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Power Cables... Really? - Page 6  

post #76 of 417

Good test, I would make sure to choose a good variety of power cables though. Some 50 ft long, some with no cable, some very shielded, some unshielded and with a microwave next to it, etc.

post #77 of 417
Quote:
Originally Posted by Dookky View Post

I feel like this could be tested with some common equipment. All one needs is an oscilloscope and a means to capture wave points on a computer (an A/D or simply plug it into your sound card and use audacity, after proper attenuation of course). Unfortunately I don't have enough money to buy an o-scope nor do I have a means to capture the waveform on a computer, YET.

 

Take both a standard and an after market cord and hook it up to the o-scope, that way we can directly compare the waveforms.

Next get those waveforms into a computer and we can run a Fourier transform and look at both spectrum.

 

From what a professor told me, added harmonics in analog signals is what he considered to be the "warmth" people speak of. But, basically each spectrum and waveform should be different. That would be DEFINITIVE proof that a power cord COULD make a difference.

 

My next concern was how much this would pass through a converter, and unfortunately my power electronics class was only an intro course, so we didn't get into this.

 

DOES THAT SOUND LIKE A GOOD TEST?

 

EDIT: Considering it should be a DC output there should be NO HARMONICS. But we all no that no converter is perfect and things like this pass through, not to mention the added noise from the switching elements (if its solid state anyway, I don't know about tube converters)


Nordost is already working on a method to measure the effect of power cords (and vibration control) on the performance of CD players, amps...

 

They used a musical signal (and not simple sine waves) and compared the ouput of a CD player before and after treatment. You can find the results here: http://www.nordost.com/downloads/New%20Approaches%20To%20Audio%20Measurement.pdf

Their measurement method is not very simple to replicate as it needs very good measuring equipment. The effects of the power cable that were measured were on the time domain and not the frequency domain (FR, THD, ...). That is why most traditional methods of measurements won't show any difference.

So far, people have focused too much on the frequency domain (like the very simple RMAA tests) and didn't account for the time domain. Recent research, like the one done by Kunchur (see here: http://www.physics.sc.edu/kunchur/Acoustics-papers.htm), has shown that the time resolution of human ears is far greater than was suspected (or taken for granted by previous research).
When doing his testing, he couldn't find a CD player that was good enough to generate the necessary test signals for his test. He had to use a high precision analog signal generator to do his test.

 

That is to say, that with the wrong initial assumptions, it is easy to construct a test where there would be no discernable difference. In my opinion, using "common equipment" to measure the effects of power cables is pointless as it will only lead to inconclusive results at best.

post #78 of 417
Thread Starter 

Indeed, now we need someone to do this! Or I suppose I could do it, I like buying equipment after all.

 

EDIT: didn't see you're post slim, i'll give it a look see when I get a chance.

post #79 of 417

Nordost and acuity also claimed to have measured differences in the frequency domain by using a sound with harmonics and testing power cords, vibration, and power filtering, so I still suggest testing how you originally wanted to, just make sure you have a few really screwed up cables.

post #80 of 417
Quote:
Originally Posted by haloxt View Post

Nordost and acuity also claimed to have measured differences in the frequency domain by using a sound with harmonics and testing power cords, vibration, and power filtering, so I still suggest testing how you originally wanted to, just make sure you have a few really screwed up cables.


But to measure those differences, they used very sophisticated equipment with good time domain performance. It is like jitter for example, Stereophile measures the jitter from the analog output of CD Players/DACs but they use an Audio Precision System 2 to do that. If they used a jittery AD (such as the one included in the emu 0404 usb), their results would be worthless.

The measuring equipment has to be more precise than the phenomenon it is supposed to measure (I am just applying logic). If one is to make such experiments, I recommend using an AD with a known stable clock (such as DCS or Lavry) even if it seems overkill at first hand.

 

I think that doing measurements is good but conducting improper measurements is worse than doing no measurements at all in my opinion.

post #81 of 417
Quote:
Originally Posted by slim.a View Post


So far, people have focused too much on the frequency domain (like the very simple RMAA tests) and didn't account for the time domain. Recent research, like the one done by Kunchur (see here: http://www.physics.sc.edu/kunchur/Acoustics-papers.htm), has shown that the time resolution of human ears is far greater than was suspected (or taken for granted by previous research).
When doing his testing, he couldn't find a CD player that was good enough to generate the necessary test signals for his test. He had to use a high precision analog signal generator to do his test.

 

That is to say, that with the wrong initial assumptions, it is easy to construct a test where there would be no discernable difference. In my opinion, using "common equipment" to measure the effects of power cables is pointless as it will only lead to inconclusive results at best.


Which doesn't have anything to do with power cords at all.  What it means is that a higher sample rate is more useful than originally thought.  To the power supply, there will be no difference between a chunky monoprice cable and a probably-costs-more-than-my-car Nordost cable.  If the device the monoprice cable is connected to is poorly shielded, then spending a few more buck for a shielded power cable may help.

 

The point is, there is no suggested mechanism of action that will allow a simple power cable to change the waveform being sent through it, to any significant degree.  There will a tiny amount of heat lost to resistance.  If the cable is very poorly made or very long then inductance or capacitance could affect the mains waveform.  Or maybe its unshielded and you just forgot to turn of your HERF gun.  Even so, it will have much less effect then the tens of yards of romex in your walls, or the miles of powerlines between you and the local powerplant.  The people who design power supplies know the mains waveforms are ugly.  They make power supplies to deal with all but the very worst.  A proper power conditioner can make a difference, but an extra six feet of conductor, no matter how pure, will not.

 

If Nordost substantiate their claims in front of some independent scientists, they'll be in for a financial windfall, since they will have either demonstrated the paranormal, or a new law of physics.

post #82 of 417

I am myself not an unbeliever in cables, but a true HATER of myths, but to be wise, good cables, ones not too expensive, are nice and fun to have. So this is a middle point among believers and unbelievers (after all, they want us to believe so we BUY, no?). I am also a tube hater , but have some tube amplifiers (DIY) in my desk.  I also bought a Phonitor (tube amps, you lose here) and has bought good cables on eBay (where else that cheap?). I am not going to have $5 cables in my Phonitor, eh? Consider this, remember that in the Middle Ages people believed that the Earth was flat? And that Witches were real? The truth is never given to the mob 

post #83 of 417

maverickronin, some audiophiles go so far as to get a dedicated AC line with very thick home wiring. Some go battery power, others use power regenerators, or big power filter. I notice a lot of "if's" in your post, some which admit some stock power cables may be insufficient. Also you assume that people always make psu's to try to deal with dirty power. Not all psu's are made the same, some are just simple ac/dc adapters.

 

Sorry to keep arguing :p but I do wonder if Nordost will benefit from their research. The cost of cable manufacturing will drop drastically when there is more demand, and when there is more demand, there will be more competition against Nordost. This lowering of price will occur for everything else this research may prove, assuming it does prove it. I am guessing they will get very little financial reward if they succeed, if I was them I'd bury it and maintain the mystique surround expensive cables, science be damned :) what good did it ever do us.

post #84 of 417
Quote:
Originally Posted by maverickronin View Post


Which doesn't have anything to do with power cords at all.  What it means is that a higher sample rate is more useful than originally thought.  To the power supply, there will be no difference between a chunky monoprice cable and a probably-costs-more-than-my-car Nordost cable.  If the device the monoprice cable is connected to is poorly shielded, then spending a few more buck for a shielded power cable may help.

 

The point is, there is no suggested mechanism of action that will allow a simple power cable to change the waveform being sent through it, to any significant degree.  There will a tiny amount of heat lost to resistance.  If the cable is very poorly made or very long then inductance or capacitance could affect the mains waveform.  Or maybe its unshielded and you just forgot to turn of your HERF gun.  Even so, it will have much less effect then the tens of yards of romex in your walls, or the miles of powerlines between you and the local powerplant.  The people who design power supplies know the mains waveforms are ugly.  They make power supplies to deal with all but the very worst.  A proper power conditioner can make a difference, but an extra six feet of conductor, no matter how pure, will not.

 

If Nordost substantiate their claims in front of some independent scientists, they'll be in for a financial windfall, since they will have either demonstrated the paranormal, or a new law of physics.


You don't seem to understand what I was trying to say, so allow me to rephrase:

 

If you won't to test the effect of a change in power cable, it is stupid to try and find a difference in a simple sine wave. What we listen to is not simple sine waves but a complex musical signal.


So far, there is no easy way to measure a musical signal properly. If you look at simple measurements like RMAA, a poor sounding soundcard such as the emu 0404 usb might measure better in the frequency domain than the $27,000 Naim CD555 Cd player. The reason is pretty simple it doesn't cost more than $100 to make a DAC with a good frequency domain performance but it take a lot more to make one with a good time domain frequency. In fact, Kunchur wouldn't have needed to use higher sample rate to generate a proper signal from a CD player. A CD player such as the Naim CD that use R2R dac chips with good digital filters can in fact generate decent sine waves at high frequencies (contrary to sigma delta DACs - see here for example).
 

Saying that "there will be no difference between a chunky monoprice cable and a probably-costs-more-than-my-car Nordost cable" is a stupid comment if:

a/ you didn't measure it

b/ you didn't even try it


For lack of understanding and for close mindedness people believed for a long time that the earth was flat. More recently all CDs were supposed to sound the same (Perfect sound forever) until people started complaining and we discovered jitter.

 

A fraction of audiophiles have been saying for some time that they noticed a difference between power cords (and vibration control devices). Nordost is trying to come up with a way to prove there is a measured difference (the same way we have ways to measure jitter today).

 

Science is constantly evolving. Some assumptions that were considered being true a hundred years ago have been revised/updated today. If you want to believe there is 0 possibility that a power cord can affect the sound, good for you. Nobody is forcing to buy a Nordost power cord.
Personally, I have found differences between power cords, so I will keep using the ones that improve the sound in my system. If at some point, measurements prove that what I am hearing is true then I would have spent my money wisely. If there is no proof (ever) that power cords can affect the sound, I still don't care as it allowed me (for whatever reason) to enjoy my system even more. The way, I see things I am aware of the risks of being "fooled" but I consider that the outcome in both cases is a win situation for me.


Back to the topic of measuring the effect of power cords, if someone wants to do the measurement, better do them right.

- Let's suppose that I am wrong, then we would have used over speced equipment for the test but we still would have good results.

- Let's suppose that you are wrong, measuring a simple sine wave to incorrect results.

 

Even if you don't agree with what I subjectively hear, the proper test conditions I suggested remain right.

 

Anyway, I have said enough on the subject. If people wish to discuss further whether it is possible or not that power cords affect the sound (other than by subjective listening), it is probably better to move the discussion to the sound science forum.

post #85 of 417

Here is a link to a link to the results of a long term power cable test run at Hifi Wigwam. An audiophile power cord, a DIY one and two identical kettle leads were covered with sheathing to disguise them and then sent from one forum member to another. At the end of the test there was no evidence that any could be differentiated accurately. A number of people claimed to hear differences, but some of those were between the identical kettle leads.

 

http://www.hydrogenaudio.org/forums/index.php?showtopic=45432

 

The likes of Nordost try to establish tests where they can find a measurable difference and link that to sound quality. They do that rather than run blind/ABX tests because they know they would be likely to fail such tests, which would be clearly bad for business.

 

If there really was a difference between cables, we would be able to accurately and reliably hear the difference. But we cannot. It is not just blind tests which prove that. The fact that so many people report not hearing differences under sighted conditions and the disagreement between what the alleged difference is and how of a difference it is, suggests inconsistency. That inconsistency would not be there if Nordost cables really made a difference.

post #86 of 417

Here's an easy way to figure out if you need an expensive power cord or any kind of power tweak. Get someone to turn on/off a fluorescent light (the light bulb replacement type) in the next room. If you can tell the light is on or off by simply listen to the headphone, then you will need some type of a tweak.

 

The fluorescent light is well known to generate RFI and odd harmonic to the power line. Because of this, the power company actually has to limit the current caused by this nonlinear loading.

 

If you can detect this real change in the power condition by simply listening to the music, then either you have very sensitive hearing or the PSU will need some tweaking. But seriously, I don't think the fluorescent light or power cable will make any difference. At least no one yet has any issue with fluorescent light.

post #87 of 417

Dvw, one thing I do stand by because you really can hear a difference is power conditioning. Without power conditioning I can hear hiss, with and I cannot. The circumstances you describe would suit a power conditioner more so than a power cord.

 

I use two of the plug in types, both cost about £30.

post #88 of 417
Quote:
Originally Posted by Prog Rock Man View Post
If there really was a difference between cables, we would be able to accurately and reliably hear the difference.


'Tis a lesson you should heed, Try, try again. If at first you don't succeed, Try, try again. Just kidding, I'm with slim.a when he says it's best not to do tests if you can't do it right. Not because I'm against pointless research, but because people like to make faulty conclusions. You falsely believe that if there is a difference it must be reliably heard. Wrong. That's like saying if a monkey could shoot a three pointer he should be able to do it consistently, when he only has to do it once, maybe once in a million attempts. Think about it.

post #89 of 417

@haloxt

 

Let me rephrase concisely.  There is no good evidence that a properly constructed $20 power cable will cause an audio device powered through it to sound any different than it will sound when powered through a $20,000 power cable.

 

I will define properly constructed as shielded enough to reject any household levels of RFI, and designed to prevent inductance and capacitance at the operating current and voltages.  A standard $1 power usually cord meets the second 2 requirements.  I do not regularly shop for power cords but, I assume it will not cost an extra $19,999 to add a braided and grounded shield.

 

The reason I can dismiss Nordost's claims without personally testing them is the same reason I can dismiss fairies and dragons without an exhaustive search of the entire universe.  All the evidence suggests that such things exist only in people's imaginations.  You are correct that Nordost's claims could turn out to be correct after improved testing methodology is developed.  And I could find a fairy in my backyard tomorrow.  Unless I managed to capture it, and submit it for zoological (anthropological?) study or otherwise collect some firm evidence of its existence, I will not decry the disbelievers, sing the praises of our new fairy overlords, or otherwise expect anyone else to believe anything I have to say on the subject of fairies, nor will I begrudge those who say that others should ignore me and go about their business as if fairies did not exist.   My personal experience is not enough to prove the existence of fairies to anyone else but me, and if I spend the next several years searching for another fairy, and never find one, then I may come the realization that my perception has failed me and that I saw something which was not actually there.

 

Nordost's claim about it's cables is a rather extraordinary one, and as such it requires extraordinary evidence.  Here's an example.  Let's say I tell you I own a dog.  It's a simple claim.  Many people own dogs, and why would I lie, it's nothing to brag about.  Now I claim I own a parrot.  Less common but still common enough.  You may want a little more evidence though.  Here's a nice high-res picture of my pet parrot.  Her name is Hikaru.  That would be plenty of evidence for most people.  What if I said I owned an elephant?  You'd at least want a good photo of me riding it down a residential street, or something else that's difficult to fake, and obviously not at a zoo.  If you lived nearby you'd want to come to house and see it in person.  Now what if I said I owned a fairy?  Who would believe me?  Pictures?  Obviously photoshoped.  Would you even waste your time to come over and look at it?  It couldn't be true after all.  Why bother?  Would anyone believe me unless I carried it around in a bottle, Legend of Zelda style, and shoved it in their face at the first opportunity?

 

Nordost's claims are in the same category as fairies.  They are, in general more plausible, but the fact that they're selling you something instantly doubles (at least) the level of scrutiny required.  Regardless of whether a there is way to measure such differences properly, if they can be heard, they can be proven to exist in a properly controlled listening test.  The fact that Nordost does not provide loaner cables to proper researchers, for proper testing, suggests that they know that their cables do that perform as advertised.

 

The reason my posts contain lots of "ifs" is because I do not claim to know The Truth.  I only claim to know what evidence the scientific method has so far revealed regarding what the truth may be.  I base my opinions on evidence, and as more evidence accumulates, my opinions will change with the evidence.  If Nordost does create a testing methodology to discern measurable and/or audible differences, and if independent researchers following the same methodology can achieve the same results, then I will have been proven wrong.  If that happens I will change my opinion and become a 'believer'.

 

This is probably as far as I can go without violating the rules of this sub-forum, so I'll have to leave it at that.

post #90 of 417

What nordost and acuity are doing is science in progress, albeit there is serious conflict of interest LOL. You claim to be a big defender of science, but I wonder, can you see how you are deterring scientific inquiry? If people want to keep proclaiming they speak for science and that the final word has been said about x y z... then fine, don't expect anything from me, or if you get anything out of me it would be out of pity at the poverty of modern man's scientific imagination. And since I follow Dr. Bronner's moral abc's, sigh I guess I'll always be giving my inane advice.

 

I have my own theories about power cables, but I most certainly have not tested a fraction of them subjectively or objectively. But despite my many strong disagreements with what you've said, it is also my personal belief that power cables don't have to be expensive to be good. In fact, I believe no power cable or home wiring is better :) something I'd like to try out but I'd likely fry myself to death trying to hardwire things together.


Edited by haloxt - 6/17/10 at 4:20pm
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