Thinking of swapping my FM3 for an HX Stomp

@jzucker, It will be a day or so before I start the new thread. I have a few distractions, right now. But, I wanted to stay in touch. The patch just gives a rough sense of the differences available. It is best to dial it in for your own taste.

I am guessing the slap will come from the presence control. The NFB Frequency will affect the way the presence control reacts. Try turning that up. And then see if that makes the presence do what you want. I will go into more detail later.
 
@jzucker, It will be a day or so before I start the new thread. I have a few distractions, right now. But, I wanted to stay in touch. The patch just gives a rough sense of the differences available. It is best to dial it in for your own taste.

I am guessing the slap will come from the presence control. The NFB Frequency will affect the way the presence control reacts. Try turning that up. And then see if that makes the presence do what you want. I will go into more detail later.
Thanks, I feel like I should pay you some type of fee. Maybe we can discuss offline...
 
Thanks, I feel like I should pay you some type of fee. Maybe we can discuss offline...

@jzucker, that is very kind -- but, completely unnecessary. I truly enjoy the elements of sound. And, I have been having a great time learning how to shape sound with the fractal modeling system. I think the ability to modify a high-quality, guitar amp sound on such a deep level, this easily, is extraordinary. Also, I am still learning. I am still constantly correcting myself. I have a lot of respect for the people here who have been working on a professional level with FAS equipment for years. I am not close to anything like that -- maybe after a few more years.

I think one possibility of customizing a bass amp to behave more like a SS bass amp is tone matching. This is only available to AxeFXIII owners. But, if an amp behaves dynamically like a SS amp. The characteristics of a particular SS bass amp could be tone matched and used in conjunction with the customized Jazz 120. Unfortunately, that does not help FM3 and FM9 owners. So, we will see how close we can get.
 
Seems to me that anybody who wants a to emulate a pure solid state amp in the Axe-Fx could do that by simply not using the Amp block. The perfect solid state amp is 100% transparent after all, so... just don't put the Amp block on the grid and you've got 100% transparency. Done.

Aside from that, you can apply whatever effects you want to the grid, like Compressors and stack whatever blend of GEQ, PEQ, and/or Filter blocks you need to get your desired EQ curve, and maybe throw in a Cab IR or two if you want to go for a mic'd cab sound, and there you go, you've got your own ideal, personally tailored "solid state" amp.

If you want distortion, there are almost 60 emulated distortion and overdrive pedals and almost 300 emulated amps to choose from that all allow you to disable the tube power section and use any given amp model's preamp section only, for what would effectively be an emulation of a "solid state" power section.

I guess, considering that, I'm a bit confused about how there aren't "enough" solid state amps in the Axe.
 
Seems to me that anybody who wants a to emulate a pure solid state amp in the Axe-Fx could do that by simply not using the Amp block. The perfect solid state amp is 100% transparent after all, so... just don't put the Amp block on the grid and you've got 100% transparency. Done.

Aside from that, you can apply whatever effects you want to the grid, like Compressors and stack whatever blend of GEQ, PEQ, and/or Filter blocks you need to get your desired EQ curve, and maybe throw in a Cab IR or two if you want to go for a mic'd cab sound, and there you go, you've got your own ideal, personally tailored "solid state" amp.

If you want distortion, there are almost 60 emulated distortion and overdrive pedals and almost 300 emulated amps to choose from that all allow you to disable the tube power section and use any given amp model's preamp section only, for what would effectively be an emulation of a "solid state" power section.

I guess, considering that, I'm a bit confused about how there aren't "enough" solid state amps in the Axe.

I understand your logic. But, solid state bass amps are not actually accurate amps. They have their own non-linearities -- similar to tubes but without the hard clipping. They are just more subtle. And, bass players will have preferences for one SS bass amp over others. Some SS bass amps are great. Some produce overtones that are widely loved. Others are forgotten. Going straight into the board with a few effects is completely valid. But, it does not have the same characteristics as a SS bass amp. Hence, a number of Amp-in-a-Box pedals appear on the market. Jazz guitarists like clean, warm, non-distorted solid-state tones, too. But, many still prefer an amp over going straight to the board. The old Polytone amps had a sound that was widely loved among Jazz guys. It was clean but not clinical -- and not easily copied. The Jazz 120 has a lot of those Jazz tones already. But it is a tube amp for a guitar. So it is looser -- because that is a common part of a guitar's tone.

Some guitarists are happy with just pedals and no amp -- some aren't.
Some bass players are happy with just pedals and no amp -- some aren't.

To some people, guitar amps all sound the same -- just distortion.
To some people, bass amps all sound the same -- just clean.
To some people, tubes all sound the same.
To some people, home audio systems all sound the same.
In general, things that are not in our field of interest will lack a lot of definition and discreet identity.

A solid state bass or Jazz music amplifier is not the same as a PA or HiFi. And, absolute transparency is not the goal of a music amplifier which is designed to be used as a tone-producing instrument.

There is definitely much less distortion in Jazz and Bass amps. And, the non-linearities are much smoother and more subtle. But, that does not make the sound in anyway less complex.

However, I do think the subtlety, of the differences between various SS bass and jazz amp models, would make tone matching quite successful. If, there was one donor SS-style amp model to use with the tone match.

Getting a tube amp to match the strengths of a SS amp is not easy -- and it is expensive. But, those are material limits that don't exist in the modeling universe. It may be quite possible to get SS performance out of a tube amp model, while keeping a measure of tube harmonic warmth and non-linearity. Certainly, not the harmonic roundness of tone/timbre that most guitarists would want -- and definitely not the distortion that guitarists like. But possibly, the kind of harmonic roundness that a Jazz bassist might want. And, maybe it won't work out. But, it will be interesting and educational to try.
 
Getting a tube amp to match the strengths of a SS amp is not easy -- and it is expensive. But, those are material limits that don't exist in the modeling universe. It may be quite possible to get SS performance out of a tube amp model, while keeping a measure of tube harmonic warmth and non-linearity. Certainly, not the harmonic roundness of tone/timbre that most guitarists would want -- and definitely not the distortion that guitarists like. But possibly, the kind of harmonic roundness that a Jazz bassist might want. And, maybe it won't work out. But, it will be interesting and educational to try.
Thank you so much for this formulation. It precisely describes my feelings about bass amps. I hope that many users will read this. At the end it is a very good argument to introduce a variety of bass amp in the FAS world. So not every user has to go through this process of tweaking. Different bass amps sound different!
 
I understand your logic. But, solid state bass amps are not actually accurate amps. They have their own non-linearities -- similar to tubes but without the hard clipping. They are just more subtle. And, bass players will have preferences for one SS bass amp over others. Some SS bass amps are great. Some produce overtones that are widely loved. Others are forgotten. Going straight into the board with a few effects is completely valid. But, it does not have the same characteristics as a SS bass amp. Hence, a number of Amp-in-a-Box pedals appear on the market. Jazz guitarists like clean, warm, non-distorted solid-state tones, too. But, many still prefer an amp over going straight to the board. The old Polytone amps had a sound that was widely loved among Jazz guys. It was clean but not clinical -- and not easily copied. The Jazz 120 has a lot of those Jazz tones already. But it is a tube amp for a guitar. So it is looser -- because that is a common part of a guitar's tone.

Some guitarists are happy with just pedals and no amp -- some aren't.
Some bass players are happy with just pedals and no amp -- some aren't.

To some people, guitar amps all sound the same -- just distortion.
To some people, bass amps all sound the same -- just clean.
To some people, tubes all sound the same.
To some people, home audio systems all sound the same.
In general, things that are not in our field of interest will lack a lot of definition and discreet identity.

A solid state bass or Jazz music amplifier is not the same as a PA or HiFi. And, absolute transparency is not the goal of a music amplifier which is designed to be used as a tone-producing instrument.

There is definitely much less distortion in Jazz and Bass amps. And, the non-linearities are much smoother and more subtle. But, that does not make the sound in anyway less complex.

However, I do think the subtlety, of the differences between various SS bass and jazz amp models, would make tone matching quite successful. If, there was one donor SS-style amp model to use with the tone match.

Getting a tube amp to match the strengths of a SS amp is not easy -- and it is expensive. But, those are material limits that don't exist in the modeling universe. It may be quite possible to get SS performance out of a tube amp model, while keeping a measure of tube harmonic warmth and non-linearity. Certainly, not the harmonic roundness of tone/timbre that most guitarists would want -- and definitely not the distortion that guitarists like. But possibly, the kind of harmonic roundness that a Jazz bassist might want. And, maybe it won't work out. But, it will be interesting and educational to try.

SS amps clip MUCH harder than tube amps.

A JC120 is a SS amp.
 
"
Ellen

Ellen

3 hours ago
Have you used a Fractal FM3 or FM9???



Highlighted reply
Janek Gwizdala

Janek Gwizdala
57 minutes ago
I haven't




Ellen

Ellen

1 second ago
@Janek Gwizdala Ok there is a discussion about you on the forum currently people were wondering, since its basically the high end professional version of the HX Stomp."


Heyyyyy Looks like your buddy hasnt used it!

Furthermore I see he thinks Mason Margella (SP?) (A known pariah in the industry) is a fine gentleman.
https://www.thegearpage.net/board/i...-re-new-statements-from-mason-vertex.2194661/

So, YMMV.

If Janek ever tries a Fractal product, GOODBYE to his pedalboard. ;)
 
Seems to me that anybody who wants a to emulate a pure solid state amp in the Axe-Fx could do that by simply not using the Amp block. The perfect solid state amp is 100% transparent after all, so... just don't put the Amp block on the grid and you've got 100% transparency. Done.
No, that's not true. Anyone who plays through an aguilar or markbass knows the amp and the preamp and their own color to the sound. No amp is 100% transparent. Not done...

I guess, considering that, I'm a bit confused about how there aren't "enough" solid state amps in the Axe.

I guess I'm confused why you can't get all your sounds out of a single tube amp because after all, a tube is a tube, right? ;)
 
No, that's not true. Anyone who plays through an aguilar or markbass knows the amp and the preamp and their own color to the sound. No amp is 100% transparent. Not done...



I guess I'm confused why you can't get all your sounds out of a single tube amp because after all, a tube is a tube, right? ;)

I know this probably isn't a popular opinion, but in the Fractal world you can make many of the amp models sound very, very similar with all the deep parameters. While the JC pre gain voicing isn't going to match ALL solid state amps, simply swapping the tone stack for one of the bass options without question gets you a SS bass amp without having to do anything to all the "tube" based parameters (honestly many have no meaning on a solid state amp and should probably be disabled and/or hidden) and something very different sounding than a JC120 ...
 
@FractalAudio, thank you for commenting.

A JC120 is a SS amp.

For this, I have no excuse. I saw the dropdown menus for the tube choices. I saw the Tube Hardness parameter react to different tube choices. And, I believed that I must have been mistaken to think the Jazz 120 was was solid-state. I should have at least pulled up a schematic to check before jumping to that conclusion.

I see now that the amp model is pretty unresponsive to changes in Tube Type and Tube Hardness. I suppose this is because the tube models are not in use. Again, I can't be sure of that. But, that would be a reasonable guess.

I have no problem with being called out for my errors.
That can only educate me and save time.
I only wish it would happen sooner, more often, and in more detail.

SS amps clip MUCH harder than tube amps.

I do understand that SS devices clip harder than tubes. However, I don't hear any hard SS clipping in the better SS Bass amps -- certainly not in most Jazz Bass sounds. My understanding is that SS Bass amps are designed with more than enough headroom and massive PSU's in an effort to specifically avoid hard clipping. And yet, SS Bass amps do produce overtones. Not in the same amount as tube amps -- but still enough to be noticed. My understanding is that overtones are created by various nonlinearities in a circuit, not just tubes and SS devices.

To me, with nothing else to compare it to, these other collective non-linearities sound like clean tube harmonics that stay clean.

But, isn't that the purpose of MIMIC and Tone Matching? To capture small discrepancies in frequency, non-linearity and dynamics? Discrepancies that are particular to an amp -- and even required to make that amp model sound realistic?

All I am saying, is that while the "discrepancies" between SS Bass amps are not big, they are still noticeable enough to be required for a realistic amp modeling experience.

And, that possibly, the differences between many of these SS Bass amps are small enough that just one SS bass amp model "blank" could support numerous Tone Match files from a wide variety of SS Bass amps?

Cliff, I have no doubt that you have chosen your company's development priorities very carefully. And, that you have serious personal money in play as a result. I have no interest in manipulating your corporate priorities.

All I want to do is to attempt to methodically tweak the Jazz 120 guitar amp model into a usable SS Bass amp model for Jazz, Fusion, Funk, etc. And then -- if I can arrive at a useful SS bass amp model -- I would like to see if a SS Bass amp Tone Match would produce results that would satisfy a player who specifically prefers a particular SS bass amp.

Perhaps, I will fail, or just get it wrong. But, then again, maybe I will get a few decent results, get a few things right, and learn something.

I am extremely aware that I am a self-taught amp-hacker and not a trained engineer.
That means, I need and appreciate as much help and information as I can get.
Unlike modifying an analog amp, I can't get my questions answered by using LTSpice.

I do some reading in the Fractal Wiki everyday.
But, I still miss some things and misunderstand others.
I very much appreciate useful honest corrections. They save me time.


On a personal note, I have to say, being told that SS devices clip much harder than Tubes did sting a little.
That is kind of square one in the realm of amp hack-dom.
And, it hurt that you would think I might be that ignorant.
Or, that I might think that SS clipping was an important part of the sound in a SS bass amp.
Really, even the idea that the only non-linearities that ever matter are tube clipping or SS device clipping
is a little off-putting. The last time I believed that was in the 1970's.

However, I do understand why, I might appear to be that dull.
Believing that the Jazz 120 was modeled with tubes simply because the UI showed a reaction to Tube choices was stupid on my part.
Jumping to that conclusion without at least checking a schematic first was stupid.
And then, developing a paragraph of hypotheticals based on a guessed conclusion was pretty much the stupid-trifecta.

So, I do understand why you would think that I might not know that SS-devices clip harder than Tubes.
Or that, I might believe that SS clipping was a factor in a SS Jazz bass amp's sound.

My early bias against tube modeling was not because I thought that tube circuits were too complicated to be modeled in realtime.
It was because I thought that all the other non-linearities in these old-tech circuits would be too complicated to be modeled in realtime.

Not just the variations in values of RC circuits in crucial positions. But also the materials and impurities that were used to make the dielectrics and the resistors.These differences are small as individual cases. Noticeable, at best, by a quick A/B comparison -- when you know exactly what you are trying to hear. But, as a collection of effects, they do become noticeable. Even a fairly naive listener can often notice the collective difference -- even if, they can't usefully describe the sum result as anything other than "mojo."

It appears to me, that you also recognized this and solved for it with your MIMIC technology -- as a summary effect.
And, that you acknowledged that it was an important difference.
And, that it had a significant effect, on the realism of the model.

Comparing a collective sum of small overtones to the subtle effect of the overtones produced by a clean tube may not be an accurate simile. But, that was the best I could do to provide a description of these other collective overtones.

Anyway, please feel free to mercilessly correct me. I am too old to get my feelings hurt much anymore. And, I have no interest in simple being "right." I get plenty of things wrong. I just want to learn as much as I can, as quickly as I can, while I still can.
 
I know this probably isn't a popular opinion, but in the Fractal world you can make many of the amp models sound very, very similar with all the deep parameters. While the JC pre gain voicing isn't going to match ALL solid state amps, simply swapping the tone stack for one of the bass options without question gets you a SS bass amp without having to do anything to all the "tube" based parameters (honestly many have no meaning on a solid state amp and should probably be disabled and/or hidden) and something very different sounding than a JC120 ...

Changing the tone control on a guitar amp to a bass tone control is a good option.
However, when switching out the default Tonestack for another, "the Tonestack Frequency will not necessarily be correct anymore."

https://wiki.fractalaudio.com/wiki/...ock#TONESTACK_TYPE_.2B_FREQUENCY_.2B_LOCATION

Also, the Jazz 120 is a guitar amp -- not a bass amp.

And, there are other important differences between a guitar amp and a bass amp besides just the tone circuit. A bass amp will have a tighter power supply and greater headroom to handle bass signals more cleanly. Some people will still like the more distorted sound of a looser guitar-style power supply. But, others might not.

PSU

In any case, the power supply can be modified to have more headroom, and to be tighter, with better transient response. One way, is to raise the amp voltage by raising the "Supply Voltage" from 100% up to 150%. This will raise the headroom. And, if raising the voltage in the model behaves the same way as raising the voltage in an analog amp, it will also increase the slew rate and the transient response. Another option, is to lower the Screen Resonant Frequency which, in my current understanding, is similar to increasing the amount of filtering, or filter caps, in the PSU. "Sag" can be reduced to 0. "Preamp Sag" can be turned OFF. Or, "Voltage Type" can be switched from AC to DC which will also eliminate any PSU sag. These are all ways to make the bass guitar sound punchier and tighter -- regardless of whether tubes are used or not. A looser or tighter PSU is a personal choice. Royal Blood might want a looser PSU and a more distorted bass note. A Jazz bassist might want a tighter PSU and a less distorted bass note.


SPEAKER Compliance, Compression, etc

A guitarist will generally prefer a more expressive, compressed, looser, and more broken-in speaker.
A bassist will generally prefer a tighter, less distorted, more accurate, more responsive speaker.

tighter (higher) Speaker Compliance
less (lower) Speaker Compression
quicker(lower) Speaker Time Compliance
tighter (lower) Cab Resonance

SPEAKER COMPLIANCE CURVE

While solid-state "Speaker Compliance Curves" are flatter than they are for tube amps -- they are still not completely flat.
A bassist, who prefers SS bass amps, might prefer a "Speaker Compliance Curve" with the resonant peaks dropped as much as halfway down.
Once again, this is another way in which the bass distortion is decreased.

PRESENCE DEPTH

Just like the Tonestack, Presence and Depth should be optimised for the lower bass range and the individual bass player's style


These are several things that should be changed in the Amp block
to transform a guitar amp into a bass amp
-- regardless of whether the amp is tube or solid state.
 
Changing the tone control on a guitar amp to a bass tone control is a good option.
However, when switching out the default Tonestack for another, "the Tonestack Frequency will not necessarily be correct anymore."

https://wiki.fractalaudio.com/wiki/...ock#TONESTACK_TYPE_.2B_FREQUENCY_.2B_LOCATION

Also, the Jazz 120 is a guitar amp -- not a bass amp.

And, there are other important differences between a guitar amp and a bass amp besides just the tone circuit. A bass amp will have a tighter power supply and greater headroom to handle bass signals more cleanly. Some people will still like the more distorted sound of a looser guitar-style power supply. But, others might not.

PSU

In any case, the power supply can be modified to have more headroom, and to be tighter, with better transient response. One way, is to raise the amp voltage by raising the "Supply Voltage" from 100% up to 150%. This will raise the headroom. And, if raising the voltage in the model behaves the same way as raising the voltage in an analog amp, it will also increase the slew rate and the transient response. Another option, is to lower the Screen Resonant Frequency which, in my current understanding, is similar to increasing the amount of filtering, or filter caps, in the PSU. "Sag" can be reduced to 0. "Preamp Sag" can be turned OFF. Or, "Voltage Type" can be switched from AC to DC which will also eliminate any PSU sag. These are all ways to make the bass guitar sound punchier and tighter -- regardless of whether tubes are used or not. A looser or tighter PSU is a personal choice. Royal Blood might want a looser PSU and a more distorted bass note. A Jazz bassist might want a tighter PSU and a less distorted bass note.


SPEAKER Compliance, Compression, etc

A guitarist will generally prefer a more expressive, compressed, looser, and more broken-in speaker.
A bassist will generally prefer a tighter, less distorted, more accurate, more responsive speaker.

tighter (higher) Speaker Compliance
less (lower) Speaker Compression
quicker(lower) Speaker Time Compliance
tighter (lower) Cab Resonance

SPEAKER COMPLIANCE CURVE

While solid-state "Speaker Compliance Curves" are flatter than they are for tube amps -- they are still not completely flat.
A bassist, who prefers SS bass amps, might prefer a "Speaker Compliance Curve" with the resonant peaks dropped as much as halfway down.
Once again, this is another way in which the bass distortion is decreased.

PRESENCE DEPTH

Just like the Tonestack, Presence and Depth should be optimised for the lower bass range and the individual bass player's style


These are several things that should be changed in the Amp block
to transform a guitar amp into a bass amp
-- regardless of whether the amp is tube or solid state.
I think you are going way too deep into trying to shoehorn one amp model into another. While I am firmly in the school that you don't need every amp model known to man modeled in the Fractal because many of them can be achieved with some slight advanced tweaks, I think this is too much effort as we are not talking about simply turning an existing model of a Marshall into another Marshall variant by tweaking a few options. I get that most of what you are doing is more academic interest here but maybe your approach is the wrong end of the pool.

Let's not forget that old bass amps were basically guitar amps with minimal modifications. Plenty of people love e.g a Marshall Super Bass as a guitar amp because it's basically a slightly darker sounding Superlead. Put a guitar amp into bass speakers and it will work as a bass amp, just not have a huge ton of clean headroom or the tightest bass ever. Not exactly concerns in the virtual realm where actual amplification for volume is a separate concern so you don't have to drive the amp to distortion for volume reasons.

I think it would be easier to try to shape a direct signal to sound like a typical modern solid-state bass amp. Running a guitar amp model as a "preamp" by disabling poweramp modeling might also yield workable results. Tube preamp followed by a parametric EQ would be probably closer to building a custom bass amp.

Fractal is limited in the bass model options at the time of writing so just compromise and use what is there and try to shape that to your liking because ultimately it doesn't matter if there is an actual model of a GK800 or whatever, all that matters is that you like the tone/feel coming out of the system and said tone works for your needs. Or like OP you can just buy another device that does the thing you want as a preset sound.
 
@Iaxu, you may be be right. There is definitely some windmill-tilting in my DNA.

But, I still believe it would be nice to have a SS bass amp model with a working Presence and Depth control.

Perhaps there are some preamps with something like that? Are you aware of any?

And, now that I know there are no tube amp parameters to be concerned with, the number of essential amp parameters has become much more focused.

Also, the Speaker page offers a number of useful tone-shaping parameters that are lost when only using a preamp.

Most importantly, there is still the outlying possibility that with a complete SS bass amp model, a Tone Match could be successfully used.

I would very much appreciate your thoughts, here. You have been involved with the Fractal universe much longer than I have.

Have Bass amp tone matches been successfully used? I suppose now that I have the question I should search it our myself.
But, thank you, Iaxu, your thoughts are very much appreciated.

I agree that the old bass amps were basically guitar amps with minimal modifications. But, the modern bass amp scene is nothing like that anymore. I would like to see those modern bass amps imported as Tone Matches -- if possible. At this point, I am in full speculation mode again. I only have an FM3 and know nothing about the possibilities or limitations of Tone Matching, apart from what I have read. I does seem to me that because the differences in sound are more subtle for SS bass amps than guitar amps, there may be some possibilities for getting the sound of a modern Bass amp model without have to have the amp modeled exactly.
 
I agree that the old bass amps were basically guitar amps with minimal modifications. But, the modern bass amp scene is nothing like that anymore. I would like to see those modern bass amps imported as Tone Matches -- if possible. At this point, I am in full speculation mode again. I only have an FM3 and know nothing about the possibilities or limitations of Tone Matching, apart from what I have read. I does seem to me that because the differences in sound are more subtle for SS bass amps than guitar amps, there may be some possibilities for getting the sound of a modern Bass amp model without have to have the amp modeled exactly.
Modern bass amps focus on a high output clean Class D poweramp. As an example, the Darkglass Microtubes 900 seems to be largely a Darkglass preamp paired with an ICEPower poweramp module. For reference, so do the Fender Tonemaster guitar amps or the Seymour Duncan Powerstage poweramps. Obviously different models of the thing but the point applies, these same poweramp modules are used by a lot of bass amps. How the signal is shaped going into it is what makes one sound better than another and a lot of bass amps go for that "tube goodness and overdrive from a real tube preamp" thing even today.

That's why I gave the idea that maybe a tweaked guitar preamp model into a parametric EQ (simply because that's what many bass amps have) or even more EQ blocks would work as the sound shaping tools.

You will find older SS bass amp models that do have more of a character of their own and maybe Tone Match would do for those.
 
I think turning the Jazz 120 into a bass amp through tweaking the advanced parameters is a noble effort, but not knowing which advanced parameters actually do anything, or if they do something exactly what, complicates it greatly. I think you’d need to start with a base line of what actually does what to avoid wasting hours tweaking controls that do nothing or not what you expected.

-Aaron
 
Changing the tone control on a guitar amp to a bass tone control is a good option.
However, when switching out the default Tonestack for another, "the Tonestack Frequency will not necessarily be correct anymore."

https://wiki.fractalaudio.com/wiki/...ock#TONESTACK_TYPE_.2B_FREQUENCY_.2B_LOCATION

Also, the Jazz 120 is a guitar amp -- not a bass amp.

And, there are other important differences between a guitar amp and a bass amp besides just the tone circuit. A bass amp will have a tighter power supply and greater headroom to handle bass signals more cleanly. Some people will still like the more distorted sound of a looser guitar-style power supply. But, others might not.

PSU

In any case, the power supply can be modified to have more headroom, and to be tighter, with better transient response. One way, is to raise the amp voltage by raising the "Supply Voltage" from 100% up to 150%. This will raise the headroom. And, if raising the voltage in the model behaves the same way as raising the voltage in an analog amp, it will also increase the slew rate and the transient response. Another option, is to lower the Screen Resonant Frequency which, in my current understanding, is similar to increasing the amount of filtering, or filter caps, in the PSU. "Sag" can be reduced to 0. "Preamp Sag" can be turned OFF. Or, "Voltage Type" can be switched from AC to DC which will also eliminate any PSU sag. These are all ways to make the bass guitar sound punchier and tighter -- regardless of whether tubes are used or not. A looser or tighter PSU is a personal choice. Royal Blood might want a looser PSU and a more distorted bass note. A Jazz bassist might want a tighter PSU and a less distorted bass note.


SPEAKER Compliance, Compression, etc

A guitarist will generally prefer a more expressive, compressed, looser, and more broken-in speaker.
A bassist will generally prefer a tighter, less distorted, more accurate, more responsive speaker.

tighter (higher) Speaker Compliance
less (lower) Speaker Compression
quicker(lower) Speaker Time Compliance
tighter (lower) Cab Resonance

SPEAKER COMPLIANCE CURVE

While solid-state "Speaker Compliance Curves" are flatter than they are for tube amps -- they are still not completely flat.
A bassist, who prefers SS bass amps, might prefer a "Speaker Compliance Curve" with the resonant peaks dropped as much as halfway down.
Once again, this is another way in which the bass distortion is decreased.

PRESENCE DEPTH

Just like the Tonestack, Presence and Depth should be optimised for the lower bass range and the individual bass player's style


These are several things that should be changed in the Amp block
to transform a guitar amp into a bass amp
-- regardless of whether the amp is tube or solid state.

Few things...

The JC120 while a guitar amp was designed to be loud and clean with a lot of headroom. I owned and gigged one for the better part of a decade, and it was clean up to gigging volume in a 4 piece without needing to be miced up for smaller clubs. It had an additional distortion circuit (which sounded horrible), but I never used it (and doubt many do).

The PSU shouldn't mean too much in this case as we are in the virtual realm where we can dial in a clean Princeton to be the same volume as a 100 watt plexi. And again...we are speaking about a solid state amp, but I yield to your knowledge here.

Presence and depth...doubtful as my guess is these are tied into the tube power amp modeling which shouldn't have any effect here on a solid state amp, but who knows.

Regarding speaker parameters...sure mess with things, but really simply changing the tone stack to a bass option makes a very, very audible and immediate difference to me making the JC120 sound like a bass amp without much fuss.
 
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