Another re-amping thread...

    Hello KPA users!


    On my quest to achieving the best re-amping recipe, I ran into some phasing situations. I would like to share some thoughts and also ask for your opinions.


    Here is my setup:


    KPA -> SPDIF (Left/Git Studio) -> Audio interface -> Reaper (this records a dry track)
    KPA -> SPDIF (Right/Stack) -> Audio interface -> Reaper (this records a stack track)
    KPA -> Direct out -> Audio interface (instrument input) -> Reaper (this also records a dry track)


    So far, so good. Now when I look closer, both dry tracks (spdif and inst. input) are offset by some ~80 samples (the spdif one being late compared to the direct out one).


    And then when actually re-amping, using either of the dry tracks, the newly recorded track will typically have an offset of some 475-500 samples compared to the dry track.


    I am assuming these offsets are caused by the A/D conversion and the KPA's processing delay, and there is probably some latency induced by my audio interface as well.


    Sure I can always use some kind of click recording and realign the tracks when done re-amping. Still, I am surprised by there numbers.


    Are all you KPA re-ampers observing pretty much the same behaviour?


    BTW, I am currently trying out a Focusrite Saffire 24 DFP Pro which I am using to perform these tests.


    All the best

    Hi,
    I did not use the KPA for recording guitar tracks yet. The fact that it has to be the digital master makes it impossible to connect it to my studio setup...but that´s another story ;) so I cannot comment on the I/O latency. But I´d like to chime in to report another problem with reamping, that certainly is connected to yours:
    I like to stack sounds on top of each other when reamping, using one source track, i.e. a Diezel Herbert heavy tone plus a Rectifier plus a Plexi. This is the way I work for several years now, with great results! Most of the engineers I know do it this way, too.
    Unfortunately it is not possible to do this with the KPA. You´ll get tracks that are randomly out of phase with each other. Not the complete track, but random parts, so you can not align them afterwards!
    Kemper tech support already confirmed, that the KPA works with a dynamic latency control.
    The KPA is THE ONLY DIGITAL DEVICE I know that switches the internal latency on a random basis. You can stack reamping tracks from real amps with POD tracks and with VSTplugin tracks and with Sansamp tracks etc. (yes, you´ll have to phase align them after reamping, but that´s possible because of constant phase handling) - but as soon as a KPA track comes into the game, you will not be able to get this one in phase with the others!


    I suggested some kind of "latency switch" between a reamping mode (with constant phase but maybe higher latency) and a live mode (with latency/phase handling like it is at the moment).


    This problem is not relevant for live playing (only if you´re goining to mix two KPAs or a KPA with another real amp) or for recording single tracks, or for reamping single tracks. This may be the reason why those reamping issues are not considered as a major problem here on the forum...zero replies after a few days...
    For studio use, randomly switching latency is a showstopper!


    Please Kemper techs, fix this!!! :thumbup:

    This is interesting. And corresponds with some of my observations. I have tried to measure the latency of different firmware versions several times before, and noticed that the latency is jumping up and down. I have noticed that after a while it settles, but it is very jumpy after a profile change. According to my measurements the latency is bigger after a change, and it slowly settles to a lower value. I have measured the average latency ~ 3.3 ms on the newer public betas.

    Hey guys, thanks for chiming in, appreciate the info!


    r_u_sirius: The "latency switch" you are referring to for reamping/live is a great idea! For me this is a must, as I will have many use cases where I'll be using the Kemper for reamping. I may not be stacking tracks at the moment (dual/quad tracking only), but I'm sure I'm sure a day will come where stacking will needed. BTW, you are using spdif for reamping, right?


    Anyone having an opinion/idea/experience on this subject is welcome to chime in!


    Thanks again! :thumbup:

    My 2 cents is if you are a pro or considering Pro Tools - there is a great deal on the Avid Eleven Rack + Protools 10 for $650


    The Eleven Rack is a powerful tool by itself - but IMHO it makes the perfect Re-Amping Audio Interface for guitarists who use ProTools.


    ProTools 10 now supports third party Interfaces too, so in my case I will the Eleven Rack as a Re-Amping solution in Protools for the KPA,


    Then swap out the Eleven Rack interface with my MOTU 828 MK3 (+ Presonus FireStudio 2626 Adat out into 828 MK3) for full band recordings in Protools.

    Elantric, please forgive me if this seems like a stupid question (hence, I am a pro, but not that much pro!), but how would the use of the Eleven Rack be a solution to the latency issue? ?(

    The Eleven Rack is for KPA Re-Amping - which is an offline process with the Guitar in its case.
    I'm not saying it solves any Latency issues.


    But the Eleven Rack has a wonderful interface with Protools - where new guitar parts are recorded as separate tracks


    One Dry Mono guitar track - (like using a D.I. straight from the guitar pickups )
    and a stereo track which represents the Eleven Stereo processed output.


    So for using the Eleven as an Interface for KPA for reamping, its a simple process of connecting the SPDIF I/O to the KPA and roll the dry guitar track from Protools and try different KPA presets until you find the sound you want.

    Elantric, thanks for your response!


    I am actually quite familiar with the re-amping process. What striked me though while trying to figure out the best re-amping workflow using the KPA was the latency/offset difference between tapping a clean signal from spdif vs direct out.


    As I am sure the Eleven Rack is also an awesome piece of gear, to me the KPA should be a tool on its own as far as re-amping goes. I mean, using it with any decent audio interface should do it, right? The Saffire Pro 24 DSP is working great for me so far.


    As r_u_sirius mentioned it, it appears the KPA is inducing some dynamic latency... this might be the source of the observed offset.


    It would be cool to have M. Kemper's input on this one! 8)


    Thanks again!

    Sorry Elantric, but your 11Rack/ProTools/audio interface suggestions are a little OT ;)
    I´d prefer to focus on the KAP´s latency issues here, instead of discussing workarounds with other gear, if you don´t mind.


    Maybe you should start a new thread about KPA with audio interface? It might get some attraction....I myself don´t care much about this functionallity.
    8)

    Elantric, please, you are missing the point here!
    This topic is about the internal KPA latency, which is obviousliy different for analog and digital outputs, and which behaves dynamic (confirmed by kemper tech), what leads to random phase problems when reamping more than one track from one source track.


    DAW delay compensation is another story.

    I deal with Latency with every piece of gear i own that employs A/D- DSP - D/A


    I deal with it in the studio in the manner stated above. (re- allign post processed tracks)


    Live use is an entirely different matter - but know this - every point of signal conversion from analog to digital or digital to analog WILL add latency


    A/D Latency should be a stable number


    D/A Latency should be a stable number


    However DSP Latency will be a variable function - dependent on the processing currently being performed by the DSP in the current patch. i.e. add more FX = added latency in the DSP block.


    (These are very typical issues of all modern DSP based gear and not an exclusive "problem" with the KPA)




    But when I see a title called "Another re-amping thread..." i figured live use is not on topic.


    But if you need verification that the KPA's SPDIF I/O has lower latency than the KPA's analog I/O - I can confirm this.
    Sorry if this appears off topic


    I'll no longer post here.

    Elantric, thanks for your input. As you mention it, AD/DSP/DA involves dealing with latency sooner or later. I know about latency compensation. But my observations with the KPA, besides the obvious latency induced by the AD conversion, are:

    • direct out vs spdif out (git) infers different latency values while recording a dry track
    • re-amping either from spdif input or analog input also infer different latency values


    I still haven't tested/experienced the randomness r_u_sirius is referring to, but he has apparently confirmed it with Kemper support.


    m. Kemper: if you peek this thread, please take into consideration r_u_sirius' idea of some switch to allow turning on/off this random latency. This would be great! :thumbup:


    Cheers guys!