Some minor things to add that have partially been covered:
–If noise is coming out of both channels the problem is somewhere in the power supply. If the new tubes don't fix it then the problem is in the power supply circuit.
–ARC feels that their products (and many others) sound better with no cover installed, but they can't recommend that. (Don't blame them.) The acrylic cover sounds like no cover at all, which is why they started shipping the Ref 5 with the acrylic, unless a metal cover is ordered. The Ref 6 has acrylic top and bottom covers.
–ARC switched to a thicker acrylic cover a couple of years ago. The original acrylic covers would often have a little dip over the 6550, which runs hot. It's an output tube that's used in the power supply!
–If a product comes from the manufacturer with the tubes packed separately then you should never ship that piece with the tubes installed. Shipping companies don't treat our stuff gently, and the tubes can come loose!
–I have my tube electronics in a cabinet but leave plenty of space above, and I took the back off.
–If noise is coming out of both channels the problem is somewhere in the power supply. If the new tubes don't fix it then the problem is in the power supply circuit.
–ARC feels that their products (and many others) sound better with no cover installed, but they can't recommend that. (Don't blame them.) The acrylic cover sounds like no cover at all, which is why they started shipping the Ref 5 with the acrylic, unless a metal cover is ordered. The Ref 6 has acrylic top and bottom covers.
–ARC switched to a thicker acrylic cover a couple of years ago. The original acrylic covers would often have a little dip over the 6550, which runs hot. It's an output tube that's used in the power supply!
–If a product comes from the manufacturer with the tubes packed separately then you should never ship that piece with the tubes installed. Shipping companies don't treat our stuff gently, and the tubes can come loose!
–I have my tube electronics in a cabinet but leave plenty of space above, and I took the back off.