Modeling Questions

[holgar]

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.

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.

Having the Volume pot from the unused chanel would be perfect.
Turning up the Volume of the Normal chanel while plugged into the High 1 Input sounds much better than jumpering the inputs IMHO.
The amp stays tight and bright, but the added Volume fills the low freqencies in a beautiful way.

 

[Aleksi]

On the topic of authenticity, do we actually know which models are truly accurate and which ones are modified or even based on something else entitrely?

I know Cliff considers the Mark EQ to be a poor design, but would it be possible to have both an authentic and ideal model of the EQ?

 

[James Freeman]

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.

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.

Yerp, 100%

On the topic of authenticity, do we actually know which models are truly accurate and which ones are modified or even based on something else entitrely?

Nope, but we trust that Fractal proritizes stock authenticity over anything else, particularly now in Cygnus X-2 era.
This also applies to naming the models, if the amp is not stock or was modified digitally by Fractal, it should be labeled as such.

 

[Budda]

Having the Volume pot from the unused chanel would be perfect.
Turning up the Volume of the Normal chanel while plugged into the High 1 Input sounds much better than jumpering the inputs IMHO.
The amp stays tight and bright, but the added Volume fills the low freqencies in a beautiful way.

If you arent jumpered, plugged into hi1 and hearing a difference bringing up the norm1 it is because you are raising the noise floor of norm1. If the unit isnt jumpered, the second volume should have no effect.

I say this because i just brought my 75 mk2 in for this exact behaviour, thinking it was internally jumpered. Nope, mine just has none of the factory tweaks to reduce noise and using high vol only plugged into norm channel still changes the sound lol.

 

[James Freeman]

If the unit isnt jumpered, the second volume should have no effect.

I explained in the previous page that Volume 2 forms a voltage divider and has an effect on Channel 1.

 

[Budda]

I explained in the previous page that Volume 2 forms a voltage divider and has an effect on Channel 1.

Interesting - i just rewatched my videos and on ch1 lo, ch2 vol has no effect. Ch2 lo, ch1 brightens it up considerably.

 

[James Freeman]

Maybe it is a good time to refresh the Plexi models with the other volume and fix other small mistakes?
That is Treble, Normal and Jump for all Plexi models with both volume controls that affect each other.

 

[FractalAudio]

Maybe it is a good time to refresh the Plexi models with the other volume and fix other small mistakes?
That is Treble, Normal and Jump for all Plexi models with both volume controls that affect each other.

What small mistakes? I'm not aware of any.

The models sound great and a lot of time was spent on them, perhaps more than any other models. If they don't work for you there are hundreds of other models that may work better for you.

 

[James Freeman]

If there is any that is.
They sound fantastic, I especially like the Post-PI configuration.

 

[yek]

At the very least the Wiki needs to be updated to inform people this model was modified and is not a "standard" Plexi anymore.

Done.

The wiki is hosted by Fractal Audio but Fractal Audio isn't responsible for its contents. Information in the wiki is always based on facts and common knowledge, wherever verified and validated by documented statements from Fractal Audio. There was no mention of the removed virtual resistor in the Plexi High 2 model before, because that information hadn't been shared yet.

 

[InsideOut]

What small mistakes? I'm not aware of any.

The tolex has a small ding in it which ruins the entire experience for me.

 

[aens]

The tolex has a small ding in it which ruins the entire experience for me.

Those dings do make a difference especially when you mic your amps like this:


Jokes aside my previous JCM amp did make a sound you can mic if you use a loadbox, turn up the master volume high enough and mute the power amp after loadbox. Did not trace the sound properly but IIRC it was maybe coming from the transformer.

 

[James Freeman]

This video is worth your time.



When playing on Channel 2 (Normal), the volume control of the unplugged Channel 1 acts like a low pass filter, it puts the mixing 500p cap to ground through Volume 1.

 

[Budda]

Imagine thinking ch2 low is not useable lol

 

[Random Hero]

Yup, all the pots are log pots in our reference amp.

The "classic" Plexi tonestack is #4 (Plexi). In the advanced menu you can choose from all the different tonestacks via the Tonestack Type parameter.

So to get the 100W to act more like it doesn't have log pots, set the tonestack to Plexi rather than default? That's number 79 in mine, rather than 4?

 

[Random Hero]

Sorry posting again...

This thread has blown my mind. Changing the 100W Plexi tonestack makes me hear it far more like I'd expect. The stock 100W is a little warmer than the other models but setting the tonestack to "Plexi" opens it right up.

Aside from changing the presence cap value (also blown my mind) what other tweaks can we do here to simulate stuff in the real world? Obviously I know about the bright cap, the Jose mod stuff and changing the master volume position. But anything else like the presence cap?

 

[FractalAudio]

So to get the 100W to act more like it doesn't have log pots, set the tonestack to Plexi rather than default? That's number 79 in mine, rather than 4?

The default tone stack for the Plexi 100W is #53 (Plexi 100W). The equivalent tone stack w/ linear mid and treble pots is #4 (Plexi). #79 is a Dumble tone stack which is the same as #4 except it is plate driven instead of cathode follower driven.

Our reference 100W Plexi has log pots for all pots in the tone stack.

 

[FractalAudio]

Sorry posting again...

This thread has blown my mind. Changing the 100W Plexi tonestack makes me hear it far more like I'd expect. The stock 100W is a little warmer than the other models but setting the tonestack to "Plexi" opens it right up.

Aside from changing the presence cap value (also blown my mind) what other tweaks can we do here to simulate stuff in the real world? Obviously I know about the bright cap, the Jose mod stuff and changing the master volume position. But anything else like the presence cap?

The taper doesn't change the tone. It only changes where a given tone occurs for a knob position. For example, if the treble pot is a log taper you simply turn it up higher to get the value of a linear taper pot at a given position.

 

[Random Hero]

The default tone stack for the Plexi 100W is #53 (Plexi 100W). The equivalent tone stack w/ linear mid and treble pots is #4 (Plexi). #79 is a Dumble tone stack which is the same as #4 except it is plate driven instead of cathode follower driven.

Our reference 100W Plexi has log pots for all pots in the tone stack.

Different on an FM9?

 

[Random Hero]

The taper doesn't change the tone. It only changes where a given tone occurs for a knob position. For example, if the treble pot is a log taper you simply turn it up higher to get the value of a linear taper pot at a given position.

Just noticed this setting it to 10. Thanks for clarifying. Makes sense why my usual Bass 3/Mid 10/Treble and Pres 7 settings sound different when changing the tonestack.