How accurate is Fractal's amp modeling?

York Audio said:
All I gotta say is that there's magic in FW15. So far I've been able to match all of my high gain amps, but yesterday I wanted to see how Fractal's AC30 compared to a '94 Korg Era Vox AC30 I recently picked up for a gritty Voxy tone with a tube screamer in front of it. The test was more about determining accuracy rather than dialing in a perfect tone, so I just threw a 57 in front of a cab to see how comparable the amp and the model were.

For anyone questioning the accuracy of Fractal's amp modeling, rest easy... you'll save yourself a lot of time and money. Maybe some of you can hear a difference, but if someone played me either of these clips on their own, I'd have no idea if I was hearing a real amp or a modeler.

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I've played that clip 1/2 a dozen times, and don't hear a meaningful difference. Maybe clip 2 has a little less low mids, and maybe a little less treble extension, but which one is the real amp?? NO IDEA!
FractalAudio said:
The hard part is getting the dynamic frequency response and dynamic gain response accurate. What makes a tube amp "breathe" and sound "organic" is the constantly varying frequency response and transfer function. That is extremely difficult to model accurately. It requires intricate knowledge of exactly how a tube amp works. Even profiling and AI approaches can't do that. All they do is learn a static transfer function. The problem though is that the transfer function is dynamic. The frequency response is constantly changing and the transfer function is continually changing as well. Our algorithms model that stuff. The frequency response and the transfer function are dynamic. The virtual power tubes for the AC30 models even go into Class-B operation if you drive them hard, just like the real amp. No black-box approach can do that.
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^This is amazing!
 
FractalAudio said:
Our Vox models are based on a fairly new AC30HWHD head. The model matches that particular amp very well. Will it match an AC30 from a different era exactly? Probably not.

I don't nitpick minor deviations in frequency response because no two amps the same. People listen to clips and it's always the same types of comments: "Clip A has more lower mids" or "Clip B has less high treble". Yawn.

What I do nitpick are the things that make a model sound and feel like a "real" amp. Anyone can get the static frequency response the same. That's easy. Do an EQ match. That's what everyone else is doing. Take a crude algorithm and do an EQ match to "fix" the inaccuracies. Yawn.

The hard part is getting the dynamic frequency response and dynamic gain response accurate. What makes a tube amp "breathe" and sound "organic" is the constantly varying frequency response and transfer function. That is extremely difficult to model accurately. It requires intricate knowledge of exactly how a tube amp works. Even profiling and AI approaches can't do that. All they do is learn a static transfer function. The problem though is that the transfer function is dynamic. The frequency response is constantly changing and the transfer function is continually changing as well. Our algorithms model that stuff. The frequency response and the transfer function are dynamic. The virtual power tubes for the AC30 models even go into Class-B operation if you drive them hard, just like the real amp. No black-box approach can do that.

Are our algorithms perfect yet? Probably not but in my not-so-humble and biased opinion 15.xx firmware was a significant improvement and has the "mojo" of a real tube amp.
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This is exactly why Fractal is a massive improvement over the many other modelers that I’ve tried. I can finally turn the volume down on the guitar with a model 50 watt plexi and have it to the right thing. I don’t have to tweak all the time to make my FM3 sound passable. . . it sounds great every time.

Which amp is PLEXI 50W HIGH1 based on? I have a late-68 Lead clone that I absolutely love that sounds quite a bit different compared to the model. I’m curious why the difference is so much. Could be that my amp doesn’t match the circuit of the one you modeled.

The good news is that if I tone match the plexi (using logic since I have an FM3) and bake the results into the speaker IR the amp and FM3 sound pretty darn similar.
 
Jack Napalm said:
I think we are at the point that the question needs to be turned around. It's not how accurate the AxeFX is? It's can a tube amp sound as good as the AxeFX? You have considerable more control in the AxeFX to make it sounds any way you want. You don't with a tube amp.
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I bet there is a corksniffer out there saying "I felt a great disturbance in the force". You might be marked as a heretic.

That stuff still takes time. I think given enough time, people will get over the need for actual tube amps
 
such minor minor differences in that clip. incredible. I've played real Vox's next to each other that sounded far more different.
 
I've done this exercise myself numerous times.

I recently tried to mimic the sound of my Randall Brahma module on the Fractal. I decided to use the Smallbox model since I figured they were close. I dialed them up and could here a minimal difference but could not identify which was which. Changing the preamp tube type in the Fractal made it even closer. "I think there may be a difference? I'm not sure now..." kind of close. Well within the margin of turning a knob just a hair.

I had a Kemper at the same time and it absolutely was not closer, even after repeated refining. On top of that, the tradeoff was the experience of an amp head behind glass and you can only change what you put in front of it or behind it.
 
I cancelled my Quad Cortex preorder today. I was interested in the capture functionality but I just can't believe that the results will be better and I know I prefer the Fractal way of routing so much to other things. I was going to try the QC and return it and decided "why go through this again and again? The dude has it nailed."
 
Chris Hurley said:
I cancelled my Quad Cortex preorder today. I was interested in the capture functionality but I just can't believe that the results will be better and I know I prefer the Fractal way of routing so much to other things. I was going to try the QC and return it and decided "why go through this again and again? The dude has it nailed."
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Now you can order a FM3 + FC6 with the same money. Or only a FM3 and save some cash.

Edit: I guess you already have a Fractal product. 🤦🏽‍♂️
 
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Mark-B said:
Not being an overly technical player these days, still, thought I would pick-up a Satriani song the other day. There I was - messing around trying to find an amp for that. ..??? ...What does Satch play!?? ...looked it up! ..a JVM.. As luck would have it, the AXEIII comes loaded with those! ..Sounded good to me right off the bat. Feedback, Harmonics, all there.

I ain't no Satch', but that amp sounds like him. ..and that's as technical as I want to get with the whole "modelling" ..situation.
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Did you look at the JS410’s in the amp selection? those are actually based off Satrianis amps.
 
York Audio said:
I used a Matrix GT1000FX for that clip. The AC30 went through the Fractal LB-2 and into my Axe-Fx III so both amp and model had the same impedance curve (LB-2) and amplification source. The Matrix sent that signal to a Matchless 2x12 with a 57 on it.
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not to hijack but I think having used your ir’s you have a great ear, have you ever compared your matrix with a powerstage 700?
 
kmachman said:
Did you look at the JS410’s in the amp selection? those are actually based off Satrianis amps.
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Thanks! ..I’ll have to take a look at those. I stuck a tube screamer in front of the JVM Red, wound that out little, went a tiny-bit bright on the TS tone, set all the amp’s EQ at 4, master at 10, a tiny-bit of tweaking here and there and I was able to nail that tubular, harmonic, Satriani tone really quickly.

I really don’t like to spend huge amounts of time sifting through the all the options trying to find a tone, so my faith was somewhat restored in the Google for spitting out that info on Satch’s setup with the minimum amount of fuss! :0)

..Realy kinda cool that we can do that. Research what amps an artist uses, pull them up, and find That sound really quickly. Biggest compliment we can pay this box and those who made it I suppose. Without getting too technical, it just does the job really-well, all-round. Creates sounds as it should.

Anyway, ..Thanks again for the info, Take Care, Have a Great New Year! :0)
 
Hear no difference. Fractal ROCKS!!! In stead of worrying about the minutiae, grab your guitar and play.

You could have posted two clips (same recording) of only the real amp and some people would analyze the difference in the tones.
 
Mark-B said:
Thanks! ..I’ll have to take a look at those. I stuck a tube screamer in front of the JVM Red, wound that out little, went a tiny-bit bright on the TS tone, set all the amp’s EQ at 4, master at 10, a tiny-bit of tweaking here and there and I was able to nail that tubular, harmonic, Satriani tone really quickly.
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What cabs did you use with that rig?
 
I think A is the real amp based on the top end info alone. Extremely close considering the amp is the same exact one modeled.
 
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