Loud "internal" clipping with a specific rig - Input and output levels are fine

  • Hello, this is a trouble I noticed last month and I already opened a support ticket about it.


    In a specific rig I hear I very loud pop if I strum hard and I use some studio equalizers.


    In this clip I tried to strum hard (not really hard to be honest). In the last seconds I strummed softer and the noise is gone away, before showing up again in the last strum.
    https://soundcloud.com/ale-102/loud-clipping-kpa


    It's a commercial profile (silver jubilee clean) with the original cabinet. If I put the cabinet and stompboxes in other rigs, pop is still present, louder or softer depending on the rig type (clean or distorted)
    If I turn off the cabinet in that rig, the pop seems to go away.
    I have noticed the same thing with another rig, but I don't remember which one because I was gigging and I did not even stored it. All I can recall is that I put a fuzz and a wah in the stomps section.


    Before replying, please consider the following:
    _The Kemper support team, once I sent them the rig, confirmed that they can hear that noise too, so my KPA isn't faulty.
    _input and output led are green: the clean sense is 0 and rig volume is about 25%
    _the recording has been made with spdif output, but with other rigs everything is fine (no noises, no pops)
    _I can hear the noise with all outputs, including headphones
    _guitar and cable are fine, I tried with other guitars and cables and nothing changed.
    _there are two studio equalizer in the stomps and effects section. I can post the settings, but I just tell you that the first eq volume is +2.6 db and the second eq volume is -3,8 db
    _if I lock the cabinet and the two studio equalizers, the noise is still present in other rigs
    _rig isn't corrupted, it weighs about 5 kb
    _already tried a system reset
    _already tried to downgrade firmware


    Mr. Kemper said that it's impossibile to "internally" clip the KPA. I actually think that some rigs profiled with very high volumes may cause that sort of clipping.


    Thank you for your attention chaps :rolleyes:

  • Alex, did you check all the Amplifier settings (Definition, Power Sagging, etc.)? Are any of those set to extreme values?

    Go for it now. The future is promised to no one. - Wayne Dyer

  • Alex, did you check all the Amplifier settings (Definition, Power Sagging, etc.)? Are any of those set to extreme values?


    Yep, definition is 5.0, power sagging 4.8, pick +0,8, direct mix 2.3. The other parameters are 0, so no extreme values


    About the 2 equalizers:


    First studio eq, stomps section:
    Low gain 2.9 Low Freq 401.4 High gain 0 High freq 2999.8 Mid1 gain 2.3 Mid1freq 678.2 Mid1qfactor 0.324 Mid2gain 0 Mid2freq 1499.2 Mid2qfactor 0.707 Mix 100% Ducking 0 Volume +2.6


    Second studio eq, effects section:
    Low gain 1.3 Low Freq 200.1 High gain 1.3 High freq 5015.0 Mid1 gain 1.3 Mid1freq 1007.0 Mid1qfactor 0.707 Mid2gain 0.9 Mid2freq 1499.2 Mid2qfactor 0.707 Mix 100% Ducking 0 Volume -3.8

  • If you roll off the EQ under 0db what happen? Just to get a clearer portrait of the issue behavior.


    I tried to lower the post studio equalizer volume in the original rig (the one which I recorded) and clipping had more or less the same amount of volume, proportionally lower of course.
    Then, I tried another time to disable the post studio equalizer, keep the pre studio equalizer on and strum really hard with my les paul. Clipping was still there! Harder to obtain but clearly hearable. I'll try other tests (you know, I want to experiment only with cheap headphones, because these loud pops are not good for speakers), but my thought now is that the combination of cabinet + studio equalizer may cause this issue.

  • I don't think it's a clipping. It's true, it's impossible to overload digital modules with such a floating point maths. You should have - say - 1,000 times the signal level in order to clip.
    It has to be some kind of glitch.
    Could you check whether all the parameters in the Cab section are flat, and if they are not set them flat and see what happens?


    If Mothership can reproduce the issue with the same rig, it makes no sense to try different guitars, cables etc. the bug has to be found within the rig parameters IMO.


    Let's see what happens, I'm curious :D


    Talking about headphones... loud pops are much worse for your ears... I'd lower the MAster volume and use loudspeakers ;)

  • Could you check whether all the parameters in the Cab section are flat,


    Yes, they're flat. For completeness, below you can see all the settings and what is enabled in the rig (only the two studio eqs), so I can't make mistakes. Rig volume is -14,8, gain is 0
    Beg your pardon for the image size :D


    [Blocked Image: http://imagizer.imageshack.us/a/img742/4441/PsZvml.jpg]


    [Blocked Image: http://imagizer.imageshack.us/a/img901/1603/diPUBP.jpg]



    Talking about headphones... loud pops are much worse for your ears... I'd lower the MAster volume and use loudspeakers



    Don't worry, I use them with very low volume, no harm at all at my ears ;)

  • OK, so if the cab parameters are all flat I believe it's a profile born weird (not sure that makes sense in English, but I guess you get my point :D)


    Same for the other one, of course :/

  • What kind of pick are you using on the guitar? Is it metallic? I'd imagine a noise like that if it touched the pickups or something.


    Still expect this to be an issue with profiling, incorrect profiling to be precise. Since the issue could be replicated, I'd say there was some element in the profiling process or maybe the refining process that caused that popping sound. Could even be something like a torn speaker flapping or something, the way the Kemper recreates an amp is truly bizzare and I've heard of people who just made a noise into a microphone as a test and got profiles out of it.

  • What kind of pick are you using on the guitar? Is it metallic? I'd imagine a noise like that if it touched the pickups or something.


    Still expect this to be an issue with profiling, incorrect profiling to be precise. Since the issue could be replicated, I'd say there was some element in the profiling process or maybe the refining process that caused that popping sound. Could even be something like a torn speaker flapping or something, the way the Kemper recreates an amp is truly bizzare and I've heard of people who just made a noise into a microphone as a test and got profiles out of it.


    Well, I use an ordinary tortex pick. No problem with other rigs. The noise made when pickups are touched is more similar to a "slap" in my opinion


    Do you think it's a torn speaker issue? If think this should be hearable from the start

  • Alex, you are not alone, in this matter. I had this same sound on several profiles, and it was unpredictable, as to when it would occur. I ended up sending it back to Kemper, and was told by my sales rep, that they couldn't really find the problem, but replaced the board in it anyway. So, over the past year, when is got it back, everything seemed fine, and so I took it out on a gig last week. Suddenly, one of my lead patches started doing this really loud clipping noise, just like before, and I had to stop using the patch, just to get through the gig properly. A hard strum brings this obnoxious noise out, and I cannot figure out what is causing it either.

  • Since the behaviour is unique to a few profiles, that leads me to think the issue is not with the Kemper, but with the profile being used. I don't have this behaviour on my Kemper and I don't think it's some sort of software glitch. Just seems likely that something is wrong with the profile.


    I did note that it's almost like an internal clip in your Kemper, since those popping sounds coincide with the highest peaks in your recording, though those do not seem at clipping levels at the output.


    The noise goes away if you turn off the cab section. What if you try a different cab? We can probably narrow this down, but as mentioned, since Kemper Amps has reproduced the issue with said profile, in all likelihood there's something defective.