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Unexplained distortion coming from my amp?

Discussion in 'Amps and Cabs [BG]' started by RayO5421, Apr 4, 2009.

  1. RayO5421


    Jan 15, 2007
    Toms River NJ
    Hey all,
    I am playing on a 4ohm Avatar 410 cab and a GK 1001 head. With that combo, I should be getting 700 watts of power because the head can run at 8 or 4 ohms. Its always sounded sick for me, pretty gritty, yet very loud and clear. The only I problem I had once was it turned off without warning but this was due to overheating and not letting the fan do its buisness (I now just turn everything down and put it on mute so the fan can run and drive off the heat when I'm taking a break).

    Recently at practice, it sounded really awful and it was noticeable by me as well as bandmates. It was like a really bad distortion but the volume wasn't affected at all, it was almost louder than normal on the same settings I always use.

    I was wondering if anyone has a had a similar experience and mabey has an explaination? Could it be my older instrument cable? Or mabey the battery in my active bass? I am using a Speakon cable to connect the head and the cab so I'm pretty sure thats not the problem as I hear those cables are necessary to run the GK amps at the 4ohm high wattage range.

    Thanks for your help!
  2. Batteries are cheap so start there. Then replace your cables. guitar and speaker. Then if no difference it's tech time.

  3. spode master

    spode master

    Jan 21, 2007
    If you pushed your amp into thermal shutdown, you very well may have damaged an out put component or at very least caused a solder joint to weaken and become intermittent.

    If your pushing the amp until it sounds gritty, without distortion effects, then chances are your driving your power amp into clipping, which is not what they are designed to do.

    Eliminate simple things first like BassmanPaul says.

    But I will stress this, you do not want to get a gritty sound from clipping your Power amp stage, if you have a distortion pedal, or your saturating a tube pre amp that's fine.

    There is no type of cable necessary to run any sort of ohm range other than, one with sufficient gauge, to not burn up. The amp or cable don't determine the ohms, the speaker does.

    I see a repair tech in your future.

    Good luck.
  4. ^Those heads are designed to be pushed into clipping - the poweramp starts to growl when pushed, Mr Gallien made a post to comfirm this in a recent thread.

    To the first poster; it sounds like you have something that's not letting the fan do it's work properly? But yeah replacing and the battery would be the first thing I would check.
  5. There is a possibilty that (if it is the 1001rb , not the mark II) that you have a cap that is failing on the preamp board. Do as BassmanPaul suggests first. The 1001rb II preamp board (the voicing changed some) can be ordered from G-K parts and is a simple replacement.
    G-K parts 209-234-7300 ext 120 M-F 9am to 4pm PST USA
  6. RayO5421


    Jan 15, 2007
    Toms River NJ
    Well my head isn't technically clipping because the light never turns on. I think its just the tone and settings I use that make it sound the way it does and it sounds pretty darn awesome, not distorted like the way it did the other day.

    The problem I had was explained to me by a GK technician. I was practicing for about an hour and a half at a relatively loud volume; enough to make the variable fan go on. I turned off the head and took a break and then go back to playing. Something from starting the head up at a hot temperature will apparently make the head shut off when it gets too hot.

    Mind you this happened ages ago when I first got the head and it hasn't happened again since. I now just hit the mute switch and turn all the knobs down to zero so the fan can blow excess heat out when I take breaks from playing.

    Thanks for the suggestions, I'll try replacing batteries and cables first.
  7. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    Turning the knobs down makes absolutely no difference if the amp is muted. If anything, turning them down may cause you to try playing with them set wrong. And in the moment, you may turn something too high.

    Mute the amp and leave the knobs alone.

    It's also possible you've damaged your speakers, but first try batteries and cable, then borrow a head to test the cabinet.
  8. +1 to what Rick says. Just mute the amp and let it cool itself down between sets.

  9. spode master

    spode master

    Jan 21, 2007
    I'd like to see that thread, are you sure its not one of the stages before the power amp that allows the amp to go into distortion.

    I think its typically not a good thing to ride the voltage rails of the amp for too long.
  10. this is the thread; http://www.talkbass.com/forum/showthread.php?t=516196

    I have a 1001-II so I don't know what it's like to 'ride the rails' as it's so loud but it's dicussed a bit in the thread.

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