skammila, I'm having the same issue and although I haven't tried the humidifier the thing which fully helped was switching to an optical connection via toslink. But that sound was somehow muddy in comparison so I went back to a wire at the expense of the pops.
But maybe you can get some glass toslink, I heard they are good as the metal ones, mine is very bad all bent, with plastic fibers.
edit: I'm saying for the transport-dac connection, your problem might be unrelated.