Axe-fx power amp modelling possibly still not up to par?

mortega76 said:
Scott Peterson said:
I do think the power amp modeling is up to par, I think it exceeds 'par'. In clean to lower gain amps - which is an enormous spectrum of amps - the power amp is much more 'in play' than the super hi-gain modern metal brootlz. So a better 'test' of power amp capabilities would those amps that the power amp - and I am referring to Plexi type sounds in particular - are a tremendous component of the end sound.
Thanks for chiming in Scott...
I think you need to pay a lot more attention to Scott's second paragraph. This was my exact reaction on reading your post, too. You say that you think there may be an inadequacy for the power amp modeling because "high gain" stuff is not sounding the way you want live but you do think it is up to par for the clean and mid gain stuff.

Unless you can cite some specific quality or component w.r.t. the power amp modeling that comes into play for high gain, I think you are really barking up the wrong tree to think the root cause of your issue might be some kind of short coming in the power amp modeling. Power amps affect the tone for any rig, sure, but they are nowhere NEAR the make or break component for the overall sound for the high gain stuff that they are for the mid gain and crunch sounds. I would honestly think any amp simulator that is sufficient for mid gain sounds would be more than adequate for metal rather than the other way around (i.e. the requirements for crunch power amp modeling is a super set of the requirements for HG power amp modeling). So, if you think it is sufficient for crunch, you might want to dig in and learn about some of the deep editing parameters since it is probably more than adequate for what you're trying to do (IMHO).

IMHO, as a metal guy, I'd say metal is one of the most forgiving styles out there for power amp variation. In fact I think tube power amps are hardly a requirement for metal at all. Solid state amps can make some amazing tones for this genre.

Don't get me wrong, I don't doubt that you are struggling getting the sounds you want and I don't think anyone is doubting that you're not being open minded in general, but, as Jay has been indicating, it sounds like you may need to dig deeper into the mechanics of the tones you're seeking and get a better grip on the landscape at large before thinking the tool set you have needs to be called out as insufficient.

And as for A/Bing amps, no one is saying you have to do that to get good sounds, in general. They're saying you have to that to MATCH a sound. It's completely immaterial that one unit is digital and one unit is tube/analog. You'd have to A/B if you really wanted to match one tube amp to another or if you wanted to match some patch on your Axe with a real world amp, too. It's a two way street. Matching two things is in essence a comparison process. If you don't want to compare things don't try to match them. :)
 
I think the amp sims are above par (i.e. pretty damn good), but one thing I swear is missing is transformer grind. I've mentioned this before, and being an advanced degreed engineer that builds my own amplifiers and has been fortunate enough to play and own many low gain classic amplifiers, the models don't grind. Don't flame me if you don't know what OT grind is or don't believe it can be heard or happen. It does, I hear it, and its missing.

BK
 
BK-Amps said:
I think the amp sims are above par (i.e. pretty damn good), but one thing I swear is missing is transformer grind. I've mentioned this before, and being an advanced degreed engineer that builds my own amplifiers and has been fortunate enough to play and own many low gain classic amplifiers, the models don't grind. Don't flame me if you don't know what OT grind is or don't believe it can be heard or happen. It does, I hear it, and its missing.

BK
No worries, I don't think anyone is claiming perfection as the current state. ;) Mostly just trying to help the OP identify the real root cause of his specific concern and what can be done to address it with the tools at hand, which still seem way more than adequate to me...

Maybe if someone identifies a genuine modeling shortcoming or enhancement in the general case, Cliff can update the algorithms to include the feature if it's well understood/code-able/etc, though! :cool:

I'm an engineer, too, but I live in the digital world, so most of my amplifier electronics study was in college, so any experienced (i.e. substantial :) ) technical input is always interesting to see since a lot of the deep details are hazy for me.
 
BK-Amps said:
I think the amp sims are above par (i.e. pretty damn good), but one thing I swear is missing is transformer grind. I've mentioned this before, and being an advanced degreed engineer that builds my own amplifiers and has been fortunate enough to play and own many low gain classic amplifiers, the models don't grind. Don't flame me if you don't know what OT grind is or don't believe it can be heard or happen. It does, I hear it, and its missing.

BK

I'd say if it was measurable, Cliff would have put it in there. Prolly 'under the covers' sort of stuff.

But I don't know. And I couldn't tell you what it is if asked!

R
 
If this doesn't do it for you nothing will...

Core_Saturation.gif
 
Just my thought about this interesting topic...
  • To my limited audio memory, modeled amp sound almost identical to real[/*:m:8t18kubb]
  • I could not replicate (Verve monitor) the sound of my Peters, or match my preamp (Masotti X3M), but they aren't modeled (Cliff offers to model them if I supply schems, but I can't)[/*:m:8t18kubb]
  • I could make Axefx emulation sound at least as good as commercial tube amp[/*:m:8t18kubb]
  • I think the amp sim is good enough[/*:m:8t18kubb]
  • I think the preamp could be improved: ie, I remeber Cliff does not add sag to preamp, because he had no evidence of this effect; I remember I measured at least 10 volts drops with a multimeter on a first stage of JTM clone, but I trust more Cliff than one time experiment :lol:. My X3M regulated tube preamp is stiffer than hell, but very 3D, so I don't think this is a problem but an advantage over real preamp [/*:m:8t18kubb]
  • I feel the lack of a hint of "life" compared to my real amp, there are at least some peak I can't replicate with Axefx (too narrow Q, changin frequency... I don't know) [/*:m:8t18kubb]

Conclusions: the Axefx is good enough for RNR. If anyone will point put any real hint, I think Cliff will figure a way to improve that aspect.
 
Ive been saying for a while now that some of the preamp sims need work. Comparing the 3 recto sims (power amp disabled) running into the fx loop return of a dual rectifier or a mesa 2:100 the axefx never had the same richness or depth as the head. Say what you want but if there is a more plain way to measure this single part of the axe then please share it with me so i can try it (i guess i could record the real recto with fx loop out vs the axe-fx preamp sim but listening to preamps recorded dry gives me indigestion and headaches. Remember when running preamp sim only all the advanced power amp parameters cant be used to "fix"'the sound. In fact every time i plug a decent tube preamp into one of my many tube amps the depth, dimension, openness and richness is always there (varying degrees, but always there) With the axefx, not so.... it always sounds "tunnel-ey", for lack of a better word. (yes cab sims are off)

I am thankful for update after update that cliff graciously provides for free but its a shame that for the last couple of revisions it only contained power amp tweaks.... When imho the basics need a checkup (at least the recto preamp sims). I will say that running the mark iv preamp sims into my mark v showed more of the same results but in that case it is less scientific because they are different (yet similar) amps and nailing the mark graphic eq on the axefx isnt the easiest.

Ive broached the subject in a thread once and from memory, cliff replied saying that the preamp sims, where possible, are tested this way (into the real amp's power section) and that they are accurate. If this is true then i must be doing something very wrong or my axe-fx is defective.

Note: When comparing the mic'd sound of amps or listening at recorded tones the gap between the axe-fx and real amps become very small (non existent in some cases).... my findings above pertain to live sounds running into a real guitar cab only.
 
BK-Amps said:
If this doesn't do it for you nothing will...

Core_Saturation.gif
That's not an accurate graph for anything but a single-ended output stage, and there are no SE amps modeled in the Axe-Fx. In a push-pull topology, the quiescent (bias) current in the power tubes flows through two matched but opposing sets of primary windings in the OT, cancelling the DC magnetization of the core that can be a problem in SE designs. The distortions that result from a p-p output stage are due to core hysteresis near the zero-crossing point and to symmetric core saturation (which emphasizes odd harmonics) at high output levels.

The degree to which OT saturation affects sound is highly dependent on the amp model and on how hard you drive it. Whether it has been specifically modeled in the Axe-Fx, I can't say, but I can say that there's nothing missing from the models of the vintage amps I owned and made a living gigging with some 35 years ago.
 
zenaxe said:
mortega76 said:
Scott Peterson said:
I do think the power amp modeling is up to par, I think it exceeds 'par'. In clean to lower gain amps - which is an enormous spectrum of amps - the power amp is much more 'in play' than the super hi-gain modern metal brootlz. So a better 'test' of power amp capabilities would those amps that the power amp - and I am referring to Plexi type sounds in particular - are a tremendous component of the end sound.
Thanks for chiming in Scott...
I think you need to pay a lot more attention to Scott's second paragraph. This was my exact reaction on reading your post, too. You say that you think there may be an inadequacy for the power amp modeling because "high gain" stuff is not sounding the way you want live but you do think it is up to par for the clean and mid gain stuff.

Unless you can cite some specific quality or component w.r.t. the power amp modeling that comes into play for high gain, I think you are really barking up the wrong tree to think the root cause of your issue might be some kind of short coming in the power amp modeling. Power amps affect the tone for any rig, sure, but they are nowhere NEAR the make or break component for the overall sound for the high gain stuff that they are for the mid gain and crunch sounds. I would honestly think any amp simulator that is sufficient for mid gain sounds would be more than adequate for metal rather than the other way around (i.e. the requirements for crunch power amp modeling is a super set of the requirements for HG power amp modeling). So, if you think it is sufficient for crunch, you might want to dig in and learn about some of the deep editing parameters since it is probably more than adequate for what you're trying to do (IMHO).

IMHO, as a metal guy, I'd say metal is one of the most forgiving styles out there for power amp variation. In fact I think tube power amps are hardly a requirement for metal at all. Solid state amps can make some amazing tones for this genre.

Don't get me wrong, I don't doubt that you are struggling getting the sounds you want and I don't think anyone is doubting that you're not being open minded in general, but, as Jay has been indicating, it sounds like you may need to dig deeper into the mechanics of the tones you're seeking and get a better grip on the landscape at large before thinking the tool set you have needs to be called out as insufficient.

And as for A/Bing amps, no one is saying you have to do that to get good sounds, in general. They're saying you have to that to MATCH a sound. It's completely immaterial that one unit is digital and one unit is tube/analog. You'd have to A/B if you really wanted to match one tube amp to another or if you wanted to match some patch on your Axe with a real world amp, too. It's a two way street. Matching two things is in essence a comparison process. If you don't want to compare things don't try to match them. :)
I understand what you are saying about comparing to another amp to mimic the tone as closely as possible... but... None of the other amps needed to be A/B'd to any other amp to have that mid range meat that was missing from several of the amp sims that we tried on the Axe-fx... the only one that had some of that meat was the BRIT800.
 
too_much_power said:
Just a little question, how did you A/B the 5150 and the axefx? Thru the same cab? Two identical cabs next to each other?
In both situations the Axe-fx was A/B'd with Mills Acoustic cabs... the 5150 was A/B'd at an earlier date on a Mills Acoustic cab with K100/V30 in X pattern and the Axe-fx was running into another Mills cab with the exact same setup. These guys don't skimp on getting the good stuff... I'm glad I met them... but I'm sure my wife isn't glad because now I have this burning sensation in my pocketbook!!! It could just be Herpes... I'm not really sure... ;)
 
BK-Amps said:
I think the amp sims are above par (i.e. pretty damn good), but one thing I swear is missing is transformer grind. I've mentioned this before, and being an advanced degreed engineer that builds my own amplifiers and has been fortunate enough to play and own many low gain classic amplifiers, the models don't grind. Don't flame me if you don't know what OT grind is or don't believe it can be heard or happen. It does, I hear it, and its missing.

BK
Thanks a lot for chiming in... we're all in this together to make this thing we call the Axe-fx as best sounding to as many folks as possible... I understand that folks will always disagree with what "great tone" is but at least we can push this beast to evolve for the better.

I'd love to hear some examples of with and without grind...
 
Cron said:
Ive been saying for a while now that some of the preamp sims need work. Comparing the 3 recto sims (power amp disabled) running into the fx loop return of a dual rectifier or a mesa 2:100 the axefx never had the same richness or depth as the head. Say what you want but if there is a more plain way to measure this single part of the axe then please share it with me so i can try it (i guess i could record the real recto with fx loop out vs the axe-fx preamp sim but listening to preamps recorded dry gives me indigestion and headaches. Remember when running preamp sim only all the advanced power amp parameters cant be used to "fix"'the sound. In fact every time i plug a decent tube preamp into one of my many tube amps the depth, dimension, openness and richness is always there (varying degrees, but always there) With the axefx, not so.... it always sounds "tunnel-ey", for lack of a better word. (yes cab sims are off)

I am thankful for update after update that cliff graciously provides for free but its a shame that for the last couple of revisions it only contained power amp tweaks.... When imho the basics need a checkup (at least the recto preamp sims). I will say that running the mark iv preamp sims into my mark v showed more of the same results but in that case it is less scientific because they are different (yet similar) amps and nailing the mark graphic eq on the axefx isnt the easiest.

Ive broached the subject in a thread once and from memory, cliff replied saying that the preamp sims, where possible, are tested this way (into the real amp's power section) and that they are accurate. If this is true then i must be doing something very wrong or my axe-fx is defective.

Note: When comparing the mic'd sound of amps or listening at recorded tones the gap between the axe-fx and real amps become very small (non existent in some cases).... my findings above pertain to live sounds running into a real guitar cab only.
You bring up a great point Cron... I'm assuming it's the power amp modeling... for all I know it's the pre-amp modeling that is the culprit. And yes... this is only an "issue" with live sound via cabs... definitely not with recording direct tones.
 
Jase2677 said:
I ran into an engineer once that explained that an antenna has to be a certain length.
You're leaving out a huge part of what a bona fide engineer would have told you: that "certain length" is relative to the wavelength of the RF carrier.

Well with modern communication via cell phones, they needed smaller and smaller antennas. So, what they did is make a circuit that basically has the same specs as the piece of wire.
Uhh, no. The frequencies are very high and the wavelengths therefore very short. When you have a short wavelength, you can use a short antenna.

I think part of what happens with this is there is undiscovered characteristics to things like the piece of wire that are not quite the same as the actual piece of wire.
That's the argument that is invariably used by folks with no real grounding in a subject. In the case of audio - specifically vacuum tube amplifiers - the reality is that whatever "undiscovered characteristics" there may be, the ones that have already been discovered and documented are the ones that make an audible difference.

Before you start looking for new "undiscovered" phenomena to explain something you don't understand, it only makes sense to learn as much as you can about what is already known. That's enough to keep most of us busy for several lifetimes....
 
mortega76 said:
Sidivan said:
Hold on a second... Mortega, what are you using to drive the 4x12 cabs?
I was originally using a Class H QSC GX5 then I moved to Class AB Peavey PV1500.

Hmm... that should work. The way I'm looking at this is you say it sounds great direct, but loses something when going through your live rig. So, you have think about it as "What's different between these setups". Surely, you're using the power amp sim in both situations, so it's most likely not the sim. If you need to add some wild PEQ settings to go into your live rig, it would tell me the difference is in your cabs. Using the cab sim direct with the same amp settings as NOT using a cab sim and going into a 4x12 is going to yield drastically different results. You may need to setup 2 different versions of your patches. One for live EQ'd for studio and one EQ'd for your 4x12 cabs.
 
Jase2677 said:
So, what you are saying is that nothing I posted has any relevance to anything whatsoever?
If you had to condense my entire post into one sentence, you could certainly do a worse job than that.

I am also having trouble understanding the "folks with no real grounding in a subject."
Apparently so.

It sounds as though a person can eventually study hard enough to understand how to tweak an amp?
Here's what I responded to (which you included verbatim in your indiscriminate quote of my entire post): "I think part of what happens with this is there is undiscovered characteristics to things like the piece of wire that are not quite the same as the actual piece of wire." That is completely unrelated to "how to tweak an amp," and I much prefer that you not attempt to explain how you managed to connect the two.
 
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