There's never any popcorn around when you need it....😉
I always thought a power chord what something the lead guitarist did???
In the USA, typical load panels have breakers rated at 10 kiloamps fault current. Meaning, a short at the equipment can do wonderful things to the wiring if it is insufficient for the need. It depends on how far you are from the panel.
The NEC clearly states what is required for bonding safety (well, as clearly as that book can be, which I note is not the best for clarity).
The better option is to use a cord sufficient for the task, and to control the loops formed by any grounding conductors and the signal cables.
I see no attention paid to that, and that is very important.
Me personally, I use the cords that come with the equipment. Understanding loop "goop" has allowed me to run multi-kilowatt portable systems with zero hum and zero noise. But that's just me. (Actually, not me but my roadies... my 9 year old daughter and 12 year old son. well, ok, back in 2002.) It would take 15 minutes to setup two systems, they were so cool. Sigh, the good old days.
Others have detailed the important aspects of the power cord, so I do not feel the need to spew stuff ad nauseum.
Specific questions, no problem.
John
ps. Recently purchased a Behringer mixer/power unit, 4 xlr mikes, 8 input channels, 250 watts per channel output, for convenience when loaning a system to others.
The IEC cord input states "90 watts" line draw.. Yah,..
Apparently Behringer has figured out how to make power out of thin air.. go figure.
I always thought a power chord what something the lead guitarist did???
In the USA, typical load panels have breakers rated at 10 kiloamps fault current. Meaning, a short at the equipment can do wonderful things to the wiring if it is insufficient for the need. It depends on how far you are from the panel.
The NEC clearly states what is required for bonding safety (well, as clearly as that book can be, which I note is not the best for clarity).
The better option is to use a cord sufficient for the task, and to control the loops formed by any grounding conductors and the signal cables.
I see no attention paid to that, and that is very important.
Me personally, I use the cords that come with the equipment. Understanding loop "goop" has allowed me to run multi-kilowatt portable systems with zero hum and zero noise. But that's just me. (Actually, not me but my roadies... my 9 year old daughter and 12 year old son. well, ok, back in 2002.) It would take 15 minutes to setup two systems, they were so cool. Sigh, the good old days.
Others have detailed the important aspects of the power cord, so I do not feel the need to spew stuff ad nauseum.
Specific questions, no problem.
John
ps. Recently purchased a Behringer mixer/power unit, 4 xlr mikes, 8 input channels, 250 watts per channel output, for convenience when loaning a system to others.
The IEC cord input states "90 watts" line draw.. Yah,..
Apparently Behringer has figured out how to make power out of thin air.. go figure.
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Double insulated equipment.
A double insulated component doesn't need/have a ground wire. That's up to the manufacturer to make it double insulated, and in that case, the component won't use the ground wire as it has no pin in the IEC connector.
That said, it is strongly suggested that you only make a cable with 3 conductors, in US parlance; Live black, Neutral white, Earth green. If you dont know what to do with the shield, or cant find AC rated cable with a shield, dont use it. Make sure you have properly terminated and properly insulated connections, follow all manufacturer recommendations and use only mains AC rated materials and components.
This is the best advice in the thread.
🙂
Using standard power cords here too. However, also using a very good power conditioner so don't need fancy power cables. Conditioner is a used Monster HTPS 7000 MkII from ebay. It was designed by own (former member) Richard Marsh, and current member Demian Martin (@1audio ). They did a good job. Highly recommended.
Nothing wrong with the standard power cords - the ones that are included with everything. Except, that they are not shielded, at least all the ones I got!
So I started thinking about the shield and reading DIY cable topics. Looking at all the quality bulk power wire, most of it is shielded.
When I saw this, I thought, I should order the decent quality shielded bulk wire and make my own cables. Since there are lots of options, I simply wanted to find out what is the criteria of selecting or building a good power cable. That's pretty much it. Gathering useful data to make an informed decision.
So I started thinking about the shield and reading DIY cable topics. Looking at all the quality bulk power wire, most of it is shielded.
When I saw this, I thought, I should order the decent quality shielded bulk wire and make my own cables. Since there are lots of options, I simply wanted to find out what is the criteria of selecting or building a good power cable. That's pretty much it. Gathering useful data to make an informed decision.
OK, I need to ask. Are you being serious? If so, no issues with that. I am seriously asking by the way.
Well not being correct, that's for sure. There is no burn-in of metal conductors, Ohm's law applies, pure and simple.
Some people will disagree, of course. IMHO it hasn't been shown that some what they say they hear in cables is physically impossible, although they might be well wrong about causation. There was some discussion about possible measurements in another thread:
https://www.diyaudio.com/community/threads/daves-attempt-at-a-null-test.403488/page-6#post-7460674
https://www.diyaudio.com/community/threads/daves-attempt-at-a-null-test.403488/post-7460696
https://www.diyaudio.com/community/threads/daves-attempt-at-a-null-test.403488/post-7461484
https://www.diyaudio.com/community/threads/daves-attempt-at-a-null-test.403488/page-6#post-7460674
https://www.diyaudio.com/community/threads/daves-attempt-at-a-null-test.403488/post-7460696
https://www.diyaudio.com/community/threads/daves-attempt-at-a-null-test.403488/post-7461484
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Well Ohm was dismissed at first, and Ohm's law still is widely misunderstood (its an observation on the bulk properties of (metallic) conductors at constant temperature, it is not the definition of R as the ratio V/I, although he also intruduced this). Ohm's law holds to very high precision for most metals, at realistic current densities, to less precision for non-metals, and not at all for some substances
Put simply Ohm observed that R was not dependent on current density (or time). It is a function of the type of metal, temperature, and strain field (hence strain gauges). It applies roughly to electrolytes (much less linear) but fails completely for insulators, gasses, vacuum, some semiconductors.
Put simply Ohm observed that R was not dependent on current density (or time). It is a function of the type of metal, temperature, and strain field (hence strain gauges). It applies roughly to electrolytes (much less linear) but fails completely for insulators, gasses, vacuum, some semiconductors.
Okay. If we measure for Ohms, then we will find ohms. If we measure for excess and or directional noise, we may or may not find something there. If we put a copper wire in a Teflon jacket we may find it is a triboelectric generator. If we want to show that a wire is an antenna, we can do measurements for that. Or, if we drive enough current through some speaker cables we might find the cable itself is an electromagnetic transducer.
Regarding the last possibility above, one forum member described the effect at: https://www.diyaudio.com/community/threads/daves-attempt-at-a-null-test.403488/post-7459087
Anyway, IIUC there have been some cases of power cables affecting the sound of amplifiers. If so, then IMHO maybe we should be looking more broadly at the physics before declaring the claimed effect as imaginary. That's all.
Regarding the last possibility above, one forum member described the effect at: https://www.diyaudio.com/community/threads/daves-attempt-at-a-null-test.403488/post-7459087
Anyway, IIUC there have been some cases of power cables affecting the sound of amplifiers. If so, then IMHO maybe we should be looking more broadly at the physics before declaring the claimed effect as imaginary. That's all.
NEC has guidelines on how to wire a building (the local govt. turns those into rules). UL has similar guidelines on power cords, plug strips (power taps in the vernatcular) and even home entertainment systems. They are all focused on safety and quite valid. There usually is a catastrophe or a lawsuit behind each requirement. The ground wire's function is to cause the current limiter (fuse or circuit breaker ) upstream to open. it doesn't contribute much to lower noise. If its a shared ground for several outlets and any of those have products with line filters the ground will be noisy. Isolated grounds are the correct fix but not an easy retrofit. However a GFCI is an accepted alternative to a safety ground. Probably a better alternative.
A shielded power cord is useful to keep the noise conducted from the device (computer, or anything with digital electronics) inside the cable and not interfering with other stuff, like your antique phonograph. Normally you want the shield tied only at the end closest to the noise. in practice you get what the vendor made and move on. . .
I have made power cords with controlled impedance and explored RF termination to keep the junk inside. The junk today can be considerable. Power line communications is used quite a bit even in the distribution system. The transmitters can puse 3A at up to 20 MHz into the power line. Its whats needed to get very far. And it will get into audio if you don't have a filter.
Line filters are a mixed problem at best. Most (except medical rated ones) tie caps from line and neutral to ground. If your ground is not a really good ground it will have some of that leakage on it. If your ground is floating you now have 60V (in the US) on your chassis. And it will follow your audio cables through the mesh of connections. See Jneutron above for another take on this problem.
Safety on DIY power stuff cannot be overstated. Personally when I build a power cord I hipot it to at least 1 KV just to be safe. I'm concered when I see audiophile stuff with no safety approvals where they should be. I'm doublly concered about audiophile fuses. How can you know it will open per specification. Fire is a much more likely problem than electrical shock with bad execution. Even if you don't get electrocuted, explaining to your significant other that the sound was spectacular just before the house burned down would be fun to watch.
A shielded power cord is useful to keep the noise conducted from the device (computer, or anything with digital electronics) inside the cable and not interfering with other stuff, like your antique phonograph. Normally you want the shield tied only at the end closest to the noise. in practice you get what the vendor made and move on. . .
I have made power cords with controlled impedance and explored RF termination to keep the junk inside. The junk today can be considerable. Power line communications is used quite a bit even in the distribution system. The transmitters can puse 3A at up to 20 MHz into the power line. Its whats needed to get very far. And it will get into audio if you don't have a filter.
Line filters are a mixed problem at best. Most (except medical rated ones) tie caps from line and neutral to ground. If your ground is not a really good ground it will have some of that leakage on it. If your ground is floating you now have 60V (in the US) on your chassis. And it will follow your audio cables through the mesh of connections. See Jneutron above for another take on this problem.
Safety on DIY power stuff cannot be overstated. Personally when I build a power cord I hipot it to at least 1 KV just to be safe. I'm concered when I see audiophile stuff with no safety approvals where they should be. I'm doublly concered about audiophile fuses. How can you know it will open per specification. Fire is a much more likely problem than electrical shock with bad execution. Even if you don't get electrocuted, explaining to your significant other that the sound was spectacular just before the house burned down would be fun to watch.
Note that the primary purpose of the Safety Ground/Protective Earth circuit is to trip the circuit breaker if there is a 'ground fault' (short circuit) to the chassis. a GFCI will not perform this function. a GFCI is only for human safety, it will trip when current is flowing thru a human or other path than the supply cord.
You can get ground fault interrupter circuit breakers if you want. My house has ground fault interrupter wall sockets in areas where there is water (kitchen, bathrooms, garage, outside). Bedrooms by code must have ground fault interrupter circuit breakers in the main panel.
"it will trip when current is flowing thru a human or other path than the supply cord." which is what you want regardless of the way the power is disconnected. A GFCI will trip if there is stray current to ground of the supply cord as well. If you have excessive leakage fron line to ground or to anything else the GFCI will open and that happens at 5 milliAmps. The 15A breaker needs 4 minutes to open with 100A, to get a quick response you need almost 1000A. https://www.eaton.com/content/dam/e...s/f-frame-time-current-curves-tc01200002e.pdf The GFCI seems like a much better solution to the insualtion breakdown problem short to chassis problems.
All of the wiring leading to the outlet into which the cord is plugged is unshielded, so I don't see how shielding the last 6 feet or so will help. A shielded power cord would simply dutifully conduct any noise on its unshielded power line house wiring into the equipment it is powering. The only way I see a shielded power cord working is through placebo effect. If you, in your heart of hearts, believe that the shielded cord will help, then go with it. For you, it will work. There is certainly no harm at all in using a shielded power cord, however. If the cord has good build quality, aesthetics, and most importantly UL/CE safety approvals, then it's good to go. That last condition is the most important one to me. Alas, most fancy audiophile-oriented cords don't have that.
+1
You know this from RF spectrum analyzer measurements of shielded power cables, or mathematically derived it from Maxwell's equations? Or, maybe are you just guessing?
"All of the wiring leading to the outlet into which the cord is plugged is unshielded" Not always true. If your house is wired with conduit or "BX" it is "shielded". The goal of a shielded power cord is to keep radiated noise inside. It does work to a degree. The RF losses on power wiring are pretty high so a 6 foot cord can make a difference (especially if you are trying to meet FCC or similar). There is a ferrite loaded jacket material that will make a bigger difference in noise but I'm not sure how to buy the stuff.
Power standards around the world vary significantly. In general they are focused on safety and mostly work. There are local issues you need to be aware of. In the US the power has a definate ground (earth) connection. Some places the power is floating. That requres different approaches to connections and safety. 120 V 60 Hz is the standard in the US and variations all through the western henisphere and Taiwan. 220-240 in Europe with varying grounding and plug types (more an effort to protect local industries than real safety). Australia uses a connector invented by Edison but never used in the US and 220. Japan uses a two pin variation on the Edison connection the US uses except one pin is "ground". Seperate ground connections are not common in Japan. Also 50Hz on one side of the country and 60Hz on the other, making synchronous motors a complicated issue. I'm not up on China, the middle east or Africa. I can only keep so many different ways to distribute power in my head. The point being that you should make an effort to understand your local requirements and safety rules before going near things like power cords or line filters.
Power standards around the world vary significantly. In general they are focused on safety and mostly work. There are local issues you need to be aware of. In the US the power has a definate ground (earth) connection. Some places the power is floating. That requres different approaches to connections and safety. 120 V 60 Hz is the standard in the US and variations all through the western henisphere and Taiwan. 220-240 in Europe with varying grounding and plug types (more an effort to protect local industries than real safety). Australia uses a connector invented by Edison but never used in the US and 220. Japan uses a two pin variation on the Edison connection the US uses except one pin is "ground". Seperate ground connections are not common in Japan. Also 50Hz on one side of the country and 60Hz on the other, making synchronous motors a complicated issue. I'm not up on China, the middle east or Africa. I can only keep so many different ways to distribute power in my head. The point being that you should make an effort to understand your local requirements and safety rules before going near things like power cords or line filters.
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As a test engineer of 40+ years' experience, to me it makes no sense to shield just the last few feet of a long transmission line. If noise is an issue on a power line input to a device, I'd specify a power line filter, rather than depending on a cord to do that. The shielded cord certainly won't hurt anything, though. Another problem with the cord is that if it's a detachable one, then it's possible that some other unshielded cord could be accidentally used instead, and there went your 'filter'.
I guess what I'm trying to get at is that your opinion seems to be somewhat at odds with that of @1audio. IIUC, he is very much a measurement guy with a well equipped lab. Presumably, he speaks from the position of having done measurements, whereas it more or less sounds like you are relying more on intuition in this case? Also, part of what makes me suspect that 1audio is likely onto something is the high levels of domestic EMI/RFI at MHz and GHz frequencies we see today. Six feet of shielded line might have a substantial effect at such frequencies, or would you disagree?