Strange noises inside my kemper!

Especially if you have a strat type guitar, make sure the pickups are not causing this by being too close to the strings when you play high on the neck. The magnetic field from a pickup can pull the string in and out of tune.

I'm trying hard, but what exactly am I supposed to hear?

no, i dont hear anything out of order.

Yeah, I hear aliasing in there.

I just listened in my DT880 Pros; maybe it's just the soundcloud encoding, but I don't hear aliasing. This is something else, I think.

Cheers,
Sam

To me, it sounds like the resonance you get from the string "behind" the fretting finger interacting with the fretted note. Eg. the resonating part of the string from the nut to the 12th fret, in your example. In theory, this resonance shouldn't be picked up by the pickups, but depending on the guitar, I've found that it sometimes can be heard, although more likely on a semi-hollow body. I'm not discounting that it could be aliasing, by the way, just that the sound clip isn't clearly demonstrative. Maybe due to the encoding (it's a little difficult when there are artefacts added by soundcloud).

Cheers,
Sam

Ok, just listened again in a quieter environment (my kids had a friend over earlier, haha!). I can hear a kind of amplitude modulation, a bit like an lfo applied to the note when you bend, but I don't hear any lower frequency. I guess I need to check through my monitors, though. If it is aliasing, check your input and clean sense. Hitting the ADC too hard would explain it.

I'm not quite sure how the perceived pitch of the ghost note could move in the opposite direction to the fretted note and be the product of aliasing, however.

Cheers,
Sam

This happens on every profile you use?

I definitely heard it at :14 after you pointed it out.

I have experienced similar things but haven't noticed it in a while. Maybe they fixed it in a firmware update or I'm just used to it now. What firmware version are you running?

1. It's not called antialiasing but aliasing ( there are antialiasing filter to prevent aliasing) - this is effect when some freqency is sampled with too low sampling freqency.
Bassicaly when signal has frequency larger then fs/2. you have to use a filter with high freqency cutoff <= fs/2 but every filter has some disadventages - there is no ideal filter with infinite high slopeand suppression.
2. I've also noticed that the KPA has some "combo" spectrum above the 10kHz range witch may be the results of the used antialiasing lowpass filter.
Non ideal real filter example:
[Blocked Image: http://www.analog.com/library/analogDialogue/Anniversary/Graphics/figure52lg.gif]
3. This may be also a differential intermodulation freqency distortions - ihave also noticed that the KPA has some more audiable distortions of this kind then usual tube amp -but this is only happening with two or more tones but you used one tone(note). KPA patented algorithm is based on analyzing this frequency inter-modulation distortions.
4. I have also noticed I have heared on my PRS some additional high freqencies on high E string - but I also heard this tones without any amp with guitar itself.

So there is a many factors to take into the considerations.

Quote from Michael_dk

I don't know if it's every profile, I think it is not always equally evident. But it's definitely not tied to specific profiles or specific profileRS. Also, it is most prominent on the bridge pup.

I am running the latest public release firmware. Updated yesterday after noticing the problem; didn't change anything.

Yep, it is still present in the KPA but nowhere near as prevalent as it used to be with earlier firmware revisions. I notice it with unison bends sometimes, and with 5th diads sometimes as well. I was tracking a cue the other day and had to go through 10+ profiles to find one that had a small enough amount of it to use the KPA on the piece. It is the one "chink in the armor" of the KPA in my opinion. Hopefully they will find a way to eradicate it altogether.

With unison bends you have inter modulation from the guitar strings. You cannot have two close frequencies and not have that, it's nothing to do with the Kemper, you could hear it with your guitar unplugged, and it's why double stop bends sound the way they do.

@OP - have you tried playing the guitars through some real amps with similar settings to eliminate the possibility that it's the guitar setup? Old strings will also result in pick warble just as much as pickups being close to the strings. Also fret buzz could be a culprit.