power amps problems

Discussion in 'Amps and Cabs [BG]' started by glocke1, Sep 22, 2002.

  1. glocke1


    Apr 30, 2002
    I am having a severe problem with clipping using my demeter/QSC RMX 850 pre/poweramp combo.

    Last night I was playing an outdorr gig using the above equipment with a single bagend 15" cabinet.
    The poweramp was set in stereo, with the gain turned all the way up. I was controlling levels using the volume knob on the demeter.

    Right form the start, clip led started flashing, and my sound was very harsh and distorted. This has happened at practice befroe, but never to this extent, and never right away.

    Can anyone offer me advice on what may have been happening? Is this the proper way to set it up?

    Also, could it have been a problem with power? Everything was run off of one power strip, lights, PA, guitar amp....everything...

    Also, once I swithced to my backup head (meas boogie walkabout), it stayed cleab for about 5 minutes and than started clipping and getting distorted....
  2. The most obvious possibility is that the amp was starving for power -- try running the amp from a dedicated outlet and see if it helps . I don't run my amp in stereo so I don't know if that could cause the problem , but try running it bridged in mono . Hope this helps --- good luck .
  3. If you're running only one cab, why run in stereo? Unless you're using a "Y" cable, then you're only running one side of the amp in stereo, which wouldn't be stereo. I'm not sure it would be stereo either way.

    Seems like bridged-mono might be an answer (depending on the wattage of the cab), or better yet, parallel mode.
  4. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    You had way too much coming off one outlet!

    In most shows, lights suck up the most power. Then the PA, then the backline. Put them each on their own AC circuit for best results and least chance of the whole thing going down.
  5. FunkySpoo

    FunkySpoo Supporting Member

    Feb 6, 2002
    Would the power amps gain being turned up all the way have anything to do with it?
  6. were you running one channel of the amp? try the bridge feature (see your manual).

    are you using huge amounts of low - boosted eq?
    try the 30 hz filter on the amp, and ease off the low boost.

    everything on one power strip? not a good idea....

    you can only do so much with one 15" spkr, is your drummer and guitarist really loud onstage?