I'm doing some research to try and build my own high quality power cable. I always like DIY projects, and the good cables are all way to expensive for me. $1800 for a power cable? Yeah, i'll pass on those. In my research i came across a property of wires called the skin effect. Its a little complicated, but i think i get the idea, which is that heavy gauge wire has a very low resistance to DC and low frequency AC signals (like the mains power frequency) but they actually have a higher resistance to higher frequencies. Correct me if i'm wrong. The way i see it, a very heavy gauge cable could be used to filter out the type of high frequency noise on the AC line that expensive cables claim to get rid of.
Is this a decent theory? If so, what are the benefits of using different materials? Is silver really any better than copper? It sounds like silver is better at high frequncies, so would i actually be better off with something cheap like really heavy gauge copper?
Also, what kind of frequncy range is the noise on a power line usually at? Mega of giga hertz? Or much lower?
Your strongest signal on your power cord is, of course the low frequency 60 hz power. Anything in the Mhz or Ghz range is inaudible and will probably not amount to a rats ass. Any high frequency noise on the power cable should be shunted to ground by the filter caps in your power supply. If the caps in a power supply will reduce a 60 hz ripple current to acceptable levels, then signals in the Mhz or Ghz range have no chance. If you have a noisy amplifier, it probably has nothing at all to do with your power cable. If you're picking up radio stations with your amp, then you need some high frequency filtering in your preamp, not a fancy power cable. I would think that heavy gauge wires would be less flexible and more likely to break. The quality of having low impedance at dc and low frequencys while having the impedance increase with frequency is called inductance. It would be much easier to put an inductor in series with your power line than resort to using thick gauge wire.CHeck out http://en.wikipedia.org/wiki/Choke_%28electronics%29 (http://en.wikipedia.org/wiki/Choke_%28electronics%29). There may be issues other than high frequency interference to consider. If you have a really high power amplifier, you may want to have a power cable rated for the required current. I guess there may be something I'm not considering, and I'm sure anyone with more experience than I will point it out if I am wrong, but I really do not see any need for special power cables.
Look further into skin effect. COnsider at what currents it comes to light, and in what sorts of conductors, and at what frequencies. Further, read up on who has to consider skin effect as an important consideration - in other words where does it come up in daily use. A 9v battery circuit need not concern itself with it, but a high tension cross country power line might. I think putting it in its proper context might shed some light onto whether it applies to your amp's power cord in the slightest, or not.
Perhaps the skin effect is relevant for engineers working for the power company and anyone working on rf applications. But I really think the skin effect is irrelevant when considering power cables for audio amplifiers.
Skin depth for copper @ 70F is 8.5mm - much more of an issue, skin effect, at higher frequencies. Permiability of the material is also in the equation - iron/steel wire is only used at the center of high energy transmission lines - can you see why?
Note that there is a gradual change in phase as you increase "depth" into conductor. For more fun google skin effect and super conductor. Now I would pay $1800 for SC mains cables ;)
Ok, suppose you had a power cable that had some measurable skin effect for high frequency noise. How much impedance will this create for a short power cable. And, you're talking about a high impedance signal to begin with. Plus, once again, in the power supply, you'll have at least one really large capacitor that will easily shunt this hf interference to ground anyway. So I still do not see how this is relevant to power cords for amplifiers.
ok this isn't as practical as i hoped. But what do the high priced IEC cables have that a standard shielded cable doesn't? The shielding blocks the EMI, and a heavy gauge wire makes sure that there is no current loss, so what else could it possibly do? It seems the only two problems that a cable can fix/ prevent are already taken care of.
I think most expensive power cables are made for the sake of being expensive. There are, however, things to consider when choosing speaker cables, audio cables, etc.
Because your power chain does not end on the cable (although that's all that comes with your amp when you buy it).
Much more important is *WHERE* you plug it.
But don't worry, the solution is easy (if a little expensive):
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=110-439&vReviewShow=1&vReviewRand=2818820
*Please* read the reviews and comment..
Because your power chain does not end on the cable (although that's all that comes with your amp when you buy it).
Much more important is *WHERE* you plug it.
But don't worry, the solution is easy (if a little expensive):
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=110-439&vReviewShow=1&vReviewRand=2818820
*Please* read the reviews and comment.. (//http:///%3EMuch%20more%20important%20is%20*WHERE*%20you%20plug%20it.%3Cbr%20/%3EBut%20don't%20worry,%20the%20solution%20is%20easy%20(if%20a%20little%20expensive):%3Cbr%20/%3Ehttp://www.parts-express.com/pe/showdetl.cfm?Partnumber=110-439&vReviewShow=1&vReviewRand=2818820%3Cbr%20/%3E*Please*%20read%20the%20reviews%20and%20comment..)
:lmao:
Hahahahah. After reading the reviews, I think I need to buy a hundred of those. I think I'm in the wrong business.
Anyone had any experience with these? They almost seem to simple to be true, but they're so darn cheap.
All this for a 1% improvement? hardly worth ansering.... :-*
Phil.
Quotewhat do the high priced IEC cables have that a standard shielded cable doesn't?
Marketing.
Okay, shielded mains cables do make sense when you are trying to get your design through FCC type 16/15 testing. Unintentional radiator - more of an issue with Class D (PWM) amplifiers and power supplies.
Maybe for FCC testing, but the real world, it might not help much unless you shield the power cables in the walls of your house.
Mmmmm, maybe you haven't dissected any consumer/computer electronics lately?
QuoteMmmmm, maybe you haven't dissected any consumer/computer electronics lately?
Well, honestly, I haven't too recently. However, I have disected quite a few consumer/computer electronics, and I've yet to run into any shielded power cables. I've seen shielding in other stuff, but not power cables.
Shielded mains cables are used in Industrial and hospital environments to prevent interference from mains into the equipment. These equipment usually measure in micro volts of some thing and very suseptable to mains noise. The screen does not help if teh grounding is noisy. They also use clean earth which is separate from electrical earth.
These equipment also have line filters to filter wide band noise.
The skin effect always exists, but very very negligible at mains frequencey. The higher frequency you go, the current at the center compared to the outer conductor goes towards zero. The dead area also increase with frequency. This increases the effective ac resistance (impedance) of the cable. In practice, they use tubular conductors for high frequency or use litz wire for smallar currents- many fine strands of thin wire insulated from each to improve effective current.
There is no need for these cables in guitar amps, unless it is a marketting hype.
Good grounding methods are just what is required.
regards,
mandu