Be aware of the digital sonic artifacts (aliasing) in your KPA!

    I hope that's a good clue for a fix, I'm not happy with the aliasing either and hope it gets fixed, even if I end up selling it, i'd like to hear it sounding the way it was intended. I trust it will get fixed soon, I've owned and used Virus synths before and the support has always been great.

    OK, I followed MikeB's instructions "in the How to reset your Kemper to factory defaults (I solved all my problems) PLEASE READ IF YOU ARE HAVING ISSUES" to see what would happen and things got even more interesting!


    First of all, going back to v1.04 and re-initializing the Factory Rigs did me a favor because I ended up with two versions of the "Wet Queen" patch, A and B. One of these two, (and I'm not sure which one at the moment, but I'm thinking "B") is the Factory Restored patch, while the other (probably "A") is probably the up-to-date Wet Queen patch that I used to create my original Aliasing Test results earlier in the thread.


    If you go and revisit the demo at KPA Aliasing Test Suite, you'll see five files:


    1) KPAaliasing Test - Original test using original v108 firmware and patch
    2) WQ 104 Patch A - using v104 firmware and patch A (probably using my original demo WQ patch)
    3) WQ 108 Patch A - using v108 firmware and patch A (again, probably using my original demo patch - this result behaves like Example #1)
    4) WQ 104 Patch B - using v104 firmware and patch B (probably using the factory restored WQ patch)
    5) WQ 108 Patch B - using v108 firmware and patch B (again, probably using the factory restored patch)


    Now, I'm glad I retested using both patch variants because the result is this:


    When using Patch A, the stomp box aliasing at :14 is there in spades. When using Patch B, it's minimal (phew!) - Independent Of Firmware Version. So, the stomp aliasing appears to be a patch-related issue.
    When using the V108 firmware, the "grit" that you can hear in the Amp section around :26 is there. But in V104, it's not. So, the grit appears to be a firmware thing.


    The original "KPAAliasingTest" demo was the worst case, effectively the same as 3) "WQ 108 Patch A" having both aliasing -and- grit present. That doesn't mean there's -no- aliasing when things are working right, you can still hear it but it's definitely tolerable!


    -djh

    Edited 4 times, last by dhodgson ().

    Quote from dhodgson

    When using Patch A, the stomp box aliasing at :14 is there in spades. When using Patch B, it's minimal (phew!) - Independent Of Firmware Version. So, the stomp aliasing appears to be a patch-related issue.
    When using the V108 firmware, the "grit" that you can hear in the Amp section around :26 is there. But in V104, it's not. So, the grit appears to be a firmware thing.

    Great investigative work by dhodgson and mikeb - I hope Kemper knows of your findings. Now, those of us concerned must decide whether to do this for now, or hold out for the fix.


    dhodgson, are you planning on staying in V104 for now?

    Miles,


    I went back to the v1.08 firmware since I'm not really dependent on the stomps, but if I had to record something critical that did I might think about it.


    More oddness: I saved the two different Wet Queen patches under different names and did a binary diff to see how they were different... and they weren't! Except for the names & dates, of course. There's more going on here than meets the eye.


    I'm with Mike - firmware problems that result in tonal changes? That's just hair pulling! And I probably wouldn't have noticed it if it wasn't pointed out, because at normal levels of drive it's the kind of thing that I might write off as "just a typical modeler artifact". The grit thing has me curious, though - an intentional change, or not?


    -djh

    Now that you have exposed the "grit", I tend to think it is the cause of another artifact I have been noticing all along: a slight gritty distortion on an otherwise perfectly clean amp profile. If you take a profile such as the Avalon VT737SP done by Baktus, strip it of everything but the amp profile, it should be squeaky clean, but no matter what you do there is always a little bit of digital hair on it--and it sounds to me exactly like the grit you demonstrated in your sound file.

    Edited once, last by miles ().

    Well, one thing I've been keeping an ear out for is the "always on" soft clipper that CK mentioned to me at one point. There really isn't a perfect level of cleanliness to be had supposedly even your rig is the profile of a straight wire. One of the surprising things about Line6's PodFarm plugin is how click-resistant it is - it's very tolerant of the kind of digital audio artifacts result from bad edits, for example. So, I wouldn't be surprised if Kemper decided to do something similar, preferring to soft-clip loud, clean signals on input as a safety against impulsive overshoots or other possible hard clips. But that would sound smoother/cleaner/more consistent than the grit effect.


    But the gritty bit sounds unlike what I'd expect if soft saturation was causing it. Because the alias-test probe signal is flat in terms of volume and frequency dynamics, it's funny that there would be this little "attack envelope" of amusical distortion being added to the front of a bend in v1.08's WQ amp model where there isn't any complex harmonic variation to be found in the source. And I couldn't think of where that might occur in the real amp world on such a simple signal, either - so, all I can do is wonder. If it was an attempt to add a bit of artificial sonic complexity to the attack of notes, well that would be a curious new line of thought but Occam's Razor makes a bug more likely.


    -djh

    Quote from dhodgson

    Well, one thing I've been keeping an ear out for is the "always on" soft clipper that CK mentioned to me at one point. There really isn't a perfect level of cleanliness to be had supposedly even [if] your rig is the profile of a straight wire.
    -djh

    It would be good if the soft clip could be turned on and off. With soft clip always on, it's seems impossible to accurately profile a tube DI, or a Neve 1073 for instance, without the KPA adding its own soft clipping effect. To be able to profile the character of such devices would be rather nice.

    Quote from ckemper

    I should mention here, that I mentioned in a similar thread, that we are working on these issues.


    You have to forgive us Christoph, we just like to play Sherlock and try to figure out what's really happening inside this box of tricks. Not because we want to reverse engineer the KPA or because we're trying to make a fuss and noise, but simply because we want to understand what's going on, to work out what the causes are so that we can avoid them and give useful advice to others if they experience this, and so that we can give the best feedback to you to save you time with tracking down and solving these issues. We want to help, and no-one likes to feel useless.

    Quote from Per

    to forgive us Christoph, we just like to play Sherlock and try to figure out what's really happening inside this box of tricks. Not because we want to reverse engineer the KPA or because we're trying to make a fuss and noise, but simply because we want to understand what's going on, to work out what the causes are so that we can avoid them and give useful advice to others if they experience this, and so that we can give the best feedback to you to save you time with tracking down and solving these issues. We want to help, a

    This exactly what motivates my posts. Also, I fix computers for a living so it is my job to figure out software and hardware combinations for clients. I can't speak for other people but I have played my guitar about 30x more with my Kemper than without it and that is all any musician can ask. something that speaks to your inner artist! The Kemper delivers this better than ANY other equipment I have ever used.



    :love:

    Quote from and44

    if X=A - 5 over C divide by 1 - then if X=B then OH NOES!


    there fixed it. just add that to the code..job done.
    took me a few secsonds, dunno what all the fuss is about to be fair! :)


    It is often a bit like that.
    But it take some time for a new release, as we perform some stages of quality assurance, even with a public beta.

    Quote from ckemper

    It is often a bit like that.
    But it take some time for a new release, as we perform some stages of quality assurance, even with a public beta.


    CK, I hope you realise I was just messing around.. and this was not aimed at you being slow, or me being a fool about it. was just a silly mad 5 mins of fun to brighten up our day :)


    we cool?
    Peace
    A