I used a largish (10kVA) balance power isolation transformer with my active DBL system...not only was ALL transformer noise banished (6 power amps, one preamp supply, one Snaxo supply, one CD power supply, one tuner power supply, one Prefix supply and one Armageddon) , but the system sounded very much the better too. A greater than component-level upgrade for less than component level pricing (well, it was $2500 back around 2004...its around $8k now). BUT it is not a plug in option- two ground spikes have to be undertaken and it needs to be professionally wired in to a 50A double voltage feed. But then again, I've seen people who spend longer rebuilding a Fraim than it took for two electricians to have this 200-lb box plumbed in.
This particular transformer was made by EquiTech-who mainly do pro-studio transformers. BTW I had sockets that also had non-balanced power, so it was trivial to swap back and forth. The improvements were immediately obvious to even a casual listener. There are a few threads about our collective experiences here-the first person to use one with a Naim system also pioneered the first XPS2T.
