I took care of my hum problem some time ago by putting all of my "wall-wart" power supplies on a dedicated power bar fed from a ground loop isolator (ie. an isolating transformer - or 1:1 AC transformer.) For a hundred bucks you can get one that will be rated high enough to feed lots of low-current components. (The transformer is heavy and runs "hot" all of the time so take care as to where you put it.)

If I did not have wall-warts, but still had a hum problem, I'd probably use the transformer to isolate the pre-amp - in your case the 950. After that I'd keep trying different compoents - and combinations thereof. (However you'd have to buy one heck of a big transformer to handle the needs of a power amp - not even sure if one's available for home use.)

Certainly won't hurt to try such a transformer - and most electrical supply stores will let you return the transformer if it does not do the trick.

Jeff Mackwood