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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
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!
lornecherry
135 posts
 
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
ktsteamer
7 posts
 
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.
haoleb
82 posts
 
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.
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