Noisy ethernet cables

@erik_squires , You probably want to stick with shielded Ethernet, regardless of the Cat #

Why? Many devices don’t have connectors that support the shield connection. Worse, shields connected at both end are prone to creating ground loops. They are designed for high speed communication of digital data, not for ensuring the lowest analog system noise. Shielding one end can work, but still back to the issue of whether your connection supports the shield.

This is another one of those audiophile group thinks (not offence @erik_squires ). People just assume shielding must be better, therefore it must sound better. Shielded at both ends cable was designed for noisy commercial environments, not for your typical home use. The shields are to protect from external noise, in a high noise environment. It was not targeted at home environments. The shield at both ends is a recipe for ground loops where they would not have existed with unshielded cable..

@erik_squires , sorry that is wrong.

Many shielded ethernet cables ARE shielded on both ends, and that shield connects to case ground on both ends. Audio circuits often have capacitive couping to case ground if not a direct connection from the DC ground to case. Surprisingly many linear supplies use a grounded plug, as do most things with metal cases and integrated AC supplies.

POE, if compliant to the specification is also galvanically isolated.

If you don't know how your shielded cable is built, you are better off in most cases not using a shielded cable because to your point, the data portion of the transmission is galvanically isolated.

@erik_squires ,

With the twisted pair, you wound need to be running them pretty close. Packet bursts could demodulate to audible frequencies so there is a mechanism for the noise transfer even if the transmission frequency is high. I suspect this would be not much of an issue at 100M or 1Gig, more at 10M though since those high frequencies would be too high to even be demodulated as bursts at the power level.

@erik_squires ,

Except the Ethernet connector, metal shell, where the connector plugs into, is usually connected to the metal enclosure to improve the EMI. Even before shielded Ethernet cables were common, most connector shells were metal to form a seal with the metal enclosure for EMI purposes. I am well aware of Ethernet implementation (hence why I know POE is galvanically isolated if done to the specification).

Signal grounds very commonly have capacitive connections to case grounds where they exist for noise reasons.

In the average home environment, unless you are co-running your Ethernet in long run in parallel with a seriously noisy AC like in industrial/commercial, there really is no need for shielded. There simply are not the noise sources to make a difference. As you noted, it is already galvanically isolated.

@erik_squires , I would have more faith in a lower cost, higher volume product from a lesser vendor, that has the proper equipment for testing, and probably more experience, that a boutique vendor who in many cases is winging it.

I am not saying that is exclusively the case, but measurements by Stereophile/ASR have shown enough "high end" equipment to have questionable performance, even on the basics, that I have some confidence that is correct. I would expect the larger high end vendors to be designing "properly", at least I would hope that is the case. Fortunately, this is an easy one to test. Measure the resistance/capacitance from the Ethernet jack -shell to the case.