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preamp / power amp settings

Discussion in 'Amps and Cabs [BG]' started by jacove, Feb 29, 2004.


  1. jacove

    jacove

    Apr 12, 2003
    Aalborg, Denmark
    The other day I experimented with my current rig Aggie db680/QSC plx3402 (stereo one channel) into Berg HT322, I've always thought that the rig wasn't quite loud enough, I know that the QSC 3402 needs some juice so I dialed in tone with the gain set to 11.00 and the pre-amp master cranked all the way up. I suddenly discovered that the tone somehow opened up and became clearer, not just louder. But it made me wonder if cranking the pre-amp (master) full would do some harm, will the pre-amp clip, how would this affect the power amp or speaker?

    I then took the speaker plug out and turned the QSC full up with the same pre-amp setting and the clip light on the QSC just blinked when plugging hard. Does this mean that now I'm running the QSC on full power.
     
  2. 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
    Yes, when the clip LED lights up, the amp is at maximum output.
     
  3. Shouldn't you have a load on the amp at all times??? Yikes!

    You might also try bridging. There is lots of strings on this subject especially with QSC amps. Just connect is properly, make sure you have the amp setting right, and be careful with gain. I was against bridging for a while, now I prefer it.
     
  4. kmacleish

    kmacleish

    Nov 19, 2003
    Atlanta, GA
    Solid-state amps don't really mind that much if you run them hard with no load, but don't try it with a tube amp. The power tubes will be subjected to excessively high voltage swings and may arc internally and do various other bad things.
     
  5. inazone

    inazone

    Apr 20, 2003
    Colorado
    So is OK to have the red light flash or should you back down just a bit?
     
  6. metron

    metron Fluffy does not agree

    Sep 12, 2003
    Lakewood Colorado
    Definitely back down if the amp is in the red. By that point the signal is usually distorting.
     
  7. jacove

    jacove

    Apr 12, 2003
    Aalborg, Denmark
    well, the red light is only flashing when hitting the string very hard for example when plugging a string, so I guess it's OK, thanks for all your replies! ;)
     
  8. jacove

    jacove

    Apr 12, 2003
    Aalborg, Denmark
    also, I don't run the QSC full up when playing, I just want to make sure that I can drive it to full power.
     
  9. 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
    If you don't hear distortion and your loudspeaker can handle the power, it's okay to have the clip LEDs flash a little.

    If you're driving the very minimum load impedance the amp is rated for, though, I'd back off to help avoid overheating.