[Request] Shielded Power Cable

[woodyohill]

LOVE your site and videos. Would love if you could do a video or review of shielded power cable (with drain wire) vs an off-the-shelf power cord! Would love to get this one debunked!

 

[Lambda]

love to get this one debunked!

What is there to be debunked?
A shielded is gonna shielded the electric feed.
Some do a better job then others...
The Question is does it matter.
This can't be answered in general. you can only show it has has no effect on the tested equipment.

 

[Speedskater]

A couple of decades ago, some desktop PC's and some printers came with shielded AC cords (and often ferrite chocks). Mostly to keep the interference in.
But you can't just test the cord, it's a situation specific problem. And a rather rare problem at that!
You need a component that's an interference source and another component that's susceptible to interference at that frequency and the cord needs to be in a position to act as an interference antenna.

 

[Lambda]

A couple of decades ago, some desktop PC's and some printers came with shielded AC cords (and often ferrite chocks).

Back in the days PC cases where made out of 2mm thick steal and had rf gaskets everywhere.
Now PC use 10x the power and they make glass windows in the case

 

[lemnoc]

Back in the days PC cases where made out of 2mm thick steal and had rf gaskets everywhere.
Now PC use 10x the power and they make glass windows in the case

And no requirements for CE approval which is quite bizarre !

 

[amirm]

LOVE your site and videos. Would love if you could do a video or review of shielded power cable (with drain wire) vs an off-the-shelf power cord! Would love to get this one debunked!

What is an example cord of this type?

 

[MrPeabody]

The only discernible reason for a shield on a power cable would be to reduce noise radiated from the cable and picked up by other electrical equipment. But it is pointless, because an noise transmitted into the power cable from the component using that cable would enter the house wiring, which won't be shielded. This is why components are generally supposed to use blocking filters to stop noise from entering the power cable, as Amir explained in one of his videos. A test of this sort would be a total waste of time. What would it be expected to do? How would you measure the effectiveness at doing whatever it is supposed to do? Very curious.

 

[wwenze]

Back in the days PC cases where made out of 2mm thick steal and had rf gaskets everywhere.
Now PC use 10x the power and they make glass windows in the case

And no requirements for CE approval which is quite bizarre !

"Open chassis requirements for board manufacturers suggest that most EMI needs to be suppressed at the board level."

https://www.intel.com/content/dam/s...thermally-advantaged-chassis-design-guide.pdf

However the paper continues with:

"The chassis, however, should provide at least 6 dB of EMI attenuation or Shielding Effectiveness (SE) throughout the spectrum. The goal of 6 dB assumes the board complies with FCC Part 15 (Open Box Test)."

 

[Speedskater]

The only discernible reason for a shield on a power cable would be to reduce noise radiated from the cable and picked up by other electrical equipment. But it is pointless, because an noise transmitted into the power cable from the component using that cable would enter the house wiring, which won't be shielded.

This type of interference doesn't travel very well in AC power wiring systems. So the closer to the source the stronger the problem.

 

[VintageFlanker]

What is an example cord of this type?

This type, I guess:

Assuming the Ground should be attached to the shield through the drain wire... Which quite surprisingly isn't in most Audiophile Power Cords...

 

[paulraphael]

A couple of decades ago, some desktop PC's and some printers came with shielded AC cords (and often ferrite chocks). Mostly to keep the interference in.

This question has occurred to me ... is there value in shielding a power cord to keep it from being a transmitting antenna? I wonder about this especially for environments like recording studios, where there are nests of power cords and interconnects all over the place.

 

[Speedskater]

In the lower post #10 photo, with two exceptions, it seems reasonable.
1] the ground wire should be inside the shield.
2] Teflon is a poor choice for the dielectric. AC power is at low frequencies. Chose a dielectric that has poor high frequency (interference) performance.
But still, seldom is a shielded power cord needed.

 

[solderdude]

This question has occurred to me ... is there value in shielding a power cord to keep it from being a transmitting antenna? I wonder about this especially for environments like recording studios, where there are nests of power cords and interconnects all over the place.

The interconnects in studio are nearly always shielded balanced cables so is no problem. Mains cords in studios also are regular cables, not shielded

 

[Lambda]

This type, I guess:

What a load of BS!

I don’t get cabalphiles.
Assuming for a moment i want to believe.
This heat shrink tubing looks cheap and armature.

And if i want to use Audiophile power strips or power conditioners, Why use the cheap s***t NEMA plug made from stamped sheet metal

why not:

Or Harting

Or Lemo:

 

[Harmonie]

Eupen cables are pro and not expensive and you can DIY

https://www.audiosciencereview.com/...d90-balanced-usb-dac-review.10519/post-556805

 

[Harmonie]

What a load of BS!

I don’t get cabalphiles.
Assuming for a moment i want to believe.
This heat shrink tubing looks cheap and armature.

And if i want to use Audiophile power strips or power conditioners, Why use the cheap s***t NEMA plug made from stamped sheet metal

why not:

Or Harting
View attachment 117638


Or Lemo:

 

[MrPeabody]

This type of interference doesn't travel very well in AC power wiring systems. So the closer to the source the stronger the problem.

Perhaps you could say this in a more quantitatively meaningful way?

 

[Speedskater]

From a test on balanced audio cables, the info can be extended to power cables:
There are important implications of this data with respect to radio frequency interference to audio systems. For all practical purposes, any VHF or UHF interference that is injected into audio cables more than a few tens of meters from their associated electronics will be significantly attenuated before it can be detected. This means that what matters to the system is the signal strength in the immediate vicinity of the potential detector (victim electronics).

My research on RF susceptibility of condenser mics, published as AES preprint 5720, confirms this hypothesis. A 5 watt VHF and UHF transceiver and a 2 watt 850 MHz digital cell phone were used to inject interference into more than 50 mics. For all but a few mics with extreme susceptibility, no interference could be caused to the mics more than about 1.5 m along the cable from the mic using standard digital audio cables, and even within that distance, susceptibility was confined to one or two maxima along the transmission line. Similar results have been observed with mic and line level input and output stages

 

[dfuller]

The interconnects in studio are nearly always shielded balanced cables so is no problem. Mains cords in studios also are regular cables, not shielded

Yup, I make it a point to run everything I own over XLR with balanced operation. Keeps noise down. I get nasty ground loops from my computer if I don't.

 

[MrPeabody]

From a test on balanced audio cables, the info can be extended to power cables:
There are important implications of this data with respect to radio frequency interference to audio systems. For all practical purposes, any VHF or UHF interference that is injected into audio cables more than a few tens of meters from their associated electronics will be significantly attenuated before it can be detected. This means that what matters to the system is the signal strength in the immediate vicinity of the potential detector (victim electronics).

My research on RF susceptibility of condenser mics, published as AES preprint 5720, confirms this hypothesis. A 5 watt VHF and UHF transceiver and a 2 watt 850 MHz digital cell phone were used to inject interference into more than 50 mics. For all but a few mics with extreme susceptibility, no interference could be caused to the mics more than about 1.5 m along the cable from the mic using standard digital audio cables, and even within that distance, susceptibility was confined to one or two maxima along the transmission line. Similar results have been observed with mic and line level input and output stages

I'm uncertain as to exactly what problem or issue is supposedly correctable by using a power cable with a shield. When I wrote that any noise inserted into the power cable by the component using that cable would enter the house wiring, and you responded by saying that this type of interference doesn't doesn't travel far, my interpretation was that you were saying that since it travels only a short distance, it would potentially make sense to shield the cable given that the RF noise is only going to remain on the AC wiring for a short distance roughly matching the length of the cable from the wall outlet to the component. But I'm not entirely certain that my interpretation was correct.

Also, if you could provide a link to the article you excerpted, I will take a look at it to see if I can figure out what the writer is saying.