So here is a cautionary note about the 661 and heat, it seems that the unit might be fairly sensitive to heat.
My story is that last year I recorded a lot of nature sounds in the Gobi and as a result a hiss developed in one of the channels (this is a Oade Supermod by the way). There were a bunch of shows I wanted to record so I didn't send it off right away and the hiss was low enough that for loud things it wasn't a problem for me, but was obvious on quiet sounds. Finally I sent it back to Oade to get fixed. He suspected that it was one of the modified parts, but that turned out to not be the case, it was in fact on the main PCB. After a long wait I got the unit back in good working order until a couple of weeks ago when working in Seattle in 90 degree heat, the hiss returned. The first time this happened, mine was the only unit Oade was aware of with this problem, but now someone else who records in the desert is having the same issue. A few days ago I took my unit to record in the desert (mid 80's temp, hey, it's already noisy now, might as well, right?), and the hiss is now a ugly hum. I know heat is bad for electronics, but considering I was using it within the stated operational temps (104 degrees), it was a bit of a surprise.
Doug is currently working Marantz to see what the deal is. Luckily summer seems to be winding down, but if you are in a hot environment you might want to be careful.