new to this,need help

i have a parasound preamp,proton tuner,cd and proton amp stacked on top of each other in that order. (preamp on bottom) all new. the first problem i had was a very low hum in the system. i tried another outlet and this went away. now for the second problem, i first turn on the preamp, then the amp.no problems or sounds. when i then turn on the tuner, even though i have cd selected on the preamp, i can hear very faint radio signals coming through the speakers. what's going on? i also get a very low hum when i turn on the cd, but i assume this is because i have a cheap cd, am i on the right track. also could someone suggest an acceptable cd player. thanks very much.