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Post by teseract on Nov 24, 2012 0:08:14 GMT -5
Apologies if this has been answered before. I tried the search function but "hum" gets removed from the search as it's only 3 letters long (  ). I walked into my TV room this evening and heard a loud humming, not unlike a fan going bad. At first I thought it was my TV, then I realized it was coming directly from my XPA-3. I started unplugging speaker cables one by one, etc. to see if I could eliminate it. Then my toaster popped up the buns I was toasting and the hum vanished. Is this anything I need to worry about? The toaster is on the other side of the house (literally as far away as two objects could be and not be outside) on a different circuit... could a transformer or something in the XPA-3 be "humming in synch" with my toaster? It's odd since it doesn't do it with the microwave or the toaster oven... just my 4 slice KitchenAid toaster. Thanks, M.B. |
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Post by wcparks on Nov 24, 2012 0:22:39 GMT -5
May want to try a cmx-2
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Post by knucklehead on Nov 24, 2012 0:40:43 GMT -5
Or try making toast when the XPA-3 is not on.
Sounds like a ground problem. Doesn't matter how far one plugin is from another they are all connected in one manner or the other. Doesn't sound like a lot to worry about unless you start getting other things that induce noise in the XPA-3. You are blaming the XPA-3 when it is quite possible that the apparatus generating the interference could be your preamp or CD player - TV box - whatever source was on at the time. You'll never know until you do some investigating. Could be a bad RCA cord.
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Post by teseract on Nov 24, 2012 0:54:11 GMT -5
Oh, I'm not blaming the XPA-3. I was just wondering what the heck was going on. I'd bet on a $45 toaster being bad before a several hundred dollar piece of electrical equipment.  I guess I'll just turn off the XPA-3 when I make toast, unless I decide to try a CMX-2. |
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cawgijoe
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Post by cawgijoe on Nov 24, 2012 9:03:14 GMT -5
Humming or ground loops can be a real hassle. I had a problem with a low level hiss coming from my speakers a year or so ago. It took me a day or so to isolate it. Turned out to be my receiver. I've got a friend who is a EE and he suggested grounding the receiver to my Surge protector with a plastic coated copper ground wire. I used a screw on the receiver and connected that to the surge protector.....another screw there......problem solved....silence.
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selkec
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Post by selkec on Nov 24, 2012 9:36:40 GMT -5
Oh, I'm not blaming the XPA-3. I was just wondering what the heck was going on. I'd bet on a $45 toaster being bad before a several hundred dollar piece of electrical equipment. I guess I'll just turn off the XPA-3 when I make toast, unless I decide to try a CMX-2. unplug everything from the xpa3 leave nothing connected but power of course. Then make toast and see. If you hear nothing. Its coming from another component. And like the other post said try the cmx2 or a power conditioner if you have one on hand. It will not make the xpa3 sound anydifferent unlike some on here will tell ya. I know because I listen louder than any member on this forum. My xpa5 into my belkin never has any issues |
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Post by solarrdadd on Nov 24, 2012 10:16:46 GMT -5
if you own your home (not renting) and if you can either do it yourself (only if you know how) or pay to have a licensed electrician do it, i recommend running a new dedicated 20a circuit to your gear. this will remove any other electrical loads from the same circuit as your gear. you will get the best quality of power from the utility and you will also have plenty of future growth power wise. you will also be able to make those cute little toaster pastries (that we suspect your really doing) as well as listen to your music at the same time.
best of luck, please keep us posted as this saga unfolds!
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Post by The Mad Norseman on Nov 24, 2012 11:41:36 GMT -5
Humming or ground loops can be a real hassle. I had a problem with a low level hiss coming from my speakers a year or so ago. It took me a day or so to isolate it. Turned out to be my receiver. I've got a friend who is a EE and he suggested grounding the receiver to my Surge protector with a plastic coated copper ground wire. I used a screw on the receiver and connected that to the surge protector.....another screw there......problem solved....silence. cawgijoe - You left out an important bit of infomation that others would find very helpful, that is - on what part of your receiver did you attach the ground wire? (I'm not having this problem, but if I were I'd want to know...). |
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Post by sharkman on Nov 24, 2012 12:36:39 GMT -5
That is strange. A toaster is a pure resistive load, but a very watt hungry one. You would expect some other household items to create issues before a toaster or kettle, like a fridge, freezer, blender, etc.
Anyway, if the two circuits are on the same line feed coming into your panel(there are only 2) then the neutrals could be cumulative and maybe that's causing something. Try this, plug the toaster into another kitchen plug or two to see if the hum persists. The idea is to try to get the toaster onto the other line feed so that the neutrals subtract(since they would then be 180 degress out of phase).
Either way I wouldn't worry about this one other than to not make the toast while XPA is on, if moving the toaster plug around doesn't help. It may be hard on the power supply.
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Deleted
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Post by Deleted on Nov 24, 2012 12:36:46 GMT -5
This is always caused by a ground loop; you have two grounds in your ht system.
Probably the toaster is defective and leaking AC into the ground. But that shouldn't cause problems (other than electricuting you while making toast); ground circuits are always full of noise.
But you have two grounds in your system. The AC hum on one ground (which the toaster is plugged into) is travelling thru your HT system to reach the other ground (all signals are always are seeking ground), injecting hum.
Perhaps your subwoofer is plugged into the same circuit as the toaster? The hum then travels down the rca interconnect shield (ground) to your preamp ground. Ground loop. Just like cawgijoe's ground loop with his receiver, which he fixed by shorting out with a piece of wire, bonding the two grounds.
Fix is simple, get rid of the grond loop. All your equipment must plug into the same circuit, preferably the same powerbar; if the powerbar is surge protected, so much the better, though that will make no difference regarding ground loops. If you have CATV coax, its shield must be bonded to the same ground, also the ground wire on your turntable.
Cable boxes are a common source for noise. Cheap, the power cord plug is two pin: not grounded. Noise comes into the cable box via the shield ground of the CATV coax, and out the shield of the HDMI cable to your Pre/pro. Plugging the power cablebox powercord into the powerbar doesn't work; no third pin ground on it's plug. You have to ground the coax (which is why good HT surge protectors have connections for the coax.
It's that simple. No ground loops, there is no path for the noise to enter your system. $20 powerbar.
Sincerely
/b
p.s. Most people don't understand how surge protectors work. The think that they work by redirecting the billion volts of lighting into the ground. Now that is how a lightning arrestor works on an antenna tower, but not your stereo surge protector..
Equipment surge protectors work by eliminating the ground loop paths thru your equipment to ground. No path, no current flow and no damage. A boat can't fight a 100 foot wave; but easily floats over it. A bird isn't hurt when it lands on a 100,000 volt powerline because there is no path for the current to flow.
In the same way, your equipment simply floats over a 10,000 volt lightning pulse, because the surge protector has removed the paths thru your gear.
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DYohn
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Post by DYohn on Nov 24, 2012 12:38:22 GMT -5
Yes, it's a ground loop. You need to get the Emotiva toaster!! ;D
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cawgijoe
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Post by cawgijoe on Nov 24, 2012 13:01:46 GMT -5
Humming or ground loops can be a real hassle. I had a problem with a low level hiss coming from my speakers a year or so ago. It took me a day or so to isolate it. Turned out to be my receiver. I've got a friend who is a EE and he suggested grounding the receiver to my Surge protector with a plastic coated copper ground wire. I used a screw on the receiver and connected that to the surge protector.....another screw there......problem solved....silence. cawgijoe - You left out an important bit of infomation that others would find very helpful, that is - on what part of your receiver did you attach the ground wire? (I'm not having this problem, but if I were I'd want to knows...). I just loosened one of the chassis screws on the back of the receiver....near the bottom and attached the ground wire there. Tightened it up. |
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Deleted
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Post by Deleted on Nov 24, 2012 13:08:40 GMT -5
> This is always caused by a ground loop
Not always. Equipment with a faulty power supply (usually leaky filter capacitors) will also inject AC hum into the system. Not likely with newer equipment.
/b
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Post by sharkman on Nov 24, 2012 13:24:41 GMT -5
The thread starter has said that the hum was coming directly from the amp, not the speakers. Does a ground loop behave that way? I thought grounding issues would show up in the speakers.
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Deleted
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Post by Deleted on Nov 24, 2012 13:33:29 GMT -5
> The thread starter has said that the hum was coming directly from the amp, not the speakers. Does a ground loop behave that way? I thought grounding issues would show up in the speakers.
Good point. If the sound is coming from the amplifier itself, which lacks a speaker, it must be something mechanical in the amplifier: like bad fan, or loose buzzing transformer laminates.
I don't see how that would have anything to do with a toaster or ground loops. I presume the thread starter has repeated the incident by making more toast, to be sure it wasn't coincident.
/b
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Post by sharkman on Nov 24, 2012 14:05:24 GMT -5
Okay, what we have with the XPA-3 is a toroidal transformer, so no laminates. And it has no fans.
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twism
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Post by twism on Nov 24, 2012 15:38:46 GMT -5
This might be way off but is it dc offset? I had a hum from my amp on my subs when a kitchen light was on. I bought the cmx2 and it took care of the issue.
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Deleted
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Post by Deleted on Nov 24, 2012 17:50:00 GMT -5
If it is truly a mechanical hum from the amplifier, take the lid off the amp, make some toast, and look-see what is humming. when you locate the part, call Emotiva for help. The torroid will have a powerful magnetic flux, it could be as simple as a metal bracket not bolted tight, buzzing in the flux.
Sincerely
/b
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Post by AudioHTIT on Nov 24, 2012 18:42:31 GMT -5
"Buzzing in the flux" ... I like the sound of that.
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Deleted
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Post by Deleted on Nov 24, 2012 18:56:19 GMT -5
> "Buzzing in the flux" ... I like the sound of that.
Yeh, if the flux capacitor shifts out of phase, it could cause a spatial quantization shift in the time/space continum, resulting in interferance in nearby areas, like the kitchen. Do you notice temporal shifts in the toaster: is the toast always over or under done? ;-)
Sincerely
/b
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