Bend with 2 notes ore more, a.h, NUMERICAL NOISE !!!


    I'm hearing phase interference here (what sounds like ring modulation), but it's hard to tell if it's from the Kemper or simply from your strings/frets/pickups. Would it be at all possible for you to record a dry DI signal from the guitar without the kemper of you doing the same thing? (if possible run it so that you can monitor it through the kemper to make sure you're getting this effect).

    And here's how the offending segment sounds through a standard studio compressor (not the Kemper) with an extremely short attack and release and high ratio, 96k aif 24bit file :


    http://www.per-anders.net/gene…pressed_mistercsignal.aif


    I roll back the compressors ratio till you have the clean signal at the end of the repeating block.


    The "ghost" frequency that you hear that's rising and lowering in opposition to the bend and gives that somewhat nasty ring modulator tone is nothing to do with the kemper, it's simply phasing between the two strings (and possibly a pickup pole being too close to those strings). The natural compression you get within any amp or modeler with high gain will accentuate the effect, but the problem is at the guitar/signal in end rather than an aliasing effect.


    I believe it is possible to hear digital aliasing artifacts at 44.1, but only in terms of harmonic interference and it'll still be really high up in the frequency range, like 18khz or so, even clock jitter is typically impossible to detect and that can cause quite low frequency (relatively speaking) noise. What I think you most often hear are things like string phase interference from the guitar itself, or that reverb which is of course in essence a very short echo, if the reverb density is too low or the predelay is at a bad position it can effectively create a harmonic of the wavelength between reverberations (that's why certain spaces are tuned) all reverbs are not alike, and of course the natural frequency emphasis effects of compression as you see here. I'll be honest that's mostly what I'm hearing here in these examples.


    Of course I could be totally wrong, I certainly have more cloth ears than golden, but so far from this thread what I've learned is that the Kemper Reverb needs to have a density control because it's density is just too low and is causing an audible flat harmonic. But not that there are audible "numeric" or aliasing artifacts. Maybe my hearing just doesn't go up that high anymore.

    Ok. Guys my test remap is with A REAL AMp micd. This is not the Kemper so I u are hearing this then I got the same result running his dry guitar signal into an actual amp. It's in the bend, pickups and how the distortion is responding to the note intermodulation. With a different guitar into my real amp bending notes I got not as much but certainly that modulate effect that happens when you Bend 2 strings and pitches are modulating. So if u are heading the same thing in my remap then it's not the Kemper.

    I do a lot of double bends (a la Gilmour) and honestly I do not hear anything different from different the same with amps or other distortion pedals. Some types of distortion pedals emphasize this type of intermodulation more than others but I am not hearing any of the "digital hash" that I used to get from say my Line6 modelers.

    Quote from MisterC

    Again, i like this profile and sound but sometimes the sound just going weird, never had such things with real amp.


    For you, all is fine here ???


    http://soundcloud.com/mugiwara-4/test-kpa-bend-yjm-01h


    Yes, and I have heard that on a real amp, generally when my pickups were too close to the strings or i needed a refret, and sometimes just because that's what happens with two strings together because of phase interference. Listen to the version I posted further up the page : http://www.per-anders.net/gene…pressed_mistercsignal.aif


    And then to this by Audioholic a post or two before mine:


    http://www.energiestudios.com/Files/Test.mp3


    Do you hear the same things as you're hearing with the Kemper? Because neither of those used a Kemper.

    Also don't forget that as you push for more trebly sounds that are closer to a DI'd attenuator/loop out signal than a mic'd cab sound (something we're more used to with modern production because it's been dependent on amp sims for a while now which all sound like that) you're going to emphasis and push these sorts of tones and frequencies that just aren't as clear with a real amp.


    In your latest example for instance you've got a profile that's extremely compressed and pushed at the treble end (no idea if you've added more presence and treble or removed the cab completely), far more so even than your original signal which you can hear being compressed in a neutral way in my clip. This is going to emphasize some of the nasty stuff that happens to the high end with distortion and compression, harmonics in frequencies that you wouldn't normally hear in an uncompressed signal but which are a part of the source itself.

    Quote from MisterC

    Again, i like this profile and sound but sometimes the sound just going weird, never had such things with real amp.


    For you, all is fine here ???


    http://soundcloud.com/mugiwara-4/test-kpa-bend-yjm-01h


    I think since I reamped your signal to a real amp and those same warbly sounds came out, its not the kemper, its what is happening when two notes are being intermodulted and bended like you are, I got the same result with a real amp from your dry signal. so this happens even in a real amp

    So I've done some further experimentation with this, just to see what causes the harsher effects, so that maybe we can find a solution for ourselves and for Christoph (and everyone can be happy). So following a slightly more scientific method than "what I hear is X" lets look at exactly what happens to the waveform's frequency spectrum as we apply compression.


    First up here's the original waveform, extremely logarythmic range, but you can see the natural harmonics and the root's, this is the opening little bend up and down from MisterC's dry no-processing source :


    [Blocked Image: http://www.per-anders.net/waveform_to_begin.JPG]


    So, lets see what happens if we apply what is effectively a hard compressor similar to what happens with most amps, i.e. zero the attack and release, high ratio, low threshold :


    [Blocked Image: http://www.per-anders.net/waveform_fast_releaseandattack.JPG]


    Eeek, now check out all those frequency "echoes" or "ghost" frequencies caused by the hard limiter/cutoff, severe phase interference ahoy! This is what's causing those dischordant sounds.


    Now, I decided that the most logical explanation was the fast attack and release resulting in what's effectively a limiter rather than a compressor, and causing additional frequencies as it's pushing the sound into effectively square waves.


    Given that the logical next choice is to reduce those and see what happens, so lets do that.


    So lets dial them both back :


    [Blocked Image: http://www.per-anders.net/waveform_slow_releaseandattack.JPG]


    Now that's looking a little nicer, it's louder and compressed, but we've reduced the square wave effect of all out obliteration, and so we have far fewer ghost frequencies, exploring a little further we can see what causes the worst offenders :


    Here's a waveform with the attack down to 0, but a slower release :


    [Blocked Image: http://www.per-anders.net/waveform_fast_attack_slow_release.JPG]


    and now the opposite, a slow attack but fast release :


    [Blocked Image: http://www.per-anders.net/waveform_fast_release_slow_attack.JPG]


    As you can see the attack causes our most noticeable but even harmonics, while the release causes many more but less noticeable "filament" harmonics (in the last one the makeup was pushed to show the effects), which sound more like a higher bg noise floor.


    Now the trouble is that this is just for standard compression. With distortion there's no such thing as attack and release and the compression is a natural byproduct of the distortion AFAIK (although perhaps Christoph could set me right here). This is why I think certain amp profiles have more or less of this effect, just as in real life some have more or less, their distortion just happens to result in more or less limiting/compression or faster compression than others.


    Given this I'm really not sure what can be done about it, it seems a fundamental issue and core part of distortion full stop. It's not really an aliasing issue because the same signal can be produced by analog equipment with the same harmonic content.


    Perhaps Christoph could work out some clever system to compensate, I hope he can find the time to read this and respond whether that's possible or just unfeasible.


    It might be possible to scultp the sound around this problem by placing a compressor in front of the amp with custom settings for attack and release and reducing the amps actual gain (and the distortion sens control), maybe reducing the distortion sens could help those with this issue on the Kemper, maybe just playing with the in amp compression controls (Sag, Pick Attack and Amp Compression) could help. Or perhaps it's just a case of this is inherent to certain amps and sound and the only solution is to either accept that or move on and use different profiles that don't suffer from it as much.


    christoph - Any suggestions?

    Quote from Per


    Why are you responding to me question with what sounds like an attack? Please relax, im trying to help you. I can hear several things including harmonics caused by you pickup poles being too close to you strings, some fret issues, flat harmonic caused by the fixed length reverb and frequency attenuation caused by the noise gate. What you identify as aliasing could quite easily be any one of those, theres a lot of other stuff going on that means I can't specifically identify one aspect alone as being aliasing rather than something else. You didn't answer my question. What happens when you disable the reverb and noise gate? What happens when you move your pickup poles away from the strings?


    The reason that I am asking you is in order to eliminate these extraneous "problems" and get to the core sound in order to really hear the problem on its own.

    sorry if it sounded like an attack, it was not.
    the pb was here also without the reverb and noise gate.just to tell you and introduce myself i'm 43 years professionnal musician and like guitar "TONE" so i test and use a lot of gear , i also have a torpedo vb101 (exemple of amp crancked in torpedo http://rbul1.free.fr/torpedo6.mp3 ) so i can crank my amps or profile them with kemper...my guitar is a tyler burning water and works great.: it's not an instrument pb.i know about gear i'm fan of effect , routing etc.
    the first thing i noticed is with dirt stompbox in kemper because i wanted to try the fuzz....take a clean amp profile, push the gain of the fuzz virtual pedal (or another dirt pedal) , and you will notice some digital aliasing (as another one guy of this topic noticed too) (and i use to have line 6 DM4 , vg99 and axe fx ultra, no pb .. and it seems that i'm not the only one who noticed that on dirt pedal of kemper)
    after i played a direct profile in my tube amp , and noticed the same aliasing (some strange sound "behind" my note , listen carefully..http://rbul1.free.fr/kemper.mp3 "behind my note" : definitly some digital noise.
    i tried profil my amp (via load box of torpedo ) same thing.
    is it a "direct profile" pb ?maybe ...but why this pb is in the factoiry stomp box too ?
    ?(

    Just to clarify, I was referring to digital aliasing in the stomp distortions, especially the higher gain models - It is easiest to hear this problem when playing a single high note bend (either up or down). You will notice a new sound or tone being generated that has nothing to do with the natural harmonic structure of distortion - many times it sounds like an additional note in the background (resembling some 'outer space, science fiction, flying saucer' effect). 8o It is not a natural product of analog distortion, but has been a problem with numerous digital modelers in the past.

    All modelers known to man 8o

    Quote from audioholic

    Ok. Guys my test remap is with A REAL AMp micd. This is not the Kemper so I u are hearing this then I got the same result running his dry guitar signal into an actual amp. It's in the bend, pickups and how the distortion is responding to the note intermodulation. With a different guitar into my real amp bending notes I got not as much but certainly that modulate effect that happens when you Bend 2 strings and pitches are modulating. So if u are heading the same thing in my remap then it's not the Kemper.


    Well, since i'm not a technician this closes the discussion IMHO.
    I hope that CK will implement a feature allowing us to reduce this kind of behavior, adjusting it to taste.
    Maybe an hi pass filter on the stack controls could solve it.

    Quote from Radley

    many times it sounds like an additional note in the background (resembling some 'outer space, science fiction, flying saucer' effect). 8o It is not a natural product of analog distortion, but has been a problem with numerous digital modelers in the past.

    It's exactly what i hear in my sample and at the beginning the distortion is from the amp.


    I think the Loulou sample is very eloquent :
    http://users.skynet.be/fb817866/jcm800higain.mp3



    Per: tahnks for those experimenations, i must say that i'm not so interested by those technical explenations but great job !
    But all this don't erase those flying saucers sounds that disturbing me !
    It's not an amp without cab, the cab is a Marshall 1960 by Tills (available in the 1st page) with no change and the dist on at te the end of the sample.

    I think most part of this is the mindset of knowing that the KPA is digital. It's simply the two notes intermodulating with each other and creating this phasing effect. It happens with any amp, any modeler, really anything with distortion going on. This is simple physics in my opinion.
    On the other hand, I sometimes hear strange artifacts going on in the KPA, what I just can't tie to anything. Most of the time I feel like that some exact, lower quality profiles are creating these noises and artifacts, but I don't feel it coming from the KPA itself. It would be great to get some official info on this.

    Use your ears, not your mathematical sense.

    As some other users mentioned before this wobbling tone is a normal effect you can get this with tube-amps as well. Wobbling is always a sign that two ringing notes have nearly the same pitch und so they inluence each other you can hear it if you tune your guitar or if your pole pieces are too close to your strings, this makes a similar wobbling effect.


    The problem is that digital gear has much more possibilities to emphasize some parts of your tone. If you are not able to use them correct you will emphasize unwanted parts of your sound. Some hints to improve your tone if you do not want to emphasize this wobbling effect:
    1.) Don't use too much of the compressor, better work on your vibrato
    2.) Don't use too high noisegate settings, it is better to wax pickups or improve the shielding of your guitar, or lower your volume when you don't play
    3.) Use good quality Cables (not expensive ones just not the cheapest)
    4.) Do not use to much gain. Try to improve your palmmutes, hit Strings clear and hard, mute unwanted strings
    5.) Use the TS to clean up unwanted high frequencies
    6.) If you don't like the wobbling tone, do not emphasize it with your playing technique :P

    Edited once, last by Kermit ().