McIntosh MC 2106: HUM!!!

Hi Moose - looks like you answered your own question.  One of the (however many) components you disconnected/connected is either not connected properly,  is using a cable that has issues, or is plugged into a different AC circuit than it was in previously.  Start with the basics- amplifier and speakers with nothing else connected.  If no hum, then connect the pre/pro. - If humming- there is your problem.  If not, then connect first source and keep repeating until you find the culprit.   Good Luck!

Hi Guys.  It's great that lifting the ground stopped the hum, but you have not fixed the cause of the hum.  Using a cheater plug is a temporary measure - the ground is there for your safety!  FIX the cause of the ground loop and lose the cheater plugs.