The only difference I see between a Differential/Balanced amplifer hookup and a Class A/B is what to do with the ground wire...
I have a Luxman but I have never hooked up an REL to it (yet).
So if you want to start the "safe" way to see if things work out. Connect the red wire to + of R channel. Connect the yellow to + of L channel. Do not connect the ground but tape over it.
https://youtu.be/jDoY5sVT0XQ