ARC Reference 10 melting polycarbonate cover

That`s the one that ARC originally installed in the Ref. 10.

If the cover is warped, you haven't provided enough ventilation for the chassis! Those tubes require that air be able to circulate through the unit.

The top needs about 4 inches to breathe. This is a common complaint if it does not. The last I heard, you could buy a metal top plate, but ARC claims it has a slight negative impact on sound.

Thanks for your answers. I decided to remove the cover and see what happens. Maybe, will make a couple of holes over the 6550's.

That sounds like the Wizard of Oz...damned Dorothy!