From a picture in the UK audio mart. Looks like its a cover of some sort to stabilize or insulate the cans...
That certainly looks like what is reaming in my caps , hope it a warranty issue ( joke)
Does anyone out there own one of these? My other question was about heat, I see that massive heat sinc so its probably there for a reason. The unit does get warm+, it sounds like it should, I had it hooked up to my Klipsch KG3 speakers and it sounded fine.