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Legacy Amp models consider revisiting? Full honest request and opinion

SoZo

New Member
Full honest opinion.
Pros:
I own a III (and LOTS of amps) if you know who I am.
I use the III for live ... I really like lots about it !!!
I think the audio quality throughout the unit is impeccable digital quality.
I have VERY accurate monitoring and studio live rooms and have done and still do TONS of amplifier development vintage and current.
Some of the amp models are very unique and go beyond what a tube amp can propose to do.

Request:
I notice a similar characteristic throughout lots of the legacy modeling (mid heavy and big miss on the bottom end {either way too much and loose or totally lacking}. Any thoughts about revisiting say the legacy amp modeling 5150 etc.... which honestly has barely changed from the II models.

Thanks !
John
 
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IronSean

Experienced
This mirrors some of what I've heard in for example this video:


The Axe FX track sounds very good, but the open low string notes are very thin in a way in a way the real amp and some other modellers are not. The muted notes still sound full though, but just something seems off about the open notes, specifically at 9:32.

Edit: though I do wonder if the input eq defaulting to a low cut could be the cause, and just was not adjusted for that video.
 

SoZo

New Member
IronSean

Does sound good agree...! Truthfully, NOT identical but very good in this example for sure !

Maybe my issue is the knobs do not react nearly the same... perfect example in this video screen shots when he switches between the sources. My go to on this amp is as in the vid. Bass Treble 1 oclock mid 11 oclock, the III mid is past 2 0Oclock and presence and depth totally different. This makes for hours of tweaking and maybe and some of my difficulty...
Still all good thanks for the help!
 
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SoZo

New Member
One last observation.... Maybe I was WRONG on other modelers come closer.... On that video ALL of the modelers are CRANKED in the mids to come close to the amp with the mids scooped... Maybe its just a modeler thing ?

Thanks ! Good honest discussion... just trying to get the most out of it !

 
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IronSean

Experienced
Some other details are that amp pot tolerances can vary wildly, and those pot tolerances can mean a real amp can be 20-40% off from ideal in the worst cases: https://wiki.fractalaudio.com/wiki/index.php?title=Amp_block#Controls:_authentic_or_idealized

Another detail is that I think Presence and maybe depth uses a different taper in the Axe FX for a more linear behaviour. ie, on some amps you wouldn't hear anything until the presence was at 3/4, but on the axe the effects appear much earlier for finer control.
 

SoZo

New Member
Some other details are that amp pot tolerances can vary wildly, and those pot tolerances can mean a real amp can be 20-40% off from ideal in the worst cases: https://wiki.fractalaudio.com/wiki/index.php?title=Amp_block#Controls:_authentic_or_idealized

Another detail is that I think Presence and maybe depth uses a different taper in the Axe FX for a more linear behaviour. ie, on some amps you wouldn't hear anything until the presence was at 3/4, but on the axe the effects appear much earlier for finer control.

Yup thx I intimately understand this ... but 20-40 is not correct more like 10-20 max
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
Yup thx I intimately understand this ... but 20-40 is not correct more like 10-20 max
I routinely see more than 20%. Full-scale resistance is often off by up to 20%. Mid-scale resistance is then off by another 10-20%. For example a 1M linear pot might be 800K and then off another 40K at mid-scale for a total error of 28%.
 

SoZo

New Member
Again love the unit just constructive comment ...
Everyone Be safe !

John
 
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SoZo

New Member
I routinely see more than 20%. Full-scale resistance is often off by up to 20%. Mid-scale resistance is then off by another 10-20%. For example a 1M linear pot might be 800K and then off another 40K at mid-scale for a total error of 28%.
Yea thats a lot.... I have seen 20 lots but not 40 either !

John
 

jlynnb1

Axe-Master
are any of these videos using identical cabs?

I also know some of these cough Kemper cough cough do some stuff under the hood that pure representation doesn't do.
 

SoZo

New Member
are any of these videos using identical cabs?

I also know some of these cough Kemper cough cough do some stuff under the hood that pure representation doesn't do.

Not sure they could as the IR would be platform dependent so probably not empirical data ... !!!!!
I get much closer then most of these examples !!! I find its just some tweaking on the bottom. I 100% rely on dynamic depth to imitate what a tube amp does because a tube power section works on current draw and demand not voltage like Solid State.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
Not sure they could as the IR would be platform dependent so probably not empirical data ... !!!!!
I get much closer then most of these examples !!! I find its just some tweaking on the bottom. I 100% rely on dynamic depth to imitate what a tube amp does because a tube power section works on current draw and demand not voltage like Solid State.
Depending upon the amp the low frequency response can be highly dependent upon the load. So selecting the right Speaker Impedance Curve becomes important.

Dynamic Depth is a non-physical tweak. It uses what I call "Inverse Homomorphic Processing". Anything other than zero is deviating from authentic. It's not wrong to use it but it will be less accurate.

The power amp modeling IS current modeling. Power tubes are essentially current sources (with some finite resistance in parallel). Dynamic Depth has nothing to do with this.

The other big thing is Master Volume. As you raise the MV the power tubes will saturate on the lows and highs first which causes the tone to have more midrange and vice-versa.

Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control.

Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion.

The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."
 
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