What can modeling amps model?

I guess this is a big topic potentially. I'm just trying to understand first, in what ways do amps differ tonally and how much of that does does not ultimately come down to frequency response characteristics that can be adjusted with tone controls or an EQ pedal. Secondly, I'm curious which of these characteristics can modelling amps successfully approximate.

So I think I'm on safe ground by assuming that the frequency characteristics of different amps often ARE differernt and I would think that this COULD, at least in principle, be manipulated with tone controls or EQ pedals/software. That is, maybe amp A is more boomier than amp B but you could increase the bass knob and maybe decrease the treble knob on amp B to bring it into the same frequency realm as Amp A.

Do different cabinet/housing designs (e.g., closed vs open back) affect amps in ways other than simple frequency response. I have seen amps or software that let's you select different cabinets. But the amp itself has a particular housing (e.g., open vs closed back) so how successful can an open backed modelling amp be at replicating the sound of a closed back amp. If the difference is just that one is more bassier than the other, I would think that this could be modelled by adjusting the EQ. But maybe it is more, or other, than that.

Then there is, I would guess, the dynamics of the response of one amp compared to another. That is, as the gain or input to one amp increases, maybe it starts to compress and saturate sooner than another. I have no idea how modelling amps do what they do, but I would think that this is one of the main things that modelling amps try to simulate insofar as all of the modelling amps I've seen have settings for "American" vs "Brit" etc (even if they don't use that term [like ISF on Blackstar amps]) style and I think that's one of the main differences.

Speaker size. Well, if a given modelling amp has a single 8" speaker, I would think it is fundamentally incapable of accurately simulating a Fender Twin Reverb for example with it's 2 12" speakers. Like the saying about not being able to get blood from a turnip. But how much does speaker configuration contribute to the unique (I presume, haven't heard one in person) sound of a Fender Twin? Can a modelling amp, maybe with a smaller speaker, recreate something like this just at a lower volume?

Related to this, I hear people talking (or see them writing) about the unique and powerful sound of a stack, for example- one that "moves a lot of air." Is moving a lot of air something that you only get with big speakers driven by a high watt amp? Does it basically equate to volume? Will a high wattage amp with a big speaker(s) move a lot of air even at a low volume? Or does a big high-wattage amp at low volume sound like a small wattage small speaker amp at a higher volume. Are smaller speakers (like the twin 3" speakers on a Yamaha THR) more limited in volume or in their ability to deliver good bass response or both?

I have heard people talk about amps with a tight, focused bottom end vs others that are more flubby (I think that's the term I heard). What contributes to this? It doesn't sound appealing. Does anyone like a flubby bottom or is that just the mark of a lower quality, prersumably less expensive, speaker?

Sorry to go on. I guess if I were going to distill this down to a couple of key questions, they would be, (A) what are the sonic characteristics of different amps that are reflected in something other than frequency characteristics (i.e., something that can't be compensated for by adjusting tone knobs and EQ settings), and (B) which of these other things are modelling amps able (or not able) to model?

I can't answer a single one of those questions, but you've really put a lot of thought into it. I'm looking forward to being educated by the responses!

Dave...

Modelling amps can model a lot but to me they present a representation. Hands down the amp I use the most is my Rolland Micro Cube. 3 watts of tone from acoustic to something like Judas Priest. And this is important because it's no fun playing Priest with an acoustic tone - at least not to me.

Gear is a lot of fun and I enjoy messing about with mine. If you think you might want to create your own tones, an effects board

may be something to consider. I just spent the last hour playing with mine. And play is the operative word.

I love my modelling amp. But by way of background, I played electric guitar around 40 years ago and had a big Marshall tube amp. I had limited pedals and while I had a great sound I was limited.

I recently started playing again. I just play at home and I went to buy a new electric. The guy convinced me to buy a Line 6 Spider v 30 amp even though I didn't really know what a modelling amp was.

Fast forward 18 months and I can get almost any sound I want out of my amp. I can choose from around 40 different amps, matched with differnet cabs and even mics and a whole bunch of pedals and effects. I have a compressor and a noise gate and I can set them all up in whatever order I want. I can go from clean to surfing with the aliens. Beach Boys to AC DC. Whenever a GT song lesson has a particular set up, I can match the settings and get much the same sound. It matches the amps including the various controls they have.

While it comes with a range of presets, I have set up a lot of my own and learnt so much in the process. Recently, I have been practising seven nation army from Mikes lesson and discovered that I have a whammy pedal and I have been able to set it so that it plays one octave lower to effectively give me a bass. How cool is that.

With my presets I bought a footswitch for about $50 that simply moves you from one preset to another. So I often have different pre sets for differnet parts of the songs and I can move between them using the foot switch.

The amp is USB to my computer and I can set it up on there with a good visual on the screen.

My one proviso is that early on I did not like the sound direct from my amp but it was great through my headphones. I realised it was the speaker. So I bought a small 3 channel mixer and some nice powered monitor speakers and I can play backing tracks from my computer mixed with the line out from my amp and the sound is great.

So I am really using my amp as a multi effects unit. But for a couple of hundred dollars I have access to such a broad range of sounds.

Stephen,

I hear you. I started guitar about 35 years ago, had some equipment (a Carvin electric and I think it was a Peavey tube amp). I don't even remember what happened to that stuff but I think, like a lot of people here, there were a lot of other happening in my life and it just sort of fell by the wayside. It's amazing how the technology has changed since then. I mean, some things remain the same but modeling amps, software emulations (like AmpliTube). So many options now and, as you say, so affordable. Imagine how much it would have cost to have all the options at your fingertips that you now have with your $200 Spider. Anyway, glad you're happy with your setup. I'm really eager to get an amp but am trying to pace myself with the hardware (1 learning module, learn 10 songs, buy a piece of equipment, go to next module, repeat) and it's hard to shop right now anyway with the stores closed, and this is definitely the kind of purchase I'd like to check out in person, if for no other reason that to figure out how much volume/wattage I need, or don't need (I'm pretty much a "bedroom" player in a small house (and due to Corona, my wife is now working from home). I like that a couple of the amps I'm looking at, like the Katana, allow you to switch between different wattages (for the Katana I think it's between 50, 5 and 0.5W).

Dave

I have the Katana 50 MK II and it does allow you to switch from 50W to 25W to 0.5W as you were saying. As I think I said somewhere else, the amp is waaaay better than me. One thing I found out right away is that out of the box I got a lot of annoying buzzing and humming even on clean at low volume. Fortunately you can suppress it using the Boss Tone Studio software so it's pretty easy to solve, but still I was surprised to have to do that.

Originally Posted by: dlwalkeI'm just trying to understand first, in what ways do amps differ tonally and how much of that does does not ultimately come down to frequency response characteristics that can be adjusted with tone controls or an EQ pedal.[/quote]

This is potentially a heavy discussion. There are many resources on the web about this. Here's a decent one that goes into some detail.

https://www.guitarplayer.com/technique/all-about-classic-tube-amp-circuits

In short, the differences between the general categories of guitar amps are due to a few interconnected factors.

1. Pre-amp tubes & how they are used in the circuit.

2. Power tubes & how they are used in the circuit.

3. Type of design (class A, B, AB, etc.)

4. Topology of the circuit design.

And that's even before you get to speakers & enclosures.

So, the answer to your question here is that is a great deal that affects the basic tone beyond the EQ controls that cannot be adjusted to make say a Fender Twin sound just like a Marshall JCM 800.

Also, the term frequency response can refer to the amp signal output or the speakers.

Originally Posted by: dlwalkeSecondly, I'm curious which of these characteristics can modelling amps successfully approximate.[/quote]

Depends on who you ask. :)

In my experience, modeling amps can & do successfully model a wide variety of amps, effects, speakers, microphones & acoustic environments (halls or rooms).

There is a case to be made that "the real thing" sounds different. But quite a few blind tests have been done to demonstrate that modelers are quite good at modeling.

The only difference I've noticed is the playing experience. I can & have dialed my Line 6 POD in to simulate playing through a Boss SD-1 into my cranked Marshall JCM800 half stack. The resultant recorded sounds are virtually indistinguishable from each other.

The thing that is extremely different is the playing experience.

It feels very different to play through the POD than the Marshall. When I say feels, I mean physically, in a tactile way how each system responds to my fingers/hands motions. And of course even if I turn up my PA or studio speakers with the POD blasting, it's not the same physical playing experience as playing in the room through my amp.

Originally Posted by: dlwalkeSo I think I'm on safe ground by assuming that the frequency characteristics of different amps often ARE differernt and I would think that this COULD, at least in principle, be manipulated with tone controls or EQ pedals/software. That is, maybe amp A is more boomier than amp B but you could increase the bass knob and maybe decrease the treble knob on amp B to bring it into the same frequency realm as Amp A.[/quote]

I think you would have a very difficult time doing that. Based on my personal experience I would be tempted to say, no, you can't. But I leave that thought experiment to a more knowledgable electrical engineer. I know a few amp designers. I think I'll ask them when I get a chance.

But more to the point: why? If you want the sound of a Fender Twin, get a Twin. If you want the sound of a Marshall then why would you buy a Twin & then buy boxes & effects in an attempt to make it sound like a Marshall?

Originally Posted by: dlwalkeDo different cabinet/housing designs (e.g., closed vs open back) affect amps in ways other than simple frequency response.[/quote]

Very much so. I'm assuming at this point you mean the freq response of the amp.

Originally Posted by: dlwalkeI have seen amps or software that let's you select different cabinets. But the amp itself has a particular housing (e.g., open vs closed back) so how successful can an open backed modelling amp be at replicating the sound of a closed back amp. If the difference is just that one is more bassier than the other, I would think that this could be modelled by adjusting the EQ. But maybe it is more, or other, than that.[/quote]

Modeling amps are fundamentally about software emulating hardware. So, there might be differences once you get to the hardware stage. But a great deal of modeling units are just software. So, it's kind of apples & oranges to make that comparison.

Consider also that there can be a considerable difference between the sound of any given amp as you hear it standing in the room playing through it & the recorded sound of you playing through the amp. And in some applications all that matters is the end result as a recorded guitar part sounds coming out of a stereo system. Or of a guitar mixed in with the rest of a band all coming through a PA system.

All that will either match or not someone's preconceived experience or expectation of what an amp is "supposed to sound like".

Originally Posted by: dlwalkeThen there is, I would guess, the dynamics of the response of one amp compared to another. That is, as the gain or input to one amp increases, maybe it starts to compress and saturate sooner than another.

You bet! And then you have to factor in the technique, touch & dynamics of the guitar player! It's complicated. :)[br][br]

[quote=dlwalke]I have no idea how modelling amps do what they do

There are many great sources on the web for this topic. Examples:

https://en.wikipedia.org/wiki/Amplifier_modeling

https://www.premierguitar.com/articles/Amp_Modeling_Reality_Check

[quote=dlwalke]Speaker size. Well, if a given modelling amp has a single 8" speaker, I would think it is fundamentally incapable of accurately simulating a Fender Twin Reverb for example with it's 2 12" speakers.

To my knowledge most modelers that have this speaker option are only software.

[quote=dlwalke]Is moving a lot of air something that you only get with big speakers driven by a high watt amp?

Yes. You can plug a modeler into an amp or PA & turn it up. You can use a modeling amp that has enough power to play loudly & get the same result. Either way, moving a lot of air refers to loud volume.

[quote=dlwalke]Will a high wattage amp with a big speaker(s) move a lot of air even at a low volume?

No, low volume equals moving only a little air. :)

[quote=dlwalke]

I have heard people talk about amps with a tight, focused bottom end vs others that are more flubby (I think that's the term I heard). What contributes to this? It doesn't sound appealing. Does anyone like a flubby bottom or is that just the mark of a lower quality, prersumably less expensive, speaker?

Looks like I've got some reading to do tonight! :)