Profiling adds quite some hiss on high gain amps SAMPLE EDIT

    I do have an AXE 2 here so I took this opportunity to try some profiles. Since the beginning I thought that the high gain profiles have more hiss than expected. Some hiss is actually added when profiling.You cannot hear it at the time of profiling if you compare reference and Kemper amp because your amp is connected to the KPA input section so there's even more noise than when the profile is done.But if you want to hear it just unplug your amp in from the KPA send when you are ready to profile and listen..You'll hear quite some noise reduction.You'll also hear that the sound isn't the same if you plug your guitar direct in it . Unless my unit is defective which I doubt ...
    This is kindda of expected..anything you put in front of a high gain amp will add noise except some high end buffers like Cornish.But I wonder if the input section could be made a little more silent and transparent ..Christoph ?


    thanks


    BRUNO


    EDIT : check page 2 for sample example

    Edited once, last by BRUNO ().

    "You'll also hear that the sound isn't the same if you plug your guitar direct in it ."


    +1


    This is one of my two criticisms of the KPA, the other being the Kemper doughnut you get after profiling with a cut in the lower mids.

    Vintage amp obsessive

    Quote from schneidas

    On a slightly related note: I still think the KPA is in deep need of a much improved noise gate!
    I really hope Kemper is working on improving the current one...


    Working on less hiss would be even better..gates do not remove noises..they mask it ;)

    Quote from professortweed

    "You'll also hear that the sound isn't the same if you plug your guitar direct in it ."


    +1


    This is one of my two criticisms of the KPA, the other being the Kemper doughnut you get after profiling with a cut in the lower mids.


    I too have noticed a fairly consistent dip in the 200 to 400z range after profiling - in fact, I have now come up with a standard post EQ (studio EQ) that I automatically apply to my finished profiles to boost these frequencies - it works rather well.

    All modelers known to man 8o

    Dude, relax and two to accept help with a modicum of grace. Hum and hiss can amount to the same thing, i.e. they're both just noise. It's hard to gauge from your description whether you're talking about hum caused by poor grounding/shielding or high pitched hiss caused by poor quality pre-amplification/ada, both will result in noise just at different frequencies and both can be described as hiss sounds. If it's lower then, yes, try the ground switch. If it's higher or more general white noise then chances are it's internal to the KPA.


    Do you also get the same noise when using SPDIF input with the Kemper? If not then that puts the issue on the AD side in the KPA. Likewise when you use SPDIF output is there any difference or is it an inherent part of the profile?


    Have you been able to check directly during profiling using a DAW to re-amp and properly compare the sound from the amp and the sound from the Kemper at that point (and then the sound once profiling has finished and you've stored the preset and loaded it up in the browser just in case something is changing after profiling)? This is the only way to listen to the two sources side by side without hearing playback through the amp itself (i.e. record a dry guitar track, send it back through the kemper and then through the amp using the switch on the keepers front while recording the return, then finally play back just the recorded signal to compare side by side).


    I've not encountered the particular problem your'e experiencing where you're getting more hiss than was in the original signal path at the time of profiling here, but I do find the path to be quite hissy/noisy unless the ground has been switched and even then the KPA signal path is not as clean as I would like given the sorts of compression that you encounter when dealing with guitar amps. But I always profile with a DAW as otherwise there is no way of hearing how close/far the profile is from the source. Here's hoping that Christoph can add the looper idea I posted to allow comparison without the amp blaring at the same time and without needing a daw.


    I made it clear that it is hiss ..not hum..and nothing that the ground switches can fix ..in my book hiss is absolutely not a lower frequency noise and this is the first time I hear someone mention the word "hiss " like this ?
    This hiss is expectable anyway..anything you put in front of a high gain amp will add hiss..and so to get the profile process going on there's no other way than this...but if hiss is unavoidable I think something could be done to avoid that kindda bad buffer effect you get on a profile set up ..If I plug my Cornish buffer in front of the KPA it sounds a bit different but not like that and sure not worse .once the reference amp is looped into the KPA it doesn't sound the same and it sure is for the worse..the difference is very noticable.now there's no way to really compensate for a sound difference that happens between the guitar and amp front unless you insert something again .
    I didn't try the SPDIF in..SPDIF out doesn't have anything to do with this problem anyway .That noise is generated before the reference amp
    Of course I did compare the original and profile OUT of the profile process .there are two levels of noise..one being added while profiling and some of it dissapears once you get everything done but a part of it remains .That's why some profiles in the exchange are totally unusable considering the amount of noise present
    thanks ;)

    Quote from Radley


    I too have noticed a fairly consistent dip in the 200 to 400z range after profiling - in fact, I have now come up with a standard post EQ (studio EQ) that I automatically apply to my finished profiles to boost these frequencies - it works rather well.

    interesting. not very familair with eqs but i imagine with the tone matching/eq tricks you can compare what frequencies are missing and literally fill in those gaps?

    Quote from Radley

    Sorry - It's a bit late to fire up the Kemper tonight, but I believe the boost is around +5 db at 350z at 1 octave. I'll double check tomorrow...

    Wow, 5 db really is a lot 8|


    I am also very interested in the question how the KPA´s buffer changes the guitar signal that is coming out of the direct output. When you put the direct out signal into an audio interface it is obvious that an impedance correction has already taken place, otherwise you would lose all the high end frequencies.
    Check here:


    Dry signal recording for reamping - KPA Direct out vs DI Box


    Though the direct out signal quality is very high, this might perhaps pose a problem to a guitar amp that is expecting a high impedance signal. Has anyone with a little more knowledge about these kind of things compared those signals?

    Quote from BRUNO

    Do you know what the ground switches are for ? ground loops ..ground loops and hiss are absolutely not related ;)


    But yes, they are!
    Cutting ground loops by the switches can prevent hum AND hiss.


    The profiling process will not add hiss. But the hiss is recorded and kept during the A/B comparison, to make it fair.
    Once you save the profile or switch to browser mode the recorded hiss is thrown away.

    Just did some recordings of it :


    Hiss test


    All 3 samples are heard through the return of KPA..first is the reference amp with guitar direct in it in profiling mode..second is the reference amp with kemper inserted between guitar and amp ready to profile.
    Third is the profile in browser mode.
    You can clearly hear the huge amount of hiss that profiling ready is adding..a lot of it will dissapear once profiled and stored but some is still there... Compare for ex. 0.02 to 0.41


    Thx


    BRUNO

    Quote from ckemper

    Where is the gain positioned on sounds where the noisegate is not sufficient?

    Well it is "high gain"... so the gain is set as high as 10.
    I know you guys think this might be a ridiculous setting, but it is not. The amp profiled (not mine, btw) was not highgain to begin with... so I add the preferable amount of gain to get the "response" out of this profile that I like. It gets there obviously with the gain on full (for this particular profile) but, of course, noise gets amplified which the noisegate cannot cut well enough. To get a good cut, it has to be set on 4 minimum.


    The thing with the noisegate is this however: When I reduce the guitar's volume to "1" (volume pot on the guitar, NOT on the profiler), the sound cleans up nicely - but, with the noisegate on, I get a kind of "doubler" effect. Like a small ambiance sound. With the noisegate off, the "doubler" effect is gone. The noise is "through the roof" then, obviously.