If you have sharp eyes, you may have seen the Klark-Teknik DN-410 Equaliser (aka 'Equalizer' in American) in my equipment rack.
It's made in England and looks really cool to boot.
The bandwidth goes from 2 octaves down to .08 of an octave! That would be like less than one note.
Fortunately, as the manual says "The unit can be quickly re-configured to accomodate either XLR wiring standard by removing the top cover and changing the orientation of 4 plug-in links per connector, as shown on the adjacent PCB legend."
There are 2 screws on either side of the top cover to remove.
Very tidy PCBs and wiring.
I'm always a little surprised when I open up modern gear, since I'm so used to seeing point-to-point wiring in old radios and amps.
Note the two cylinders - they're the output transformers.
Just as the manual says, there are the jumpers and the PCB legend. You can see my unit is still wired for pin 3 hot. The jumpers are connected 'horizontally' according to the PCB.
So I'll just need to remove them and flip them around.
There are 2 sets of 4 jumpers which prove to be a bit tricky to remove. I manage to get a small screwdriver under one of them and pry it up.
The tops of the jumper housings are fragile - I accidentally cracked the tops of 3 of them.
However, it won't affect their operation. I'm just noting this in case you try this. There may be a tool to remove this sort of connector, but I don't have one.
Simple. But I'm not sure about "quickly."