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Can ethernet cables cause ground loops?

ThatM1key

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I always wondered does ethernet cables cause ground loops? I was told all my life for the most part that ethernet cables can carry surges and ground loops but I never really encountered this.

Our internet for the most part is stringed across various network switches and routers via different outlet points. My main "Hifi" setup has Ethernet involved, luckily I hear no noise at all. My small home theater setup has many devices hooked up and I do hear noise at very high volume but no ethernet is involved in that setup. I am a bit scared to hook up my AVR and TV via ethernet because I don't want to potentially add even more noise. Am I overrating/overthinking this or am I right to think like this?
 

DonR

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It is possible but I have not encountered it ever with Ethernet. Ground loops usually make themselves apparent only at the terminal devices of the network like TVs, DACs, AVRs, etc.
 

Hayabusa

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I always wondered does ethernet cables cause ground loops? I was told all my life for the most part that ethernet cables can carry surges and ground loops but I never really encountered this.

Our internet for the most part is stringed across various network switches and routers via different outlet points. My main "Hifi" setup has Ethernet involved, luckily I hear no noise at all. My small home theater setup has many devices hooked up and I do hear noise at very high volume but no ethernet is involved in that setup. I am a bit scared to hook up my AVR and TV via ethernet because I don't want to potentially add even more noise. Am I overrating/overthinking this or am I right to think like this?
F1.jpg


Normally the schematic looks something like this...
So if executed correctly no ground loops!
 
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DVDdoug

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Right... Ethernet is transformer-isolated so there is no ground. The exception could be PoE (Power over Ethernet) which is rare.
 

DonR

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Right... Ethernet is transformer-isolated so there is no ground. The exception could be PoE (Power over Ethernet) which is rare.
I have seen some admittedly rather poor examples where the shield is connected to the main circuit ground. Nothing like that from a reputable manufacturer though.
 

EdTice

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Right... Ethernet is transformer-isolated so there is no ground. The exception could be PoE (Power over Ethernet) which is rare.
The other exception is Cat 6A cabling/devices which do have a grounded sheath. If you try to use these in your home audio setup, though, the audio device will not have the ground connected on the jack so it still shouldn't matter.
 
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ThatM1key

ThatM1key

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Thank you for the replies, I will keep this in mind for the future!
 

AnalogSteph

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If you live where standard network cable is UTP (like in the US), the potential for ground loops is fairly low. That being said, any networked device that is IEC Class I tends to connect FGND to chassis ground, which in turn is connected to PE. If you do have shielded cable as is common over here in ol' Europe, this results in substantial potential for ground loops.
 

EdTice

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Huh? I think I have a grand total of one shielded Ethernet cable in my collection.
Cat 6a is shielded and is rated for longer cable runs. For in-wall wiring, cat5/cat6 have a maximum distance of 100 meters which really ought to be enough for anybody. But if houses require longer runs, yeah, there might be cat6 around. I don't know what happens if you have cat6a in the wall and use a cat6 patch cable. If you are going to connect audio equipment to ethernet that's wired cat6a and you think that's causing a ground loop issue, get an ethernet switch (not a hub) that supports the desired long-distance network speed. Use the appropriate cabling between the switch and the in wall-port. Use a non-shielded cable (short length) between the switch and audio device. Make sure its a switch and not a hub. The terminology is somewhat backward compared to how it's used in audio. A "switch" reads each packet and then only repeats the packet on the appropriate ports. Hence your unshielded length to the switch will be fine and the switch will repeat the packet to the rest of the network over grounded connection for longer cable run. Where most switches used to be all plastic you do now see metal near the jacks and I believe this is for shielded cable although I don't pay much attention anymore as I have WiFi in my house.
 

Cbdb2

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You can get any cat cable shielded or not. Ive installed cat cables in hundreds of locations and only used shielded ones once. The cable is already very noise immune due to the twisted balanced pairs. The only ground connection in a cat cable is the shield if there is one (except for POE). For the shields to carry thru you need shielded jacks and connectors, special switches and patchbays. Very unlikely your home system has these special devices, so very unlikely you will get a ground loop.
 

EdTice

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You can get any cat cable shielded or not. Ive installed cat cables in hundreds of locations and only used shielded ones once. The cable is already very noise immune due to the twisted balanced pairs. The only ground connection in a cat cable is the shield if there is one (except for POE). For the shields to carry thru you need shielded jacks and connectors, special switches and patchbays. Very unlikely your home system has these special devices, so very unlikely you will get a ground loop.
You are correct that I did not word my answer well. You can use shielded ethernet cables in pretty much any application. But, as you've said, if you aren't using the proper equipment, it's the equivalent of wrapping them in aluminum foil yourself. In order for the shielding to be grounded, though, you need equipment which is grounded and has the appropriate connectors. I can certainly see this being present in residential situations in larger homes. If it is present, there's no reason you can't use a grounded switch and shielded cable to connect to the network and then an unshielded connection to the audio device. The idea is, if such grounding is present, this is the one situation where a "ground lift" can be done safely. You use a switch that can have grounded and ungrounded connections and you use an ungrounded connection for the audio device.
 

mansr

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Almost all Ethernet jacks on equipment are shielded, the only common exception being laptops. If two devices are connected with a shielded cable (with shielded plugs), their grounds will be joined and ground loops can form. Patch panels and in-wall wiring aren't really relevant to most domestic situations.
 

mansr

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Allow me to summarise the situation as I see it:
  • Unshielded cables (UTP) are by far the most common everywhere in the world.
  • Switches and computers almost always have shielded Ethernet jacks.
  • Broadband routers vary; I have examples of both.
  • Patch panels typically have unshielded jacks, but few people have those at home either way.
If ground loops are a concern:
  • Use an unshielded cable to connect the affected equipment.
  • An unshielded cable can connect directly to a shielded patch panel; there is no need for an intermediate switch.
To answer the question in the title, yes, Ethernet cables can cause ground loops if they are shielded. Unshielded cables can't cause ground loops since they have no ground wire. PoE complicates matters a little, but it's rarely used with audio equipment anyway.
 

EdTice

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Allow me to summarise the situation as I see it:
  • Unshielded cables (UTP) are by far the most common everywhere in the world.
  • Switches and computers almost always have shielded Ethernet jacks.
  • Broadband routers vary; I have examples of both.
  • Patch panels typically have unshielded jacks, but few people have those at home either way.
If ground loops are a concern:
  • Use an unshielded cable to connect the affected equipment.
  • An unshielded cable can connect directly to a shielded patch panel; there is no need for an intermediate switch.
To answer the question in the title, yes, Ethernet cables can cause ground loops if they are shielded. Unshielded cables can't cause ground loops since they have no ground wire. PoE complicates matters a little, but it's rarely used with audio equipment anyway.
Thank you. This is the same answer I was trying to provide but yours is worded much more eloquently.
 

Lambda

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Because of the balanced and transformer isolated nature of Ethernet, the high frequency content and the twisted pair construction. the shield dose not need to be connected to ground to be effective.
May (most) devices don't connect the shield to ground.

Cat >6 usually do
Shielding is typically maintained from one cable end to the other using a drain wire that runs through the cable alongside the twisted pairs. The shield's electrical connection to the chassis on each end is made through the jacks. The requirement for ground connections at both cable ends creates the possibility of creating a ground loop. This undesirable situation may compel currents to flow in the network cable shield and these currents may in turn induce detrimental noise in the signal being carried by the cable.

If you have to devices with ground connected to shield and a shielded cable. you can have ground loops.

in this cases use a unshielded cable.

BTW Cat rating and cable type don’t directly correlate.
stp_construction.png

you can have a s/stp cable that is technically only cat5.
the other way around its hard...

Most of my installation is "cat7" S/STP cable. but the installation is not even proper cat6 because of the termination hardware used.
Don’t relay matter because 2,5G Ethernet works fine even with a short peace of cat5e cable from the wall plug to the PC.
 
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