Axe-Fx Firmware Version 21.00 Release Candidate 2 (Beta 8)

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York Audio said:
That makes perfect sense. Thanks for clarifying. I like Electro-Harmonix power tubes for non-Mesa amps (Mesa brand for Mesa amps), and your amp is probably biased a bit hotter than mine... add tube age and usage differences to the equation and you've got the recipe for a big can of worms. I'm gonna mess with the bias a bit and see what happens. I think I remember you saying something about the 5150 factory bias being really cold. Do you have a ballpark idea where to set bias to get it close to factory specs?
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Since Mesa does not manufacture tubes and selects tubes from different world tube manufacturers, they can vary in brand and country. This can alo attribute to final depth and tone. We have 3 triple recs, in our arsenal, with Mesa tubes. They all sound different. But cranked, they sound awesome.
 
York Audio said:
I fully agree with you and understand that potentiometers can vary pretty significantly from amp to amp, and cumulative differences using multiple potentiometers can make a really big difference in the end. I know a few amps have needed little things tweaked here and there in the firmware and just wanted to offer an A/B you mentioned to see if anything was "amiss" that would support what that user was experiencing.

Here's a new comparison. Knobs around noon and subtly tweaked for a good match. With Depth at zero, they're remarkably similar. Even my frequency analyzer showed both the real amp and model with nearly identical frequency peaks! Then I set the Depth at 10 on the amp and model which is where our two units seem to vary the most (not necessarily bad, just different). The third section has the model's Depth frequency lowered from 180Hz to 140Hz. My amp still outputs more low end energy, but sonically it sounds more similar in the low-mids and cleans up that area a bit. Maybe our amps have something different happening in the Depth portion of the circuit that's causing the change? I don't know, but hopefully this helps the other user (sorry for forgetting your handle) to get things in a good spot while also confirming the accuracy in the "knobs at noon" scenario you mentioned.




I couldn't agree with you more. If you've heard the recent amp/model comparisons I did with the SLO and Mark IV, they're very similar, and I mention that the subtle differences are akin to trying to match two physical heads that will also have little differences by nature. I matched those by ear and turned knobs accordingly and was blown away by how close they are. In this instance, a user noted that the 5150 sounded more mid-forward than the real amp, so Cliff asked for an A/B. I set the controls identically in case it brought out something he would hear that might explain the mid-forward claims, and finished by happily saying that I would make adjustments if needed. We've seen "fixed wrong X value in Y amp" pretty regularly in firmware release notes over the years that get amps and models even closer... I just wanted to offer help in case that was the situation here.

I've got a bunch of amps that I compare to the Fractal all the time, and confidently tell people that it easily has the most accurate modeling of any product on the market. Any contributions I make are always well-intended and solely meant to either show accuracy between amp and model, or to help address something that might, but not always, need correcting. Even if the model doesn't change, I'm still gonna play the crap out of it. :)
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Thank you for these comparisons and explaining in such good detail. I have been tweaking the freq or the depth knob to a lower frequency to get the same effect you are talking about. It's a nice confirmation on my end to know I was hearing things correctly. What do you use for a freq analyzer? Pro Q3?
 
FractalAudio said:
Depth is dependent upon the speaker load. If your load doesn't match the internal speaker impedance curve exactly the response will be different.

When I'm testing amps I have a special speaker impedance curve I use that is derived from the particular LB-2 that I use. The curve included in the firmware is a typical LB-2 response. Due to component tolerances the resonant frequency and magnitude can vary as much as 20%.

Furthermore with the depth all the way up it is easy to start overdriving the power amp in the bass range. Again, due to pot tolerances the amp may be overdriving more or less than the model for a given MV setting.

I make mistakes. I'm only human. I'm also transparent about when I do. I don't have to divulge this in the release notes. Every amp was tested for 21.00 and I re-tested the 5150 the other day and it matches our reference amp.
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I can't say enough good things about fractal. This post right here shows the dedication of Cliff and his team. Lil ol me asks him to check an amp and he does and lets us know. Then one of the best IR makers in the business chimes in and we get to see their conversation and learn from both of them. FAS and the members on the forum are great. Thank you @York Audio and FAS
 
Tommy Tempest said:
Since Mesa does not manufacture tubes and selects tubes from different world tube manufacturers, they can vary in brand and country. This can alo attribute to final depth and tone. We have 3 triple recs, in our arsenal, with Mesa tubes. They all sound different. But cranked, they sound awesome.
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You’re totally right. The tubes Mesa selects based on their specs tend to sound better in my amps than when I use other brands that are probably slightly outside of Mesa’s preferred tolerances. I’ve spent an absurd amount of time tube rolling my amps and it’s normally the difference between good and great. It’s never bad… just that one tends to feel like a better fit than another.

jwa174900 said:
Thank you for these comparisons and explaining in such good detail. I have been tweaking the freq or the depth knob to a lower frequency to get the same effect you are talking about. It's a nice confirmation on my end to know I was hearing things correctly. What do you use for a freq analyzer? Pro Q3?
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I like Pro Q3. It gives you instant results and you can get really nerdy with the tone match if you want.
 
Before I purchased my AxeFX3 I was dumb and not a very good guitar player. Now I feel like I have a university degree in amp design, electronics, physics, etc. Today, I am still dumb and I'm still not that great at playing guitar but at least I have a head full of fractal and fractalyte knowledge to draw from when the need arises.
 
York Audio said:
You’re totally right. The tubes Mesa selects based on their specs tend to sound better in my amps than when I use other brands that are probably slightly outside of Mesa’s preferred tolerances. I’ve spent an absurd amount of time tube rolling my amps and it’s normally the difference between good and great. It’s never bad… just that one tends to feel like a better fit than another.


I like Pro Q3. It gives you instant results and you can get really nerdy with the tone match if you want.
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"I’ve spent an absurd amount of time tube rolling my amps"


I think we all did back in the day :)
 
normanaj said:
Before I purchased my AxeFX3 I was dumb and not a very good guitar player. Now I feel like I have a university degree in amp design, electronics, physics, etc. Today, I am still dumb and I'm still not that great at playing guitar but at least I have a head full of fractal and fractalyte knowledge to draw from when the need arises.
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+1
 
Since we're talking about impact of different tubes on the tone - is there any way to simulate the effect of pulling 2 tubes on a 100W amp? Supply sag?
 
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