I understand there is a difference of opinion about shielding interconnects. Twisting the wires tightly together (Cat6 Ethernet, Morrow, and others) is said to provide noise rejection without shielding.
But what about power cords? I have always assumed (perhaps wrongly) that power cords are more likely to give off EMI due to the higher voltage they carry and so should be shielded. Is that right?
I think the general consensus is that if you shield a PC (and the shield is grounded) it should only be connected to ground on one end.
I have used copper foil and conductive carbon fabric mesh over aftermarket cords it is most effective with antenna RF drain to male ground pin. Thus noise external and internal RF is removed.
One can easily hear improvements before and after in lowered noise floor and better fidelity across the spectrum. Cords with addition of an internal silver wire RF drain also improve. Foil is fragile but results over weave address shorter wavelength frequencies better.
No, no and no on SPG, Single Point Antenna grounds - Cable Shield Grounded At One End Only - EMC Standards
SPG are RESONANCE circuits and NOT a RF ground that attenuated RF. The reason people think they work is when a terrible earth ground differential (ground loop) mitigated at the EXPENSE of RF shielding not the other way around. Fix your broken ground to remove the ground loop and this also allows true RF shielding.
Transfer impedance, SEED and absorbing clamp or any RF shield test require a total and complete GROUND and at both shield ends to attenuate RF for ingress or egrees. Power cords are not āhigh-voltageā and if RF is an issue at the IEC outlet it is RF being inductively or capacitively couple to the outlet and into the cable (egress). Most all modern devices include low impedance ground path to RF.
The FCC has class A and B RF limits on equipment that use āopenā IEC connectors. If it passes the UL antenna field tests, no special cord is needed. If it FAILS you need a special design cord that is CAPTIVE to the device (no open IEC socket).
## FCC Class A vs. Class B Emissions Standards
Because theyāre designed for use in commercial and/or industrial settings, Class A devices are permitted to have higher levels of radiated emissions. These environments have less potential for interference with residential electronic equipment. Class B emissions standards are more stringent. Devices in this class are intended for use in a residential setting.
The rationale behind the stricter standards for Class B emissions is that home devices are more likely to interfere with radio or television reception ā as well as other electronic devices, such as personal computers ā if they output an excessive amount of emissions. - What Are FCC Class A Emissions? - Compliance Testing
This is REALLY how it works. A shield has to have BOTH ends grounded to be a RF shield, or you are building a resonance circuit that is usually WORSE at removing RF, never better (see the sourced paper). An open ground end breaks a ground loop that is from a broken ground system and is NOT to be confused with RF shielding, ever.
Another place to go on shields is in here; Technical Papers: Iconoclast Cable
Shields and Grounding.
I know the science is hard and can take decades to learn, but it is what it is. Myth is easy, the truth can hurt. Do the hurt!
Best,
Galen
Thank you!
Dragging up an old topic - but one that has three different recommendations. Iām not trying to pick a fight, but I do invite comments about what has worked for the forum members or to which camp you belong.
The first camp is articulated by Galen stating that both male and female ends of the power cord shield must be grounded:
Second, in a year old video @paul states that shielding should be terminated on the male end of the power cord and NOT both ends (time stamp 1:45):
Then, in this thread from 2020 Power cable selection for conditioners and regenerators @Paul says that the IEC end of shielding is the proper way and that is how PS Audio Power cables were designed:
So, what do community members think?
Thanks!
I go with Galen, he has the credentials and experience.
I donāt know what is right, but my system likes the PS Audio power cables best of all Iāve tried. . . regardless of shielded or not or how they are shielded. But all our systems are a bit different.
This power cord business is a strange one. I must have heard over at least 20 power cords in my system, and they all sound different. On paper Galen is right (as he always does) that data tells you the fact. But grounding is only a small part of contributing factors. The different material used seems to make a bigger difference to me, and of course design in structure is a major factor too.
Yes, good points. I wonder if shielding really even matters in some systems/environments. For instance, as Galen points out a grounded shield at both ends is essential for mitigating RF. But I wonder if RF intrusion differs greatly depending on environment, thus the impact on SQ is subject to environment.
I go with Al Angen as he has the ears and the gears. 
A lot of truth in that.
I just get lucky that I stumble on to things that seem nice.
and what does @aangen say about shielding? Or better yet, what shielding does he spend his money on?
Rabbit hair.
Paul uses SPG to sell a āshieldā, but avoids the ground loop issues with improper bonding on a lot of home earthing systems. However this breaks the shield too making it an antenna. The exact same cable with NO SHIELD will work better and not inductively couple RF resonance into the cord.
Again, for those interested, I have the lab paper on this issue and it isnāt imagined, but a repeatable and even resonance frequency based on length calculated fact Only when a shield is grounded to EARTH (green wire / chassis) will it attenuate EMI/RF. This isnāt a debate, it is repeatable measurements. Quick mental test; Will a coaxial cable work with the outer shield unterminated at one end? No, and also why coaxial systems WORK so well. But, it will pass noise with one end lifted.
Do you want RF resonances in an unterminated shield to inject RF into the cord? That said, the power supply is passed by UL to the strictes FCC regulations and will manage ingress or egress just fine. Only specific devices (VFD drives the eorst offenders) need shielded power cords to prevent EGRESS, not INGRESS to pass FCC class B industrial limits. My PS Audio P20 passes this test just fine to calss A limits, and I use unshielded cables, a LOT of them! No noise at all with a dedicated 20A circuit to the box.
A shielded cord you like with BOTH ends grounded is best. Youāll like it exactly the same unshielded. Or, a cord you like with a SPG ground needs to be made with NO shield or ground both ends.
Paul could also design the cable such that those that can use proper shield grounding can, and attenuate RF. Those with a poor ground differential can have a smaller issue using SPG (RF resonance coupling) than the HUM from a bad ground. All youāre doing is replacing a really bad problem with a far less and inaudible one. But rest assured, a SPG does NOT shield noise, it inductively couples it to the core componets. No shiled test will work unless a shiled is terminated at both ends; SEED, transfer impedance, absorbing clamp or any other.
Again, the data tells you all this, I donāt. Iāve worked and tested this stuff for nearly 40 years now. We sell the DATA, nothing else. Any theories remain theories and we point them out as such until such tome we figure out how to measure them (open short impedance as an example) and or back that into a calculation (skin depth as an example).
Best, Galen Gareis
I donāt give such things any consideration at all. I buy very high quality cables so I donāt have to worry about these sorts of issues.
Some of my power cables allow me to lift the ground. I played with it once. I donāt remember the results.
It would be fun to get a bunch of us in a room with cables that allow lifting the ground and see if anyone notices. We could write a five page white paper on our findings.
If there is one true correct design I would think manufacturers would mention it more.
Thanks for your thorough responses as always. I understand about 10% of it. What ever the right answer is I have really enjoyed my modest power cord upgrades that do have one sided shield grounding that seem to be performing without issue despite the science.
Human preference is illogical. e.g. I much prefer the experience of driving my 1962 Fiat D600 (on a sunny day for short trips in light traffic) even though my high end Volvo has been engineered with much more finesse, safety, and performance - itās just not as fun. But the Volvo is the logical answer.
Stumble away. Some of us have ears, and you are one of those āsomeā.
@tomhail, youād be best served to go straight to the horse, of course.