Why Power Cables Affect Sound

Actually, I believe folks here are confusing photons with protons.  If you get photons in your cables, your least problem is sound quality.   Rather you have an arc happening inside the cable, which won't stay inside the cable for long.Signal and energy travels in the E and H fields on the wire, which are at right angles to one another. I think some folks were trying to state this in words of some sort.For more information on some of the aspects of why power lines can affect sound, see my other post: A problem with AC Power you may not have considered. 

Please explain how the noise of the switching of a full wave rectifier in a power supply can pass back through the primary winding of the power transformer and through the power cord and end up on the AC mains.

I can answer this question - what happens is the spike is transmitted both via radiation and by conduction through the transformer.   Power transformers do have a bandwidth and it is surprisingly wide.  I don't believe I have ever measured a line isolation transformer with less than 100KHz of bandwidth, although they are not always flat.  

So, the diode switching on and off creates a current surge when it turns on and another when it turns off.   Given we have inductance in the transformer as well as the line itself, the current starting and stopping abruptly causes a spike in noise on the line.   That spike is sent out through the power cord and will affect anything susceptible nearby on that line. Some amplifiers designs have components to squash that spike internally when it is created, others do not. 

The voltage spike is dependent upon the change in current divided by the change in time times the inductance.  That is, the bigger change in current when the diodes turn on or off creates a bigger spike.  The change in time is dependent on the turn on or turn off time of the diode, determined internally by the design of the diode.   The inductance is both the transformer and grid together.   

erik_squires is right, one does not want that noise coupling into audio equipment.   If one has a transparent power cord connected then that equipment has to deal with the noise.   If one has a power cord connected that doesn't conduct the noise, then the equipment doesn't have to deal with it.  

@jea48  - "Well designed"  what does that mean?   If you look at the power cords out there, they all have widely differing design concepts.   If you had a power cord that intrinsically attenuated noise say 40+ dB from 30KHz out to 1 GHz while having 0 dB at 50 or 60 Hz, then sure it would keep the noise out.   If there is one out there that does it, I have never heard of it and it probably wouldn't be using copper or silver for a conductor.   The only way I know how to do it is with a filter. 

@elizabeth She has a good point.  I designed a power cable with a built in line noise filter and I wanted to sell it for $99.00.  The idea was I would publish the measured performance it produces, at least folks would know what they are getting.   Well, I couldn't do it at that price point.  Even if I built 1000 of them, I still couldn't do it for that price point.   The world does not need another $600 power cord - I don't care how good it is - there are other options.

I also need a power cable that was 24 feet long, at that distance making one started to make sense since the factory ones get pretty pricey at those lengths.   Unfortunately Pangea doesn't make one at that length and when I called the company I discovered it can't be custom ordered either.  So, I am building it. 

@mrdecibel - one thing that might pacify the naysayers is some real science in the marketing and advertising from some power cable companies.   Gosh, it is sadly lacking with some companies and I get real squeamish about shelling out a few hundred dollars based on nothing more than advertising and few raving comments from unknown people.    Yeah, some companies allow a full refund if it doesn't improve the sound but I am still out the freight and I am not willing to put my freight money based on ads.   There is plenty of information in this thread as well as this site to confirm cable differences but that is not advertising and little of it is science.

Actually, if one had a spectrum analyzer then one could see the improvement since it is easy to measure the power output with and without the new cord for a given piece of music.    Once you have it hooked up, there is a LOT you can measure.  Granted, not every audiophile has an expensive chuck of test equipment lying around.  

I would be most audio companies don't spring for the equipment, though.  Too pricey and it is mostly useful for R&D rather than production.

@phomchick - Actually I doubt most cable companies could afford the R&D equipment to define their products improvements.   I suspect most of these guys are small shops.

Guys, Two things -

First, I have a question - does anyone know when the first audiophile power cord was announced or sold?  I know it came after interconnects but I was wondering what year it was.  Mid 1980's?

Second - Regarding why equipment manufacturers use standard power cords instead of audiophile ones is partly cost, which was already discussed, but the main reason is a UL listing.   Few PC companies have gone through the cost of getting UL approval on their cables.   Should something go wrong and a fire result, it is the amplifier manufacturer that will be sued.  yes, perhaps the cable company will be sued as well, but that amplifier company has no defense since they opted to use a non UL approved product.  Simply building a PC with UL components does not make it UL listed.

Funny, all this time I thought this thread was about power cords and they sound the way they do rather than digital vs analog and magnets versus phooby dust.  Maybe I need new glasses?

@doitwithlife - Rather than explain why, can you explain what the differences are?  That is, voltage waveform differences, current waveform differences, mA, mV, etc.  

Why?  Because you have to sell your product.   First a buyer has to believe your product is worth at least what you are asking.  Second, the more you add cost, the more the retail climbs, making it harder to sell and harder for the buyer to justify the cost.   Third, no matter how much a power cord improved the sound, there are folks out there who won't believe it and aren't willing to spend more bucks for something they don't believe helps.  Fourth, it is one thing to buy a quality line cord that is mass produced, UL/CSA approved, and is independently tested safe; it is another to make a better line cord in small quantities that adds another 100 bucks to the retail price.   It is impossible to compete with economy of scale in manufacturing - that is a factory making 5000 line cords a day and you in your small factory struggling to make quality audio gear at 10 pieces a day.  

As for the car / tire improvement, one manufacturer was sued a few years back for doing just that.  They chose a 3 season tire that clearly outperformed the 4 season one but was sued when the owner crashed during wet weather.   All cars today are sold with all season tires, just for that reason.  

@Geoffkait - Actually, no.  Don't forget, you have markups involved as well.   Distribution, reps, dealers, freight, warranty, UL codes, all that adds a percentage.  That 50 dollar cable will add an easy 250 to 300 bucks to the retail price before the customer sees it on the shelf at his favorite dealer or spiffy catalog. 

Is that Model HPSPC High Performance Spiffy Power Cord you want to use UL/CSA approved?  No? So a fire, which may have nothing to do with the amplifier but is related to the outlet on the wall, gets the manufacturer sued.   They chose to put a non UL approved cord in their product and they will most certainly lose in court.  Of course if you do replace their UL/CSA cord with the HPSPC and the place burns, the manufacturer is safe.

Don't underestimate audiophiles, you might consider the Analysis Plus Oval to be awesome, but I'd bet my next paycheck there are others on this board who would disagree and prefer a different power cord.  Do you seriously expect them to fork over 250 bucks for a cable they won't use and then go out and buy another $XXXX audiophile power cord?  Or, "Why should I spend that much when I can go buy Brand A power cable for only $99 and it sounds better to boot?" 

I do agree that the power cord should be of quality and heft, but that is less than a dollar in quantity, if that.   One audio company for which I consulted some years back, purposely tossed in a cheap RCA interconnect, even though their power amplifier was well reviewed in the press numerous times and most of the reviewers mentioned getting better interconnects to bring out the full potential.  Their reasoning was "An audiophile is going to buy better cables anyway and we have no idea what they prefer.   At least they get something to plug it in while the figure out what they want to do."