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Apple Computing Products:
macOS - Desktop Hardware
humming speakers on iMac
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<blockquote data-quote="John T" data-source="post: 1250940" data-attributes="member: 178054"><p>Curing an earth loop can be a most frustrating problem if you don't know the circuit layout of the various components.</p><p></p><p>I would start, for the time being, by getting rid of the UPS. It's only confusing things for the moment and it <u>may</u> be causing some.</p><p></p><p>It's a case of a system of elimination....</p><p></p><p>You say you had no problem when the speakers were used via your PC. Did your PC have a two or three pin power plug? I'm not familiar with your speakers but assume they are of the powered variety i.e. they have their own inbuilt amplifier. Do they have a two or three pin power plug? Not all appliances have an earth connection at their power plug (they have a two pin plug) They are either completely isolated from the mains or pick up their earth connection via the appliance they are connected to.</p><p></p><p>Earthing problems with audio equipment often arise when two appliances, when fitted with their own earth connections are connected together - this forms a "loop" which results in a mains hum.</p><p></p><p>Therefore, should your speakers have a three pin plug this is where the problem could be. In order to check it, you'll need to disconnect the earth lead from this plug. They will still be grounded via the neutral lead to your iMac.</p><p></p><p>Hope this helps. As I said, locating an earth loop can be a tricky problem! <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p></blockquote><p></p>
[QUOTE="John T, post: 1250940, member: 178054"] Curing an earth loop can be a most frustrating problem if you don't know the circuit layout of the various components. I would start, for the time being, by getting rid of the UPS. It's only confusing things for the moment and it [U]may[/U] be causing some. It's a case of a system of elimination.... You say you had no problem when the speakers were used via your PC. Did your PC have a two or three pin power plug? I'm not familiar with your speakers but assume they are of the powered variety i.e. they have their own inbuilt amplifier. Do they have a two or three pin power plug? Not all appliances have an earth connection at their power plug (they have a two pin plug) They are either completely isolated from the mains or pick up their earth connection via the appliance they are connected to. Earthing problems with audio equipment often arise when two appliances, when fitted with their own earth connections are connected together - this forms a "loop" which results in a mains hum. Therefore, should your speakers have a three pin plug this is where the problem could be. In order to check it, you'll need to disconnect the earth lead from this plug. They will still be grounded via the neutral lead to your iMac. Hope this helps. As I said, locating an earth loop can be a tricky problem! :) [/QUOTE]
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Apple Computing Products:
macOS - Desktop Hardware
humming speakers on iMac
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