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Post by drumace on Mar 27, 2018 7:05:54 GMT -5
Hi guys,
Yesterday I received a 3rd XPA-1L ordered on eBay to drive my center channel.
The good news is that it looks in a good shape, even the packages.
The bad news is that after hooking the amp to my center channel, I noticed that the amp is buzzing through my center channel speaker (can be easily heard).
It buzzes even when no audio cable is connected to it (only power cable and speaker cables).
I changed power cable, changed power socket and still, it buzzes the same. It gets even worse if I change it to class A.
I even disabled the ground on the power cable to eliminate the possibility of a ground loop and yet, the buzz remained the same.
I never had any buzzing in any of my power amps (and I have two other XPA-1L gen 2 and an Anthem amp in my audio system).
Please advise.
Thanks
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Post by kybourbon on Mar 27, 2018 8:03:22 GMT -5
Hi guys, Yesterday I received a 3rd XPA-1L ordered on eBay to drive my center channel. The good news is that it looks in a good shape, even the packages. The bad news is that after hooking the amp to my center channel, I noticed that the amp is buzzing through my center channel speaker (can be easily heard). It buzzes even when no audio cable is connected to it (only power cable and speaker cables). I changed power cable, changed power socket and still, it buzzes the same. It gets even worse if I change it to class A. I even disabled the ground on the power cable to eliminate the possibility of a ground loop and yet, the buzz remained the same. I never had any buzzing in any of my power amps (and I have two other XPA-1L gen 2 and an Anthem amp in my audio system). Please advise. Thanks I'd contact the seller and notify eBay immediately and ask for a refund/return. |
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Post by Gary Cook on Mar 27, 2018 14:43:10 GMT -5
Is it "buzzing" or "humming"? As they sound when you speak them, humming is a lower frequency than buzzing. Humming is generally an earthing issue so it may be as simple as the earth wire coming loose while shipping. Also, since you have tried a different power cable and speaker wiring, have you tried another speaker, just to be sure?
Cheers
Gary
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Post by leonski on Mar 27, 2018 19:27:15 GMT -5
Do you have a wall plug tester? Very low chance of Hot / Neutral reverse. Very low.
I wish I was there with my DVM. Are you anywhere in SoCal?
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Post by drumace on Mar 28, 2018 5:25:49 GMT -5
Hi guys,
Here's an update after having further tests-
I disconnected the center speaker from the XPA-1L and connected it back to my old Anthem power amp. The XPA-1L remained only plugged into the wall.
The center speaker sits on a shelf above the XPA-1L with about 4" clearance.
I wanted to see how the XPA-1L behaves without anything connected to it so I turned it on.
Surprisingly (or not), I heard the same buzzing through the center channel above it (once again, no cables running between these two).
I then raised the speaker channel and the buzzing sound from the center speaker went lower and lower until they disappeared when it was high enough.
Placing the center speaker back and the buzzing returned.
I then pulled the XPA-1L from its place, put it on the floor far from anything, plugged it to the wall and turn it on.
I could clearly hear the XPA-1L itself making a buzzing noise.
I listened to the two other XPA-1L I have when they are turned on and they were silent.
So, is it buzzing or humming, not so sure but the frequency is 50Hz as the wall power frequency in my country.
In any case, looks like the XPA-1L has some technical faults which needs to be fixed and the only way to do it is to use a local technician even though the XPA-1L is under a warranty because shipping it to the US will cost a lot (probably more than the fix itself.
Any comments to help me get through this awful situation?
Thanks
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Post by Gary Cook on Mar 28, 2018 6:32:17 GMT -5
50 hz is "humming", have you tried the power cable from one of your other XPA-1L's?
Cheers
Gary
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Post by drumace on Mar 28, 2018 6:34:27 GMT -5
50 hz is "humming", have you tried the power cable from one of your other XPA-1L's? Cheers Gary No but I tried couple of cables and wall sockets so my guess is that it is not the cable or the wall socket. |
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Post by Gary Cook on Mar 28, 2018 14:25:11 GMT -5
50 hz is "humming", have you tried the power cable from one of your other XPA-1L's? No but I tried couple of cables and wall sockets so my guess is that it is not the cable or the wall socket. Just eliminating the last piece from the puzzle of why 2 X XPA-1L's don't suffer from earth loop hum and 1 does. Assuming that, since you said you weren't in the US, the power point end plugs have been modified to suite the local configuration. Maybe the 2 that work OK have been "modified differently". For example leaving off the earth wire connection or maybe switching the active and neutral. Cheers Gary |
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Post by drumace on Mar 28, 2018 14:34:58 GMT -5
Hi Gary,
I never modify power cords. I replaced the US power cords with standard local power cords, the exact same as I use in every other component on my audio system so it’s not a power cord issue.
Just for the record, I even eliminated the earth on the original power cord using a 2 pin adapter and nothing changed.
BTW, it’s interesting that the seller’s name is also Gary :~}
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Post by Gary Cook on Mar 28, 2018 14:41:40 GMT -5
I swap the plugs on my cables from the US spec to the Australian spec, that way at least I know that I'm using the cable spec the manufacturer supplied. I have serviced a few XPA-1L's, but never one with 50 Hz hum, so sorry I'm not of more help. Although a loose internal earth connection would be the first place I'd look.
Cheers
Gary
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Post by leonski on Mar 29, 2018 10:23:36 GMT -5
Hi guys, Here's an update after having further tests- I disconnected the center speaker from the XPA-1L and connected it back to my old Anthem power amp. The XPA-1L remained only plugged into the wall. The center speaker sits on a shelf above the XPA-1L with about 4" clearance. I wanted to see how the XPA-1L behaves without anything connected to it so I turned it on. Surprisingly (or not), I heard the same buzzing through the center channel above it (once again, no cables running between these two). I then raised the speaker channel and the buzzing sound from the center speaker went lower and lower until they disappeared when it was high enough. Placing the center speaker back and the buzzing returned. I then pulled the XPA-1L from its place, put it on the floor far from anything, plugged it to the wall and turn it on. I could clearly hear the XPA-1L itself making a buzzing noise. I listened to the two other XPA-1L I have when they are turned on and they were silent. So, is it buzzing or humming, not so sure but the frequency is 50Hz as the wall power frequency in my country. In any case, looks like the XPA-1L has some technical faults which needs to be fixed and the only way to do it is to use a local technician even though the XPA-1L is under a warranty because shipping it to the US will cost a lot (probably more than the fix itself. Any comments to help me get through this awful situation? Thanks Move amp AWAY from speaker. Speaker is NOT magnetoically shielded and is interacting with the magnetic field from the transformer of the amp. Possible to put something between to 'block' the magnetic field? I don't know. Mu Metal? An ordinary piece of magnetic steel? It is NOT unheard of for transformers to buzz. As a test? Move speaker near one of your OTHER 1L amps. If it buzzes, it's 'normal'. If NO buzz, then your new amp is indeed defective in some fashion. |
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Post by drumace on Apr 17, 2018 13:06:09 GMT -5
Hi guys,
Sorry for the delayed response.
I tested the rest of the XPA-1L I have and all generates a noise through the center speaker so I’ll have to find a solution for that (maybe the magnetic shielding tape I ordered from Amazon).
As for the humming amp, the issue is with the transformer. It makes audible noise when it is on. This is not the case with the two other XPA-1L amps I have. They are silent (and both in class A and A/B).
Emotiva tech guys asked me to tight the bolt and it didn’t help. Then they ask to loosen the bolt. I’m a little concerned about it but looks like I don’t have other options.
I’ll update when I have some more news.
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Post by garbulky on Apr 17, 2018 14:18:20 GMT -5
Hi guys, Sorry for the delayed response. I tested the rest of the XPA-1L I have and all generates a noise through the center speaker so I’ll have to find a solution for that (maybe the magnetic shielding tape I ordered from Amazon). As for the humming amp, the issue is with the transformer. It makes audible noise when it is on. This is not the case with the two other XPA-1L amps I have. They are silent (and both in class A and A/B). Emotiva tech guys asked me to tight the bolt and it didn’t help. Then they ask to loosen the bolt. I’m a little concerned about it but looks like I don’t have other options. I’ll update when I have some more news. If the hum of the transformer is caused by a DC Offset in your power, that can be treated by the Emotiva CMX-2 (not the CMX-6) |
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Post by drumace on Apr 17, 2018 15:06:40 GMT -5
Hi guys, Sorry for the delayed response. I tested the rest of the XPA-1L I have and all generates a noise through the center speaker so I’ll have to find a solution for that (maybe the magnetic shielding tape I ordered from Amazon). As for the humming amp, the issue is with the transformer. It makes audible noise when it is on. This is not the case with the two other XPA-1L amps I have. They are silent (and both in class A and A/B). Emotiva tech guys asked me to tight the bolt and it didn’t help. Then they ask to loosen the bolt. I’m a little concerned about it but looks like I don’t have other options. I’ll update when I have some more news. If the hum of the transformer is caused by a DC Offset in your power, that can be treated by the Emotiva CMX-2 (not the CMX-6) OK but I would expect that if there’s a DC offset issue then it will affect all XPA-1L amps I have and not just a specific one, especially since they use the same power outlet. Am I wrong? |
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KeithL
Administrator 
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Post by KeithL on Apr 18, 2018 9:24:49 GMT -5
A transformer is mechanically just multiple coils of wire wound around a core of some sort of metal. The magnetic field produced by the current flowing through the wires causes them to WANT to vibrate (they push and pull on each other). In addition to that, the core itself flexes in time with the magnetic field. (Some small transformers are embedded in a block of rubber or coated with varnish to prevent the wires from moving - but this is impractical on large power transformers.) The bottom line is that, due to small differences in winding tightness or core shape, some transformers are a tiny bit noisier than others. It may vary slightly (over a period of years) as the transformer ages... And it may vary depending on how warm the transformer is. It doesn't indicate that anything is wrong electrically... Because the vibrations occur at line frequency, which is a rather low frequency, it tends to be carried through whatever the unit is sitting on. (And, if so, some felt pads under the feet, or those squishy rubber ones, can often help.) It can also be aggravated by loose hardware (allowing the transformer to vibrate.) In a given transformer, it is also usually louder with 50 Hz line power than with 60 Hz line power. DC offset tends to aggravate this situation because it causes excess current to flow in the primary winding, and it heats up the transformer. A distorted power waveform can also cause a transformer to mechanically buzz a little bit (but it's usually a buzz more than a hum). As a generalization, the magnetic field produced by your local line frequency permeates everything. Therefore, you can hear what seems to be "the same hum" from a variety of sources at the same time. It sounds like, along with any transformer noise, one of the inductors in the center-channel speaker's crossover (inside) is picking up hum directly. It's sort of unusual, but the crossover coils in some speakers can act as a sort of "magnetic pickup" and pick up the magnetic field in the air - and "play" it through the speaker. The toroidal transformers used in most modern audio gear tend to have relatively low field leakage (compared to older types). However, if that's what's happening, it's going to be VERY difficult to block it entirely with shielding (the amplifier already has a steel cover). Magnetic field drops as the square of distance..... So, if your speaker is sensitive to stray magnetic fields, the best solution is simply to avoid placing it within several inches of anything with a large transformer in it. Hi guys, Sorry for the delayed response. I tested the rest of the XPA-1L I have and all generates a noise through the center speaker so I’ll have to find a solution for that (maybe the magnetic shielding tape I ordered from Amazon). As for the humming amp, the issue is with the transformer. It makes audible noise when it is on. This is not the case with the two other XPA-1L amps I have. They are silent (and both in class A and A/B). Emotiva tech guys asked me to tight the bolt and it didn’t help. Then they ask to loosen the bolt. I’m a little concerned about it but looks like I don’t have other options. I’ll update when I have some more news. |
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Post by leonski on Apr 23, 2018 23:54:02 GMT -5
You can 'fix' any DC Offset problem with an (admittedly) pretty Good Sized Isolation transformer configured for 'balanced' operation. Lots of other garbage will get eliminated at the same time.
Based on drumace's last answer, that's not the solution, anyway, but rather a non-magnetically shielded speaker as cause.
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Post by drumace on Apr 28, 2018 13:01:46 GMT -5
Update - Even when I place the amp far from the center channel (for example, above one of the 2 other XPA-1L amps I have, I hear buzzing noise from the center channel when the XLR cable is connected. I don’t hear such noise from the 2 other amps on similar speakers.
Bottom line - the amp is now out of my system as I believe is not operating in its best and should be checked thoroughly by a professional.
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Post by leonski on Apr 28, 2018 14:28:02 GMT -5
I just read the part about XLR cable. This is a so-called Balanced connection having a seperate ground and a + lead and a - lead. Trouble is there is more than ONE correct way to wire such a cable. Swapping the cable to another amp, does it still hum than? This is a bunch easier than moving amps around! www.clarkwire.com/pinoutxlrbalanced.htmStandard for such connection. Is it possible the amp in question has an internal swap of Plus and Minus? I don't know. Some OTHER cable fault? Swapping cables might provide either more information or some relief. You could ALSO try a single ended connection, and see if THAT changes the result. In any event, PLEASE post back when you get to the bottom of this. |
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Post by drumace on Apr 28, 2018 14:35:41 GMT -5
The cable I use is the same XLR cable I used with the previous amp (Anthem MCA-5). No buzzing/humming issues observed there.
The cables I'm using are Blue Jeans Cables.
I'll keep posting updates when I'll have some news.
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Post by leonski on Apr 28, 2018 14:44:08 GMT -5
Thank you.
Just trying to help. I guess the NEXT test would be with the 'buzzing' amp and a single ended connection. That would eliminate the possiblity of an internal problem or mis-wire of the balanced interface of the amp?
Man, I HATE problems like this. So much time and effort to make something right which should just WORK.
Not to 'dis' Blue Jeans, but I use Mogami Balanced. I DO have several single ended Blue Jeans cables at other parts of the system including some 18" jumpers used at my Parasound Amps....
Cheers:
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