Distorts but then comes clean

Discussion in 'Amps and Cabs [BG]' started by Spacewoman, Jun 20, 2020.

  1. Spacewoman


    Dec 3, 2018
    Why does my amp, a Gallien-Krueger MB150S-iii, distort and clip when I change the input level (e.g., by pressing the PAD or low cut button, or even by switching from one to two pickups) but then come clean after a while?
    Doesn't seem right.
  2. Crud buildup in the switches would be the usual suspect. Could be some weird circuit failure, as indicated by the bass pickup change doing the same thing. No idea how. Maybe you just need a new battery in your bass.
    Bassdirty likes this.
  3. Jim Carr

    Jim Carr Dr. Jim

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    Great little amp.
    Can you supply more details? What steps have you taken to "trouble shoot?"
  4. BassmanPaul

    BassmanPaul Inactive

    If the beast has an Effects Loop link Send and Return with a signal cable to exclude that from the list of possible causes.
  5. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    I'd confirm the issue with another bass.

    This sounds like DC offset at the input of the amp or output of the bass.

    More likely a on board preamp issue/ active bass issue.

    Check bass battery / check instrument cable. Or try a passive bass
    Bassdirty likes this.
  6. Samatza


    Apr 15, 2019
    The usual cause is dirty connections, pots and FX loop connectors.
    This is especially true if they haven’t been used in a while.
    Clean them first and see how it goes.
  7. Spacewoman


    Dec 3, 2018
    Thank you very much for replies. I tried putting a short cable across the effects loop, but it didn’t make any perceivable difference. And the problem remains irrespective of whether I use an active or passive bass. So it’s not due to a low battery. Dirty connections therefore seems to be the most likely culprit. I assume we’re talking about the PAD and low cut switches themselves, not simply the input jack, in which case I think I’d better take it to my local technician guy since I’d rather not open up the amp myself.
    Here is a short video of what I’m talking about. I depress the bass cut (though you can’t quite see me do it in the clip). Then I get static, and then it comes good. Often it takes much longer to come clean than in this example.
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Try switching that switch about 50 times and see if that helps.
  9. Spacewoman


    Dec 3, 2018
    Turns out the switches need replacing. All good now.
  10. BassmanPaul

    BassmanPaul Inactive

    Glad you got it sorted. We likes to help a Damsel in Distress we does! :)