Really you need to extend your troubleshooting to figure out where the problem is.
Try hooking up PC to pa70g and see if you get the hum while watching movies to check out the audio out port on pa70g.
Try hooking up 360 or ps3 to pa70g and see if you get hum.
Unplug the audio speakers from audio out port on pa70g, do you hear hum.
With your blue ray player, if you listen to sound through the internal speakers of pa70g do you get hum if you turn the volume all the way up.
Check if you have any audio options on the blue ray player, maybe there is something you can adjust.
Replace the audio speakers you are using with pc speakers in your house or plug in headphones ijnto the pa70g and see if you get hum.
You see, I just gave you lots of things to trouble shoot, I do it all the time on stuff. It will narrow down for you where the problem is coming from, it could be blu ray player, the cables, the speakers, etc.
Let us know what the problem was when you find it, most times it's something simple, or bad cable that is not insulated right or one of the settings is not adjusted right.
Have fun with your pa70g, and you can always post these type questions in the pa70g thread, and more guys that own the pa70g can help you.