Digital isolation between Ethernet hub and streamer

Move over Network Acoustics, GigaFOILv4-INLINE,  iFi LAN iPurifier Pro |, and all the others.

As far as I can tell, these filters provide galvanic isolation in one of two ways, by either using transformers (i.e., the NA filters) or optical isolation (i.e., GigaFOIL and others).  Don't most good servers/streamers also provide some form of isolation?

The last cable my streamer sees is a fiber optic cable but, even when it was an Ethernet cable, none of this stuff made a reliably discernable difference in the sound of my system, and I have owned the NA eno and muon systems (including their Ethernet cables), GigaFOILv4-INLINE, and others. I could say I heard differences, but that would require talking myself into it, YMMV.

@erik_squires - I agree about surge protection.  Unfortunately, outside of a Belkin unit in my server/IT room, and my Isoclean Power A60 that filters all of my front end stuff in my system room, I don't really use it.

When I mentioned isolation for purposes of this discussion, I was talking about as provided by all the small boxes that are available to purchase.  Since running optical from my server room directly into my Sonore Sig Rendu SE Deluxe, none of the other stuff has done a thing for me.  I do use an optical break (2 converters and two LPSs) directly out of my router, and then after the server, I use Sonore's opticalModule to convert the Ethernet output into a fiber optic output that goes into my system room and into the Sig Rendu SE...

I was reading the A’gon thread about the "Stereo Times Most Wanted Components" and saw that a digital isolation device had made the list (Aardvark Ethernet Isolator). I did a shallow dive into these isolation devices and found out that network isolators are typically electromagnetic voltage transformer modules that provide electrical isolation, improve signal integrity, and minimize electromagnetic interference (EMI). The module itself appears to cost around $10.

In addition to the StackAudio SmoothLAN Network Filter ($250) discussed in this thread, solutions that seem similar include:

• English Electric EE1 Network Isolator, for $295,

• Crux Audio LAN Noise Filter, currently priced at $250,

• Aardvark Ethernet Isolator, for $450 or $900,

• CAD Ethernet Control, for $1,250,

• EverStar MI-300 Ethernet Galvanic Isolator, for $87, and

• emo System’s EMOSAFE EN-70HD, for $172

I have no idea what would make one device actually sound better than the others, especially since they all seem to be based on a filter module costing around $10, but audio reviewer Roy Gregory apparently discerned a difference between three of them and wrote about it in this article at Gy8, where he (predictably?) explains that the performance gets better as the price goes up, from the English Electric EE1 (good) to the Aardvark Ethernet Isolator (better) to the CAD’s Ethernet Control (best). Setting aside the perceived hierarchy, I am curious how the improvements can be so precisely graded for a product category that many believe provides subtle differences/improvements, if any.

Looking into the non-audio system related uses (i.e., industrial and medical networking) I learned that, at least in the case of medical applications, Ethernet isolators should conform to the requirements of IEC 60601-1 for galvanic isolation devices in the medical field.

This made me curious whether most/all component devices that interface with an RJ-45 Ethernet cable already include transformer isolation so I found this:

A typical Ethernet port includes isolation transformers, common mode chokes and port termination as shown in Figure 1. The transformers have a minimum isolation rating of 1500 VRMS (2.1kV) as required by the IEEE 802.3 standard for Ethernet interfaces. Common mode chokes are often integrated with the isolation transformers and serve to reduce EMI emissions. Ethernet ports are commonly terminated using the “Bob Smith” technique. This termination uses a 75 Ohm resistor for a common mode impedance match at each signal pair, collectively connected via a high voltage 1000pF capacitor to chassis ground. The purpose of this termination is a further reduction in common mode emissions.

Figure 1 – Ethernet Interface Components © Semtech Corporation 2020

Maybe somebody more familiar with Network related devices can explain whether this type of isolation is typical for Ethernet endpoint ports in devices such as switches and streamers and, if so, why do we need an additional in-line device? IOW, are these commercial "audiophile" filter devices fixing a problem not in evidence and, also, what is so different about them that they can affect the sound to the extent as reported by the reviewers and end users?