Why is the P.A. Off switch part of the Sag Control?

[sprint]

I've never understood why P.A. on/off does not have it's own switch since, as I inderstand (or possibly misunderstand) Sag does not regulate the amount of P.A. influence (MV would be closer to that?). I guess it doesn't matter where the P.A. on/off switch is, but is there a reason it's co-located in the Sag control?

 

[mr_fender]

Sag is mostly a result of the higher dynamic current flow of the power tubes. If the amp has less power supply filtering and/or uses a tube rectifier, the sudden onrush of current caused by big signal transients causes the B+ voltage in the amp to be pulled down or "sag". It's sort of like how your lights in your house might dim for a split second when a big electric heater or motor kicks on. The more the B+ voltage sags, the more the amp tends to compress and break up. Having no sag at all would make for a much more stiff and clean sounding power amp section, so it kind of makes sense that turning it all the way down disables the power amp modeling. In reality all amps sag at least a tiny amount since there is no such thing as a perfect current source.

 

[X1Nx]

I don't really know about your question, but the thing that slightly bothers me about it is that I would prefer to be able to add that pa emulation at the end of a specific chain output for the foh, and have another chain to a fx return of a tube amp simultaneously without having to sacrifice my 2nd amp block, and duplicate my entire fx chain (post amp block) just to bypass 1 parameter. I brought this up in the latest firmware thread but not sure if fractal will address the issue. You would think with the number of outputs, and routing options on the axe fx3 there would be a better way around this but I haven't yet found a satisfactory solution. People will mention solid state, or frfr, but I can't come to terms with the thought of retiring my tube amp because of this. Hopefully they take it seriously since I'm sure there's hundreds if not thousands of players out there that would be stoked about it.

 

[mr_fender]

It's been requested many times over the years, but is most likely never going to happen. Isolating the power amp modeling would likely allow easier reverse engineering of Cliff's hard earned power amp tone wizardry through signal analysis and such. Can't blame him for wanting to protect his hard work from would be copy cats.

 

[X1Nx]

But is it not possible to keep the amp block as is and have the addition of another block so as to still safeguard his algorithms, and solve the issue for the users? I see a lot of people even at pro levels working around the issue in ways that are just disappointing

 

[X1Nx]

If you can disable it I don't see how that makes any difference

 

[sprint]

But is it not possible to keep the amp block as is and have the addition of another block so as to still safeguard his algorithms, and solve the issue for the users? I see a lot of people even at pro levels working around the issue in ways that are just disappointing

Could you take this to another thread please, as it's not related to the question I created this thread for.

 

[sprint]

Sag is mostly a result of the higher dynamic current flow of the power tubes. If the amp has less power supply filtering and/or uses a tube rectifier, the sudden onrush of current caused by big signal transients causes the B+ voltage in the amp to be pulled down or "sag". It's sort of like how your lights in your house might dim for a split second when a big electric heater or motor kicks on. The more the B+ voltage sags, the more the amp tends to compress and break up. Having no sag at all would make for a much more stiff and clean sounding power amp section, so it kind of makes sense that turning it all the way down disables the power amp modeling. In reality all amps sag at least a tiny amount since there is no such thing as a perfect current source.

Understood, however the P.A. on/off switch still seems out of place to me even given the overall importance and influence of the Sag mechanism. Going from P.A. off to Sag = .01 is a dramatic change in tone and feel and even has an associated "pop" when changing from on to off or off to on. - the rest of the travel of the Sag control is not even close to that dramatic - so why does it not have it's own switch like pre-amp sag does? As I said above, it's not that important really, though Sag is one control that I always thought I may want to request a modifier on either for PA switch or the actual Sag control but having the 2 co-located would confuse that possibility.

 

[mr_fender]

I'd guess because for most users it's not something that gets toggled or changed all that much per preset and he didn't want to dedicate a separate control to it. For most users, you either use power amp modeling or you don't, so there's a global switch for disabling it in the setup menu.

 

[sprint]

I'd guess because for most users it's not something that gets toggled or changed all that much per preset and he didn't want to dedicate a separate control to it.

Well ... I suppose ..., but there's like 1000s of controls in this thing! - in this one instance he co-locates a binary function with a variable one just to save having one more switch control in the amp block!? - seems odd.

Thanks Mr fender for spending some of your Friday night entertaining my obsessive curiosity - have a great weekend

 

[Dave Merrill]

so why does it not have it's own switch like pre-amp sag does?

Pre-amp sag? Not in front of my Axe, but I don't remember such a thing. Sag is part of the power amp, isn't it?

 

[Smittefar]

There is a preamp sag switch on the Pwr Supply page in AXE-EDIT III

 

[guitarnerdswe]

Pre-amp sag? Not in front of my Axe, but I don't remember such a thing. Sag is part of the power amp, isn't it?

Preamp sag toggles whether the pre amp and power amp are treated like a head with the same power transformer etc, or as a separate pre and power amp ala rack gear. If the output section sags in a head, the pre amp does too.