Power Cord Testing

[Sarius]

Sarius: you are correct. Statements quashing line cord involvment, for the most part, are simple extensions of assumed knowledge.

However, the people who claim to hear differences are also at fault here. What, with their magical, grain boundary, motor-generator, dielectric involvement, jitter, plating, strand jumping crapola..How in the world is anybody to take that garbage seriously, hence take their anecdotal observations seriously??................


Cheers, John

Ah... thank-you. We agree 100%. People jumping all over me might note that I never said that I believed this, I said that I couldn't find any good data either way. Clearly I'm not going to find it here either. As someone who has three research based degrees, and spent 15 years doing engineering R&D testing, I think I've got a reasonable handle on how scientific inquiry is done. Politeness will cause me to refrain from further comment about the quality of the responses I received.

For the record, I've already solved my power cord issues. I did decide to replace my stock cords with a little beaut that's 14 AWG and completely shielded, the shield tied to ground at both connectors. The cost? $6.50 ea delivered. No, not a typo. Did Dancing Virgins appear on top of my speakers stripping away Veil after Veil....... well, I'll just let that be my secret.

 

[jneutron]

It is the job of the amplifiers power supply to deal with this NOT the power cord. Applying a band aid to heal an open gangrenous wound does NOT a cure make. :

It is the job of the power cord to deliver power. It is the job of the supply to keep stuff off the rails.

It is the job of the safety ground within a line cord to keep us free from electrocution risks. Unfortunately, the ground loop that results is a "perk" for the line cord.

Three port design of power amplifiers and other audio equipment is hideously dismal, there is no consideration for ground bounce effects which are conducted into the chassis.

Most audio situations do not warrant deep looking for line cord issues, there is no ROI.

But sometimes, the virtual image can be affected by the ground loop.

I am always amused when an exotic cable vendor claims to have an optomized solution which of course they cannot validate empirically. They often quote a real engineering problem (which usually has little or no bearing at audio frequencies) they solved, yet reject the proven countermeasures to solve it empircally. :

Not only can they NOT validate empirically, they have no clue what they are doing...lights are off in engineering land..you'd think they had a hammer fall on their head..

Only through their casual and uncontrolled listening tests have they allegedly discovered nirvana. I often wonder how they know they couldn't go any further by analytically analyzing the "problem" and using known material sciences and proven EM theory to take them to the next level.

They can't. E/M theory is beyond them.

Stabbin in the dark.

Cheers, John

 

[mtrycrafts]

While I have never heard the 'effect' of changing a power cord, friends of mine who don't seem particularly prone to delusion have, expressing surprise that they heard any difference with borrowed cords (so no purchase justification involved). There is also a consistency of reports found on the web, enough so to make one curious.
.

How do you know your friends are not prone to delusion? How did you test your friends? Are they somehow exempt from being delusional when it comes to audio? Obviously you didn't test their claims for this difference under DBT conditions, or you would have known that they are delusional when it comes to audio. So, you see, you have failed your inquisitive duty yourself, so please, don't try to blame others for your failures.

Since when does consistency of testimonials should make anyone curious? Is it so hard to reason this out without actually taking instruments to power cords???

How about you test your friends in a meaningful manner instead of having the tail wagging the dog. then, you can see how valid their testimonials are.

I hear similar consistency about psychics, homeopaths, holistic healers, astrologers, dowsers, etc. The world is full of consistent reports, yet be worthless. Why would power cords be placed on a pedestal not worthy of?

 

[mtrycrafts]

Ah... thank-you. We agree 100%. People jumping all over me might note that I never said that I believed this, I said that I couldn't find any good data either way.

Not quite correct.
Given the mass of information on the web claiming that there is an effect, no valid research to be found disproving it,

Why not go after the claimants to prove their side? After all, they do have the burden of proof/demonstration of claims, no?




early I'm not going to find it here either. As someone who has three research based degrees, and spent 15 years doing engineering R&D testing, I think I've got a reasonable handle on how scientific inquiry is done.

Well, then, you know or should know who has what burden of proof, right???

 

[Bruno Putzeys]

Hi I don't normally follow the forums but Gene pulled me over to look at this one for a sec.

The basic premise should be that if the power cord makes a difference to the sound of the equipment, the equipment is faulty cq badly designed. Actually, it's a good test. If you go out to buy gear, the shop-owner will be too happy to demonstrate that the most expensive mains cable improves the sound. If you can hear a difference (after correcting for expectance effects!) you know you don't want to buy that piece of gear.

It's quite easy for a power cord to become involved in the sonic equation if:
1)The equipment is unbalanced (ie. has no differential inputs and balanced outputs) AND the circuit ground is hard-wired to mains ground (or if it's balanced but it's got a pin 1 problem). In this case, ground currents, introduced in ways already mentioned by others in the thread, will simply be added to the signal through ground loops.
2)The equipment either produces large amounts of conducted RFI or is very sensitive to them. Some of these expensive mains cords have shielding and ferrite beads and effectively help reduce the problem.

Option 1 shows that the problem is reduced if the mains ground isn't hardwired to the audio (secondary) ground. Of course, this requires adherence to double-insulated safety standards! Don't lift the ground on equipment that has a ground prong!!! The irony is that "exclusive audiophile gear" almost invariably sport IEC inlets whereas mass-market gear has 2-wire mains inputs. That's because when you make 10pcs/year you can afford 10% of your clientele phoning in with hum problems whereas if you make 50000, well... you'll think twice.

The best solution, however, is to use differential (balanced) signalling throughout AND wire the connectors per AES48. This standard says that pin 1 goes to chassis and not to the PCB. Only pins 2 and 3 should go to the PCB, with the PCB only grounded at the chassis. This insures that the audio reference is not the chassis potential and that ground currents through the audio cables have a separate conductor (the shield) and will be diverted through the chassis. In this way you can have your cake and eat it: hard ground the chassis to safety earth and not have ground loops causing hum. In fact, you will have ground loops, but your music is safe!

Option 2 can only be addressed by good design. Up to a few 100MHz, the onus is on the circuit board designer. If the bare circuit board has EMI problems below 300MHz, don't bother putting it into production. Above 300MHz, circuit board design only goes a so far, and you'll need to take further care at the chassis layout and construction.

 

[Sarius]

That's because its really not worth wasting ink on.............

Gene,

If you conduct a properly designed test there are only two possible outcomes. If, as you expect, you find no effect, you will have definitively debunked one of the more pervasive myths, one that has instantiated itself throughout the audio world. A myth that is costing gullible buyers thousands, if not, million of dollars of wasted money every year. That I would suggest would be well worth wasting ink on. I was, perhaps wrongly, under the impression that challenging such myths one of the missions of this site.

It's not like a belief in the efficacy of these wondercords is limited to some lunatic fringe, you find these things in every store both actual and virtual and they are heavily pushed in most publications. As currently there is simply no debunking out there to point to, I fail to understand why the site that claims to be devoted to finding the truth in audio would not wish to put this to rest once and for all.

 

[Johnd]

If you conduct a properly designed test there are only two possible outcomes.

I fail to understand why the site that claims to be devoted to finding the truth in audio would not wish to put this to rest once and for all.

If I could interject here...

The former is simply not true, or, it looks at the issue too simply. A proper test on power cords would test not only whether it works or not, or whether it "improves" the sound or not, or introduces less noise or not, etc. It would look at all these things, and more.

In response to the pursuit of the truth...One needs not dispel all the myths, untruths, and blatantingly misleading marketing schemes to pursue the truth, or even find the truth. Only if a theory is based on sound principles, and has advanced at least some amount of empirical evidence, as Gene noted above, is it then a worthwhile venture to disprove and debunk those fallacious assertions.

 

[Sarius]

If I could interject here...

The former is simply not true, or, it looks at the issue too simply. A proper test on power cords would test not only whether it works or not, or whether it "improves" the sound or not, or introduces less noise or not, etc. It would look at all these things, and more.

There is a saying "Excellent is the enemy of Good".

I would suggest that the claim seems to be that if one were to monitor the amplifier power inputs, while the amp is under dynamic loading, through first the stock cord, then through some wondercord- that you would see no difference at all on the input 60 cycle sine wave.

I, and most reasonable people, would accept that if no differences can be detected at the power input through two cords representing the extremes of the product , then there could not possibly be an effect on the sound.

If, for some reason, a difference was detected at the amp inputs ....... then that would be interesting....

..... and, only then, worth a deeper look. If the input sine waves just kept happily marching on with no changes in amplitude, phase, and any frequency additives while the amp was driving difficult speakers at high volumes with demanding material....... then there would be, IMHO, definitive data that could be referenced to debunk the power cord myth and of great value for the many people thinking about such a purchase.

Subjective listening doesn't need to be a part of it at all.

 

[gene]

I would suggest that the claim seems to be that if one were to monitor the amplifier power inputs, while the amp is under dynamic loading, through first the stock cord, then through some wondercord- that you would see no difference at all on the input 60 cycle sine wave.

I, and most reasonable people, would accept that if no differences can be detected at the power input through two cords representing the extremes of the product , then there could not possibly be an effect on the sound.

Most people whom believe in audio cable voodoo aren't reasonable. They reject any form of onbective anaylsis or measurements as proof and they also reject controlled DBTs to eliminate biases. IN fact, some forums BAN the discussion of DBTs!

I spent over 2 years debunking cable myths and quite frankly got a little tired of it. The cable soothsayers minds are already made up and I have little to no desire to change them. The exotic cable vendors will continue to rip these folks off b/c the FTC won't step in and fry them since they are relatively small potatoes in the grand scheme of things. In the end, the cable soothsayers are happy with their newfound religion, and the exotic vendors are happy to sell them their medicine. More sensible people will avoid all of it with a 10ft pole. So the world goes on.

In the meantime, we focus on more relevant topics in audio that affects system performance

 

[jneutron]

If, for some reason, a difference was detected at the amp inputs ....... then that would be interesting....

..... and, only then, worth a deeper look. If the input sine waves just kept happily marching on with no changes in amplitude, phase, and any frequency additives while the amp was driving difficult speakers at high volumes with demanding material....... then there would be, IMHO, definitive data that could be referenced to debunk the power cord myth and of great value for the many people thinking about such a purchase.

Subjective listening doesn't need to be a part of it at all.

The ability to test the output for the salient changes does not exist in the measurement world. (A testable claim, of course. I have not found the required equipment, but that doesn't mean it doesn't exist).

For differential localization, the ITD/IID parameters must be measured, to a relevant level. This is as low as 5 uSec for ITD, and god knows for IID, perhaps as low as .1 dB..

Nobody I am aware of, can accurately measure to .1dB or 5uSec, with an impedance as low as 2 ohms, from 20 hz to 20 Khz.

Far too many measurement error sources.

The use of dbt to detect such differential localization may be insufficient for the task. Localization acclimation would confound the test regimen.

Cheers, John

 

[Sarius]

The ability to test the output for the salient changes does not exist in the measurement world..........

John,

I might mention that I'm an ME not a EE, but are you telling me that the ability to clip into the input power terminals of an amp (the connector that the power cord plugs into, if I have my terminology wrong), and look at the input 60 cycle/ 120 V sine wave out of the wall as it enters the amp, while the amp is playing does not exist in the measurement world? I'm shocked

As I said.... I, and I think most reasonable people, would accept that if no changes were to be found in that input, that we can (finally) put the power cord issue to rest.

Now, I know that you, and others have explained to me that it's 'impossible' that we could see any changes.... and you know... I'd almost believe you (all) except for the fact......

That in my previous job I did testing support for a bunch of high test analysts who were modeling mechanical systems on Cray X and YMP's (note the plural) back when they were 'da bomb' in supercomputing. I spent many hours discussing my test results with them, and we saw many 'impossible' things that were real head scratchers. Thus I learned, theory can only take you so far, then you've got to look. When you're dealing with complex system interactions in a dynamic environment, the simplifying assumptions will kill you. That's why we all hated the dynamics classes, where as static's were fun.

I would suggest that when you're dealing with an impedance load than can go from 3 Ω to 30 Ω in a millisecond or less combined with voltages presented that can equally rapidly vary by a factor of a hundred or more and a requirement that those voltage amplitudes must exactly track the input voltage in real time, that the explanations offered to this point might well prove over simplistic, as were the very complex models of what would have seemed like relatively simple mechanical systems proved to be.

More in Heaven and Earth.... ya da ya da ya da.......

 

[jneutron]

John,

I might mention that I'm an ME not a EE,.......

ewwww...

but are you telling me that the ability to clip into the input power terminals of an amp (the connector that the power cord plugs into, if I have my terminology wrong), and look at the input 60 cycle/ 120 V sine wave out of the wall as it enters the amp, while the amp is playing does not exist in the measurement world? I'm shocked .......

No.

I was speaking of the output of the amplifier into the audio load presented by a speaker. This is, after all, where any considerations of effect must be found, yes? Nobody cares about the rails per se, but the output.

Cheers, John

 

[jonnythan]

When someone spends $500 on a power cord, do they spend $50,000 to upgrade their house wiring to the same type of cord? Do they upgrade their circuit breakers with $1000 audiophile-grade breakers? What about the main transformers supplying the house?

What difference does the last 6 feet make when there's 100 feet of standard 12-gauge screwed into a $2 outlet?

 

[jneutron]

When someone spends $500 on a power cord, do they spend $50,000 to upgrade their house wiring to the same type of cord? Do they upgrade their circuit breakers with $1000 audiophile-grade breakers? What about the main transformers supplying the house?

What difference does the last 6 feet make when there's 100 feet of standard 12-gauge screwed into a $2 outlet?

The difference is this:

Your amplifier references it's input to the ground of the outlet that it is plugged into.

If you plugged the preamp into an outlet on the other side of the house, you will create the ground loop from "heck", and will hear all sorts of garbage through the speakers.

Cheers, John

 

[Sarius]

ewwww...

No.

I was speaking of the output of the amplifier into the audio load presented by a speaker. This is, after all, where any considerations of effect must be found, yes?

Cheers, John

Actually, No. What I'm suggesting is, that given the complexity of systems in dynamic environments, and the truly wierd counterintuitive results that I've flumoxed some very good PhD analysts with in mechanical testing, that it is credible that there could be some effect 'at the rails', if I understand correctly what 'rails' are. If you look in the manner that I suggest, and there isn't any effect, then the whole thing is put to bed. If something of interest is seen.... than....well.... that's interesting.

I do know that in ME theory, the nice simple quasi-static equations that we like to use 'cause they're easy go out the window as soon as the system interaction get complex and frequency gets added into the equations. I have reason to believe that something similar happens over in your electron world. Just from the little I know about what's happening on the output side of the powersupply in an amp... it's got to be pretty wild, what with it trying to shove out a high amplitude signal into a low impedance load one millisecond and suddenly seeing a much higher impedance the next with the signal jumping around by maybe a factor of a hundred.

Now, while I know that the input side is 'supposed' to be shielded from all this chaos, and with a quasi-static draw, it probably is. It seems credible to me that under the kinds of complex demands made, that more might be going on than simplistic models are revealing. A very simple look would tell...... I simply can't understand the 'resistence' to taking it. If I still had access to the resources that I used to have, I'd do it myself, but unlike was suggested, a simple multimeter won't cut it, I need to see the actual input signal... better to be able to also see it in the frequency domain too.

Like I said, simplifying assumptions will kill ya, and I simply don't believe that, in the absence of any data, that people can be making credible statements about what may or may not be going on 'at the rails' (assuming that 'the rails' are where the wall power meets the rest of the amp) without looking in this complexity of potential system interaction.

 

[jneutron]

Ah. sorry, I was not clear in my terminology.

A rail is the power supply dc line. Measuring the rail, is measuring the voltage of the power supply line to ground.

If there is sufficient fluctuation on either or both rail, (plus or minus voltage sources), some of that fluctuation can get into the audio circuit.

I am speaking about the grounding system in general. The current that can flow through the ground is capable of inducing voltages in loops of conductor within the chassis of the amplifier. More specifically, the rate of change of current within the ground will, as the induced voltage is actually proportional to the rate of change of the magnetic field that results from the current.

If the ground current is coupling to the input, or to some portion of the amplifier circuit which affords a high voltage gain, this coupling will generate an error voltage. Typically, a home setup does not duplicate a lab arrangement, so this kind of error mechanism is not spotted.

The best example is that of hum. While an amplifier does not exhibit this behaviour at the manufacturer's location, when connected with the "uncontrolled environment" that typcially exists in the home, it occurs.

Cheers, John

 

[majorloser]

When someone spends $500 on a power cord, do they spend $50,000 to upgrade their house wiring to the same type of cord? Do they upgrade their circuit breakers with $1000 audiophile-grade breakers? What about the main transformers supplying the house?

What difference does the last 6 feet make when there's 100 feet of standard 12-gauge screwed into a $2 outlet?

You should drive a solid gold ground rod for the equipment, run the whole system on batteries/inverter with gold wires, cover the room in lead shielding and apply a vacuum

(or just live with it)

 

[gene]

The difference is this:

Your amplifier references it's input to the ground of the outlet that it is plugged into.

If you plugged the preamp into an outlet on the other side of the house, you will create the ground loop from "heck", and will hear all sorts of garbage through the speakers.

In the # of years I have been reviewing equipment, its been rare for me to find amplifiers with poor grounding schemes to even produce the type of scenario you are discussing. That being said, I don't spend much time reviewing ultra expensive esoteric gear, so as Bruno points out, all bets could be off there.

IF you have a ground loop problem, it will easily manifest itself as a low level hum in your system. A magic power cord will likely NOT resolve this.

I have found using STAR grounding schemes in my systems pretty much nukes any potential ground loops.

Much of the better consumer gear these days don't make a PCB to Earth Ground contact and much of the good consumer gear often don't even have a 3rd prong connector so this becomes even less of an issue.

Not sure its worth barking up this tree when there are far more significant issues in audio to deal with like the Room and the Loudspeaker Interaction with the Room, and getting quality Beer into the room, but the latter is left for another discussion

 

[jneutron]

In the # of years I have been reviewing equipment, its been rare for me to find amplifiers with poor grounding schemes to even produce the type of scenario you are discussing. That being said, I don't spend much time reviewing ultra expensive esoteric gear, so as Bruno points out, all bets could be off there.

IF you have a ground loop problem, it will easily manifest itself as a low level hum in your system. A magic power cord will likely NOT resolve this.

I have found using STAR grounding schemes in my systems pretty much nukes any potential ground loops.

Much of the better consumer gear these days don't make a PCB to Earth Ground contact and much of the good consumer gear often don't even have a 3rd prong connector so this becomes even less of an issue.

It is not a matter of looking for poorly designed amp grounding. Nor, is it required that the third prong be there. Neutral is indeed an acceptable path for unwanted error currents.

The fact that you have not witnessed something does not mean it does not exist. It is also clear that if the effect is there, it is sufficiently small that it does not call attention to itself.

A difference that makes no difference, is no difference.

I have seen systems (well ok, heard) that hum as a result of power draw. This being the recharging of the cap bank as a result of drain by the output system into the load causing recharging ac line current to generate input ground induced voltages.

If you have a ground loop induced hum, you are hearing 60 hz induction into the input system. If you are able, through hook or crook, to be able to reduce the hum, you have simply reduced the coupling. The frequency response of that coupling is proportional to frequency (or more exactly, rate of change of current)..this is why light dimmers are soooo bad.

Coupling of the line cord of the amp to it's input is far more notorious. The amp draws haversines, which are very rich in odd order harmonics. If enough coupling is present, this can manifest as an error at the input with 3rd order components. If it is supply induced harmonics, as in bridge to caps, it will be 2nd order harmonics. (such is the workings of non linear devices).

If the amp draw is indeed causing input error via the line cord, it can easily be masked by the output power of the audio signal..If it is very small (as it almost always is), it may or may not be discerned.

Magic cords are worthless, most of the white paper stuff is worthless. If there is indeed a line to input coupling, playing with cords to solve the problem are a crapshoot at best. There is no understanding of the problem, no understanding of the solution, nada..

I also use star based line cord solutions, as I concur with you. The worst case I had to deal with was a 100 foot run of unbalanced ic's between an amp and a source. I fixed the problem by running the power cord 100 feet, wrapped tightly around the unbalanced ic's. problem solved.

Cheers, John

 

[gene]

A difference that makes no difference, is no difference.

So what's the problem

LOL. I luv ya man