Here's an objective reason why the Axe Fx is better than the Helix and other modelers/profiler:
That noise might not tell you anything by itself, but it represents one of the aspects that make FAS modeling so great: unpredictability.
I obtained this track by recording a little sample with a patch in which I had 2
identical amp blocks hard panned, then inverted the phase on one channel and summed them to mono.
If you do the same with the Helix (I did) you'll get just silence and a bit of floor noise.
This means that amp models in the Axe FX add some "randomness" to the tone, every note you play sounds slightly different than the previous ones and this is what happens in a real tube amps too.
If you want to understand why that happens read what Cliff said in
this old interview:
"Nowadays, when most people do modeling, they use what are called wave shapers, which is basically just a nonlinearity in math. So they’ll say you can either use polynomials or piecewise polynomials. I believe a lot of the earlier company that begins with an L used a thing called a piecewise polynomial, which basically says if your input signal is over a certain value, then this is your function. If it’s between this value and another value it’s this function, and you splice all those polynomials together.
There are other approaches where you just use a polynomial or trigonometric functions and things like that. The problem with all those approaches is they are static – they’re a static transfer function. So whenever the input is here you know the output is… I mean, you can plot it on a piece of paper. You always know. Real tubes, on the other hand, have memory. They don’t have memory themselves, but they have memory due to their parasitic capacitance. Due to the actual terminal impedances, most designers will put a cathode cap on there, and a lot of times there will be a capacitor on the plate as well and possibly on the grid.
So those capacitors remember the charge that was on them, because charge can’t bleed off instantaneously. Or at least it can’t without burning up the traces on the board. So G2 Modeling is actually like a wave shaper, but it has memory, and so the transfer function changes over time based on the memory of the function. And it’s also based on the feedback and the frequency and everything else, so just like a real tube that transfers function changes with amplitude and time.
That, however, is a very CPU intensive process. It requires a lot of steps to simulate that. Simulating just one triode is almost as much horsepower as the entire modeling in the old Axe-Fx. When you start stringing together three or four triodes the algorithm is much more CPU intensive. You couldn’t run that on an Ultra and have any horsepower left for anything else, maybe just a basic delay and a reverb and something. Customers wouldn’t be very happy if they had an inventory of fifty effects and they could only use an amp, a cab, and one effect at a time. So the only way around that for the Axe-Fx II, given that we’re kind of at a plateau in DSP processing speeds right now, is to put two of them in there. One of them is dedicated to just the amp modeling and the other one does all the other stuff."
