I'm building a couple of power cords using Furutech plugs and cable. The cable has a braided copper shield which, as I understand it, should be connected to the ground wire at one end of the cable―either the device end or the power source end. Or maybe both, I don't know. Any suggestions would be appreciated.
They add about 6dB of coupling between the mains leads. That reduces differential mode noise. Not much use on common mode.
In total noise reduction it has a bit of other effect as measured. However as the inductance of the ground connection is so high that had almost nothing to do with anything of practical value.
If the shield is grounded to the case it acts as an antenna and can increase the EMI noise level.
If connected to the safety ground, it will couple any noise found there into the common mode AC line EMI.
So the answer is it does not need a connection, but the AC safety ground side is a much better choice if you must ground it.
Well the interference antenna doesn't end at the wall receptacle. But the other interference antennas (I mean the other hi-fi components power cords) are all nearby.
Jim Brown often writes about these kinds of interference problems:
Antenna Action The most fundamental cause of radio interference to other systems is the fact that
the wiring for those systems, both inside and outside the box, are antennas. We may call them
"patch cables" or "speaker cables" or "video cables" or "Ethernet cables," or printed circuit traces,
but Mother Nature knows that they are antennas! And Mother Nature always wins the argument.
and about power cords and Ham radio:
Power Supply and Control Wiring can also act as antennas. When I bought the house I owned in
Chicago, I upgraded the electrical wiring and put all of it in steel conduit (EMT). This shielded the
wiring, so that only the short power cords between equipment and the wall outlets could act as
antennas. The house I recently bought in California is wired with no conduit, using unshielded
parallel conductors. Thanks to its length, and the fact that it is not shielded, this wiring acts as an
effective receiving antenna for the RF I am transmitting, and an effective transmitting antenna for
the RF trash generated by computer equipment, power supplies for low voltage lighting fixtures,
and even battery chargers.
That's the "Pin 1 Problem" that Neil Muncy (RIP) first wrote about some 23 years ago.
It's why shields and steel conduits should only be connected to the chassis.
Jim Brown's remedy for power line interference is correctly chosen and placed ferrite chokes:
"RFI, Ferrites, and Common Mode Chokes For Hams" (skip over the Ham sections)
http://www.audiosystemsgroup.com/RFI-Ham.pdf
"Understanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems"
http://www.audiosystemsgroup.com/SAC0305Ferrites.pdf
"New Understandings of the Use of Ferrites in the Prevention and Suppression of RF Interference to Audio Systems"
http://www.audiosystemsgroup.com/AESPaperFerritesASGWeb.pdf
"RFI, Ferrites, and Common Mode Chokes For Hams" (skip over the Ham sections)
http://www.audiosystemsgroup.com/RFI-Ham.pdf
"Understanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems"
http://www.audiosystemsgroup.com/SAC0305Ferrites.pdf
"New Understandings of the Use of Ferrites in the Prevention and Suppression of RF Interference to Audio Systems"
http://www.audiosystemsgroup.com/AESPaperFerritesASGWeb.pdf
Remember folks the snake oil peddlers and others MUST invent a "problem" that their product will solve, so any of you proposing an application / solution to said product is aiding their marketing in this thread. In some cases they can point to a forum discussion like this one as some sort of validation because often there is zero censuses. I say show me the problem 1st before proposing solution. But audiophiles like the thought of extreme components somehow working in their favor by 6 dB ( majick and numerology ). haha
Sure if I live under a broadcast AM transmitter AND I use audiophile approved minimalistic gear I might see a problem and I have no doubt this so called shield could indeed make it worse before better. But otherwise youll have better luck investing that money in the state lotteries.
Sure if I live under a broadcast AM transmitter AND I use audiophile approved minimalistic gear I might see a problem and I have no doubt this so called shield could indeed make it worse before better. But otherwise youll have better luck investing that money in the state lotteries.
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It's just a statement by an interference expert written 7 years ago, it's not a contradiction.
I don't know about Mr. Brown, but I don't agree with that.
Especially because filters work best well above 100 kHz and much component power supply noise is well below 100 kHz.
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