like a bad instrument cable. Today I cut it back to half power and saw no difference. Turned it off, flipped it back to full and for about 2 minutes it was a MARSHALL, I was grinning ear to ear,then back to muddy,fizzling shot.So i stumble across this forum and start to look around and seems it is an issue with a PCB which causes the bias to drift,creating this overload which the tubes try to soak,which makes heat,heat loosens tube sockets,creates cold solder joints,and so on.The board is $250-$300 dollars and I'm not convinced that it is a permanent fix. Mine still has warranty on it still and we will see how that goes bright and early. I have little faith in warranties and less in the marshall authorized repair shops within the whole state that I live in,all 10 of them.
     
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  3. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    "...the note/chord sorta “falls apart” into crackly fizz instead as it fades..."

    That's the bias.
    The colder it's biased, the more it will fizz as it decays.
    (what you hear is crossover distortion)
    What you are hearing is: the output tubes are trying to shut off.

    That's why hotter bias sounds better.
    If you bias it hot enough: the note will decay without the fizz. No crossover distortion.

    That is also why: amps are biased with a scope.
    We can see the distortion.
     
  4. mikebinthesky

    mikebinthesky Member

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    I notice it a bit with my JCM800 2203x-not so much the fizz but when letting a note fade it just kind of abruptly ends-not sure if thats normal or not
     
  5. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member

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    Welcome to the forum new MFR
     

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