High pitch feedback/squeal -> Ground loop problem ?

  • Hi,


    I received my profiler yesterday, I did a quick test with O.S version 7.1.4 installed by default with default profiles and everything seemed fine (from what I recall).

    I then took the time to update the OS to the latest public Beta and add a few profiles freshly downloaded. When I plugged my guitar I experienced a sort of feedback sound through my headphones. Since the OS did not seem really stable (Profiler froze several times) I thought it was due to the OS so I reverted back to the latest public (7.5) but same thing occurs.

    I continued the investigation and tried all those things :

    • Change Power strip
    • Use power socket directly and change power socket in the same room
    • Use power socket from an other room
    • Turn all the lights off
    • Apply Factory Reset on the Profiler
    • Try different Jacks
    • Try different guitars single coils and humbuckers
    • Try different headphones (Closed headphones only)
    • Play the guitar outside of the room with a long jack and headphone cable extension

    Nothing really worked, but here are my findings :

    • Headphones are closed so there is no way the signal goes from the headphone to the pickups
    • It occurs with clean and crunch sounds -> Of course the more gain, the more noise in addition to the feedback noise
    • Feedback stops when I mute the strings with my hand or turn the volume to zero on the guitar, however it doesn't really decrease when I turn down the volume
    • Strangely enough, it seems that Single coils introduces less feedback than humbuckers (I tested with my Telecaster, SG and LesPaul)
    • Feedback occurs when the jack is connected to the profiler but not to the guitar (without touching it)

    Good thing is that I managed to mostly ged rid of it with the input noise gate:

    • I have to set it to almost 7 for humbuckers with profile which have gain set to noon or more and 5 for clean profiles.
    • 6 to 6.5 for Single coils seem to work well for saturated profiles and 4 for clean.
    • Unfortunately it seems that it affects the tone (probably negligible but still) and sustain

    Is it normal ?

    Am I the only one experiencing this (I searched a bit but did not find real answers) ?

    Is my unit faulty ?

    Is it a problem with the headphone input (Unfortunately I don't have monitors yet and my unit is non powered, so I cannot test anything else)?

    Are there any setting I am missing ?

    Do you all use the noise gate input ? If yes to which extent (because the value i have to apply seem pretty high)?


    I can leave with the noise gate trick however since it is brand new and it's not cheap I would rather make it repair or exchange it while I can. Especially since I plan to use it a lot with headphones


    Thanks in advance !

  • I had the same problem.
    It occurred when the input section was locked.
    It includes the noise gate level which was then set to zero for all rigs (before that the level was saved in the rig)
    That also appeared at the same time, when i did an OS update to a beta version.
    not sure if the locking was done by the upgrade or by myself :/

  • Cool, how did you fix it ?

    How do you unlock the input section ?

    How can you tell that the input section is locked (visually I mean on the profiler itself) ?

    It may be due to a bad manipulation on my side, I need to read the instruction manual ...

  • Cool, how did you fix it ?

    How do you unlock the input section ?

    How can you tell that the input section is locked (visually I mean on the profiler itself) ?

    It may be due to a bad manipulation on my side, I need to read the instruction manual ...

    the locked status is indicated by a lock symbol on the right side of the display. To lock or unlock a section you need to press the lock button while you are in the section you want to lock or unlock. But from your description I really doubt that this is the reason for your issue.

  • Thanks for your answer, I received a lot of thing to try from the support as well (try different inputs and outputs to find out what can be the root cause), I will try them all and will let you know the outcome.

    I'll also check if the input section is not locked, just in case and let you know.

  • Thanks for your answer, I received a lot of thing to try from the support as well (try different inputs and outputs to find out what can be the root cause), I will try them all and will let you know the outcome.

    I'll also check if the input section is not locked, just in case and let you know.

    If you press and hold the lock button, anything that's currently locked will be lit. Pressing a lit button should turn the LED off, meaning that block/section is now unlocked.

    “Without music, life would be a mistake.” - Friedrich Nietzsche

  • Hello,


    As discussed I come back with my findings.
    First interesting thing, when I came back from work and turned on the Kemper, The problem was gone. I played for 10/15 min and decided to have dinner. When I came back the problem was back.

    So i tried different inputs and outputs it did not change anything and the problem persisted, I also reset the unit (RIG button + System button pushed while turning on the unit) but it didn't help either and the input section was not locked.


    Here is a video of the problem :
    https://photos.app.goo.gl/qY43U2R1jUE5nNwJ9


    The sound is coming from my keyboard amp, I reproduce the problem with all my electric guitars.


    The good news is, the profiler is not faulty, because I can reproduce the issue by plugin my guitars to the keyboard amp directly
    .


    If I plug my electro Yuk or my acoustic guitar to the profiler the problem disappears


    So I think the problem is related to pickups ? Due to interference ? Or electric problem (It is not a ground issue since everything is grounded properly -> I double checked yesterday)?


    Do this ring a bell, do you have any idea what I can try ?


    I tried turning off almost everything in the house or unplug it, but I guess if it was purely electrical I should be able to reproduce the issue with any guitar plugged in correct ?

  • playmo77

    Changed the title of the thread from “High pitch feedback sound with headphones” to “High pitch feedback/squeal”.
  • Is there an audio interface in the equation?

    Sounds like ground loop problem with interface connected to pc I've had before.


    * Back of profiler, there are series of red buttons which are ground lifts- if you haven't already- try pushing those, see if anything changes.


    * if you have more than one device connected to your audio interface (inputs and outputs - anywhere), disconnect them until noise stops. Troubleshoot from there.


    *You could always test your house wiring, but pretty unlikely that's the cause. You can get a tester at a hardware store for cheap. Really doubt that's your problem, though.

  • Yes I think it is q ground loop problem.

    It appears only with my electric guitars, It disappear when I touch something metallic on the guitar (bridge, strings, pickups ...)

    I have the same problem with all my amps in the house not just the kemper

    And the problem is not present when the guitar is unplugged or volume is zero


    I'll order one of these and see how it goes ...

    I'll let you know but I think I have isolated the problem.

  • playmo77

    Changed the title of the thread from “High pitch feedback/squeal” to “High pitch feedback/squeal -> Ground loop problem ?”.