Modeling Questions

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Cliff, what are the actual differences between Plexi 50W High 1 and 2?
Seems like High 2 has much more bass and does not correspond to just a 0.68uF on V2a as the Wiki suggests, which supposed to boost 3-4dB above 300Hz and not bass.

Preamp response only:
Plexi 50W 1+2.png

plexi 50w wiki.png


EDIT:

This is what I expect from 0.68uF on V2a:
50W High 1 vs 100W 1970 preamp response only.

50w vs 100w 1970.png


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1/2 the internet forums are about what passive component Eddies '68 Plexi had 😆, so yes, the difference between all the Plexi models in the AxeFx is very important and should be clarified to the minute detail.

I think the Wiki needs a major update regarding the Plexi amps, there were probably a lot of tweaks over the years and the information can be outdated.
 
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James Freeman said:
Cliff, what are the actual differences between Plexi 50W High 1 and 2?
Seems like High 2 has much more bass and does not correspond to just a 0.68uF on V2a as the Wiki suggests, which supposed to boost 3-4dB above 300Hz and not bass.

Preamp response only:
View attachment 132168

View attachment 132169


EDIT:

This is what I expect from 0.68uF on V2a:
50W High 1 vs 100W 1970 preamp response only.

View attachment 132170


---

1/2 the internet forums are about what passive component Eddies '68 Plexi had 😆, so yes, the difference between all the Plexi models in the AxeFx is very important and should be clarified to the minute detail.

I think the Wiki needs a major update regarding the Plexi amps, there were probably a lot of tweaks over the years and the information can be outdated.
Click to expand...
Plexi High 2 has a 0.68uF cap on V2A and the mixing resistor for the normal channel removed.
 
FractalAudio said:
Plexi High 2 has a 0.68uF cap on V2A and the mixing resistor for the normal channel removed.
Click to expand...
That resistor is very important, it forms a 470k+470p/470k divider throught Volume 2 (normal) pot to ground, or 470k+470p/1470k when Volume 2 is full, even when using only Channel 1.

By removing that resistor you've doubled the low frequency voltage into V2a. :D

This circuit only has a handful of components, every component is important and affects the sound, no need to remove anything.

In fact, add a passive Volume 2 to Channel 1 Treble only models for maximum authenticity, or fix it internally at 0, it affects the sound. :)
 
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James Freeman said:
That resistor is very important, it forms a 470k+470p/470k divider throught Volume 2 (normal) pot to ground, or 470k+470p/1470k when Volume 2 is full, even when using only Channel 1.

By removing that resistor you've doubled the low frequency voltage into V2a. :D

This circuit only has a handful of components, every component is important and affects the sound, no need to remove anything.

In fact, add a passive Volume 2 to Channel 1 Treble only models for maximum authenticity, or fix it internally at 0, it affects the sound. :)
Click to expand...
You're assuming that Cliff made this mod... ;)
 
James Freeman said:
He literally just said "mixing resistor for the normal channel removed.", so yes, I'm assuming said resistor was removed.
Click to expand...
Not what I said...

The amp may have been modded when Cliff purchased it. You've insinuated that Cliff removed it when quite possibly he purchased an already modded amp and modeled it.
 
unix-guy said:
Not what I said...

The amp may have been modded when Cliff purchased it. You've insinuated that Cliff removed it when quite possibly he purchased an already modded amp and modeled it.
Click to expand...
Unfortunately there was a lot of that , different parts and values , it probably explains why the same amp the same years sound different
I remember an article with Joe Perry and he talked about going into a room with 10 different Plexis and trying them all out , and he said out of the 10 there was 1 or 2 that just had this magic compared to all the others and they were all plexis same spec, same year but for some reason one just stood out
So what really was a stock plexi, do we really know
 
Marshall back in the day did not always build to their schematics, rather they built with what parts they could source in quantity at the the best prices.

Then, once sold someone would mod it anyway, so what you're getting these many years later could be anything circuit-wise, and though you're hoping that the iron is correct, a lot of vintage Marshall iron eventually went up in flames as well (especially with early generation power soaks/attenuators).

That said, when they went they did produce a show stopping plume of toxic smoke before cutting out completely LOL! :fire:
 
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Yeah, I thought it was 'flavoring', sounds like overcompressed flubby mush, here I was trying to compare the same Plexi with and without the 0.68uF cap on V2a.
Completely removing the mixing resistor is NOT a common mod at all according to lengthy search at Marshall and Metropoulos forums, well, maybe because it sounds like crap. 😆

Is it a good time to bring the old Plexi 50W High 2 up to Cygnus standards (remove flavoring) like you just did with Brit Silver and many other amps?
At the very least the Wiki needs to be updated to inform people this model was modified and is not a "standard" Plexi anymore.
 
James Freeman said:
Yeah, I thought it was 'flavoring', sounds like overcompressed flubby mush, here I was trying to compare the same Plexi with and without the 0.68uF cap on V2a.
Completely removing the mixing resistor is NOT a common mod at all according to lengthy search at Marshall and Metropoulos forums, well, maybe because it sounds like crap. 😆

Is it a good time to bring the old Plexi 50W High 2 up to Cygnus standards (remove flavoring) like you just did with Brit Silver and many other amps?
At the very least the Wiki needs to be updated to inform people this model was modified and is not a "standard" Plexi anymore.
Click to expand...
Bold Strategy Cotton GIF by MOODMAN
 
My opinion doesn’t count for much, but I’d also prefer that amp models match the real circuits as a baseline. Deviations from that are ok as long as it’s a choice for the user.

In a world where we throw stones at the TMP because it only sounds 95% like the real amps, the best gear on the block needs to make sure its models are beyond reproach in the accuracy dept.

Fractal’s modeling algorithms are exceptional. When Fractal’s circuits are accurate in the virtual domain, the sound is accurate too. Creative choices by the designer can just as easily be interpreted as modeling inaccuracies if we aren’t aware of the mods, and what one person thinks sounds better, another person might think sounds worse. A model that matches the real gear is always a defensible baseline, and mods are gravy if they’re optional.
 
SwirlyMaple said:
My opinion doesn’t count for much, but I’d also prefer that amp models match the real circuits as a baseline. Deviations from that are ok as long as it’s a choice for the user.

In a world where we throw stones at the TMP because it only sounds 95% like the real amps, the best gear on the block needs to make sure its models are beyond reproach in the accuracy dept.

Fractal’s modeling algorithms are exceptional. When Fractal’s circuits are accurate in the virtual domain, the sound is accurate too. Creative choices by the designer can just as easily be interpreted as modeling inaccuracies if we aren’t aware of the mods, and what one person thinks sounds better, another person might think sounds worse. A model that matches the real gear is always a defensible baseline, and mods are gravy if they’re optional.
Click to expand...
I agree. The models should be as accurate to the real thing as possible. You can always make modded versions and label them Mod, like the Brit 800.
 
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