I built my rack (2xN72's, 4xA12's and 2xJ99's) in the fall of 97. I had a heck of a time reducing hum and finally got it down to an acceptable level.
You must mean the fall of 2007?
Now I see a new PSU has been released to supposedly fix some of those issues. I am also going to be moving to Europe and I'm not sure if PS02 works with 220V or not.
You probably have a PS03, not a PS02. Does it have 3 status LEDs along the top of the board? If so, it's a PS03 and will work with 220V with no modification required. Just plug it in to a 220V outlet and it will work.
Is it possible to trade in the PS02 for a PS03?
Yes. E-mail
sales@seventhcircleaudio.com for details.
Would the PS03 solve the humming issues?
If you have a PS02 and
if the +30v output is sagging under load,
then a PS03 will make a difference. If the hum is loud in the N72s but not in the A12s then swapping the supply may fix it, but I suspect any problems you're having are due to some other cause.