The reason they have not done anything about it is beacuse it only affects a high impedance headphones. I have never had a problem with speakers, even quite sensitive ones. And cost is a key, of course, since every expense at factory level is mutiplied manyfold moving through importers/distributors and dealers. The cheapest option for fixing this (except the one sugested by Kevin Gilmore) might just be to move the main trafo over to an external case....
You are probably right about that. The hum is stronger in the channel that has it's otput transformer closer to the main transformer. Here is a cure suggested by Kevin Gilmore... I have not gotten around to try it (yet), it requires some skills: http://www.head-fi.org/t/686511/magnetic-shielding-of-trafo-inside-leben-amp
I have tried flipping the schuko for the Leben and other stuff, with no result. But never tried to get all right at the same time.... However - if I unplug everything else, and try plugging in the Leben both ways (with the schuko)I should hear a difference - if my hum issue is about polarity - rigt? Also - you have a link to that tool you are using - or a similar one?
I have not tried any of that, I might be getting a DC filter, I think, but mostly I don't bother since I have different amps for the high imp headphones. Local power does seem to vary on such things, I have only tried it three places in the same area of my home town, so I shouldn't generalize, I am under the pression that 230v users such as myself are more at risk for hum than 110v.
HD650 is not for people who prefers the treble to be highlighted. To me it sounds like you want the HD600. Someone should tell Apogee that they are wearing the HD800 backwards in their Apogee ad, haha: