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


    I cannot reproduce the crackles in any version. Do you record thru Spdif?
    Does it crackle when you play guitar?
    Anyone else have crackles?

    Quote from ckemper

    I cannot reproduce the crackles in any version. Do you record thru Spdif?
    Does it crackle when you play guitar?
    Anyone else have crackles?

    CK,


    I'm not sophisticated enough to notice these artifacts - I just love your creation. I just wanted to give you some encouragement.


    I also wanted to thank you for spending as much time as you do on these forums, following up personally on issues. This is very reassuring and to be commended! :thumbup:

    Quote from schneidas

    I don't have crackles via S/PDif.
    However, I think the guys mean aliasing and not crackles per se...

    I get crackles if I put the Comp in front of the Pure Boost and turn off the noise gate, like static noise.., but as soon as you play or turn the noise gate on then is gone...

    "Music is enough for a lifetime, but a lifetime is not enough for music" Serghei Rachmaninoff


    Quote from ckemper

    I cannot reproduce the crackles in any version. Do you record thru Spdif?
    Does it crackle when you play guitar?
    Anyone else have crackles?

    Yes, I have crackles that sound just like Cubase when it overloads the CPU - you probably know how that sounds ;)


    I do have them only just after I switched to another Rig and only for the first couple of seconds and then it works fine. It doesn't happen most of the time so there must be kind of a pattern I haven't figured out yet. I think it is when I'm switching from a clean to a distorted profile but I have yet to verify that. Anyway it seems more of an issue of the loading process and not a general problem with the actual profiles. Will look into it deeper later today when I find the time.

    I have a few pops that seem to be happening randomly (via SP/Dif) every now and again - although they are pretty rare, but they usually happen every 5 - 10 minutes for no apparent reason (even while playing and not messing around on the KPA or PC).


    Hmm, let's see... We got Crackle and Pop.


    So, just Snap's missing for the party! :P

    Quote from schneidas

    I have a few pops that seem to be happening randomly (via SP/Dif) every now and again - although they are pretty rare, but they usually happen every 5 - 10 minutes for no apparent reason (even while playing and not messing around on the KPA or PC).


    Hmm, let's see... We got Crackle and Pop.


    So, just Snap's missing for the party! :P

    I had this out of the box, had to perform a system reset to get it to stop.

    Quote from mikeb

    I had this out of the box, had to perform a system reset to get it to stop.

    Yes, I had tried this as well but it didn't change anything.
    I still get a pop every now and again. But they appear to happen pretty randomly, and sometimes I can play for 30 mins to an hour without a single one...

    Quote from mikeb

    Could be that you have to perform a flash format. I could not get my Kemper working correctly until I did that (volume problems, gain, noise)

    I have done a flash init and complete format of the KPA as well. Even after that it still happens every now and again.

    I'm doing a S/PDIF reamp loop for these tests Chris, digital in, digital out, clocked by the KPA. I was concerned that it might be my gear, LOL but if that was the case, then the bypass test should be crackling too. I've heard bits drop on rare occasions here and there before, but not like this or on the last version. Is there something else I can try? Send me an email if you need to get ahold of me directly, as I'm not on the KPA boards every day.


    -djh


    Quote from ckemper

    I cannot reproduce the crackles in any version. Do you record thru Spdif?
    Does it crackle when you play guitar?
    Anyone else have crackles?

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


    9) WQ 110 Rev 7448B - S/PDIF Reamp #1 <- NEW
    10) WQ 110 Rev 7448B - S/PDIF Reamp #2 <- NEW
    11) WQ 110 Rev 7448B - Analog Reamp <- NEW


    Sorry I've been sick in bed past couple days, or I would have gotten this out sooner. The focus for this test is the CLICKS.

    Reamp Mode........Bypass...........Stomp Only........Amp Only................Both On
    9) S/PDIF.........Rare Clicks......Clicks............Short Grit + Clicks.....no clicks or grit
    10) S/PDIF........Rare Clicks......Clicks............Long Grit + Clicks......no clicks or grit
    11) Analog........No Clicks........No Clicks.........Clicky Grit.............no clicks or grit


    I'm not going to talk about the aliasing qualities this time, just the clicks. There is noticeable clicking in Stomp Only and Amp Only mode when reamping via S/PDIF using the KPA as external clock. Likewise, the "grit" artifacts that you can hear at the beginning of Amp Only mode varies - it usually sounds like #10 when using S/PDIF, but on one (one!) occasion I got the shorter-than-usual example you can hear in #9. Thirdly, even in Bypass mode using S/PDIF an occasional sample is dropped - you can hear one or two clicks that are so brief you might not even notice.


    With regards to Analog reamping, you don't get the clicks, but the character of the Grit in Amp Only is different - it's got a less obtrusive but "clickier" character though. And you can really hear the analog noise, sheesh - this is what things sound like with the noise gate completely off when not digitally reamping.


    -djh

    Edited once, last by dhodgson ().

    Yes, there are random crackles and clicks in the S/PDIF input of the KPA.


    I turned off the amp stack and fx in the KPA and went DI through the S/PDIF output and recorded this pristine clean track in ProTools (with the KPA as the clock). I then confirmed that there were no clicks or crackles whatsoever, and so the KPA digital out seems fine.


    But, reamp that clean track back to the KPA, and that's when the crackling starts. It is very random, and seems to happen only when playing. Occasionally it's one click at a time, others it's a short series of crackles. :(

    Edited once, last by miles ().

    In this first file you will hear a few light clicks--I am digitally reamping and digitally monitoring the KPA.


    Click Test 1


    In this file you will not hear the clicks--I am digitally reamping and analog monitoring the KPA.


    Click Test 2


    This may point to the general area of the clicking problem--when the digital in and out are used simultaneously for reamping, you get clicks, but, if you reamp with analog in and digital out, it's okay, and when you reamp with digital in and analog out, it's okay.

    Edited 2 times, last by miles ().

    After installing 1.1.0.7459, the clicks and crackling in the S/PDIF are still there, here is an example:


    I am reamping a clean guitar from ProTools digitally into the KPA, and digital back out of the KPA for monitoring--stomps, stack, and effects are off.
    At 0.07 there is a click, and the crackles begin at around 0.20.


    Click Test 3


    It's audible from both digital and analog outputs now, whereas in 1.0.9.7426 it seemed to only happen with the digital outs (listen to the files in my last post).
    There also seems to be more crackles in 1.1.0.7459, and more clicks in 1.0.9.7426.

    A bit of good news: Yesterday, without any changes to the KPA or my ProTools HD system, I turned everything on and immediately noticed a lot more of the crackles and pops in the S/PDIF than usual. So, I changed to a different clean profile rig, and suddenly, all of the crackles and pops stopped. I have no idea why, but that simple change of preset has makes the problem go away. I will report if it comes back.


    A strange but welcome development.


    ----------------


    It's now later in the day, the noise came back, I did the same rig change as described before, and once again it went away.

    Edited once, last by miles ().