Also, how do you jumper the channels?
Plug into the High input of one channel. And then run a jumper cable (instrument cable, a 6" cable keeps it neat) for the Low input of that channel to the High input of the other channel.
Try it both ways, plugged into normal High, jumped from Normal Low to Bright High; and then plugged into Bright High, jumped from Bright low to Normal high. The two options will sound a litte different because the second channel of the jump is going to be attenuated since the signal comes out the attenuated Low jack of the first channel before continuing on.