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Need some troubleshooting suggestions

Discussion in 'Amps and Cabs [BG]' started by JakeAM77, Sep 15, 2018 at 10:06 PM.


  1. JakeAM77

    JakeAM77

    Sep 10, 2018
    Hey all,
    This is my first post, and for unfortunate reasons, but I'm having some amp/cab issues that just kicked up at my last show.

    I was mid song at what I thought were very reasonable levels and all of a sudden my speakers started crackling at certain frequencies (low G, for example), and sometimes cutting out altogether until I fidgeted with the gain knob a bit. All the while, i heard that it sounded alright in the house.

    I'm running an Ampeg PF-500 through a 4 ohm Avatar 4x10, and I'm not really sure where to start eliminating issues. Made me feel like an idiot on stage so I'd love to have a better understanding in case something like this happens again.
     
  2. Raf Seibert

    Raf Seibert

    Dec 16, 2013
    Texas
    Onstage, in the middle of a gig, I would immediately turn the volume down a little, just a little, and roll off a little bass. That’s just to help you get through the set. Afterward, you can consider further troubleshooting.
     
    Old Garage-Bander likes this.
  3. Wasnex

    Wasnex

    Dec 25, 2011
    Try to duplicate the problem. If the problem cleared up when you adjusted the gain knob start there.

    Sometimes controls get a little scratchy. You might be able to correct it by rotating the control back and forth. If the control is bad, you might be able to continue using the amp by setting to control to a section that is good, but probably better to get the amp repaired.

    Fiddling with the Gain may have just been a coincidence. The plug in your bass may have been under tension and not making good contact. Perhaps the cable shifted and fixed the problem when you reached for your amp.

    Good luck!
     
    Old Garage-Bander likes this.
  4. JakeAM77

    JakeAM77

    Sep 10, 2018
    Well, that's all the strange part. I believe it's a cab issue because the sound was apparently alright in the house system.

    That leads me to believe that the amp is fine. It gets better with less gain/volume/bass, but to the point where it is near inaudible.
     
  5. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    Where in your signal chain was the the "house sound send" taken (e.g. DI on your head, DI before or after a pedal board, etc.)?
     
    Eric DK and Old Garage-Bander like this.
  6. JakeAM77

    JakeAM77

    Sep 10, 2018
    XLR'd from the head.
     
  7. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    Thanks...next question is was your signal sent pre or post EQ?
     
    Old Garage-Bander likes this.
  8. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    So have you found your problem yet or are you still trying to replicate what happened on the gig? The reason I asked about pre or post send on the DI is because that either eliminates a lot of stuff in the head or keeps it in the mix so to speak.

    Additionally, without sounding like I'm questioning what you believe you heard, you need to be really sure the FOH sound was not affected. Is it possible that it was EQ'ed differently at the board and you didn't notice the problem showing up there from on stage?

    If it was showing up there as well, my first place to look would be the instrument cable and jacks (bass and head) and battery in the bass if it has one. Also any pedals or boxes (including connectors, cables and power) prior to the head are suspect and need to be examined as well. If you're 100% sure FOH sound was 100% good, then you may be looking at a head or cab issue which could be anything from internal components to wiring to connectors to speaker cables.

    The other thing about duplicating the problem at home as Wasnex suggested is that IME these kind of things often come down to a bad cable or connector and/or a weak battery in an active bass. While that's not always the case, doing some simple troubleshooting/fault isolation work can frequently save you an unnecessary trip to the repair shop - not that there is a ever a good substitute for a great technician with years of experience IMO.
    Good luck!
     
    agedhorse, Spidey2112, Wasnex and 2 others like this.
  9. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    If you have a problem in the power amplifier, the to feed to the PA would be fine.
     
    Last edited: Sep 16, 2018 at 2:10 PM
    MDBass, Bassbeater and Al Kraft like this.
  10. Eric DK

    Eric DK Supporting Member

    May 14, 2018
    Florida
    Start with your bass; from tone knobs to outputjack. Then your lead/cable from bass to input on amp. Set amp EQ to as flat as possible, gain at zero, master at/about 9 o'clock. On back of amp; check speaker out to cab input (leads/cables/connectors etc.)Try duplicating (may take some time). Note: If FOH signal was fine (probably "Pre-EQ" selected) the issue is somewhere within amps EQ circuit(s). Try cab with different amp if available. Still issue? Somewhere in cab.
    Good luck!
     
  11. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Does the amp have pre-amp out and power amp in jacks? if yes, link them with a signal cable to remove them from suspicion. Same goes for the Effects loop if the amp has one.
     
    bumperbass and Lobster11 like this.

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