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power amp sim on/off vs. sag on/off with real power amp + behaviour of presence control

deleted

Inspired
Hi,

I'm experimenting with a tube power amp recently and I read some advices on the wiki regarding this.

I have two questions:
1) Is it better to shut off the power amp sim in the global menu or via sag control? If in the global menu, do I have to shut off the sag control too, as this is still functioning?!

2) Is it still correct, that you should watch the presence control after switching off and on in the global menu? If so, where do I have to look? I don't see a difference in the amp block. I switched power amp sim on and off again yesterday, because I wanted to check out the Q12A and then back to the tube power amp + cabinet. I don't know but I think that my patches created with the tube power amp now sound different. It might be imagination but I would like to know anyway if this is a current information.

Thanks!
 

notalemming

Fractal Fanatic
1. It doesn't matter where you turn the power amp sims off, it has the same effect. If you use the global, that's all you need to do. All your presets will have the power amp sims off.

2. The presence control is boost only with the power amp sims on and 0 is the flat position. With the power amp sims off, it becomes boost & cut so now setting it at 5 would be the flat position.
 

yek

Moderator
Moderator
1. It doesn't matter where you turn the power amp sims off, it has the same effect. If you use the global, that's all you need to do. All your presets will have the power amp sims off.
Nope.

Cliff: "If you shut the power amp modeling off from the Global menu it is not exactly the same as turning it off by setting Supply Sag to zero. This is because the virtual power amp always runs. So if you shut the power amp modeling off from the Global menu the supply will still sag resulting in a more compressed response. If the Master is set high the sag can be quite pronounced."
 

deleted

Inspired
2. The presence control is boost only with the power amp sims on and 0 is the flat position. With the power amp sims off, it becomes boost & cut so now setting it at 5 would be the flat position.
I don't see any difference in value if I turn this on/off in the global menu and/or turn of sag. I'm sure we are talking about the Presence control on page 3 of the amp block, aren't we? That confuses me a bit. Cliff said that the type is switching too but I don't see any difference here either. I remember the presence was switching to a hi-cut in the past when shutting sag off (which is what he means by saying classic -> shelving control?!).
So, I assume this information isn't valid anymore?! ..
http://forum.fractalaudio.com/threads/one-thing-to-always-check.45574/#post595595


Nope.

Cliff: "If you shut the power amp modeling off from the Global menu it is not exactly the same as turning it off by setting Supply Sag to zero. This is because the virtual power amp always runs. So if you shut the power amp modeling off from the Global menu the supply will still sag resulting in a more compressed response. If the Master is set high the sag can be quite pronounced."
So, what's the common way? Global or sag? If Global, sag too?
BTW: the wiki is great. thanks for that :)
 

notalemming

Fractal Fanatic
The presence control display or position will not change. You have to do that manually. If, for instance, you have your presence on 3 & then turn off the power amp sims, it will still be on 3 but will now be cutting presence, not boosting it. You would have to turn it up above 5 to get a presence boost with the power amp sims off. Yek's post of Cliff's quote were news to me LOL! It's cool that if you use the global option, you can sill get some of the feel of the power amp sim with the sag control.
 

deleted

Inspired
The presence control display or position will not change. You have to do that manually. If, for instance, you have your presence on 3 & then turn off the power amp sims, it will still be on 3 but will now be cutting presence, not boosting it. You would have to turn it up above 5 to get a presence boost with the power amp sims off. Yek's post of Cliff's quote were news to me LOL! It's cool that if you use the global option, you can sill get some of the feel of the power amp sim with the sag control.
Ok, I understand. Thanks!
Probably it has changed in some FW update that it's not switching to "Hi-Cut" anymore but still shows "Presence".
 

deleted

Inspired
Presence turns into Hi-Cut when Damping (not SAG) is set at zero.
Oops! :) .. Ok, seems that I was a little confused :D
That means it's logical that Presence turns into Hi-Cut, because by switching the power amp sim off, the Damping will be switched off automatically?!
 

yek

Moderator
Moderator
You're mixing up things ...

Damping = negative feedback. Presence (and Depth) change neg.feedback. If there's no neg.feedback (Damping = 0), then there's no Presence (and Depth), so Presence turns into a Hi-Cut control instead.

Sag is related to the power supply. There's a close relationship with the Master Volume. If you turn off Sag, then the power amp modeling is disabled. Presence operates in the power amp section, so when power amp modeling is turned off, Presence no longer functions as such: it will turn into a shelving filter.
 
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