Hi, I am feeding my perfect working km74 with a perfect working sennheiser mzn16t and good cables all wired correctly according to the km74 schematic. Unfortunately I have too much hum that make them too noisy. Some users had same problem with that psu; there's something that don't work with the km74 from this psu? As well I am searching for the n9i schematic to try understanding what could be wrong, would you have it? Thanks!..