What is causing my speaker hum?

My speakers, Joseph Audio RM22si's, hum (unwanted noise) when the receiver is on. It was the same with my old Infinity speakers. It's there when the receiver (Denon 70Watt x 5 channel receiver) is on, but it's much louder when I'm playing a CD and then pause the CD (using a Toshiba DV333 DVD/CD player). I am using the digital out from the player into the receiver (and therefore using the D/A built into the receiver).

Is this just bad amplification? Could it possibly be bad grounding, and if so is that something I can fix? I don't think it's the CD player, because I'm using the digital out, and when that is paused there should be zero signal sent, yes?

One other very weird side note. Usually it is just white/pink style noise, but one time I heard a song playing. I'm not schizophrenic, there was actually a song playing silently in the noise, different from the one on my CD. Could that be the receiver's tuner leaking out or something coming through the power lines?

One thing I'm trying to figure out is if I buy an amplifier and plug the receiver into that, if my problems will go away, or if you guys think the problem is upstream from the amp.

If the hum is monophonic it's probably from power line. You need to use power conditioner. Try to unplug CD player and bring the volume up. If no hum or just a-little than CD-player is the guilty one. A lot of CD players have digital out but they cannot be dedicated transports for using them with DAC meaning that digital "trash" is corrected inside the CD-player. So first, try to use analogue outs, then again: digital sources are the most volatile devices to malfunctioned or "dirty" power lines and need a power conditioner even more than any amplification ones.
The hum could be a ground loop between your source and receiver; if either has a three-pronged plug try cheater plugs on all of the cords to start. There are other possibilities, but I'll leave those to other posters. As far as the song, it could be cross-talk from the tuner portion of the receiver (can you turn off the tuner function?) or else you're getting rfi through your cables, power line or equipment. I once auditioned an expensive amp which gave me a broadcast of a Rutgers University basketball game through the right channel while I was listening to other sources, and the fault was that the amp was picking up and amplifying rfi signals in my listening room. Too bad, it was otherwise a great-sounding amp (but a bad game!). You might try ferrite clamps on your interconnects or speaker cables; I'm sure others will have possible solutions as well.
If it is by a cable tv cable it could be that. Also the digital cable from the CD player to the receiver could be the problem. Does it hum when you have the rca cables from the CD to the receiver plugged in instead of the digital?
It doesn't know the words?
AAAAhhhhhhhhh. i'm not back - i just couldn't help that one and i'm wired on 2 triple espressos.
while i'm here though...WHAT'S AAAAAAAAP, fREaKS!?
I suspect that it is a ground loop caused by your cable television. If your Denon receiver is connected to a VCR or TV, then it is usually the cause of the hum. To find out for sure, disconnect and unplug everything from your receiver...all inputs and outputs including speaker wires. Start by connecting the speaker wires to the outputs of the receiver and turn it on. Does it hum? If so, then it is a problem with the receiver. If not turn it off and connect one item and listen for the hum. Repeat until you hear the hum return. It will take a while, but you should find it.
Yes the most likely cause is the cable tv. you can correct this with 75 > 300 > 75 ohm adaptors. if it is ground loop in the ac, i would hesitate to go to cheater plugs, which floats (eliminates) the grounding of your equipment - this is not safe. try reading the article on ground loop hum on the smr forums. or search any number of boards for such a thread - there have been many. good luck!
damm Kublah ... that was actually quite funny. Seriously, I suspect cable TV, ground loop, or power cords too close to interconnects or speaker wire. You might also have one bad interconnect (that cross talk you complianed about). And it may not be just one of these, rather a combination of all/some of the above(that was case with me). Well, at least you don't have tube noise to worry about!

I like Inscrutable's suggetions for you, as I doubt you're about to invest in a $1200 PS 300 power conditioner a this point. But $75 -$100 for a dedicated power outlet would be a nice start along with what Inscrutable has suggested. --Lorne
It might be the lighting in your home. If the outlet you are using for your gear is on the same fuse as a track lighting switch, then that might be it. the transformer box for your track lights might be dishing out RF interference. Also, if there is a dimmer switch located on the same line as your audio electrical outlet, that has a good chance of producing hum and buzz as well. Other culprits might be a ceiling fan, or anything else that's on a dimmer switch. The other posts saying it might be the cable TV wire and too many 3-prong cords making a ground loop are 2 of the top reasons for hum and buzz. Also keep in mind that even if you eliminate all the 3 prong cords, you might still get buzz if any of your gear is touching metal - like a tray or the metal cabinet spines. If all else fails, I guess try balanced interconnects.
OK, if you try to do something like the guy said with the cheater plug DONT, those 3 way plus have the grounding pin for a reason, and failure to crrectly plug them in can result in fatal injury to you and/or your equipment. Lethal voltages can build up if that is cut off or bypassed and can be transfered to you!. It may be a cheap/quick fix but i have to say DONT DO IT!!!!!!!!!!!!!!!!!!!
Also if there is a dimmer switch for the lights like others said that could be it too.
With the cheater plug thing - what the previous post said is correct - it is very dangerous if all your gear has cheater plugs on it. Just make sure one component doesn't have the cheater, and it's 3 prong is going straight into the wall. That way, the ground circuit is only on one piece of equipment, with all the others attached to it automatically (via the rca connects).