Anyone up for helping me troubleshoot some speaker hum?

[Chapbass]

Hey guys,

Heres my dilemma: my speakers have a very audible humming/buzzing that have been coming from them ever since I moved into my current house. I've tried some basic things on trying to figure out where its coming from, but so far no luck. Could use some suggestions.

First, heres my setup:

at the front of the room i have my AV gear:
Pioneer Elite VSX-91TXH receiver
PS3 Slim
Tivo HD (plugged into Antenna only, no cable from the wall)
HTPC

All of those are plugged into a UPS, cyberpower something, can't remember the model.

The receiver is in a 7.1 configuration, with the sub at the back left of the room (for reasons outside of this discussion ). The sub is plugged right into the wall, and the other outlet there has a power strip with my cable modem and router there.

At the back of the room is my Panasonic PT-AR100U projector.

Now, obviously the subwoofer and projector are placed on different outlets from the front of the room (and the sub/projector are not on the same outlet either).

I've noticed that the humming is worse on the PS3 than on the HTPC. What I've tried so far:

Powering off everything, running the ps3 and receiver into the wall directly, no dice.
Powering off and unplugging the subwoofer, nope (though that was a while ago, I may try again to make sure that I did it...)

I also want to try plugging in the projector to the front of the room for testing, though I'm not sure what that would tell me...

I've done some googling, and some people over on [H] mentioned maybe getting an isolation transformer like http://www.amazon.com/Tripp-Lite-IS2...g=hardfocom-20 That one, but I'm not sure if that would do anything for me.

Anyone have any thoughts on this?

 

[Howard]

With only the receiver plugged in, the speakers still hum?

Trip the breaker and see if maybe there are other outlets on that circuit that you don't know about. Make sure everything on the circuit is disconnected except the receiver when you try it.

 

[kornphlake]

I'd start by disconnecting everything but the front speakers and try listening to 2 channel stereo from the receiver's FM tuner. If there's hum it's likely the receiver and you probably won't be able to make it go away. If there's no hum start adding speakers first then components. Be certain analog interconnect cables are installed correctly and in good condition, it won't hurt to keep them away from the power cords as well as they can pick up noise from AC power cords. If you're getting hum from a digital source you've got a problem in the source or in the receiver that probably isn't cost effective to repair. It might be worth trying a battery powered source like an mp3 player as well, it will eliminate the possibility of ground issues.

 

[Chapbass]

Welllllll I plugged in just the two fronts, set it to the XM radio setting (I don't have XM), and still got a lot of hum. I think I might go to BBY and grab a receiver and see if it still makes the noise. If so, I remembered that I have a warranty on this guy until the end of October, so I might send it in and see what they can do with it.

 

[Railgun]

What changed? The house. How good is the house's ground?

 

[ericlp]

#1 problem is electrical.

go down to home depot and get a plugin circuit tester it has three lights that tell you about reverse polarity or open ground. Or you could have a bad breaker that is getting old and needs to be changed out for a new one.



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[Chapbass]

Well, heres an update:

I noticed that on my UPS if I have it plugged into any of the outlets in my living room then the "wiring fault" light is on...plug it into the kitchen and the light is off.

THAT SAID: Went to BBY today and bought an open box receiver to do some testing...Sure enough, the new receiver is whisper quiet, not the tiniest bit of hum, and just a faint hiss when its cranked to +15db (which is to be expected), and by faint i mean barely hear it with nothing coming through it from about 8 inches away.

So that said, I think I'm going to send my receiver in and see what they can do with it. Any thoughts on the wiring fault thing? I don't own the place, I'm renting it, but I don't know what my landlord would say if I asked him to send an electrician out or anything. Or since the new receiver isn't making any noise, just don't worry about it?

 

[kornphlake]

It's not uncommon for older homes to have the neutral and ground prongs wired together at some point in the circuit. It's acceptable to retrofit older installations with a GFIC outlet to protect from shock hazard (at least that was the case 5 years ago when I bought my home, I'm no electrician so don't take my word for it,) but this doesn't give a true ground for audio equipment, although most AV equipment has a 2 prong plug not a 3 prong plug so it's often a moot point.

From the troubleshooting you've done so far, I'm leaning toward the conclusion that the receiver is bad and trying to correct the house wiring isn't going to make any difference.

 

[Howard]

It's not uncommon for older homes to have the neutral and ground prongs wired together at some point in the circuit.

Damn near every installation has neutral bonded to ground at some point in the "circuit".

 

[kornphlake]

Damn near every installation has neutral bonded to ground at some point in the "circuit".

It's not uncommon for older installations to bond the neutral to the ground at some point other than the main breaker panel.

 

[Modelworks]

It's not uncommon for older installations to bond the neutral to the ground at some point other than the main breaker panel.

A lot of the older homes , it was common to see a jumper wire going from neutral to ground on single receptacles. Technically that was allowed for just a few years of the code but then replaced entirely. It is also why you still see some plugs with a wide prong on one side, just in case they are tying that to a ground point. A good example of that is electric clothes dryers. For decades clothes dryers only required 3 wires, two hot and a neutral. The neutral was tied to the frame of the appliance through a metal strap and that was considered the grounding . Now the code required 4 wires, the previous 3 and and extra wire just for ground.

Technically it is safe for a neutral to be a ground as long as everything is connected properly and nothing breaks, however, if the neutral connection were to become loose or disconnect from the service panel then you have everything that uses the neutral for ground becoming hot.

 

[FiLeZz]

Please dont think I am crazy just do it and the hum will go away.

Wire the chassis of the Pioneer to the other audio/video chassis.

I used cat 5 cable.

 

[Chapbass]

Please dont think I am crazy just do it and the hum will go away.

Wire the chassis of the Pioneer to the other audio/video chassis.

I used cat 5 cable.

Hmmm, I tried this last night, but only used some speaker wire, didn't work but i could be doing it wrong. I'm guessing this is because you're thinking the ground might be bad?

I actually had a similar thought. I took my receiver in, but unfortunately I remembered that I bought this in 2007, not 2008...so its out of warranty (holy crap its been 5 years already? lame).

That said, I cracked it open and its much more complex than I was thinking. Staring at it didn't help one bit, and I don't even know where to begin looking for things. I don't have it with me right now so I can't take any pictures or anything.


Also, anyone have any idea if that buzzing might be only on a certain stage of the receiver? As in: If I were to buy a 5 channel power amp (say, the Emotiva UPA-500), and just use the pre-amp section of the Pioneer...you think the buzzing might go away? I'm trying to come up with a way to test this idea without buying the emotiva...but I don't think I can use JUST the power amp section of another receiver..to my knowledge they don't have inputs for that, just outputs.

Any thoughts anyone?