Question about grounding?do i need one to stop hum

the area i live in is comprised mainly of older homes, many which only have the two prong outlets, i am currently using an integrated amp and cd player and a richard gray 400, when i plug the cd player in i get a large amount of hum compared to what i'm used to, i've tried experimenting with cord and cheater plugs (i always have to use these b/c of the outlets) and plugging one thing into the wall and the other into the gray unit and so forth. I rent so any rewiring work is out of the question. any advice, do i need to ground one component?, i'm just looking for any way to quiet the hum a little-thanks-mike