Hmmm... as soon as I posted the message, the hum went away. May be I should complain more often :)
Some equipments do like grounding, even more so than just with 3 prongs AC cord. My Lamm pre/power/phono has extra ground posts on the chassis and I found that background noise is reduced quite a bit more by connecting those ground post to my isolation transformer as well.
Some equipments do like grounding, even more so than just with 3 prongs AC cord. My Lamm pre/power/phono has extra ground posts on the chassis and I found that background noise is reduced quite a bit more by connecting those ground post to my isolation transformer as well.