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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.

Thanks,
Matt.
matt8268
rcprince
3,070 posts
 
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.
ljgj
955 posts
 
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?
kublakhan
717 posts
 
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!?
audiopath
92 posts
 
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.
inscrutable
313 posts
 
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!
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