Amp Squeal/Feedback Question

Discussion in 'Amps and Cabs' started by reo73, Feb 7, 2008.

  1. reo73

    reo73 Member

    Messages:
    1,139
    Joined:
    Sep 25, 2004
    My poweramp (Mesa 50/50) is squealing bigtime when a gained signal is being fed to it. I am fairly sure it is not the tubes or any other component of my signal chain. Is there another component in the poweramp that could cause the amp to squeal?
     
  2. sickboy79

    sickboy79 Member

    Messages:
    10,423
    Joined:
    Aug 17, 2006
    Location:
    Chicago
    Have you tried swapping tubes? What about the preamp that's feeding your power amp - have you checked those tubes as well? Usually (but not all cases) a squealing type sound from an amp can be traced to a microphonic preamp tube.
     
  3. reo73

    reo73 Member

    Messages:
    1,139
    Joined:
    Sep 25, 2004
    I've tried all new tubes and different preamps, even a POD. The squeal is still there in all cases which makes me think it is some other component.
     
  4. Blue Strat

    Blue Strat Member

    Messages:
    30,036
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    If you haven't removed other items in the signal chain, remove them. How else can you be sure it's not one of those?
     
  5. Zim

    Zim Member

    Messages:
    1,974
    Joined:
    Jun 8, 2006
    Location:
    Home... after 6 years on the road.
    Yeah, clean it out and try each thing one at a time. Sooner or later you find the piggy.
     
  6. reo73

    reo73 Member

    Messages:
    1,139
    Joined:
    Sep 25, 2004
    There is nothing in my signal chain other than my guitar > instrument cable> preamp > instrument cable > power amp > speaker cable > speakers.

    I have swaped out everything up to this point except the poweramp itself...guitars, tubes (in both preamp and poweramp), cables, preamps. Everytime the squeal is there which leads me to believe it is something in the poweramp.
     
  7. drbob1

    drbob1 Silver Supporting Member

    Messages:
    22,185
    Joined:
    Aug 9, 2004
    Can you tell us a bit more? Is the squeal present only when the amp is turned up? Only when a signal is fed thru the amp? Only a loud signal? Does the squeal change pitch with different notes/volumes/guitars? Can you make it squeal without a preamp present? Without a 12AX7 (there's gotta be 2 in there somewhere, right?)?
     
  8. reo73

    reo73 Member

    Messages:
    1,139
    Joined:
    Sep 25, 2004
    Let me go do some investigation on this and I will get back to you.
     
  9. reo73

    reo73 Member

    Messages:
    1,139
    Joined:
    Sep 25, 2004
    Here is more info:

    The squeal is there at any volume on the power amp and follows the volume setting.

    The squeal is NOT there when I unplug my guitar.

    The squeal is there when I turn down the output of my preamp and turn up the volume on the power amp.

    The squeal is there when I have my preamp on the clean channel and turn the power amp volume way up.

    The squeal is there and all the above is true when I feed the power amp with my POD instead of the Studio Preamp.

    Also, when I tap on the 3 preamp driver tubes or power tubes in the 50/50 or poke around with wires in there I don't hear any weird or excessive noises.

    The squeal is not there when I am playing but starts immediately when the strings are muted.
     
  10. PFCG

    PFCG Member

    Messages:
    2,806
    Joined:
    Feb 23, 2006
    Location:
    Calabasas - CA
    maybe you have a problem with your guitar. id open the electronics cavity. Try a different axe for now.
     
  11. reo73

    reo73 Member

    Messages:
    1,139
    Joined:
    Sep 25, 2004
    I have three guitars, it squeals with all three and my guitar does not squeal with my other amp.

    I am convinced it is a problem with a component in the 50/50. I going to bring my other amp home and run the preamp of it thru the 50/50 to make sure. I will probably send the unit to Mesa for service.
     

Share This Page