Some differences between real JP2C and AxeFx models?

Harrassment said:
I also have an actual JP2C and can get it to match my mic'd cabinet close enough to not worry about it and it is infinitely easier to play around with different cabinets or mics (that I don't own) than with actual hardware. Being able to save settings for different guitars also reminds me how much I have gotten used to the benefits of the Fractal rather than having to remember or continually tweak pot positions. First rule is to print this and post in on the wall for a reminder of what not to do...
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Haha! That is the best, and most fitting, pic!!!

Trust your ear-eyes, people!!!! :)
 
Snouttrout said:
To address some of the responses...I am listening through real cabinets, so the differences of sound are coming from real rectifier cabinets. IRs are not the issue. It's hard to explain, but the difference does not appear to be just due to EQ. There is a punchiness that's missing from the AxeFx--at least with my current settings--even a lower volumes. I have adjusted the speaker impendence settings to match those of my cab, and I even tried to estimate the resonant frequency with the method described on the wiki page.

I'll keep working on it. I think I might just accept that I'm going to get two different sounds. I still prefer the sound of the real amp, but I wish I could get the AxeFx to sound more like it when playing through my real cabinets.

Perhaps, what I'm hearing live wouldn't be captured well through a microphone. Maybe I'll try that next.
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My experience is that "punchiness" most often comes from the power amp section. Not
sure a Matrix is going to give you the same ooooomph and push that the JP2C power
amp section is delivering.
 
Have you tried the different brands of 6l6’s and 12ax7’s that are available In the AxeFX?

For me, the brand of a tube makes a huge difference in the tone — in both a real amp and in the model. There are definitely differences in headroom, smoothness, hardness and clarity.

Power Tube Bias and Tube Hardness further define and refine the tube‘s tone In the AxeFX.

And this:

Reducing the percentage of PI Bias Excursion (Phase Inverter Bias Excursion) will increase the clean headroom and punchiness in the Power Amp. It will also make the amp feel less forgiving — and slightly stiffer.

I would also check Speaker Compression. If it is already at zero, it is already as tight as it can get. If not, try bringing it down.
 
The Power Tube Bias on a Mesa Boogie is not adjustable. Because of that, Mesa Boogie uses a colder bias to avoid overheating power tubes. Every set of new tubes, even tubes of the same brand and model will have a different bias point. Mesa Boogie roughly categorizes their tubes by the bias voltage they require. But, there will still be a difference in how hot or cold the power tube is running. And there is still a difference in sound between different sets of matched tubes. The difference in sound you described could easily be caused by a difference in bias point that would still be completely within the tolerance of safe operating levels.

From FractalAudio:
https://forum.fractalaudio.com/threads/understanding-power-tube-bias.79049/

"Some amps are intentionally biased cold to generate crossover distortion. Small amounts add an aggressive distortion. Some amps (i.e. Boogies) are intentionally biased cold to avoid having to set the bias and thereby reducing maintenance and warranty costs.

Negative feedback around the power amp (Damping) further linearizes the power amp. So the transfer functions depicted are only accurate when Damping is zero.

In conclusion, Power Tube Bias is a powerful parameter that can allow you to fine-tune the power amp distortion characteristics to your particular style"


What I love about Fractal Audio amp models are the many subtle ways that the sound can be shaped and molded -- with ease. If you have a good ear for these differences in sound -- which it clearly sounds like you do -- understanding and adjusting the amp parameters in detail becomes a source of great satisfaction.

Your description sounds like the AxeFX model has a colder Power Tube Bias than your physical JP2C -- It is worth it to increase the Power Tube Bias a little and listen for the difference.
 
@Postretro, you might be on to something. I do remember that that I plugged into the fx loop return of the real JP2C amp (after disabling the power amp modeling in the AxeFx). This DID SOUND extremely good. However, since the power amp section is modeled in the AxeFX, I didn't think that would be the major difference. I will check again and see. I will also look at the tube bias. Thank you.
Postretro said:
The Power Tube Bias on a Mesa Boogie is not adjustable. Because of that, Mesa Boogie uses a colder bias to avoid overheating power tubes. Every set of new tubes, even tubes of the same brand and model will have a different bias point. Mesa Boogie roughly categorizes their tubes by the bias voltage they require. But, there will still be a difference in how hot or cold the power tube is running. And there is still a difference in sound between different sets of matched tubes. The difference in sound you described could easily be caused by a difference in bias point that would still be completely within the tolerance of safe operating levels.

From FractalAudio:
https://forum.fractalaudio.com/threads/understanding-power-tube-bias.79049/

"Some amps are intentionally biased cold to generate crossover distortion. Small amounts add an aggressive distortion. Some amps (i.e. Boogies) are intentionally biased cold to avoid having to set the bias and thereby reducing maintenance and warranty costs.

Negative feedback around the power amp (Damping) further linearizes the power amp. So the transfer functions depicted are only accurate when Damping is zero.

In conclusion, Power Tube Bias is a powerful parameter that can allow you to fine-tune the power amp distortion characteristics to your particular style"


What I love about Fractal Audio amp models are the many subtle ways that the sound can be shaped and molded -- with ease. If you have a good ear for these differences in sound -- which it clearly sounds like you do -- understanding and adjusting the amp parameters in detail becomes a source of great satisfaction.

Your description sounds like the AxeFX model has a colder Power Tube Bias than your physical JP2C -- It is worth it to increase the Power Tube Bias a little and listen for the difference.
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la noise said:
My experience is that "punchiness" most often comes from the power amp section. Not
sure a Matrix is going to give you the same ooooomph and push that the JP2C power
amp section is delivering.
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But the AxeFx models the power amp section as well, so I would expect to get the same punch from the Matrix GT1000Fx. But maybe the power amp section is difficult to replicate??
 
Postretro said:
Have you tried the different brands of 6l6’s and 12ax7’s that are available In the AxeFX?

For me, the brand of a tube makes a huge difference in the tone — in both a real amp and in the model. There are definitely differences in headroom, smoothness, hardness and clarity.

Power Tube Bias and Tube Hardness further define and refine the tube‘s tone In the AxeFX.

And this:

Reducing the percentage of PI Bias Excursion (Phase Inverter Bias Excursion) will increase the clean headroom and punchiness in the Power Amp. It will also make the amp feel less forgiving — and slightly stiffer.

I would also check Speaker Compression. If it is already at zero, it is already as tight as it can get. If not, try bringing it down.
Click to expand...
Do you still need to change the
Postretro said:
Have you tried the different brands of 6l6’s and 12ax7’s that are available In the AxeFX?

For me, the brand of a tube makes a huge difference in the tone — in both a real amp and in the model. There are definitely differences in headroom, smoothness, hardness and clarity.

Power Tube Bias and Tube Hardness further define and refine the tube‘s tone In the AxeFX.

And this:

Reducing the percentage of PI Bias Excursion (Phase Inverter Bias Excursion) will increase the clean headroom and punchiness in the Power Amp. It will also make the amp feel less forgiving — and slightly stiffer.

I would also check Speaker Compression. If it is already at zero, it is already as tight as it can get. If not, try bringing it down.
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Using a solid-state power amp​

When using the amp modeler with a solid-state power amp (no tubes, e.g. Matrix, Seymour Duncan, Crown) and a traditional speaker cabinet:
  • keep Power Amp Modeling turned on
  • disable Cabinet Modeling, because you're using a traditional guitar speaker
  • turn down Speaker Drive in the Amp block. Turning down Speaker Compression, Speaker Compliance and Cabinet Resonance is not required.
  • set the Amp block's Output Mode to: SS Amp + Cab
------------------------------------------------------------------------------
The speaker driver was already set to 0.
 
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@Postretro, I think I can eliminate the power amp differences. I performed a test that surprised me. (1) FM9 (with SS AMP + cab)-> matrix GT1000FX ->Mesa Boogie 2x12 (2) FM9 preamp with power amp modeling off -> JP2C amp (presence at noon) FX return --> Mesa Boogie 2x12
These sounded nearly identical!

So I will focus on the preamp settings.
 
Narrowing it down to the preamp should help you a lot.
I don't think you need my advice. You've been doing just fine on your own.

But, I can't stop myself, so....

I would tend to trust that the model is accurate. I would definitely start with that assumption. I say that simply because of my previous experiences with questioning Cliff in some way or another and then finding out that he was right. I am just speaking for myself here. And purely as a matter of odds, I would expect the model to be very accurate.

And, there are these statements by Cliff/FractalAudio
https://forum.fractalaudio.com/threads/i-am-confused-about-the-jp2c.153540/#post-1826396
"I'm not at liberty to say anything more but JP himself gave the models his stamp of approval."

https://www.thegearpage.net/board/i...reviews-tones-questions.2124913/post-31011638
"Those are great amps. The particular amp used for the models was John Petrucci's personal recording amp. I didn't want to give it back and offered to buy it from him but he wouldn't sell it."

I know you are matching your particular amp -- which is a different situation.

So, I would look at the non-circuit items that could easily change, before anything else.

1) Obviously, and everyone has pointed it out, you have to set the tone and volume controls by ear.
They won't match the physical amp. You already know this.

You have probably already read about the "USA JP IIC+" model here:
https://wiki.fractalaudio.com/wiki/index.php?title=Amplifier_models_list
It is a must-read
-- also check the links and sources.
The amp guide entries have often helped my understanding on how to adjust an amp.

2) Tube brands can vary by a lot. Tube qualities can vary within the same brand. I don't know what tubes Mesa buys for their name brand. But, you might want to try out each of the 12AX7 tubes that are available in the FM3. See which one sounds the closest to your amp. The Mullard ECC83 is generally a smoother and less aggressive sounding preamp tube.

I couldn't find specific information about what preamp tubes JP might prefer.
But, Fractal's JP-IIC+ model uses a 12AX7A Sylvania, which may, or may not, be a clue.

And, there is this quote by John Petrucci:
https://www.mesaboogie.com/amplitudes/2016/June/John-Petrucci-and-the-Story-Behind-the-JP-2C.html
"I started doing some research about the different incarnations built in the 80’s. The various transformers, power variations, original Sylvania Tubes etc. and started to consider myself somewhat of a C+ connoisseur. I even knew to look on the rear panel for the hidden Mike B. inscription written in black marker that signified whether or not that particular MK IIC amp truly was a “+” version! I ended up gravitating towards a specific sounding version that I would bring on the road and into the studio."

My guess is that John uses NOS Sylvania 12AX7A's.

I seriously doubt that MESA is putting NOS tubes in their amps. Maybe -- maybe -- in the Limited Edition -- maybe.

-- Edit: I just checked. Even the Limited Edition uses the Mesa brand 12AX7'S.

3) Preamp tube hardness is a quality of the preamp tube. Once you have determined the preamp tube you prefer.
See if fine-tuning the tube hardness gets you closer.

I have dialed a tone in from memory -- and it was very close -- only to discover that some expressive quality was missing when I compared it to a recording. Dialing in a tone while the music is playing helps me to stay close to the sound I want. It may help for you to record the sound of your amp, especially expressive licks that make the tone stand out, and have the recording playing in the background while dialing in the model's sound. Your memory for details in a sound may be better than mine. But, this has helped me speed up the process.

This may not be important. But, the earliest JP-2C's had a different loop circuit -- only on serial numbers lower than JP-000345.
https://mesaboogie.zendesk.com/hc/en-us/articles/115003821813-Does-my-JP-2C-have-the-loop-update-

After you exhaust all the possible non-circuit variations -- preamp tube types, preamp tube hardness, and alternate control settings.

And if, you still want to try out changes that affect the preamp circuit itself.

I would leave the preamp tube bias adjustments as a very last resort
Preamp tube bias is determined by a permanent circuit resistor and is not adjustable in the physical amp

The Phase Inverter, PI, is part of the power amp. I would leave that alone and look at other things.

I hope this helps.
I will be curious as to how it finally works out for you.
 
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Snouttrout said:
@Postretro, I think I can eliminate the power amp differences. I performed a test that surprised me. (1) FM9 (with SS AMP + cab)-> matrix GT1000FX ->Mesa Boogie 2x12 (2) FM9 preamp with power amp modeling off -> JP2C amp (presence at noon) FX return --> Mesa Boogie 2x12
These sounded nearly identical!

So I will focus on the preamp settings.
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This is surprising - usually folks have a harder time with the power amp section. So great news. If you figure it out, post a preset :)
 
Come on guys i tought i finally find the recipe to smoother the tone in the cab block cuts and you destroy me with that never ending list of possibilities... Poor me..
 
Hi, Can anybody have real JP2C amp that can confirm the presence knob "push in mode" taper is match on AxeFx model, I find myself always set on 4-4.5, If I use JP's setting push in mode on 6-6.5, its very bright
 
zazanroger said:
Hi, Can anybody have real JP2C amp that can confirm the presence knob "push in mode" taper is match on AxeFx model, I find myself always set on 4-4.5, If I use JP's setting push in mode on 6-6.5, its very bright
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For many reasons, listed in the wiki:

https://wiki.fractalaudio.com/wiki/...ur_amp_doesn.27t_sound_like_Fractal_Audio.27s

Amp model controls will not align with the tapers/numbers of the actual amp controls.
You have to do the control settings by ear.
 
@zazanroger, more specific USA JP-IIC "Presence Shift" switch information:

EDIT: this is true of the FAT switch. However, the JP-2C has the FAT-switch-ON built into the channel.

The JP-2C "Presence Shift" is different. It only shifts the NFB Presence Frequency.

"Presence Shift" switch OFF (default) == Mesa "Treble Pull" OFF (IIC+) / Mesa "Fat" switch ON (Mark IV)

"Presence Shift is Presence pull. Tone stack effectively has fat switch on."

On the JP-2C:
By default, Mid is at 250 Hz. When the "Presence Shift" is OFF. (1000p tone cap)
The Mid shifts up to ~500 Hz. When the "Presence Shift" is ON. (250p tone cap)
-- "Tonestack Freq" display will not change. It will still show 250 Hz.

The 250 Hz tonestack-center is the Mesa Lead tonestack.
The 500 Hz tonestack-center is like a Fender tonestack.


https://mesa-boogie.imgix.net/media/User Manuals/070494-JP2C-160317-download.pdf
From the Mesa JP-2C Manual:
"The Two PRESENCE Modes Set Up Very Differently! Pushing and Pulling Will Probably NOT Give You Two Great Sounds! You Need To Set The PRESENCE Control Differently For Each Voicing Mode! See Below “Setting”!"

There is a lot more specific and helpful information about the PRESENCE mode in the Mesa JP-2C Manual.


From the Amp Guide:

"Similar to the FAT switch on a Mesa Boogie. A popular control for lead tones because it adds body to the tone."

"The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."

“Emphasizes midrange and adds “body” by shifting the tonestack center frequency.”

"The Fat switch simply alters the tone stack treble capacitor. So the effect depends on the location of the tone stack."

"The Fat Switch multiplies the tone stack treble cap by four.
Depending upon the type of tone stack, tone control settings, position, etc.
The effect can be more or less noticeable."

"The Fat switch changes a value in the tone stack which changes the response of the stack, shifting the mid dip down and making it less pronounced. The "Tonestack Freq" parameter frequency scales all the reactive components in the tone stack which is something quite different."
 
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