First Gig and loud bassy sound

    Heho,


    I´m not a geartechfreak. So i hope you can explain following issue:


    Yesterday after 20 minutes the FOH told me, my channel gives a loud bassy sound on the PA. So he give the advice to activate the ground lift. Afte activating everything works fine. After 20 minutes at the end of the gig a overload guitarsignal comes out the PA. Everybody was shocked and the FOH have to turn down the volume. After the gig he told me that I made the loud signal. I promise in this moment I only play and don´t touch my pedalboard or anything else. Master Input and Output are green.


    So whats going on?

    Music Man JP 6-String/Piezo Pearl Redburst, Kemper Stage, Kemper Power Kabinet

    I connect my Kemper with my QSC K12 on Monitor out and on Main Out Left to the PA. Both same db and soundcheck works fine.

    Music Man JP 6-String/Piezo Pearl Redburst, Kemper Stage, Kemper Power Kabinet

    You have probably set ground lifts for all outputs.
    One output should always have the ground NOT lifted to give the Profiler a solid ground.


    Explanation:
    A so called Ground Lift switch is actually not made for "lifting the ground", but for cutting a ground loop.
    A ground loop exists when two or more devices are grounded to the wall outlet and have their grounds connected as well by the audio cables. This creates a large ring of metal and acts like an electric coil. It can catch hum like the pickup coils of your guitar do. But it can also catch noise from computer devices, too.


    Often it is enough to lift one output to cut into this loop. The Profiler itself is not grounded by the power cable, so it requires one (but not more) ground connections by an output or input.

    Quote from ckemper

    You have probably set ground lifts for all outputs.
    One output should always have the ground NOT lifted to give the Profiler a solid ground.


    Explanation:
    A so called Ground Lift switch is actually not made for "lifting the ground", but for cutting a ground loop.
    A ground loop exists when two or more devices are grounded to the wall outlet and have their grounds connected as well by the audio cables. This creates a large ring of metal and acts like an electric coil. It can catch hum like the pickup coils of your guitar do. But it can also catch noise from computer devices, too.


    Often it is enough to lift one output to cut into this loop. The Profiler itself is not grounded by the power cable, so it requires one (but not more) ground connections by an output or input.

    Uh....what? Doesn't that create a potential safety issue in the case of voltage spikes?

    Hey CK,thanks for explanation !
    That's happen to me as well (not at the gig ,but at my home studio ,when I switched everything very loud, all windows and glass doors in the house start shaking 8o ) .
    I sorted it out by panicking and random pressing ground buttons on and off , intuitively , because it sounds like a ground problem to me , anyway .


    This thing, MUST be explained in details in The Manual , by the Vai ;( :D
    Even now , I don't know which ground button has to be ON or Off ....
    ..till next glass shaking...

    1988 Branko Radulovic Hand Made Strat in Macedonia (SFRJ)

    2006 Steve Vai vwh moded with SS frets and Sustainac 2006 (Japan)

    2008 Fender YJM , moded (USA)

    2010 Tom Andersons Drop Top 2010 (made in California)

    2017 Charvel GG sig Caramelised Ash (USA)

    2022 Gibson ES 335 2011 Custom Shop Cherry of course ( Memphis)

    Edited 2 times, last by Rescator ().

    Quote from Rescator


    Even now , I don't know which ground button has to be ON or Off ....


    It's easy:
    1) Check which in/outputs with the ground switches are used (cables connected to other gear)
    2) Switch all but one off them off

    (All trademarks are trademarks of their respective owners, which are in no way associated or affiliated with soundside.de)


    Great Profiles --> soundside.de

    "switch all, but one of them off !!!"
    that's smart :D

    1988 Branko Radulovic Hand Made Strat in Macedonia (SFRJ)

    2006 Steve Vai vwh moded with SS frets and Sustainac 2006 (Japan)

    2008 Fender YJM , moded (USA)

    2010 Tom Andersons Drop Top 2010 (made in California)

    2017 Charvel GG sig Caramelised Ash (USA)

    2022 Gibson ES 335 2011 Custom Shop Cherry of course ( Memphis)

    Quote from Will_Chen

    Uh....what? Doesn't that create a potential safety issue in the case of voltage spikes?


    I asked a similar question in another thread, Here, and got no response.
    I since have emailed support with the same question, and am awaiting a reply.


    Quote from imall41

    Here is an interesting quote from CK stating that the KPA is not grounded by the power cable, and is only grounded by a connection to another device, in one of it's inputs, or outputs. Thus the importance of not using all the ground lifts simultaneously.
    Does this also mean that the KPA should not be operated without something connected to it for proper grounding?
    What if you just want to update firmware, or edit rigs?
    Is the KPA at risk if operated with nothing connected to it?


    EDIT: Ok, I received an answer from Support explaining that CK, in his quoted post above, is referring to audio grounding, not electrical grounding.
    So, the KPA is safe to operate ,without external connections, for things like upgrading firmware, or editing rigs.
    I assume (obviously)that the power cord provides AC grounding, just no audio grounds.
    Thanks Kemper Support :thumbup:

    Edited 2 times, last by imall41 ().