I have a very small hiss when listening close to the yamy80 and no music is playing. its independent of the level from the interface (firepod). No big deal and doesn't bother me at all.
I have them set to -10dB because they sound alot fuller.
when nothing connected they are silent, so they are just amplifying the firepod's output.
like I said. no big deal... now if the hiss your are hearing is strong, try better cables and connectors.
You have them on -10 dB? Isn't that full blast? I guess you compensate by lowering your interface output?