Gallien Krueger MB-Series Hissing :(

Discussion in 'Amps and Cabs [BG]' started by phnord, Jun 17, 2020.

  1. phnord


    Oct 26, 2010
    Brooklyn, NY
    I've had an GK MB800 for years now. It's had noticeable hiss all that time, that has gotten progressively worse

    I've sent it in for repair from GK a couple of times; each time it comes back a little better, but then degrades over time

    They refuse to give me a replacement; they just tune up whatever's causing this, and send it back to degrade again

    I have a feeling it's related to the input jack; if you move a cable around in there, it gets better / worse as you do, as you put pressure at certain angles

    What's crazy though is that this happens regardless of volume levels, regardless of if anything is plugged in, regardless of if the amp itself is muted.

    I can mute it entirely, turn the volume all the way down, turn all EQs – including the treble – all the way down, and the hiss will still be there.

    I can unplug the input jack after doing so, and the hiss will still be there.

    But then if I plug it back in, and put pressure at the right angle – still with it muted, still with the volumes off – the hiss can be made slightly better if I push at the right angle.

    This is noticeable on all cabs, but is most noticeable on those with a tweeter, because of the frequency range of the hiss.

    It sounds like what you'd expect line-noise to sound like when the high-end is *super* boosted. Someone hissing an "sssssss" constantly.

    Other heads don't cause this issue through my main speaker; and this head causes the issue through every speaker...

    Any advice on getting this fixed-fixed? Anyone else find this to be the case with MB-series heads?? I see mixed results in old threads, but all of those are a good eight years old now, so I'm curious to see how people have found their MB heads to pan out over time....
  2. Yes GK's Hiss
    Search this forum for: GK Hiss
    You'll get many hits

    If you can plug a unconnected cord into the effects return and get the hiss to go away, then you can try a high cut filter on the effects loop. Possibly a little graphics eq with the highs cut may help.

    If it still hisses when you plug an unconnected cord into the effects return then it's likely in the power amp section of the head. Not much you can do there unless you get a good tech who can signal trace it to find the cause.
  3. Frank S Blumm

    Frank S Blumm

    Jun 25, 2022
    Hi, I have exactly the same problem. Did You find a solution? Thanks Frank