Well, I disconnected everything from Every AB/AG terminal on the KSU. I don't have a butt set, so I hooked a 2500 between AB and AG..... and got ...buzz.
So, I guess it is the power supply. But I almost think this is a result of the design of this KSU, as it doesn't have seperate filtered/and unfilterd (AB and BB) supplies. When I had my old intercom card in, there was no hum on the T&R terminals, so it's like they built some sort of filtering into the intercom card itself, since the KSU didn't provide it. Then again, I thought AB & AG were supposed to be the filtered ones... so I'm lost again.
