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Post by teseract on Nov 24, 2012 20:04:05 GMT -5
Yes, it's the amp itself buzzing, not the speakers. To the point you can feel it resonate in the chassis slightly. It's kind of like a fluorescent light with a noisy ballast, but a deeper tone, or like there's a ticked off bumble bee stuck inside. If it's an issue with the amp it would be my luck. I have awful luck with home theater components. I don't have a sub either, I haven't had the money to buy anything big enough to not be drowned out by my Polk RTI12's. The electrical in this rental house is pretty bad, though. The original fuse panel looks to have been replaced in the 90's. They added a few grounded outlets downstairs, but patched in the old electrical too including a bunch of ungrounded outlets upstairs. The lights and old outlets aren't even wired using romex, they're just wired with what appears to be red and green (??) bulk wire, like someone got cheap back in the 50's. I'm scared to even plug a vacuum into them.  |
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Post by Deleted on Nov 24, 2012 20:37:30 GMT -5
> Yes, it's the amp itself buzzing, not the speakers. To the point you can feel it resonate in the chassis slightly.
It doesn't sound like anything is broken, just loose. Take the lid off (it could even be a loose lid) and listen carefully inside it. You can use something insulated, like a wooden chopstick, to gently probe and feel for buzzes.
You'll probably find a loose screw or bolt allowing a piece of metal to vibrate. Tighten it. Don't touch anything electrical. Unplug it and wait 10 minutes for all the charges to die before you work on it, unless you know what you're doing (obviously you can't search for buzzes with the power off).
Happy hunting,
/b
/b
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Post by doc1963 on Nov 24, 2012 20:55:37 GMT -5
At the sake of sounding like an ass, how would something loose in his amp only be revealed when the toaster is running? My God, that must be one hell of a toaster if it can vibrate your amp...!
Unless you know exactly what you are doing, NEVER put your hands inside of an amp.
From the description of your electrical system, the first call that I would make is to a certified electrician. It sounds to me like you are experiencing some serious voltage sag when your toaster is operating. A transformer will hum if inappropriate voltage is supplied to it.
You also may have some DC leakage on your line as well. Try a CMX-2. Return it if it doesn't work, but I seriously consider a dedicated line.
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Post by Deleted on Nov 24, 2012 21:58:55 GMT -5
> At the sake of sounding like an ass, how would something loose in his amp only be revealed when the toaster is running? My God, that must be one hell of a toaster if it can vibrate your amp...!
I doubt that God or the toaster has anything to do with it.
It's most likely a loose piece of metal vibrating under the influence of the xpa-3's transformer.
I suppose if the toaster really dragged the voltage way down it could effect the amplifier. But the original poster reported that it was on a different circuit; he didn't report the lights dimming.
Sincerely
/b
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Post by doc1963 on Nov 24, 2012 22:51:12 GMT -5
No disrespect intended, but a logical conclusion would be that if the amp's transformer makes no noise at all if the OP's toaster is NOT operating, then the amp is NOT at fault.
There is no way that I would advise anyone to poke around inside of an amplifier with, or even without, power applied to it. There are potentially LETHAL voltages inside. There are very specific warnings both in the manual and printed directly on the amp itself. They are there for a very good reason.... Protecting ourselves from our own stupidity.
Given the OP's description of his electrical source and wiring (and given the fact that it's a rental property) how can one be sure that the circuits are, in fact, isolated, properly grounded and/or operating at the correct amperage and voltages ? I would be willing to bet they are not.
My hunch still sides with either under-voltage at the amp or, most likely, DC offset in the line. Any appliance containing heating elements can cause distortion in an AC line.
Again, a CMX-2 can cure that.....
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Post by Deleted on Nov 24, 2012 23:25:06 GMT -5
> My hunch still sides with either under-voltage at the amp... <snip> ...Again, a CMX-2 can cure that...
Undervoltage could be the problem; but a CMX-2 doesn't regulate voltage.
It's a very simple matter for the OP to retry the toaster experiance (as I already have suggested) to see if the toaster is the cause or a coincidence.
Sincerely
/b
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Post by doc1963 on Nov 25, 2012 0:00:46 GMT -5
> My hunch still sides with either under-voltage at the amp... <snip> ...Again, a CMX-2 can cure that... Undervoltage could be the problem; but a CMX-2 doesn't regulate voltage. It's a very simple matter for the OP to retry the toaster experiance (as I already have suggested) to see if the toaster is the cause or a coincidence. Sincerely /b You're correct. The CMX-2 cannot correct under-voltage, no device can, but it CAN correct DC offset which happens to be the number one cause of hum in a toroidal transformer. That's exactly what the CMX-2 is designed to do. Since the OP's hum seems to be triggered by a toaster (which contains heating elements, also a major contributor of distortion, or DC offset, in an AC line), DC line pollution would be my first logical choice as the source of the OP's problem. Other electrical issues not withstanding, a CMX-2 is an inexpensive "first stab" at finding a cure. No need to go around ones a$$ to arrive at the elbow. If it doesn't work, either send it back, or keep it for its excellent additional line filtering properties. |
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Post by Deleted on Nov 25, 2012 1:27:17 GMT -5
Boy, you're really stuck on this. The CMX-2 cannot fix undervoltage or ground problems; it's a noise filter. It can fix DC offset, though I don't know how a resistive load toaster would cause a DC offset; not even a defective toaster.
I still suggest the "first stab" would be simply to try turning the toaster on again and see if it really is the cause, and not coincidental. That takes seconds and costs nothing.
Of course, from our armchairs we can only guess; it will be interesting to see what he finds.
Sincerely
/b
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Post by doc1963 on Nov 25, 2012 2:48:19 GMT -5
Boy, you're really stuck on this. The CMX-2 cannot fix undervoltage or ground problems; it's a noise filter. It can fix DC offset, though I don't know how a resistive load toaster would cause a DC offset; not even a defective toaster. I still suggest the "first stab" would be simply to try turning the toaster on again and see if it really is the cause, and not coincidental. That takes seconds and costs nothing. Of course, from our armchairs we can only guess; it will be interesting to see what he finds. Sincerely /b No, I'm not stuck at all. The OP has already verified that the hum is only present when the toaster is on. How many times does he need to do that.....  I have already stated that the CMX-2 cannot correct under-voltage. Nothing can. However, you might want to read up on what the CMX-2 is, what it does, and how it differs from the CMX-6. By the way, both the CMX-2 and the CMX-6 absolutely CAN correct grounding issues. Neither are simple, garden variety, noise filters. A resistive load has nothing to do with noise inductance and DC contamination of an AC line. Resistive loads cause voltage sag, that's about it. Toroidal transformers absolutely hate DC line contamination which is the leading cause of "hum" outside of a defect. A defective transformer will hum constantly while subjected to power. The causes of DC offset in an electrical circuit are many and difficult to explain, but any device with constantly cycling heating elements such as clothes dryers, baseboard heaters, portable heaters and, yes, toasters can easily change the frequency of an AC line therefore introducing DC offset noise which a toroidal transformer cannot pass. I've offered all that I can in this matter and it's up to the OP to consider the suggestions that have been offered and choose his battle wisely. Good luck..... |
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Post by teseract on Nov 25, 2012 6:53:48 GMT -5
My, what a vigorous debate. I had to move the toaster to free up table space for a late Thanksgiving dinner, so I plugged it into the outlet that I have a mini-fridge running off on a different circuit. Turning the toaster on produced no buzz. So I plugged it back into the same oulet... no buzz. So it was either a weird coincidence that I heard the toaster pop and the buzz stopped instantly, or there was a secondary load on the line (the refrigerator I think is on the same circuit) that with the toaster caused a voltage dip (odd since the portable dishwasher was plugged in across the kitchen and running when I tried it the second time, but it's on a GFI protected circuit). Or it could just be that the outlet the toaster is plugged into is old and worn out and hardly holds a plug in anymore, and it didn't have a solid connection on one of the plug terminals causing some odd feedback in the circuit. Either way, I'm pretty sure it's simply the crappy electrical in this house, but I have no way to change it unless I want to talk my landlord into doing something... which has about as much chance of happening as the gas company giving me free heat all winter. |
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Post by Dr. Feel Good on Nov 25, 2012 9:50:14 GMT -5
I've had similar issue called my electreatian over asked for the least expensive fix he suggested this: " .......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.".... works like a charm  ' |
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Post by Deleted on Nov 25, 2012 9:55:31 GMT -5
> My, what a vigorous debate.
It's refreshing to be able to explore a subject vigorously, without it turning nasty. I changed my mind twice; first to reject a ground loop; second to accept the ~possibility~ of dc offset. For me it was especially valuable to learn about "dc offset", I'm grateful to Doc1963 for making me aware of it.
It sounds like there is nothing wrong with your amplifier; just something weird that happened. It doesn't help that the home wiring is so poor; and likely won't get fixed. Get a friend who understands electricity to replace that faulty kitchen wall plug.
Having a CMX-2 probably wouldn't fix this problem; but it might. The CMX-2/6 cannot fix a bad ground, if the ground wire in the home wiring is defective; it can't make something from nothing. The CMX-6 doesn't provide dc offset correction. And the CMX-2 is available now, at a deep discounted price!
Let us know if the buzz comes back to haunt you.
Sincerely
/b
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DYohn
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Post by DYohn on Nov 25, 2012 11:35:42 GMT -5
Ah. Yes, if the buzz is coming from the amp itself it is likely DC offset. You can try a DC blocker like the CMX device. Some amps benefit from having the mounting bolt in the center of the power supply toroid transformer tightened as well. Also, never open an amplifier or any other piece of electronic gear when it is plugged into the wall unless you are trained and know what you are doing.
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Post by The Mad Norseman on Nov 25, 2012 21:17:45 GMT -5
I've had similar issue called my electreatian over asked for the least expensive fix he suggested this: " .......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.".... works like a charm ' Is there any reason that Dr. Feel Good's idea wouldn't work on the XPA-3? I mean, treat the XPA-3 as if it were a receiver - and run an insulated copper ground wire from a screw on its chassis to a ground screw on the surge protector and see if that does the trick? (I think that's what the good Doc's been suggesting,...no?). |
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Post by geebo on Nov 26, 2012 8:33:59 GMT -5
If they're humming in harmony and are in synch everything is fine. They're just enjoying themselves.
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Post by richardrc on Nov 27, 2012 4:33:43 GMT -5
Toroidal spiral laminates and windings can and do hum. This is made worse depending on the saturation of the core, ie under voltage causing more current draw, or overvoltage pushing the core into saturation. As has been mentioned DC offset will also cause transformer hum. I am keenly waiting for the 240vac cmx-2.
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