Weird. It almost begs the question if it works regardless the setting why put the switches there at all? I’m not sure tube amps feel the same way about it though.
I'm watching the recording right now. Steve said that
if the powerstation input and output impedances are set the same then things will work out fine. I think he said 8 ohms, but I don't think it's restricted to that. I don't know how it works of the top of my head, in fact he mentioned he has a patent pending so won't say much about it yet, but from what he says there is some transformer funny business going on.
Edit: Tired, so it took me a while to notice this. What Steven described could be implemented with two back-to-back impedance transformers and the powerstation in-between, and in that case the Powerstation
would need to be set to 8 Ohms in 8 Ohms out. Here's what I'm talking about:
Get two impedance matching transformers. Primary-side has taps for 4, 8, and 16 ohms. Secondary-side has a single 8 Ohm tap. Amp signal goes into the primary side of one, using the correct winding for the amp's impedance. Power station is hooked up to the secondary side of that first transformer, and is set to 8 ohms to match the secondary's 8 ohm impedance, which will result in the amp seeing the correct matching load. Then, the Powerstation's 8 ohm output goes into the 8-ohm secondary of the final transformer, and the cabinet(s) are hooked up to the proper tap (4, 8, or 16 ohms) on the primary side, which means the cab's impedance is matched too. So everything works out.
A shorter way to put it brushing over a few things and using sloppy language is that you convert the signal from whatever impedance the amp wants to 8 ohms, send it into a powerstation set for 8 ohms input, then send the attenuated signal out of the power station set at 8 ohms output, then convert from 8 ohms to whatever the cabinet wants. That way, everything is matched all the way through.
I'm not sure that's how they're doing it, there might be more sophisticated ways, but it is
a way I think. I'm pretty tired though so I could be off. Also, as long as your attenuator can be set for 8 ohms in and out, it shouldn't need to be a power station with the above scheme.