I have the 5.6, which I presume has some similarities with the 4.6. Nice build and good quality components throughout, so if the 4.6 has been properly used there's nothing to worry about. I partly agree with Eldartford: phonostage is good, and IMHO the MC part isn't half bad. Although the phonostage in my Aragon pre is better since you can adjust the load. I'd guess it'll be an obvious improvement on your Cambridge.
Any issues with a "mint" PS Audio 4.6 pre?
I've just bought one of these at auction (it is yet to get from the US to Astralia. What are the likely issues I may need to deal with regarding this unit? It has been bought as a phono stage. Is it likely to be better than my Cambridge Azur 640P dedicated phono preamp?