I'm going to post the email I received from David Phelge at Fryette in regards to questions I had about impedance curves with the Axe and the LXII power amp. Hopefully it helps:
There was a whole long thread on TGP about this. I thought I remembered them saying the opposite at the time. I remember leaving the thread feeling somewhat unsatisfied with a difference in behavior between:
- A tube amp plugged into the reactive load of the PS, which is connected to its tube poweramp which has reactivity with the speakers. That is said to be one of its advantages over a solid state device.
- A fractal emulating a reactively loaded tube amp connected to the same tube poweramp.
The answer was "The fractal isn't a real amp"... which is obviously true, but certainly seems like a cop-out, especially when you can repeatedly put the Fractal in situations of direct comparison and it always comes up really close.
I need to go hunt the thread down. Dave @ Fryette obviously knows what he is talking about but in my experience, it didn't sound like the tube amp in question when played through a PS2 unless I eased off the reactivity in the Fractal- not disabled. When the Fractal is played through a solid state amp, it compares very favorably to the real amp so I suspect the Fractal isn't off the mark in simulating a reactively loaded tube amp. 100.00% identical? maybe not but it is super close. I suspect the issue is just the combined reactivity and you don't experience it with a tube amp because the reactive load in the powerstation is calibrated for it's intended duty with the accompanying poweramp.
edit: foundit:
https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-and-power-station-2.2136319/
Edit:
Reading back through that thread years later, I continue to think that the Powerstation device is at its best doing what it says it will do: make a tube amp louder or quieter without screwing up its tone. Using either the reactive load or the poweramp by themselves doesn't get the best of what it does.
It sure looks like the load and the poweramp are calibrated to work together to make tube amps louder or quieter without screwing up their tone more than being a poweramp for some other device, including a device reactively loaded by some other load.
I see my experiment in that thread where I ran a tube amp into the powerstation reactive load and then out (via the FX send) to a solid state amp and the result was a dead sounding tone at the same reactivity switch settings.
More recently, I've run the tube amp into a Fractal x-load reactive load (simulating UK 4x12 load) and run that into a solid state amp and the result sounded very much like the amp on its own, (and very much like a similar amp modeled in the Fractal sounds through the same solid state amp. ) That tells me it isn't the Fractal- it is something else. My suspicion (again) is that the load and poweramp in the powerstation are designed to work together and if you use one or the other you aren't getting the full equation.