my speakers hum

I agree Bill above--you probably some type of ground loop and your current (no pun intended) speakers may be more sensitive and letting you hear the resultant hum.  Does the hum level stay constant with volume or does it increase with volume?  Have you tried various grounding schemes like trying ground wires between equipment and grounding to a common point like a screw on an AC outlet?

i have tried different outlets. i have not grounded to a specific point. i don't know about sensitivity between the pairs. the hum is only heard when nothing is playing.

Temporary float the ground on your amp PC with a cheater plug. If the hum goes away it's a ground loop. It could just be your cables too. If your IC's are unshielded and you've been moving gear around, unplugging cables, you might just be picking up noise. Pull out your cables and reconnect everything and keep cables clear from each other as best as possible. Keep your PC's clear from your SC's as well.

Is it possible that these speakers have been wired accidentally in reverse polarity? And I mean, internally or externally by yourself? Try flipping the Positive/Negative Poles around on the speaker cables.

Another option you can play with would be to try varing the speaker cable length between the Amp and Speaker and see if the noise goes away.