Presence Shift in USA Lead models

Discussion in 'Axe-Fx II Discussion' started by joegold, Feb 17, 2017.

  1. joegold

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    It looks like this parameter was introduced in Firmware 17.
    But I never noticed it before.
    In Axe Edit it appears on the Power Amp page of the Amp Block editor.

    Evidently this is modeling the Presence Knob Pull/Shift circuit that, iirc, was part of the power amp section of both the Mesa MKIII, the MKIV I used to own as well as the Simul-Satellite I still own.
    I always had this control in the Pulled or active setting.
    These amps simply sounded much harsher and less musical without it active.
    This is true for cleans as well as for overdriven tones.

    After discovering the switch inside the model my Mesa lead tones are finally making more sonic sense to me now.
    There was always something I didn't like about the results I was achieving via any of the Mesa models.
    I think this Presence Shift switch may have just changed all that for me.

    I was going to suggest/request that Cliff think about adding it to the IIC+ and USA Pre models, but I guess that doesn't make sense since neither the MKII power amp sections or the 2:Ninety power amps had this circuit.

    But when I had a Triaxis it was paired, usually, with my Simul-Satellite which does have the circuit and which I always had activated.
    I always thought of the Satellite as being a mono version of the 2:Ninety w/o the extra foot-switchable features.
    But I guess that was off since a real 2:Ninety doesn't have Presence Shift.
    The Satellite series were originally conceived of as a way to have the MKIV tones in stereo which is why they do have the Presence Shift switch I guess.
    Still, for me, it might be useful to have this in the USA Pre models too, anyway.
    And since I always had it activated on my clean channel tones as well, for me, it might be cool to have it in the USA Clean models as well.

    And while I'm discussing the USA Pre LD models...
    Does anybody else find these models as being too gainy?
    With Vol and Gain both at 5, my real Triaxis never had that much gain.
    I have to lower Input Trim to around 0.250 in order to get a similar gain structure to what I remember from my real Triaxis.
    I know that Cliff owns a Triaxis and that he's checked and rechecked the models several times over the years already.
    But it does seem off to me.
    I've not been able to recreate my old Triaxis tones very well on the Axe which surprises me.
     
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  2. joegold

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    PS
    Or is there another way to mimic the effect of this circuit inside the II+ and USA Pre models?

    E.g. By adjusting negative feedback somehow?
    My understanding is that the Pres/Shift circuit involves an increase in negative feedback of some sort.
     
  3. AdmiralB

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    I don't think there's a straightforward way to model it with the controls available. The shift puts a capacitor in series with the existing NFB tap to the phase inverter, which has the effect of reducing the amount of NFB inversely with frequency. IOW, it progressively blocks low frequencies in the NFB, which makes the overall presence effect 'less bright'.

    Turning resonance/depth up a little might be similar.
     
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  4. ocaptainjr2

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    I may not be understanding correctly, but I am looking at my USA Pre Yellow and Green patches and both have the Pres Shift option in there.
     
  5. admgloval

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    I was going to reply to this earlier that I thought I had seen the Pres Shift option on the Triaxis LD2 models. I remember seeing it and wondering why it was there since the Triaxis didn't have that option on it.
     
  6. ocaptainjr2

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    I wondered the same thing. I've tried it, but didn't like the results.
     
  7. AdmiralB

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    An interesting point, since presence is a power amp 'thing', and therefore hard to come by in a device with...no power amp.
     
  8. joegold

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    Hmm.
    That's not the case on my system.
    Inside Axe-Edit's Amp Block screen, with any of the USA Lead sims loaded, this parameter resides in the Power Amp tab (4th from the top of the list on the lh side of the screen).
    It's not there on the same screen with any of the other Mesa sims loaded.

    Perhaps you're looking at a different parameter on a different page?
    The Basic page parameter called "Fat" models the Pull Shift control on the the Treble pot I believe.
    Is that what you're thinking?

    Or am I missing something?
     
  9. joegold

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    I believe the Triaxis sims were modeled on a Triaxis/2:Ninety system.
    So the Power Amp pages of the sim's editor involve a sim of something like one side of a 2:Ninety power amp.
    But I could be wrong.
    At any rate, the model's power amp sim is a model of a tube power amp of some sort.
     
  10. admgloval

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    Interesting, I just looked and I see the option on the PWR tab on the front panel under the Presence control. But inside AxeEdit, the option is not under the Power Amp Tab in the amp block like it is on the USA Lead models. So it looks like it can only be enabled on the front panel. Maybe it is a bug that Cliff never noticed. Btw, on the Wiki, there is a note from Cliff that said he modeled the power amp part of this amp model on the VHT 2-90-2, not a Mesa 2-90.
     
  11. ocaptainjr2

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    I looking at the front panel. Not sure if they exist within Axe-Edit.

    Cliff has said that he is not a fan of the 2:Ninety and that the models were captured with a VHT 2502 poweramp.
     
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  12. #12 joegold, Feb 17, 2017
    Last edited: Feb 17, 2017
    joegold

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    Interesting!
    Thanks.
    The parameter *is* there via the front panel for the 3 USA Pre LD2 sims.
    But it's not there on the USA Pre LD1 Red or USA Pre Clean sims.
    And it's not there, probably for the reasons mentioned above, on the IIC+ or IIC++ sims.

    I haven't had time to try it out yet on the USA Pre LD2 sims.
    But I guess we can assume that the fact that it is not available from Axe-Edit is an Axe-Edit bug.
     
  13. joegold

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    Ah right. I think I remember reading that too.
     
  14. retnuH

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    Which never made sense to me. The Triaxis was made to go with the 2:90 and a lot of players like me love what the 2:90 adds. I'm still playing through mine with my Mesa cabs.
     
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  15. Philip34

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    Have you ever tried a VHT poweramp?
     
  16. Rex

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    Every amp model has a Presence Frequency knob. It lets you shift the Presence frequency wherever you want.
     
  17. admgloval

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  18. #18 joegold, Mar 6, 2017
    Last edited: Mar 6, 2017
    joegold

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    Sure, but how does one adjust that parameter to achieve the same effect as the Pres Shift on a real Mesa power amp if its not modeled in the amp sim to begin with?
     
  19. DestructionSphere

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    This is why I wish we could have fully separate pre and power amp blocks. I prefer the VHT 2502 to the 2:90, but everyone is different (really I wish it was a VHT 2150 instead). It'd just be nice to mix and match, even on amps that wouldn't support it in real life. The separation would also be nice because it would also act as an amp FX loop, which to my knowledge also isn't an option right now (though I'm pretty new to the AxeFX).
     
  20. admgloval

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    No idea, can't help you there. Just wanted to report that now the control is available to adjust in both places, front panel and AxeEdit.
     
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