Pre-amp vs power amp distortion in AxeFxII

[nikki-k]

I am also going to have to disagree with some of the blanket statements being made... my reasons why also add to my reasons why I want tube type selection added (among other things ).

Blanket statements about preamp vs power as far as tonality is concerned are without foundation IMO. Yes, what Cliff stated, in general, holds. However, preamp=fizz and power=good OD does not, IMO. In some cases, yes.. very much so. "Can," not (an implied or stated) "Does." With preamp circuits that utilize multiple tubes for gain, tone can be affected greatly by tube choice. Throw a 5751 in there, followed by an old Mullard, Brimar, etc perhaps, versus loading them up with some EHX or lower quality tubes. I can think of many situations where the preamp stage will not need be fizzy when pushed; but, yes.. push several stages of gain, it is can end up fizzy. Many of us are not pushing those extra stages for gain beyond gain, and for us, it is not fizzy. Want fizz in the power section? Look no further than the switch in the.. wait for it.. Power section of the Axe-Fx II that Cliff has stated will remove fizz (Grid Modeling). I understand where the blanket statement can originate, though I do not agree with the conclusion.

As for tube swapping...
For every example of tube type changes that may not sound too pleasant (for some, even many), I can provide an example that does work, if not for that amp, for another. Heck.. want a list? Though not modeled, and arguably it was constructed for it, my Legacy sounds great.. albeit different.. with the stock EL34s, or 6L6s. But, what it was not designed for was using a quad with a pair of each. I love this combination! Want another, more appropriate one? How about a JCM900, with stock 5881s (6L6s)? C'mon, Plexi lineage... a JCM800 descendent that does not have EL34s??? How about throwing some KT77s in it? It was not designed for use with EL34s, but can anyone honestly say it would sound bad with them (arguments regarding the overall tonal appreciation of the 900 series aside!)?

And now, WHY this provides for the Axe-Fx II to become the most glorious of all modifiable amps ever... Because when you stick some EL84s into an EL34 based amp, you do not need to alter the entire power section to accomodate, and run the risk of frying anything. Why would anyone want to do such a thing? For the same reason we do not have a single amplifier model; for the same reason us tinkerers pick up that soldering iron for the first time, followed by a (de)soldering bulb: because creating something new does not always succeed, but when it does!!! Turn the Axe-Fx II into a Heathkit-like playground, and I would likely end up more of a hermit than Scholz.

Because with the Axe-Fx II.. opened up a bit more.. it is no longer attempting to climb Everest, it is giving birth to landscapes no one has seen, and traversing them transcends (simple) climbing.

 

[Tone Control]

Nikki, I agree entirely, I've changed all sorts of valves to tweak an amp to suit me, usually using 5751s, 12ay7 or 12au7 valves where a 12ax7 was fitted as stock

My thought was - I can live with fixed tubes per amp model while the extra modelling detail evolves around phase inverters, etc, but eventually, I would like to see valves being modelled too.
This may of course be overtaken by Cliff finding amp models that sounds better than our favourite real amps, it must be possible

 

[viabcroce]

Agreed. The Mesa/Boogie sims are a good example of that.
They get their trademark sound out of the preamp while too much master volume makes them sound washed out, undefined and/or flubby.

Mhhh... maybe Smilzo was talking about real amps? Not sure about this.
Another thought: if the real M/B power section works differently from the models you're referring to, wouldn't it mean that the modeling can still be improved? In my Lonestar Special rising the MV gives some beautiful sounds, and there're are very few valve amps I'm aware of that don't sound better when you turn MV wheel up

 

[jon]

Pleeeeee cliff, lemme swap dem t00bs!!

Nikki said it best - and that's why I like the axe - it gives me the option to do things that I would not be able to do with a real amp. Some people want it to exactly replicate a real amp which it pretty much does already, but I don't care to copy an amp - I want to make my own (virtually) I want to put el84s I those Marshalls and kt88s in them fenders - I want to experiment! The axe is the only device that allows that kind of unrivaled experimentation.

While I appreciate all the time spent trying to match 'exactly' some of those tube amps, there are some people like me who just like the sound of the axe - it has it's own great sound, and I don't care if it matches the amps exactly or not. It's just as awesome, and even better IMHO. Virtual tube swap may detract FAS from getting those '120% more realer-er' sounds, but it's one of the most requested features, and will satisfy those who want to 'create' and not only 'copy'.

 

[nikki-k]

Nikki, I agree entirely, I've changed all sorts of valves to tweak an amp to suit me, usually using 5751s, 12ay7 or 12au7 valves where a 12ax7 was fitted as stock

My thought was - I can live with fixed tubes per amp model while the extra modelling detail evolves around phase inverters, etc, but eventually, I would like to see valves being modelled too.
This may of course be overtaken by Cliff finding amp models that sounds better than our favourite real amps, it must be possible

I "like'd" your post because I love when opinions are expressed with qualifiers .
For me, tube choice(s) can have such a major effect on tone. Going from my mixed quad (EL34 + 6L6) with my Legacy to a strict quad of 6L6 or EL34 is quite noticeable to me, even at lower volumes. I would truly love to be able to double-blind this, both for feel and tone. Heck- I would love to find out if I am actually hearing and feeling what I hear and feel with preamp tubes as well. The only reason I lean toward it being "real" (for me) rather than (simple) psychological voodoo is that I have left an amp untouched for months before, returned to it, and been able to name what tubes I think are in there pretty accurately. I am actually okay with Triode Hardness to "soften" the preamp tubes.. or is it tube? Yet more questions...

Power Tube swapping is a major curiosity for me; is Cliff *coding* various tube types in? Is it being done in some other manner? Questions.. so many questions...

 

[jon]

I know he mentioned that the new amps in the II were all done in a modular fashion, and that various tubes we're all tested and modeled in detail when they were doing gen 1, so I would guess that in the II, it would be possible. He also mentioned that he was looking at a way of the user being able to change/swap parts of the code (behind the scenes of course) with the turn of a button. I suspect this would be for tube swap, but that is 100% speculation on my part.

I would also guess that it would not be possible in the gen 1 units as these were not 'modular'

 

[Sebastian]

Mhhh... maybe Smilzo was talking about real amps? Not sure about this.
Another thought: if the real M/B power section works differently from the models you're referring to, wouldn't it mean that the modeling can still be improved? In my Lonestar Special rising the MV gives some beautiful sounds, and there're are very few valve amps I'm aware of that don't sound better when you turn MV wheel up

Yes, I think he was talking about real amps, but many of the Axe-Fx sims behave like their physical counterparts, from what I can tell. Of course, that's no "100 % sure" opinion,
because I don't know all sims well, let alone know the "originals" well enough.
BTW, I wasn't talking about ALL M/B sims in the Axe, moreso I had the usa lead 1 (= Mk IV lead) and the Recto Orange in mind. And my experience with those sims is congruent with everything I heard or read from guitarists, who either owned those M/B amps or the amps plus the Axe-Fx and told about their a/b comparison.
From what I know, the Lonestar is mostly a Fender copy design, so no wonder it sounds good when turned up

This thread just shows once again - there are hardly any fixed rules, because too much variables are involved. There can be a few hints for starting points, but beyond that, the Axe is just another amp (or multiple) and everyone has to find their way. That's also a reason why there can't be "universal" good sounding bare amp+cab presets that people are asking for all the time. People's taste and ears aside, everyone plays different and guitars sound different. The more those differences are apparent (which indicates the Axe's quality, opposed to other and earlier gen. modelers), the less are chances that a given patch sounds good with many guitars and their players.

 

[Rex]

I have no idea of the extent to which power tubes are modeled in the Axe-Fx; I do not know if there is a distinction between EL34, 6L6, KT88, etc being made, or anything *deeper*.

If your ears can't tell, it doesn't matter.

 

[Smilzo]

Mhhh... maybe Smilzo was talking about real amps?
In my Lonestar Special rising the MV gives some beautiful sounds

Both real and Axefx.
Lonestar is Fender design.

A fender champ is SE power tube class A poweramp: it should sound good when crancked, but it will fart!
A preamp is a multi-gain staging eq network. It's not the tube themselves that put out some ugly distortion... guitar amp builders tame down unpleasant low, mid and high frequency in and between the stage, to achieve musical tone. When too much low or high freq reach the power tubes, the result is the same: harsh clipping, nasty farting, confused tone.
It is more difficult to reach high level of distortion in poweramp (not the case with axefx), because of ears bleeding level, but the result will be unmusical as preamp section.

 

[jon]

+1 for the tubes themselves putting out nasty distortion - VERY unpleasant!! an amp actually CUTS out a lot of the unpleasant stuff that would be there if it were just tubes. The cab trims off the rest. If you don't have experience with a real tube amp, you can just bypass the cab block - or crank up the drive with just a tube-pre - YUCK!!

 

[viabcroce]

I wasn't talking about ALL M/B sims in the Axe, moreso I had the usa lead 1 (= Mk IV lead) and the Recto Orange in mind. And my experience with those sims is congruent with everything I heard or read from guitarists, who either owned those M/B amps or the amps plus the Axe-Fx and told about their a/b comparison.
From what I know, the Lonestar is mostly a Fender copy design, so no wonder it sounds good when turned up

LOL for the LSS XD

Thanks Sebastian, now it's clear to me.

 

[nikki-k]

I have no idea of the extent to which power tubes are modeled in the Axe-Fx; I do not know if there is a distinction between EL34, 6L6, KT88, etc being made, or anything *deeper*.

If your ears can't tell, it doesn't matter.

Quoting me without the context of the original post denies the reason that it actually does matter, and has absolutely nothing to do with "ears."

The statement, as part of my original post, was referring to our- those of us not privy to Cliff's coding- inability to know if the Power Tubes (and preamp tubes, for that matter) are being modeled discretely, generally, etc. This has nothing to do with (critical) listening; there is nothing shy of Cliff answering that will provide this answer. Anything else is purely speculative. Cliff's comments have alluded to each discrete component being modeled, and that he then "assembles them (on a virtual breadboard, if you like) into a virtual amp, inputting component values as per schematics, listening, etc." From this, one could infer he is thus utilizing a modeled EL34, 6L6, etc, as per each amp's original release type. Even if one were to assume this much and be correct, it does not provide a full picture, still. EL34? EL34BSTR? EL34L, for instance? Only the tube model and make the amp shipped with? Became a time-honored choice? Generic model, ignoring variants? Is it a single pentode and single triode type, with values being utilized to attain a "very similar flavor" for EL34 vs 6L6, etc?

Some may never hear the differences between, for instance, an EL34L and an EL34BSTR. Some may *compensate* with a simple tonestack tweak, pedal tweak, bias tweak, etc. For some, purely psychological. And some know the differences all too well. Some will feel it. Regardless, the curiosity exists. Design decision philosophies are something perhaps few of us even desire; but for some of us, that stuff is gold.

 

[shotgunn]

Mmmmm... Power tube swapping...


I'm a high gain djent djent meedley meedely meedely type player...

Sent from my iPod.

 

[Tone Control]

Quoting me without the context of the original post denies the reason that it actually does matter, and has absolutely nothing to do with "ears."

The statement, as part of my original post, was referring to our- those of us not privy to Cliff's coding- inability to know if the Power Tubes (and preamp tubes, for that matter) are being modeled discretely, generally, etc. This has nothing to do with (critical) listening; there is nothing shy of Cliff answering that will provide this answer. Anything else is purely speculative. Cliff's comments have alluded to each discrete component being modeled, and that he then "assembles them (on a virtual breadboard, if you like) into a virtual amp, inputting component values as per schematics, listening, etc." From this, one could infer he is thus utilizing a modeled EL34, 6L6, etc, as per each amp's original release type. Even if one were to assume this much and be correct, it does not provide a full picture, still. EL34? EL34BSTR? EL34L, for instance? Only the tube model and make the amp shipped with? Became a time-honored choice? Generic model, ignoring variants? Is it a single pentode and single triode type, with values being utilized to attain a "very similar flavor" for EL34 vs 6L6, etc?

Some may never hear the differences between, for instance, an EL34L and an EL34BSTR. Some may *compensate* with a simple tonestack tweak, pedal tweak, bias tweak, etc. For some, purely psychological. And some know the differences all too well. Some will feel it. Regardless, the curiosity exists. Design decision philosophies are something perhaps few of us even desire; but for some of us, that stuff is gold.

Yes - some may never experience the lovely config differences within good gear, and valves in particular, the more of this the mk2 can do - the better, I spent most of my life so far denying that this kind of extra quality existed in musical gear, preferring to believe that expensive kit was "Emperor's new clothes". I recently took an 11 month break from work, and -with some money set aside for the purpose - just went through loads of valve amps - instead of acting as the customer in a shop selling the latest mass-produced profit-making-boxes, I researched the most recommended amps of all time, and searched some of them out, or replicas of rare or old stuff (I had valve amps already, but had acquired too many of them randomly)

My playing and feel improved considerably, even after more than 25 years playing. Going further, I then was able to tweak different valve types to further home in on a combination that best suited my improving style. E.g. the Ceriatone trainwreck Express gets too fizzy for me with stock valves, instead I use an Ecc82 as the PI, what a difference! Now around 9-11 oclock there is a setting where a strat neck pickup sounds amazing then once past 12 oclock, you need the bridge humbucker for that ultra high gain sound
Fender Deluxes are very famous for this type of tweak too. I also changed the preamp valve on the drive channel on a matchless independence - I didn't want high gain, now it works for me -(lovely Class A EL34s with that chime unobtainable with any other valve) so now like a Chieftain on the clean channel, and a bit dirt on the other 2, instead of full on ragged OD. (btw EL84 lovers should try an amp built that way, EL34s don't need to be Marshally, those bigger Class A Matchless amps show EL34s are to EL84s what 6L6s are to 6v6s, the same style, but rounded with more attack and bottom end)

Also the subtle difference between a Kt66 and an EL34 in a JTM45 replica is very noticeable - these things are often perceived more by the player rather than the microphone as far as I can tell

I have recently acquired a Victoria Regal, what a joy to mix valves in that. Obviously, it is always a vintage voicing, but it will take any 1 or 2 of 6k6, 6g6, 6v6, 6l6, el34, kt66, el37, kt88, 6550, & probably something else I forgot. Great fun. I've put 6g6 & 6k6 valves from WW2 in it. It will take several diff rectifiers including solid state ones
Of course, in the end you settle on a favourite for a while, but it's nice to customise the amp the way you would a guitar, and this adds to your voice. We don't all want to sound the same I hope
Changing the tubes in the model would add to this versatility, in a way that is very tangible to the tweakers amongst us, and it is true that swapping valves is a more common experience than reworking circuits, so it does translate better to real world experience than changing the OPT spec, etc.

Anyway, the point is - someone has taken the trouble to use DSPs for something more fun than the work I did with them - a lovely guitar sound-making machine. The complexity of the underlying model is improving constantly (like weather forecast models, etc). the MK2 V4.01 is a work in progress, it looks as if more complexity is coming. By us discussing our most inspiring experiences with valve amps, Cliff will be able to assess which bit of fine detail to add next. Let's keep articulating our feelings about what makes the best guitar playing experience on the physical amps, to help prioritise this

 

[nikki-k]

Ugh, another sidetrack.. briefly..
^^^ @TC (primarily): One of the things I love about have both a Pre- and Post- PIMV (effectively, if one must ) in my Legacy head is the ability to 'tune" the *circuit* with great attention to the PI (valve). For instance, I can stick an old Brimar in there (I have several; ECC83/CV4004 (wish I had some ECC82s); long, short, ribbed, smooth.. lucky to find them.. mmmmMullard ), and depending on how I drive the PI and power tubes, produce a good variance in tone and feel.. and with the Legacy, I can opt for smoother preamp/PI overdrive (while still getting good gain!), and utilize some 6L6s for power, bias to taste, and have sweet chimey clean(ish) to singing overdrive/distortion.

I am still working toward this with the Axe. Granted, I have a far more intimate relationship with my Legacy at this point; but, I can foresee the Axe providing similar (or, likely greater) rewards .

 

[Rex]

Quoting me without the context of the original post denies the reason that it actually does matter,...

Of course you're right. On rereading your post, I see I may have missed your intent. My comment was aimed at the idea that the Axe-FX has captured the principal sonic differences between amplifiers, and that if the tube-type differences weren't captured, then it must be possible to achieve those differences without regard to tube type.

...and has absolutely nothing to do with "ears."

I can't agree with you there. If it weren't for our "ears" (or whatever we choose to call our own internal wetware audio chain), we wouldn't care about the differences.

...there is nothing shy of Cliff answering that will provide this answer. Anything else is purely speculative.

There is room for speculation, too. If there weren't, some of what you and I have posted on the forum should be stricken from the record.

 

[nikki-k]

I can't agree with you there. If it weren't for our "ears" (or whatever we choose to call our own internal wetware audio chain), we wouldn't care about the differences.

Ahhh! But you are citing result, not what provides for it.. which is precisely, and solely (at this point) what I am curious about. As an example: drawing up a schematic and wiring things up are not tasks that are hearing dependent. Subjectively assessing the design? Subsequent refinements? Absolutely!!! Right now, it is questions of design I am curious about. Once (if) those are answered, then the ears come into play

There is room for speculation, too. If there weren't, some of what you and I have posted on the forum should be stricken from the record.

Speculation in this case is fine, but, in the end, moot.. save for bragging rights The answers are objective, and Cliff is in possession of them. I have made a great deal of speculative assumptions based upon (sometimes casual) dialogue, many times sifting through indirect, implicative commenting. While I would love to have answers for a laundry list of questions, there are a few that truly gnaw at my brain; the ones I mentioned in this thread are among them. For those things I dare not become a pest in the asking, speculation is all I (we) have. A great example of speculation gone awry would be the (infamous) Mark IV thread, where Cliff outlined a previously unknown (designed) use for the Input Trim; in this case, for certain amp models, it operates similarly to the initial (and extra) Gain knob. I have made assumptions regarding the Bright Switch + Bright Cap as well (as its operation seems to vary from amp model to amp model), and wonder if I have erred very little, or greatly

But, yes.. speculation is fun

 

[Rex]

As an example: drawing up a schematic and wiring things up are not tasks that are hearing dependent.

Ah, but knowing what to draw—that's an "ear" thing from the get-go. Otherwise, it's just a drafting exercise.

Speculation in this case is fine, but, in the end, moot.. save for bragging rights

I assure you: t'weren't for braggin' rights.



You're right: it's valid to wonder to what extent tubes or any other aspect is modelled. Have at it! I learn from watching you.

That said, I'm hesitant to continue this side-discussion. I've already done my share to clutter the OP's thread. Maybe offline would be better.

But, yes.. speculation is fun

Oh, yes!

 

[Ed DeGenaro]

But the thing is that and I'll use the input trim example....any one should be able of figuring this without Cliff's hand holding.
Personally I couldn't care less whether there will be tube swap page since EVeryTHING is just attack, decay, sustain, release-EQ-and gain properties.

I was the other set of ears when we did the Uni/BiValve when I still "did time at THD"
And the Flexi-50 design was for my needs.
So I like to think I know a thing or two about tube swaps. Plus I've been through more Mullards, etc...than I care to remember.

Back to tubes...for my money the sonic differences with tubes never yielded enough pay out for me. Now feel/attack different story. Detail sonic stuff...different story. But the difference in using an AT vs. an AX is more in the intitail pick attack of the note. Same with bias. But hey if ya'all want tube swaps and Cliff wats to give it to you I'm looking forward to a few threads of pondering what 6L6 to use for THAT Petrucci tone.

 

[billmeedog]

Guthrie's simplistic genius!

That's true of the Axe-Fx AND real amps. Be aware that modern, heavy sounds are mostly preamp distortion though. Guthrie doesn't use a lot of gain. High levels of power amp gain can get flubby real fast.

The real key is to adjust the relative amounts of each. You want to balance preamp and power amp distortion for the best tone. What I do is start with the MV low and turn up the Drive until I get the desired amount of gain and sustain. Then turn up the MV until I get the desired compression. Then fine-tune each.

Cliff,

I agree, relative to most "shredders," Guthrie Govan uses a LOT less gain than his contemporaries. I've seen him three times in the last two years, and two of those three times, I was able to get very close to him (and his stage-rig) while he was playing, and I can tell you a few things for sure about his preferences when playing live:

The first time I got close to him playing, he was using a Cornford Roadhouse, (I believe) and it was loud, NOT very distorted, and very bright (I don't like as much brightness as Guthrie, but he's so damn articulate, it sort of works - LOL!)

The second time I got close to him was just a few months ago (9/29/2011 - at Berklee College of Music in Boston, MA - U.S.A.) He was (and is now) using a Suhr Badger 30, and his sound/tone WAS TO DIE FOR! Amazing! He still dials it in a little brighter than I like it to be, but the Suhr Badger's high end seems smoother and more musical (NOT "ice-pick-ish!") to me, compared to his old Cornford sound (too harsh in the treble for me) if that makes any sense?!?

In every situation I've seen him play live (in-person and in countless videos on YouTube, etc.) he clearly uses less gain than most shredders and then rides his volume-knob incessantly while playing! He does play relatively loud (he sort of needs to get those EL34's singing to get the tone he favors!) He's VERY old-school in his tonal-approach, and that is one reason why he favors single-channel tube amps. He actually gets four (4) levels of gain (realistically due to the inexact nature of riding one's volume-knob, he probably uses infinite numbers of tones!) out of his Suhr guitar-->Boost-pedal-->Suhr Badger 30:

*For the sake of comparison, Steve Vai's rock-rhythm tone has way more gain and compression than Guthrie's highest-gain lead-tone!

1.) Suhr Guitar dimed (blower-switch or volume-knob rolled-up to 10) with Boost pedal--> his highest-gain shred-tone.
2.) Suhr Guitar dimed (blower-switch or volume-knob rolled-up to 10)______________--> his 2nd-highest-gain tone
3.) Suhr Guitar w/volume-knob on about 7____________________________________--> his 2nd-cleanest-gain tone (a la Malcolm Young!)
4.) Suhr Guitar w/volume-knob on about 2____________________________________--> his cleanest tone: funk-rhythm/jazz-comping

*FWIW, Guthrie is so confident and artiuculate, he'll actually shred with his dryest and thinnest tone (like his funk-rhythm/volume-on-"2" sound!) He's ridiculously good!

Bill