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power cords

post #1 of 12
11/2/04 at 4:16am
Thread Starter 
just a little question! i know its not good to have power cords too close to signal cable but does it matter if power cords are to close to each other. because my floors like a snake pit of power cords! if so what do you do to sort the problem out?
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post #2 of 12
11/2/04 at 2:56pm
Are they decent quality shielded cords or are they basically stock cords?
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post #3 of 12
11/2/04 at 8:37pm
All your power cords are carrying the same "signal" and are in phase. I doubt that this will introduce any audible problems. If someone suggests that it will, ask them to explain to you how they have their electrical service entrance wired, as the circuit panels on most residences will make your tangle look as orderly as a bonsai garden.
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post #4 of 12
11/2/04 at 9:30pm
Isn't it possible that unshielded power cords could be conductors of RFI and EMI (or whatever you call it), and that the proximity of such cords to one another could exacerbate this problem? I don't know the answer to this, but I know that replacing the stock power cords in my system with shielded power cords made a significant difference, which leads me to ask the question.
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post #5 of 12
11/2/04 at 11:50pm
That could cause a problem. You could find out for yourself by listening with your CDP at pause and your amp at medium/high level to see if you can detect any noise coming into your system. Then separate your CDP and amplifier power cord from the rest of your power cables by suspending then from the floor, away from the your other power cables & both the CDP and AMP power cords away from each other, ( I used docking tape for this experiment) & listen again. If you cant hear any noise with the all your powercords close to each other on the floor and no diffrence with the power cords separate from each other, then you dont have anything to worry about.
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post #6 of 12
11/3/04 at 4:19am
Thread Starter 
im using stock cables, on all my kit the cable seems very much attached to the unit, so i dont think i could upgrade to shielded cables.
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post #7 of 12
11/3/04 at 7:37am
Quote:
Originally Posted by PhilS
Isn't it possible that unshielded power cords could be conductors of RFI and EMI (or whatever you call it), and that the proximity of such cords to one another could exacerbate this problem?
More than possible, I'd say it's pretty likely that every power cable in the average home is receiving, conducting, and radiating some amount of EMI (EMI is the broader term and the one used most often). Does laying them on top of one another make the problem worse? Only if you have power cords with untwisted hot and neutral, you lay them out nice and straight and flat, then tie them together without twisting the bundle. In that case, the magnetic fields provide coupling, which is why you shouldn't do that. A rat's nest is better.

But that all assumes that the EMI source is in one of your pieces of gear and is conducting down the power cable. If the EMI source is elsewhere (like your PC), then it makes no difference how you arrange your power cables. Anyway, it's cheaper to fix the source of the EMI than it is to buy new power cables for every piece of gear you own.
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post #8 of 12
11/3/04 at 5:12pm
Just some input on what I believe to be the relationship of RFI and power cords used in audio systems.

The grunge that you hear along with your musical information is attributed directly the amount of RFI that is both external and internal to your system.
The most sensitive device to that RFI is your cd player.
When the RFI is eliminated from the digital decoding you hear the high notes without the grunge. The grunge is what commonly causes listener fatigue.
There are, of course, other things that cause listener fatigue. Equipment mismatch and a acoustically poor room
The common practice among power cord makers was to shield the power cord with a braiding external to the conductors usually made of stainless steel or copper. While these do a fairly good job at protecting the power cord from external RFI they do nothing for RFI which is already present in the line or system. That is because these metal shields work on primarily a reflective principle.
So yes, shielding is important. The drawback to shielding is that it does roll off the high frequencies. The other method is to not use shielding and arrange the ground in a "spiral wrap" around the positive and negative conductors. This rolls off the highs aka also the grunge that you hear in the highs which is the most noticeable. It also kills soundstage, adds capacitance, and is a really poor cure all.
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post #9 of 12
11/4/04 at 5:32pm
I have to disagree with you on a number of points, Wolffy.

Quote:
Originally Posted by Wolffy
The grunge that you hear along with your musical information is attributed directly the amount of RFI that is both external and internal to your system.
The FCC's radiated EMI test spectrum is 300kHz to 2GHz. I've tested systems that are quite noisy in from 1MHz on up, but are very quiet below 100 kHz. The background on one these systems was black as night.

The SOURCE of a lot of "grunge" (which I'm calling the presence of noise) is often the same as the source of EMI, but what you hear is not EMI but is simply a poorly designed power supply.

Quote:
Originally Posted by Wolffy
The most sensitive device to that RFI is your cd player.
Cables and phono section (if you have one). The signals inside a CD player are relatively insensitive to EMI as there's a preamp right at the read head. The signals from a moving coil cartridge, on the other hand, are in the microvolt range for a couple of feet before they hit the pre-amp. Cable are always a problem are as they are basically antennas.

Quote:
Originally Posted by Wolffy
The drawback to shielding is that it does roll off the high frequencies.
How does this happen?

Quote:
Originally Posted by Wolffy
The other method is to not use shielding and arrange the ground in a "spiral wrap" around the positive and negative conductors. This rolls off the highs aka also the grunge that you hear in the highs which is the most noticeable. It also kills soundstage, adds capacitance, and is a really poor cure all.
Twisting the conductors/ground greatly reduces the capacitance and the local magnetic field. That's why it's done.
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post #10 of 12
11/4/04 at 11:52pm
With all due respect. RFI is a different animal than EMI. That's where my research and experience lies. The B-2 bomber is stealth because it absorbs RFI rather than reflects it. This is due to it stuctural surface which is made of carbon.

Best Regards
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post #11 of 12
11/5/04 at 12:21am
Quote:
Originally Posted by Wolffy
With all due respect. RFI is a different animal than EMI. That's where my research and experience lies.
Perhaps you'd care to clear that up for us then? The difference between EMI and RFI?

regards,

sluggo
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post #12 of 12
11/5/04 at 1:06pm
sure,
The difference is EMI/RFI stand for Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI). RFI covers frequencies specific in the range of 1kHz-10GHz.
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