HUM when I switch on components-

Ever since I switched over from my older integrated amp (marantz 2325) to newer, high end separates, I have an annoying audible "hum" coming from my system---of course my first thought is that something is not properly grounded (house electrical system)--, or possibly one of the components is culprit? or? I am sure many of you have been through this in the past--was hoping you might be able to help me to "trouble shoot" and figure out how best to address this problem--house is old--but all electric was redone with modern wiring etc---do not have details on fuse box in basement, etc. thanks---
Do you mean the hum is coming from the components or from the speakers? If it is from the components just unplug each one at a time and see if it goes away,if it does then you will know which one is the trouble.
You could have a feedback issue from your main panel. Turn the breaker off that is above and below the one you are using for your system. If this stops the hum then turn one of the breakers back on and check again. If the hum comes back then find what the breaker is supporting and work from there.
I am no pro at this by any means but I have experienced these issues before. I have also run into reverse polarity issues.
disconnect each component separately and ascertain if the hum still exists to determine which unit is causing what is most likely a "ground loop"---or use a cheater plug on each unit and see if it takes away the ground loop--but cheater plugs as a permanent solution is never a good idea since it floats away the ground. Sometimes using shielded interconnects or balanced ones can help as well.Theres alot written on solving ground loops on the internet---