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Problem with PA Distortion

Discussion in 'Live Sound [BG]' started by DaveLS, Mar 31, 2015.


  1. DaveLS

    DaveLS

    Sep 5, 2008
    Massachusetts
    I have a powered Yamaha mixer with two 500 Watt amps and recently it started having some issues with distortion. This happens at any level, gain, channel, mic, cable...

    Basically it sounds like a crackling, distortion and loss of volume. I just recently noticed that if I yell loudly though a mic on any channel, it will "cure" it for a little while. Sometimes I can get through a whole practice with it but then next time I use it, I turn it on and have the same issue. If I turn it off, then back on it cures the issue also. Any ideas what's going on here? I just use it for my practice space so I may just keep dealing with it until it gives up completely and then trash it.

    Not sure if this is the right place to ask, please let me know if not.

    Thanks!
    Dave
     
  2. WayneP

    WayneP Supporting Member

    Oct 11, 2004
    Corpus Christi, Texas


    If you’re getting this all the time, and the input gains (for the mic and other channels) aren’t set so high that the inputs are clipping all the time, then the mixer is the problem. If it’s something that temporarily “cures” like you describe, it might simply be a component on the circuit board that needs to be resoldered.

    Regards,
    Wayne A. Pflughaupt


    Administrator, Pedulla Club #45
    Administrator, Tobias Club #133
    Fretless Club #943
    Big Cabs Club #23
    My Rig: Stage and FOH Friendly




     
    Last edited: May 11, 2015
  3. DaveLS

    DaveLS

    Sep 5, 2008
    Massachusetts
    Thanks for the reply. I'll open it up and see if anything looks obvious. Maybe like a bloated capacitor?
     
  4. s0c9

    s0c9 Supporting Member

    Jan 9, 2014
    Ft.Worth/Dallas
    1964 Audio artist, Fractal Audio Beta Tester
    Have you checked your speaker cables?
    When permanently attached to the back of a power source, their own weight can strain the cable and cause loose connections..
    try talking/playing and wiggle them to see if it goes away..
    If not.. as WayneP suggested... something in the mixer.
     
  5. DaveLS

    DaveLS

    Sep 5, 2008
    Massachusetts
    Thanks. Yes I tried different mic, speaker and power cables. No change.
     
  6. WayneP

    WayneP Supporting Member

    Oct 11, 2004
    Corpus Christi, Texas
    Last edited: May 11, 2015
  7. s0c9

    s0c9 Supporting Member

    Jan 9, 2014
    Ft.Worth/Dallas
    1964 Audio artist, Fractal Audio Beta Tester
    Is that like a skinny transistor??
     
    DaveLS likes this.
  8. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    If the mixer has insert jacks, it could be those. They get dirty and fail to properly pass signal, which has to go thru the switching contacts in the insert jack.

    Get a 1/4" plug (any will do, even your bass cord). If you have contact cleaner, spritz a little on the plug (not in the jack!). In and out a few times in the insert jack (no wisecracks) will usually do the trick.
     
  9. DaveLS

    DaveLS

    Sep 5, 2008
    Massachusetts
    Thanks for all the advice. I thought it over a bit yesterday and figured out some more steps I could take to narrow the problem. I haven't had a chance to open it up and look at it yet though.

    There is a jack labeled "Mon out" which you can use to send the pre-amp signal to another power amp. When I plugged that into another power amp it still distorted.

    There is also a jack labeled "Pwr Amp In" which I believe is used to send another source into the power amp bypassing the pre-amp. So plugged in an unpowered mixer into that and I didn't get any distortion. So maybe the problem is in the pre-amp stage somewhere.

    This at least tells me it's not a cable, speaker, or a problem with a specific jack. I guess I'll have to pop it open.
     

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