It's strange, but my M9 has audible noise in headphones on both gains after about 82-83 volume value. You can think I'm crazy to use such high values, but my DAC has some kind of "quiet" output and I should use values about 65-67 on balanced output and about 75-77 on unbalanced one to listen to music with appropriate loudness. So it kinda troubles me.
Have you tried with a diff DAC, maybe the noise is from the DAC ?