Kemper Profiler MK 2

OneEng said:
This is what makes your ears so suspect. Are we to believe your ears over all those touring musicians using Kemper? Or for that matter, are we to believe your ears over all those who have had Kemper AND NAM AND QC AND AxeIIFx?

With respect to Aliasing, I happen to be a senior EE. Your explanation leaves quite a bit to be desired as well.

Without going into the mathematical theory behind how it is possible, I will state simply that if you sample at a rate twice that of the highest frequency you wish to PERFECTLY reproduce, you have no issues.

While different processing techniques can cause unwanted artifacts, those are not called Aliasing. FWIW, most internal processing these days is done with methods that provide insane dynamic range to prevent the algorithms from overcoming the mathematically limited storage of each sample. Again, I am not going to try to explain the math or the algorithms but will say that it is a fairly safe bet that the kinds of gear we are talking about here would employ these methods and make nearly all your assumptions incorrect.

In my previous post, I referred to something I hear as "Aliasing" as well, so I am also guilty. Having artifacts in the reproduced tone is not likely due to aliasing in any high end device today. It is much more likely an issue with the rest of the capture chain (microphone, placement, speaker, etc, etc).

I get you don't like Kemper and your reasons are your own. Mis-representing the quality of the sound is just way out over the line though. If you actually want a good point to be making about Kemper MK2, I would recommend the fact that the DSP and SRAM chips have not changed (the hardware parts responsible for actually manipulating and creating the sound). Only the the interface board has changed (the one responsible for the house keeping chores like GUI, loading of the DSP with a profile, running the foot controller, networking, etc). Why would there be ANY difference in sound quality between MK1 and MK2? Also, it seems pretty hypocritical now for Kemper to be selling an MK2 on the promise of more accurate profiling when they have spent over a decade claiming it isn't needed (a statement I agree with although on a different basis than Kemper has been making).

Finally, if you were in fact gigging, it is inconceivable (to me at least) that my list of concerns that rank above capture "accuracy" would not be your concerns as well. The ergonomics, reliability, and repeatability of a gig are much more often the cause of big issues in a band beyond capture accuracy where the differences are so minute that a host of touring musicians in A list bands find negligible.
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I'll respond to this word salad tomorrow when I'm sober.
 
Jarick said:
It was hard to tell with 50 pages of bullshit bickering going on lol
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Let Them Fight.gif
 
OneEng said:
This is what makes your ears so suspect. Are we to believe your ears over all those touring musicians using Kemper? Or for that matter, are we to believe your ears over all those who have had Kemper AND NAM AND QC AND AxeIIFx?

With respect to Aliasing, I happen to be a senior EE. Your explanation leaves quite a bit to be desired as well.
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trust-me-engineer.gif
 
OneEng said:
Yes it does. The thing is, no one but dogs can hear the frequencies above the Nyquist frequency. In your example, who will hear those 24KHz and above noise? For that matter, most microphones and certainly most speakers can't even reproduce those frequencies.
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Those frequencies above 24 kHz ALIAS. A harmonic at, say, 34 kHz will alias to 14 kHz. A harmonic at 47 kHz will alias to 1 kHz.

When you distort a signal you create harmonics that go into the hundreds of kHz. If you don't oversample those harmonics alias into the audible range.
 
OneEng said:
2) Aliasing is something you will likely only hear on satellite radio (and I am amazed at how many people actually listen to music on this crap). All modern devices have long ago sampled at higher frequencies than anyone here (especially anyone here) can detect.
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I think what you're missing is that partials above Nyquist are generated by almost any nonlinear processing, and especially amp sims, which will lead to aliasing in the audible range. No effects device uses a sample rate high enough to avoid that. You'd need a prohibitively expensive processor if you tried to do that. That's why oversampling the amp sim is required. But even then the result is keeping aliasing to a minimum, not elimination of it. That's why some amp sims have more aliasing than others. But please, tell us more about aliasing.
 
OneEng said:
The thing is, no one but dogs can hear the frequencies above the Nyquist frequency. In your example, who will hear those 24KHz and above noise? For that matter, most microphones and certainly most speakers can't even reproduce those frequencies.
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The issue is those frequencies above Nyquist reflect back down to the audible range due to aliasing. It's often a secondary effect compared to the main signal, but you can hear it if you have that ear (and those who can hear it, cannot unhear it).

IMHO the Kemper sounds great, is likely to sound better with the upgrades, some of those improvements will be esoteric and only matter to highly trained ears in studio environments ... and those who compare stats like null tests.
 
OneEng said:
Arguing that someone who believes a Kemper puts out such horrific crap as to not be usable by anyone that can hear is not unreasonable with the wealth of professionals (who also have ears) that tour with the device.

Agree on accuracy. A Null Test works pretty well; however, even a Null test does not measure everything. Still, I agree.

It's pointless beyond reason or I would be glad to post more.

The derivation of the Nyquist frequency is something I was required to do in college. I could easily look it up and possibly even explain the math, but why?

Everyone here believes that the theory works.

Yes it does. The thing is, no one but dogs can hear the frequencies above the Nyquist frequency. In your example, who will hear those 24KHz and above noise? For that matter, most microphones and certainly most speakers can't even reproduce those frequencies.

I believe Orvillain knows a great deal; however, if he does know signals and systems processing at an engineering level, he is misusing the term "Aliasing" and attributing it to things that don't cause it.

Processing any signal using an algorithm can create artifacts. Not all artifacts are Aliasing. .

Agree to some extent. I think every person that gigs regularly cares a great deal about weight, setup time, durability, and reliability. Most care a great deal about good tone. People that gig (at least my anecdotal evidence) don't care about how accurately a capture device captured their amp, only that it sounds good in its final form. Most people that gig at a certain level are all using IEM's anyway. It isn't like they are hearing exactly what came out the speakers.

If you go down the food chain to the hole in the wall gigs, none of those guys can afford a Kemper, Helix or Fractal. They will all be using an old tube amp and some pedals.

Fair point, except you can't determine if the modified signal is due to aliasing or something else. Note, I am not saying that a Kemper (or any other modeler) doesn't introduce unwanted output. Distortion (as an example) intentionally adds crap to the signal. It is just pleasing crap.

I am simply pointing out that:

1) Kemper sounds pretty darned good.
2) Aliasing is something you will likely only hear on satellite radio (and I am amazed at how many people actually listen to music on this crap). All modern devices have long ago sampled at higher frequencies than anyone here (especially anyone here) can detect.

I agree with you on Kemper's recent conduct. I think that the levels were particularly bad. For years they have been claiming that Profiles are as good to perfect as possible and now they are marketing more perfect profiles. And finally, it is possible that they will cripple MK1 (which has the exact same DSP chip and SRAM) to artificially keep it from sounding as good as an MK2 for business purposes. The later is just my speculation. If I am incorrect, and Kemper actually makes the "better captures" sound just as good on MK1, they I apologize for the accusation.

I think there will be about a zillion null tests performed this summer when the new algorithms in Kemper are released. Testing a device that is designed to modify a signal with engineering tools (like a frequency analyzer or scope) is useless IMO. I do have a trace on the latency of the Kemper switching from one performance slot to another (it was around 40mSec IIRC), but this is hardly that simple to quantify.
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Textbook sophistry.
 
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