Hmmmm, I'm not sure that's true. It's certainly not mentioned in any of the ARC owner's manuals that I've seen. It would also pose a potential shock hazard so it's a hard practice to recommend - even if some users with no children or pets do it anyway.I remember Leonard telling me many years ago that my preamp will sound better with the cover off. This was back when you could actually call ARC and talk to someone knowledgeable.
That won't happen with adequate ventilation. The plexi cover is a bit like the "canary in the coalmine."
Yes it will. The top of the 6550 tube is extremely close to the Plexiglas cover. If you have the preamp on for long periods of time the top will melt. I usually listen for 4 or 5 hours at a time on the weekend. When I first got my Ref 5se it sat on the top shelf of my rack. There is a still a slight dip in my Plexi cover right where the 6550 sits. When I complained, ARC sent me a replacement metal cover. According to my dealer this was a very common problem.
