jornz
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Post by jornz on Mar 1, 2013 11:19:33 GMT -5
I noticed there is a buzz coming from my speakers after connecting my XPA-5 to the UMC-200. So I spent a lot of time testing things. I found out it must be the interconnects I am using. Because if I connect the speakers to the XPA-5 and nothing else there is no buzz, if I then only connect the inteconnects to the XPA-5 the buzz appears. The buzz is still there when I then connect the UMC-200. So I'm concluding that the interconnects lack appropriate shielding. Do you guys agree?
What type of interconnect should I be using? What are the requirements with respect to shielding / buildup of the cable?
Thanks guys.
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Deleted
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Post by Deleted on Mar 1, 2013 11:29:17 GMT -5
Is the XPA-5 and UMC-200 ~both~ plugged into the same power outlet? Eveything should be, to avoid ground loops.
Try disconnecting the UMC inputs, one by one, until the hum disappears. Start with CATV.
/b
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jornz
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Post by jornz on Mar 1, 2013 11:53:03 GMT -5
Is the XPA-5 and UMC-200 ~both~ plugged into the same power outlet? Eveything should be, to avoid ground loops. Try disconnecting the UMC inputs, one by one, until the hum disappears. Start with CATV. /b Thanks for your reply. They are connected to the same power outlet. But the XPA-5 is by definition not grounded since there is no ground pin in the connector on the back. So a ground loop via the power cables can not be what is happening here. |
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DYohn
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Post by DYohn on Mar 1, 2013 11:56:21 GMT -5
It's a ground loop, with the loop happening through the RCA cables.
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Deleted
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Post by Deleted on Mar 1, 2013 12:25:10 GMT -5
Yes, its always a ground loop; with the RCA cables a segment of the loop.
> But the XPA-5 is by definition not grounded...
Are you saying the amplifier power cord lacks a ground pin?
/b
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jornz
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Post by jornz on Mar 1, 2013 14:43:38 GMT -5
The XPA does not have a ground pin on the connector on the amp itself on the back. Only the power cord has the ground pin but that is not connected on the amp side since there is no pin there.
The buzz is there when the UMC is not connected, but with the interconnects only connected to the XPA. So there is no possible loop via the RCA ground.
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jornz
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Post by jornz on Mar 19, 2013 16:59:33 GMT -5
It's a ground loop, with the loop happening through the RCA cables. After extensive testing, I think you are spot on. The term ground loop is confusing though. The loop seems to be formed in the signal ground between the RCA interlinks / interconnects and the XPA-5 / UMC-200. There is no ground loop via the power cords, since the XPA-5 has no ground pin. Anyone got any ideas how to kill this loop, the UMC-200 doesn't have balanced connection possibilities... |
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Deleted
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Post by Deleted on Mar 19, 2013 17:11:21 GMT -5
> After extensive testing, I think you are spot on. The term ground loop is confusing though. The loop seems to be formed in the signal ground between the RCA interlinks / interconnects and the XPA-5 / UMC-200. There is no ground loop via the power cords, since the XPA-5 has no ground pin.
It sound like you still don't understand what a ground loop is. Remember, Google is your friend.
<http://en.wikipedia.org/wiki/Ground_loop_(electricity)>
Also, if you look around here you will find several threads on ground loops and hum.
Sincerely
/b
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Post by garbulky on Mar 19, 2013 17:15:26 GMT -5
Disconnect any power conditioners. Try disconnecting everything BUT thge umc-200 and the xpa-5 from the circuit. After trying that, then try a different circuit.
Turn off any dimmers, washing machines, flourescent lights. Sometimes antennas and cable boxes can introduce noise.
There is a ground loop isolator you can purchase.
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Post by Gary Cook on Mar 19, 2013 18:26:59 GMT -5
I don't know that I would call ground loop noise a "buzz" more like a "humm".
Cheers
Gary
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Post by knucklehead on Mar 19, 2013 19:06:44 GMT -5
The XPA does not have a ground pin on the connector on the amp itself on the back. Only the power cord has the ground pin but that is not connected on the amp side since there is no pin there. The buzz is there when the UMC is not connected, but with the interconnects only connected to the XPA. So there is no possible loop via the RCA ground. If you've ever done residential wiring you'd quickly find out that both grounds in the wall plug connect at the same place - to a large ground bar inside the electrical panel. |
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Deleted
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Post by Deleted on Mar 19, 2013 20:49:53 GMT -5
> If you've ever done residential wiring you'd quickly find out that both grounds in the wall plug connect at the same place - to a large ground bar inside the electrical panel.
By "both grounds in the wall plug" are you referring to the neutral and the ground? If so, in an appliance, no engineer would connect a neutral to a signal ground or chassis. So neutrals are irrelevent to ground loops.
Sincerely
/b
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emovac
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Post by emovac on Mar 20, 2013 0:47:50 GMT -5
Might try one those Radio Shack RCA ground loop interconnect cables. About $15-20.
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jornz
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Post by jornz on Mar 29, 2013 7:34:21 GMT -5
At the moment emotiva tech support is looking into the issue. The XPA-5 also hums over the speakers with an iPhone used as preamp (with a stereo RCA to jack plug cable) and nothing else attached. No ground loops in this case! So there has to be something wrong with the amp. It hums on the speakers on the channels that are in use due to a cable being attached to the RCA connector. So in the case of the iPhone it will hum on the two speakers that are connected to the channels where the stereo RCA cable is attached. Funny thing is that when I insert just one of the two RCA's there is no hum.
On a side note, I went a bit overboard at one point and disconnected the entire electrical circuit in my house (including incoming cable tv / telephone) in the circuit breaker box apart from 1 circuit with just one wall socket in it. So I physically disconnected the wiring for the other circuits. Still hums over the speakers on this one wall socket...
Also tried the amp over at my parents' house, also hums there. So the whole ground loop theory seems highly unlikely now.
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