is brown tremolo going to blow my speaker?

Discussion in 'Amps and Cabs' started by monkeyodeath, Feb 17, 2009.

  1. monkeyodeath

    monkeyodeath Member

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    I've got a brown Fender deluxe amp that I'm using with an old, recently reconed EV SRO.

    It sounds great, but I notice that the tremelo, when the intensity is anywhere above 5 on the dial, cause the speaker to physically "pump" in and out, even when there's no signal.

    Is this normal, and should I relax? Or is there the possibility of blowing and ruining my speaker?

    Thanks!
     
  2. hasserl

    hasserl Member

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    No, that doesn't sound normal to me. I admit I haven't checked for speaker cone movement while turning the trem up on an amp, but it shouldn't cause the speaker to "pump" with no signal applied. The tremolo on a brown Deluxe is a bias vary style trem, which wiggles the bias voltage on the power tubes causing a shift in the operating point. I can't see why this would cause the movement of the speaker cone you describe. If there's no signal applied, then there should be none going out. I think you may have an sub sonic low frequency oscillation happening that is being applified causing the movement. I think I'd get the amp in to a tech who can put it on a scope and check it out. Doesn't sound right to me.
     
  3. Mr. Bertha

    Mr. Bertha Member

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    I thought the thumping you're describing was just an artifact of a bias modulating trem. Kinda like hum in p90 pickups, it's just there. I'm no expert, but maybe someone else can chime in. Bump
     
  4. wingwalker

    wingwalker Fuzzy Guitars

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    Those amps "pump" even with the trem is off, if the intensity it high the "pump" will be more noticeable. No worries and as for the speaker...no worries there either, those are some really stout speakers! FWIW, I know these amps well, I have one, it's my fav amp these days! Also, FYI...Ted Nugent recorded LOTS with a brown Deluxe loaded with an SRO!
     
  5. monkeyodeath

    monkeyodeath Member

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    Yeah, it's an amazing sound, and the tremolo is so rich and fantastic. Mean little amp, holy cow!

    The movement of the speaker corresponds with the tremolo settings - if the intensity is up, the movement of the cone is more exaggerated, and if the speed is up, it moves a lot faster. It's the same whether I have a guitar plugged in or not.

    Sounds like this may just be how the trem works...
     
  6. Tone_Terrific

    Tone_Terrific Member

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    Ask over in the amp tech forum.
    You have the bias and the nfb circuit and whatnot....I dunno... complex interaction may be possible.
     
  7. TYY

    TYY Member

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    Yes, this is absolutely normal. All my bias-vary trem fender amps do it. It is much more noticeable in speakers with a BIG motor- my JBLs really pump. I imagine that over time it can stretch out/wear out spiders and surrounds, but it's worth it for that sound. I haven't heard any other trem that can get that sound.
     
  8. Bob Arbogast

    Bob Arbogast Supporting Member

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    If you think about how the circuit works, by regularly varying the bias of the output stage and, as a result, regularly varying the plate current in the output tubes, then yes, of course, the speaker will move in and out. Your output transformer is doing exactly what it should: coupling variations in output tube plate current to the speaker!

    Bob Arbogast
     
  9. Jahn

    Jahn Listens to Johnny Marr, plays like John Denver Supporting Member

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    Ayep, tube bias driven tremolo for the win. Oh hold on, the bigger browns' "Harmonic Vibrato" for the win! Heck, I'll take anything but that opto stuff.
     
  10. heisthl

    heisthl Member

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    Lot less tone sucking with this type of tremolo - there is a modern day equivalent in the Fender Custom shop Vibrolux.
     

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