Where you plug it in

Nrchy was good enough (or so he thinks), to let me use his TT while he was moving to his new house. I have normally plugged the cord for the TT motor directly into a wall outlet as opposed to being plugged into my power conditioner. Nate was over to satisfy his musical needs and commented that the sound was much fuzzier from his TT than he remembered. We were examining the setup when he noticed where the power cord was plugged into. Changing the TT plug from the wall outlet to the power conditioner outlet dropped the noise threshold a noticable amount. Now if you have a TT where the only connection between the motor and the rest of the system is the drive belt, why would this change impact the sound in this manner? Has anyone else noticed this condition? I have not plugged the air pump for my ET-2 into the power conditioner but am tempted to, just to see if that changes anything. Could this just be a cheesehead thing?