Another Hum Problem Question

My Bel Canto EVo digital amp is supposed to stay on all the time. Thursday I got new balanced cables. I also got a new pre this week. If nothing is connected to my amp, it's quiet when every thing else is cut off. If I connect the balanced ICs I get a low volume hum through the speakers. You can hear it at one foot from them. If I connect the other end of the ICs to the pre, I still have the hum. If I then cut the pre on, every thing is dead quiet.
I have tried disconnecting all components to see if one is causing the hum.Nope. I tried a cheater plug on the pre. Nope.
Do I have a bad set of ICs? Bad preamp ground when it's cut off? Help--sorta since it's only anoying since it wasn't there before and goes away when using system.
claud