I had a rev D and the pre went on that (extremely low level on pre 2). Under warranty replaced for free no problem. New one was same rev D I believe (can't check anymore) - and that went as well a few months later, same problem. Now I'm on my third unit - fingers crossed it goes well. Hey, at least the warranty is reset each time!
Such a great unit (and great service) but something is definitely up with them pre's.