Ed,
I just opened up my new imac 3.4 GHz Intel Core i7, last night, booted it up and moved all my stuff over from my 2008 Mac Mini.
Alas, I am experiencing EXACTLY the same fluttering sound you posted in your recording. I am using the Brick v2 as well. It has worked perfectly in my mac mini for 3 years. NEver heard anything like this. Everything else is equal, except the new mac hardware, so this is a second data point to indicate a driver, or driver support, issue. I'll be dropping Gordon a note.