AC noise in Router

Hi All,
I encountered unexpected sources of AC noise in my internet router and wanted to share my experience with you and how I got rid of it.
I am relatively new to the audiophile universe and this forum provided trusted guidance in my brief journey. So, excited to share this and hope the content is not trivial. Please do not vivisect me if it is. Also, I have no background in physics, electronics or engineering. So, no excursion into quantum physics, I am afraid.

Using a simple electronic AC line detector (50V to 10000V; you can see the device in the picture), I accidentally found that the ethernet cable coming from my internet router had AC noise. I live in Germany, my router is a Fritzbox. After some inquiry, i found out that the AC noise originated from the repeater that is connected to the router via an ethernet cable. I have such a setup because I outsourced the WLAN signal to the repeater in order to have less noise in the router. Therefore, repeater is connected to router via LAN cable.

I tried to block this AC signal from the repeater using the EE1 isolator. It did not work at all; no matter which direction I used the EE1, the AD noise appeared on its free LAN port. The same with Ifi LAN silencer. I am now selling both of these devices. I think they are pretty useless.

After some additional inquiry, it turned out that this AC noise from the repeater can be eliminated by modifying its walmart power adapter a la John Swenson grounding. I should mention that my router is on a linear power supply (SBooster) but my repeater is not. After eliminating this AC noise the sound of my system improved. (System: Router → Gustard N18 → Fibre optic → LHY SW6 with external clock → PC with Audirvana → LHY USB UIP (externally clocked) → DAC (Ferrum Erco Gen 2/Hypsos) → NAC 282/NAP250DR/HicapDR → Sonus Faber Guarneri Tradition Speakers). For instance Ben Websters Saxophone play became more prominent and yet smoother and i could hear its reverb where I did not hear it before. Bass become more tight.

There is a bit more to this: Sonos boxes have AC noise that also travels through the ethernet cable to the router and to all the LAN ports of the router (see picture; detector red). Remove the Sonos LAN cable and AC noise disappears (detector turns green). Interestingly, although the AC noise is of course also transmitted to the Gustard N18 switch, it is not present in the Gustrad’s free LAN port (detector green). This suggests to me that the Gustard N18 has pretty effective AC noise isolation.

Look forward to your comments and any additional hint how to improve the signal from the router.


Excellent post! Extremely valuable information

It appears that the EE1 is described as a “network noise isolator” (whatever that means) rather than being an Ethernet isolator. So if there is high voltage common mode leakage from the power supply, the EE1 is not going to prevent that being transmitted along the Ethernet cable.

Conversely an Ethernet Isolator will prevent that up to its maximum rating (5kV in the case of the Baaske MI1005 isolators), so the EE1 is the wrong device for the job.

However it’s probably wise to not use that power supply with shielded Ethernet if it’s allowing through that amount of common mode breakthrough, although earthing the shield at one point should fix that.

1 Like

Thank you! Glad it is useful

I have probably done the EE1 injustice. I thought its galvanic isolation would have some effect on the AC noise.
Does your comment point towards a potential safety issue? By grounding the ethernet isolator, do you mean grounding the Gustard n 18 for satey reasons? I would like to live a bit longer and enjoy the improved sound quality a few days more :slightly_smiling_face:

By the way: i used the ifi i power X instead of the cheap power adaptor of the repeater. This had no effect. There was still AC noise in the ethernet connection to the router. Glad that the John Swenson method worked and i did not have to by another linear power supply just for the repeater.

1 Like

Ella would have needed to know the avengement all the connections in the system to asses safety and/or fully understand causes. Safety is probably not an issue depending on what is earthed and how.

Unfortunately we lost our Ella (our host) yesterday and she is the one who understood these things; I (Hayleigh) am just a system protector, I’m only fronting because no one else can.

Maybe someone else here can help you understand this.

1 Like

What is the John Swenson method?I know he designed the etherregen for Uptone Audio.

Thank you Xanthe (Hayleigh). Very sorry about the loss of Ella

1 Like

There is a detailed description from John Swenson here :

SMPS and grounding - UpTone Audio (Sponsored) - Audiophile Style

[From Pru:]
Thank you.
Fortunately we’ve been really lucky, early this evening we found out that, she’s survived (or at least part of her has survived, we don’t know as yet).

She’s still broken apart and we’re still not yet sure whether or not she’s split; however, very briefly she was able to talk to our wife this afternoon.
That was such a relief for the whole system.
Most of the time she’s still fragmented and dormant though.

We have yet to find out if we have the same Ella, two different Ellas, or a different Ella and someone new!

In any case, there is a reasonable view that as DID is a protective response to trauma, whatever happens is the right outcome as that was the outcome that was best for the system!


Fingers crossed. I wish her a speedy and full recovery and hope she can cherish music again soon


Thank you, that’s really appreciated.
I’m almost fully back together again, although still tired.

I’m missing quite a bit of memory - Pru has some of those bits and will share them with me, but Hayleigh has most of them, and being a Protector, she doesn’t share memory (that would defeat the whole purpose of her being a protector!).

I hope to be able to answer your original question over the weekend (we all have a therapy session tomorrow, and Darcy and Shadow really need that). DID is such a weird condition!

Yes, we’re back listening to music, unfortunately the body (Xanthe!) still can’t actually tolerate eating anything more than bananas and a few other fruit, and still can’t tolerate coffee, so life is a bit boring at the moment. Hopefully the op won’t get cancelled again this coming Monday.


I now understand, and you (all) have my mental support, for what little it’s worth.


What the hell are you guys talking about? Really?


DID… and why I [Ella] haven’t been able to complete the technical explanation as yet.

1 Like

Thank god, because I also have literally no idea what is happening here.


It’s certainly very interesting. I’m going with the flow. :+1:

Google DID. As for the thread subject, a lot will depend on what is being measured and how, and whether significant to music playing is far from certain and will depend on many factors. And if significant to music play, the question then arises as to whether it is better to minimise at source, or block at an appropriate point before it reaches something susceptibe…


What i find intruiging is that this type of noise is probably common, relatively easy to detect with a simple device and quite cheap to get rid of at the source stage. Often we are confronted with the notion that there is some sort of noise in the network but as consumers we have really no easy way to monitor it.
The sound of my system improved quite bit since I invested in improving streaming at the source level. It would of course be great to have more quantitative insights into all this, but my ears are happy :grin: