Amp Hum/Hiss...What to do?

Discussion in 'Amps and Cabs' started by hurleysurf, Jan 25, 2008.


  1. hurleysurf

    hurleysurf Member

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    My reissue Super Reverb has been acting up lately. I get a lot of hum/hiss/fizz/white noise. Any of those can describe it. Not a LOT as in it is in unplayable condition, but it is buggin me. I'm pretty positive its the amp as even as I turn the volume up without anything plugged in, I can hear the same hum/etc. Is this just a case of bad tubes? I want to make sure that it is the tubes for sure before I invest in new ones. Thanks!
     
  2. Rosewood

    Rosewood Member

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    The quickest way to check is sub out the preamp tubes. If you don't have any extra you could swap v1 and v2 to see if it helps. v1 is for the normal channel and v2 is for the reverb channel.
     
  3. lannyhall

    lannyhall Member

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    Just remove V1 and see if the noise goes away. If not, replace it and remove V2.
    [As you probably know, as you look at the amp from behind, V1 is the first tube on the right. V2 is the second . . .]

    Obviously, it could be one of the others. If you have extra tubes, swap out the appropriate kind, one at a time. It is VERY likely tube related.
     
  4. myles111

    myles111 Member

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    Hum is generally a sign of mismatched output tubes. Check the bias and make sure it is no more than about 10% difference on each tube. This can also be a phase inverter tube.

    Hiss is generally one of the preamp tubes in the first gain stage ... in your amp V1 for the NORMAL channel and V2 for the VIBRATO channel.
     
  5. Zero

    Zero Member

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    I have this solid state Randall combo that has a very loud hum. Which doesn't change with the master volume. If it's on "0", the hum is the same. So what I do is use a PowerSoak set to about ½ way down and turn the amp master up more. That lowers the hum floor enough so that it isn't so annoying.
     
  6. myles111

    myles111 Member

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    Have you tried a ground lift?
     
  7. Lucidology

    Lucidology Member

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    Been experiencing lots of hiss & crackle lately miss up ...
    thought I'd dig up some older threads about it ...
    If anyone else in the know could contribute .. that would be great
     

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