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Ooooh... Charts and Graphs

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yeky83

Power User
The chart with both Axes goes down to -110.

And the question "why so much noise/distortion/artifacts" remains.
Oh, you's right! :p

I don't think it's quite fair to characterize the data as "why so much noise/distortion/artifacts" though, when the Axe-Fx is clearly performing better than the competition.

Cliff has attributed the difference to aliasing/oversampling, and he's qualified to make the judgement, so I trust that. I just don't know how to differentiate general noise vs. aliasing noise. Perhaps one way to gauge how much difference aliasing/oversampling can make is to just look at II vs III. I don't think there's a big difference in the base-noise level between the two, and if so, the difference seen in II vs. III measurement is largely due to aliasing. Given this, it's not far fetched to assume we're looking at mainly aliasing performance when we're looking at these graphs.
 
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vangrieg

Power User
don't think it's quite fair to characterize the data as "why so much noise/distortion/artifacts" though, when the Axe-Fx is clearly performing better than the competition.

It’s obviously performing better no matter what that crap is. It’s obviously not useful signal. :)

And I’m not trying to disprove better performance, that would be silly.

I’m simply curious and want to understand the data presented here. :)
 

BillyZeppa

Power User
Considering that the thermal noise limit is not much lower than the III i'd say we are in good shape here.
 
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dsimms

Inspired
this is why people don't play the guitars they have.

frank-zappa-oz.jpg
 

stereotactic

Experienced
I suspect that one of the reasons my high gain amps in the 2XL + sound so great and clear is at least partially because of the nearly nonexistent noise floor. Even through my Mesa 2/90 power amps. It's very impressive. That kind of realism I don't need, I don't miss all the hiss and radio frequencies one bit...
 

stereotactic

Experienced
Are you sure it’s your amp picking up RF interference, not the guitar? Because, you know, guitars can make all kinds of funny noises into an Axe just as well.

Certainly hasn't happened since I got an Axe!

My formula was low output pickups with lots of amp gain, which then begat lots of hiss and radio frequencies, though they were less evident than the hiss resulting from lots of high gain. Methinks low output pickups in front of a high gain amp give max dynamics and general fidelity, inspite of the high noise floor
 

Clockwork Creep

Power User
I hardly understand this stuff.
So, aliasing, is like, harmonics that affects the intended signal and makes it less clear and realistic?...
Did I get it right?

As said, using two amp blocks affects aliasing in the Axe 2, and aliasing is the reason why Axe 3 only allows two amp blocks. How much worse is it? Is this difference really noticable? Graphs? :)
So far, I haven't really heard a difference between using two amp blocks and one... But I wasn't really listening closely so far.
 

stereotactic

Experienced
The amount of mechanical devices
Are you sure it’s your amp picking up RF interference, not the guitar? Because, you know, guitars can make all kinds of funny noises into an Axe just as well.

Not to muck up the thread, but I heard radio traffic regularly even when my guitar volume was turned all the way down. I live in New York City, there's more radio traffic from car service radios etc than other places...
 

Rex

Legend!
I hardly understand this stuff.
So, aliasing, is like, harmonics that affects the intended signal and makes it less clear and realistic?...
Did I get it right?
Aliasing is the creation of signals at new frequencies that didn’t exist in the original signal. The new frequency becomes an alias of the original frequency. Aliasing is caused when a signal is sampled at a rate that is too low, and/or the low-pass filtering that's applied to the original signal (anti-aliasing filter) isn’t optimally designed or implemented.

Sampling is necessary to get an audio signal into the digital form that the Axe-Fx uses to work its magic.

When aliasing occurs at high signal levels, it sounds like weird, inharmonic garbage. At low signal levels, it’s perceived as reduced clarity. At inaudible signal levels, it’s...well...inaudible.
 
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