I am using a 12VAC 10A transformer (from my junk box) in lieu of the 640P wall wart. It sounds better. I am also generating a nice clean 240VAC signal to power the transformer and my preamp by using a pure sine wave inverter running off a 12V 100AH car battery. Now I have a clean mains sine wave instead of the distorted wave from my houshold mains supply. It too is adding to my listening pleasure. Just remember to keep the battery charged. I have a theory that using this setup as much as anything, I am eliminating the mains earth connection especially in the preamp which feeds my monoblocks. Maybe not sharing the mains ground with the outers on my interconnects is making things generally cleaner, but that's just a theory of mine FWIW.
Cambridge 640P Power Supply Upgrade
So I bought a Pangea P100 for my DACMagic (made it better)and figured, hey, one "wall wart" down, lets see if my 640P can use some improvement. So I ordered another Pangea (the name sounds like a holistic skin treatment, which I think there actually is). After a couple of days of use the Pangea PS seems to kick the 640P up to another level altogether...I now can highly recommend this cheap tweek. Interestingly (to me anyway), the stock 640P "wart" PS ran kinda warm and the P100 doesn't. I think that means something, doesn't it?