the question of changing ethernet cables

Many thanks. I understand the issue better as being 2 distinct loops, shall we say. The problem I wish to solve is twofold: Firstly, now that I have the hardware, I wish to optimize the cabling and refine the system (mostly Cardas XLR). Secondly, I have a white noise (?) at the higher mids or from the mid range driver (Speakers Focal Sopra III).

To begin. I had Furutech fuses (Sicherungen) connected to the fuse box and Furutech outlets at the wall. These are 2-separate lines with 6mm2 (10 Guage) wiring. These are dedicated lines with no loop at all - direct. One line is just for the amp (PS Audio 250 sig) connected to the wall with a Shunyata Alpha NR. This has been a game changer.

I have read here and on other posts that the router and ethernet cables can induce some noise pick up. The first question has been answered; namely, despite the fibre hook up coming into the house, yes, noise can come from internal parts thereafter.

I am very impressed with Shunyata and I will look into their ethernet cable. I also saw a video and post about green computer or something like that using filters and adapters from ethernet to fibre connections. I believe the remaining hiss or white noise is coming from the router. I am almost ready to try this remedy. I just needed to clear up my quaetion. Lalitk and antigrunge2 sound like they are leaning in this direction. My plan would be to try this first and later, if necessary to replace the ethernet cable.

Oh, if I have just the amp and preamp on I have a very slight hiss, volume turned up and ear to speaker or just some inches away. When I turn the streamer on the same noise increases. I would like to have dead silence if that is possible. So, my plan is go one step at a time to reduce as much of this hiss as possible.

Thank you antigrunge2. Everything is in the attached garage, modem, router and this station system to extend wifi. Meaning the main station extender and the slaves are positioned around the house for better wifi.

The router is plugged directly into my fuse box. I have outlets built in. I can see from the wire pile up and the proximity, as well as the use of, the fuse box could add to the noise.

I just started to read about your suggestions. Pink Faun is produced in the Netherlands, which is very close to me. There is also a dealer I found in Germany. It diffently sounds like I need to add some type of filter post router and a filter converter to fiber. Then a fiber cable to the streamer/DAC. That was green computer's solution as I understand so far.

As I said, I am still looking at Lan isolators. I do have to say, this is quite an interesting science. 

Shoot! Yes, I did mean Small Green Computer. Good sounding solution and agreeable price. However, 81 Euro shipping cost is unrealistic. In the event of ethernet upgrades, I will have to look locally. I can see this needs to done by the logical explanations here. Yes, we do have a series of small lights in the ceiling. This could produce some infect as mentioned.

Another good point (Lalitk) check the gas before changing the spark plugs. I do have a new amp from PS Audio - BHK Signature 250 Amplifier - it is a hybrid with tubes. I will check with similar threads to see the FB. I just put a Shunyata Alpha NR on it. Most of the interconnects, where critical, are Cardas. I have MIT 16 speaker cables to the Focal Sopra 3 speakers. I have the PS Audio DAC/streamer and PS Audio SACD. Preamp is the primare S P32 that has no tubes. Planned is to replace with a Trinnov Altitude 16 for Home theatre. To this end I have a 7-channel Primare amp but it is not on for music. Likewise for movies only is a Primare A32 for special effects or rear surround, Atmos. Surround speakers are the Klipsch 500 series and Atmos Klipsch 400 series. Speaker cables are very heavy gauge wiring due to the distance. Again, only used with movies. Same with the B&W 855 subwoofer with upgrade. In all of this, NO, the ethernet cable is common and not shielded. Other mains cables are stock - planned is supra shielded cables. All of my cables are isolated and run through cable channels for separation and no crossover possibilities. Same as in the wall with the new wiring, they are each run through their own channel. I do not have a power conditioner yet. I am looking PS Audio 15 for the future.

The router is from the phone company and was first produced by huawei It most likely stock. I am looking into this as well. I found a dealer in the Netherlands. I'll let you know what they say.

@sns I like the idea of your upgrade going optical. As I seem to be developing a real tick for this stuff, I will look into that for the future.

Okay. Many thanks. My ignorance is slowly graduating to just a simple lack of knowledge. As I mentioned, I had a dedicated installed. That meant the ethernet had to go to another outlet because the new cables were too thick for everything to fit. To help me, the electrician left a long 5m cable so I would be flexible to finish the set up. From you guys, I just learned that I have 5m long attenae picking up every noise it can along the way. First step solved. When I get the parts needed, I will report my findings. Thank you everyone. Ignorance is not always bliss.