Ethernet cable causing hum on Uniti Atom?

Hi-Fi Corner
1

I’m experiencing a strange problem between my turntable (Technics SL-1200) and the Uniti Atom.

I’m streaming on my Uniti Atom with an Ethernet cable, not Wifi.

Now when I change to Analogue mode to listen to Vinyl records, I can hear a low volume hum when I crank up the speakers.
The hum disappears as soon as I disconnect the Ethernet cable.

When I plug in short plugs into the phono preamp’s input (Lehmann Black Cube) instead of input from turntable, the hum is not existent. The hum is only there if both the ethernet cable is connected to the Atom AND the turntable is connected to the phono preamp.

Why am I experiencing this issue? Is this some sort of a ground loop? How common is this issue?
I’d rather like to deal with the cause than with the symptoms.

Apart from streaming wireless, are there any other (affordable solutions) ?
Maybe that’s what special ethernet cables for hifi usage are made for? If so, they cost tons unfortunately… (Audioquest Diamond!)
A friend of mine recommended a small device called Blackcube Ethernet Isolator doing a galvanic isolation. Would that solve my problem? Despite its relative affordability (around 100$) I’m afraid to buy one as it doesn’t seem to be made for hifi usage primarily. Other ethernet isolators for hifi usage cost much much more.

Some additional observations:

  • using a non-shielded ethernet cable makes no difference.
  • switching the Atom’s ground to ‘floating’ makes no difference.
  • disconnecting the turntable from power makes no difference. Hum is still audible (!!!)

Thank you for your help…

2

Ethernet connections are already galvanically isolated. Theres a small transformer at the socket.
Sounds like a ground loop as you suspected.
I don’t think you need to throw ££ at the problem, my suggestion would be to check your connections.
I too have an Atom with a 1200 playing through a Rothwell phono stage. I have a ground lead from the Tonearm (SME M2-9) to the Rothwell and a ground lead from the TT chassis to a ground socket on my mains extension.
No hum from anywhere.

3

What else apart from the TT and Ethernet cable is connected to the Atom ?

4

@james_n besides the speakers, nothing else.

@raym55 If ethernet connections are galvanically isolated on the Uniti Atom, then why am I only hearing the hum when the ethernet is connected? That doesn’t make sense to me.
Besides that, where do you suspect the ground loop to be? I have a phono ground cable going to the preamp (incl. chassis), and I have a mains ground for the motor, strobe etc.
These 2 grounds are NOT connected to each other. At least if I test continuity between them, I get no resistance. Am I missing something else?

5

That’s a bit of a strange one. It certainly sounds like an earth loop but from what you say, electrically this doesn’t seem to be the case - it does sound like it is ground related though and you may need to experiment with grounding between TT, Lehmann and Atom. Where is your Atom and TT located - next to each other, next to other electrical devices and how have you got the mains connected - are both the TT, Atom and Lehmann connected into to the same mains block ?

6

Pull one of your tt ground wires, see if anything changes. If no change plug it back in and try the other one.

7

Also check location of components and routing of cables. As this is a very low level hum, then to me, it suggests that it may be magnetic induction, where the magnetic field of one of the power supply transformers is being picked up by another component or by one of the cables.

Try increasing the distance between all the components as much as you can, if the hum disappears, then you know it’s a layout problem, and you’ll be able to cure it by re-positioning the components of the system.

8

Years ago I had an issue with this sort of hum and the fix was a proper, separate, earth for the phone amp. btw earthing to the naim amp (this was an SN2) didn’t fix things. I had to do a separate earth wire from the phone amp to true earth. As a test try just getting a piece of wire and touching bare end to the phone earth and the other end to a radiator or water pipe. Just a suggestion.

9

Worth checking both connector ends, a gentle wiggle, may just be a loose’ish connection.

10

Agree to check the connections. Tho there week I suddenly experienced hum and crackling on my analogue input. Tried various ways of identifying the problem with no luck, and decided that my Superline was at fault. The next day I thought the internet was not as quick as normal and did a speed test on my PC which showed a download of around 6 Mbps imparted with my normal 65 Mpbs. I then check the Ethernet connections pushing them into their sockets, and regained my normal speed. The next day I played some vinyl and the hum and crackling had gone. It had to be the Ethernet connection between my PC and router to my surprise.

11

Plug in and out… if it persists buy a new Ethernet Cable … you can go mild or wild! I like the Audioquest, WireWorld and the Belden

12

Please excuse my late reply. Needed some time to process all your inputs and do some testing. Thank you very much!!
Please find below the results:

@james_n Today, I took my whole system apart and placed each component as far apart from each other and from other devices as possible. I literally spread everything across the living room.
As for the mains socket: I connected the devices to completely new sockets, even using extension cable to other room’s sockets.
The result: No change to the hum at all. Still exactly the same.

@raym55 no luck doing that, unfortunately.

@obsydian, @GerryMcG no luck double-checking the ethernet connection. I tried even another slot on the router.

@anon5525519 As I mentioned in my initial posting, I already tried a shielded and a non-shielded cable. So 2 different cables with no difference. I may consider a Hifi ethernet cable, but those cost tons. And as I mentioned I would prefer to solve the cause, not any symptoms. I doubt that a 2000$ ethernet cable would be the only viable solution here.

@raym55 You mentioned in your first posting that ethernet connections are galvanically isolated on the Uniti Atom. Are you 100% sure that this is the case? I did some searching, but couldn’t find any sources confirming your statement. I only found info about the optional HDMI input that is galvanically isolated.

@Xanthe As mentioned above, different positions of cables and devices don’t change the hum. (Only some radio pickup is position-dependent. But that’s a separate problem.) Also, I’d like to mention that it’s a very static hum. In contrary to a.e. radio-pickup it is not fluctuating, but always on the same volume level.

@anon4216120 I followed your advice and attached the turntables ground wire to a longer wire which I connected to the radiator. Strangely, the hum got even louder. :frowning:

Speaking about that preamp ground: Maybe it is worth mentioning that the Lehmann Black Cube has no “star ground” scheme. The ground post on the Lehmann is only attached to the case. I other words, the phono ground from the turntable is grounded directly into the Lehmann’s power ground. (The power cord has 3 pins.) Doesn’t this seem somewhat strange?
I’m not really sure if this has anything to do with the “ethernet hum” though. What do you think?

Please see the inside of the Lehmann on the picture below. The ground post is on the bottom right.

IMG_20190529_204146
IMG_20190529_204146.jpg4640×3480 3.49 MB
15

If you get no (0) resistance then they ARE connected somewhere

You may find this interesting…
http://www.thewelltemperedcomputer.com/Intro/SQ/GalvanicIsolationEthernet.htm

16

Yes Ethernet by design is galvanically isolated to meet safety standards. It most likely wouldn’t work in many setups if it wasn’t. If it wasn’t isolated it would not strictly be allowed to be called Ethernet.
However you may have a fault where the galvanic transformer is short circuited… seems unlikely.
You may also have common mode noise passing along the Ethernet lead from your router, perhaps because of a fault on your router.
Have you tried feed your Naim from another switch?
Either way it sounds like you have a fault somewhere, you just need to localise it.

17

How about $30.00
or if you can find it in the UK
I use an Audioquest Vodka $450.00 for 1.5meter

Wireworld Starlight cat8 $270.00 2meter

I suspect your hum maybe due to a difference in ground potential a very cheap way that may fix it is to buy a small 5 port powered ethernet switch and put it in-between…

18

However if that is the issue it points to a fault with Ethernet isolation transformer in the Atom, and, if the case, should get it fixed under warranty.

19

Thanks for your replies. It seems that I have some options at this point. That’s a good thing.

@Simon-in-Suffolk no, I have not tried another switch yet. In fact, the Atom is directly connected to my internet provider’s router. I may try that.

@anon5525519 Do you suggest that I should just put that switch between my router and the Atom?

@raym55 Sorry, my mistake. The ohmmeter shows 1 (or OL), same as if the probes are not touching. A very interesting link. Thank you! I will decide between that TP-Link solution and the ethernet isolator solution if an additional switch doesn’t work out.

20

If the ethernet isolator works, can I conclude that the transformer is faulty then?

21

Glad to be of help. I posted that link for reference only, I wasn’t suggesting that the products listed would provide a solution.

22

Yes… at least sufficiently to have tested by Naim. The Ethernet magnetic should be isolated to at least 1.5kV