Power cord? Why?

I see a lot of posts regarding power cords. I would like to know what sonic difference they actually make. Could anybody explain this in a simple way?

Thank you
Power cords cannot make a "sonic" difference because they make no sound. Any difference must be electronic, subsequently converted to sonic by amplifier circuitry and loudspeakers.

Electronic characteristics, unlike sound quality, is easily measured by objective instrumentation. I will not believe that power cords make any difference until someone shows me the data.

And anyway...your line cord is about 6 feet long. How about the miles of wire that the power travels before it gets to your power cord?

If you are interested, I have a bridge in Brooklyn...
But evidently not an open mind.
I have now installed all high end power cords in my system.
The difference each and every time has been,,,, surprising for lack of a better word. Everyone that has heard my system noticed a difference immediately, depth of soundstage increases, clarity, and more pinpoint
placement within the soundstage.

I suggest if you want to experiment, try a good midgrade one first and see the difference for yourself. They are really affordable on Agon, and I have bought most of mine personally on here, its the best!

Happy listening!
Although this has been asked and answered many times here, I'll add to the database of discussion.

There are many reasons power cords make a difference, and "what sonic difference they make" is dependent on a myriad of design factors such as inductance, impedance, shielding, dielectric, contacts, wire type and gauge..etc etc..

Contrary to the popular refrain "why should the last 6 feet of fancy power cord make a difference at the end of two miles of Romex?" The truth is that the "last six feet" is NOT the last 6 feet from the perspective of the component, it is the FIRST six feet. In addition, EMI and other high frequency noise and interference do not travel down power lines like debris travelling down stream-- most HF noise is radiated from point sources. This radiated noise loses intensity the farther you move awat from the source, and then most of this type of noise is gone, entirely.

Now, the relevant issue becomes what are the point sources of noise that because of proximity, are potentially the most significant in effecting system performance?

Generally speaking, components in an audio visual system are all within a few feet of eachother, they are all interconnected and are tied to a common AC source (dedicated lines help). All of these components have power supplies that radiate EMI noise, and all pass noise in varying degrees back onto the power line via ground. As you approach this combination of power supplies, all of these radiating feilds of energy and noise are converging.

A system of electronis often acts as a "loop" of sorts for radiated noise and energy fields that can not possibly be (entirely) ameliorated by traditional power supplies or out-board conditioning/filtration . The type and form of AC signal isolation applied in those "first" few feet outside a component has the potential to impact the condition of the AC signal as it passes into the power supply. Of course, power supplies have their own methods of dealing with incoming noise, but most manufacturers of electronics will admit, there is no perfect way (yet) to eliminate the effects of noise riding in on the power line.

Of course, there can be exhaustive technical discussions, arguments, counter claims and the like on these forums, but the bottom line is: you HAVE to try these products for yourself within the context of your own system to judge their value and effectiveness. And because the many power cord designs on the market vary widely in terms of quality and design, you should try more than just one type or model.

There are many studios, including those owned by Phillips and Sony, and mastering engineers, recording artists, producers etc. who have found after market power cords to be a valuable tool in improving their systems and recordings. Many manufacturers of electronics/speakers in this industry use and endorse them as well. I think we've past the point where there can be any question whether there are power cord designs that can make a positive difference in system performance. The only relevant issue left is proving to yourself whether a specific product can make positive difference --in your system. Forum Q and A's all become moot at that point.

Happy listening!
Are you asking, How does a power cord affect the sound? Or are you asking, What changes in sound do audiophiles notice when they switch power cords? The answer to the first question is, they don't. The answer to the second question is, the sky's the limit.
Here is my theory as to why they make a difference, with analysis and measurements.

Amplifiers demand current from the power-line when the capacitors in their power-supplies become momentarily discharged due to high-current transients in the music signal. This discharge condition must be quickly recharged from the power-line, through the power-supply transformer, or a voltage sag will occur. Such voltage sags can cause audible distortion at the loudspeakers. If the power-line has significant series inductance in the path from the power panel to the amplifier, this can prevent the capacitor bank from recharging in time to prevent a voltage sag from occurring at the amplifier output transistors. With a low-inductance cable, the voltage drop across the cable will be insignificant during high-current transients, minimizing the voltage sag. This allows all of the current needed by the output transistors to be supplied when they need it, resulting in fast, dynamic response to transient signals.

A typical 6-foot 14 AWG rubber cord and 25 feet of ROMEX has inductance of 7.2 uH and resistance of 235 mohms, ignoring the plug resistance effect. Therefore, the voltage drop at 20kHz will be I*(wL+R)= I*(.905+.235) = I*(1.14). With a 6-foot low-inductance cord and 25 feet of ROMEX, the inductance is 5.9 uH and the total resistance is 147 mohms. This is an 18% reduction in inductance and a 37% reduction in resistance. The voltage drop for this combination will be I(wL+R) = I(.741+.147) = I(.888). So at a fixed dynamic current I, the voltage drop in the entire power feed at 20kHz is 22% smaller with the low-inductance power cord. I would consider 22% to be significant. The reality is even more compelling. When you add in lower plug and receptacle resistance and the fact that the di/dt on the power cord will have spectra well above 20kHz with some amplifiers, the low-inductance cord makes an even bigger difference.

And please don't give me a lot of flack about 60Hz current in power cords. The currents are very high in frequency - just measure them...
Eldartford, I may be interested in that bridge in Brooklyn, but first I have to buy Viridian's open mind. Maybe, in between the two, I will mortgage my home to rewire right back to the Hydro-Québec generating facility in search of the absolute sound and of "emotion" from my system. Remember in selling that bridge these immortal words from the son of a local pawnbroker here: "money talks and bullshit walks". From a bitter, bitter man.
Eldartford & Bomarc, you should consider joining the "Flat Earth Society". After all, if the earth was round, we would all slide off! And if the earth were round and also rotating, we would just be flung off into space. About the same logic here as you guys make in your posts! Or perhaps your systems are just not of the caliber to benefit from the sonic improvements of a good after market power cord. Kind of like re-jetting the carburetor on a Yugo to get better performance!
I beg to differ. Powercords do change the sound of any system. Or, am I the only one that hear a difference in every powercord I've plugged into my system? (That would be an argument for me having golden ears. However, I can't hear the difference between different isolation tweaks under my cd player.)
When Nikola Tesla discovered the AC system we have today, it was rushed into service because the Direct Current System in use had serious problems. In the process of changing one system for another, no one considered changing cabling systems because for its time, the DC cabling system appeared to work well enough.

A century later, cracks are appearing in the dam. As electrical equipment develops with greater sophistication, flaws in the cable delvery system are becoming more apparent.

At the consumer end, the old DC designs must give way to a new type of Power Cable developed specifically for Alertnating Current. Why? When AC is transferred through cable that is designed for DC, large amounts of distortion are created. Any high tech electrical device will suffer performance degradation when AC is conveyed without consideration of its unique characteristics; we call this phenomenon AC Pulse Distortion.

How is this distortion created? Every time AC switches phase a pulse is sent through the cable structure and resonates to the tone of the AC pulse. (This is what you hear when your car passes beneath transmission lines with the radio on.) Any signal, like music superimposed over this tone will instantly become modulated, therein lay the problem.

The traditional solution has been to dampen conductors by heaping large amounts of insulation on the structure. This is an attempt to solve an electrical problem with a mechanical solution...it is basically ineffective and certainly not elegant.

Through years of rigorous research, a solution has evolved and in the process a whole new technology has been developed. A breakthrough came with the realization that phase pulse intensity is controllable and that created a solution to a very large problem.

This accomplishment breaks the link between cable structure and resonance of the AC pulse. Music may now manifest in its original pristine state with no background noise.

This new advancement is implemented without the use of traditional electrical components such as resistors, inductors, capacitors, etc., because these devices are highly resonant and contribute to the problem.

Major Point: If all the essential peices of an audio system were soldered together with no cabling used, the pulse effect would continue to exist. ONLY within the domain of electron transfer (cabling) can this situation be confronted, maipulated and defeated.
Gotta say, these things make a difference. Power cords *and* outlets. I NEVER would have thought this to be the case!

Just some personal background to so you know how entrenched in the nay-sayers' camp I was. Undergrad in Physics and Math. 5 years engineering in aerospace - electrical, RF, and systems design. Graduate degree in Mechanical Engineering and an MBA. Hence, I have a background to understand the physics and bull shit marketing; this power cord stuff was nothing but snake oil.


If your systems has a threshold of resolution, you will hear a difference. And you have nothing to lose - most of these power cord guys give you a home trial period - why not try it for yourself?

Understand, the audio system is quite complex - from electronic design, to room treatment, to vibration management, on and on there is work to optimize the system. Take advantage of this amazing Forum and learn!

try these simple exercises with the cords you already have and see if they change the overall sound of your system:

1. put the heaviest gauge cords on the most current hungry components. mine are all marked 16/3 or 18/3. 16 is heavier. the insulation can be deceiving. read them if you can.
2. route the cords away from your interconnects. by some miracle of engineering alot of cords exit their components via the left side when viewed from the front. in any case, place your power strip on the side which provides the least interaction with your interconnects. If a power cord must touch an interconnect make sure they cross one another at right angles.
3. keep the power cords apart from each other, even by an inch. don't coil any excess. don't bundle them together even if it looks tidy.
4. keep the accessible metal surfaces of the plugs free of oxidation. i use car wax but i'll bet there's something more trick to clean the copper or brass they're made of.

quite by accident, i'd ignored one or more of these simple procedures while setting up a new rack and found my system immediately sounding thin. getting all of them right restored its full body.
fatparrot...If you read my comment you will note that I did not say that special power cords can make no difference. I simply remarked that the difference, if any, would be of an electrical nature and therefore able to be objectively measured. I am a scientist: like the ones who disproved the subjective opinion that the earth must be flat. Show me the data about power cords. I am anxious to be enlightened.

And Pbb...sorry, the bridge has been sold.
To the "unbelievers", please read and respond to the thread entitled "Philips SACD 1000 / power cords in general accordingly.

Prior to doing so, please be aware that i too was an "unbeliever" up until about 5 years ago. In fact, i was involved in a thread that "debated" the effects of AC cords that had 60+ responses in less than 4 hours time. Most of those responses were between a small group of individuals on both sides of the fence. My position was similar to those promoted by Eldartsford, Bomarc, Pbb, etc... i.e. i was under the impression that a power cord could NOT alter the sonics of a component. That was until i tried various power cords on different components and did hear a difference. As such, all of my previous posts were done in haste as i had relied on "common sense" and my prior level of education on the subject rather than first hand experience and trusting one's own senses.

As discussed in the thread that i linked to, i was able to measure a difference in frequency response / apparent sonics when changing power cords. Granted, this was an "impromptu" test that wasn't performed under lab grade conditions, but the conditions that were present were as close to identical for both DUT's ( Device Under Test ) that could be achieved at the time. As such, any errors that were in place for one cord were also present for the other and would cancel each other out in the end readings.

While i can't explain the differences in perceived sonics and measured frequency response abberations in "techno-speak", i do know what i heard and i do know what the test instruments confirmed. How susceptible or noticeable other designs / systems are to such changes, i don't know. Sean

PS... I wish you folks could see one of the highly intellectual T-shirts that i wear. It says "I used to have an open mind, but my brain kept falling out" : )
I don't really understand the measurments thing at all. Who cares how something measures unless the function of the DUT is to be measured? Audio gear is to be listened to so the only thing of importance is how it sounds. History is riddled with people measuring the wrong things or not having sufficent sensitivity in the measuring systems to accurately judge the DUT. Audio gear in particular seems to show a pretty large chasm between how things measure and how they sound. I have been reading the graphs since the early days when Dick Heyser joined Audio and, other than items that are just broken, I havn't been able to correlate a lot of measurements with what I hear. Not to discount that there may be someone else out there that can accurately judge a component by measurements alone. Pbb, if you wish to buy my open mind be sure to bring a very small box.
The only one who can convince you is you.

To those who say, "Convince me", I say, "Sorry, I'm too busy." I don't particularly care whether you can hear the difference a power cord makes, or not.

But to those who are interested in learning, I say, "Try." Make sure your system already performs well--a poor quality or badly matched system won't show differences in power cords well, or at all. Then you can try a cord or two, listen to recordings you know well, and see what you hear.
The higher the resolution capability of my system evolved , the easier it became to discern the changes various "tweeks " imparted on my system. Pc s have only recently become relevant to me. The introduction of the Elrods were at once apparent. The proof is in the listening and with my system , its obvious . To me it is anyway.
Viridian: As i've mentioned before, i do think a lot of what we hear can be collaborated with specs. That is, to a certain extent and taking into account that the specs and testing were done in proper fashion. Obviously, spec's can be made to lie and / or be presented in a manner that is less than completely telling.

Being able to decipher and interpret which specs are most important and "telling" of how a component might perform is no different than the clues or "evidence" that a well trained detective has to decipher in order to put the pieces of a crime together.

As we have all seen, a good "investigator" can crack cases whereas a less skilled "investigator" could look at the very same "clues" and come up with a different interpretation of events and / or have nothing to go on at all. While it is true that a lot of what the "super snooper" comes up with is based on "educated guesswork" and requires "logical deductions", it is sometimes spooky what one can conclude by looking at the spec's / test results and corraborating this with what one actually hears.

Having an idea of what all those charts / graphs mean is a good starting point, as you can't interpret what you can't understand. After all, if test results meant absolutely nothing, we would not have been able to refine products / designs to the point that we have today. Good luck trying to make something better when all you have is guesswork to go on without some way to measure / substantiate the various changes made along the way. Sean
There has long been "discussion" about whether psychic (mind reading) powers exist. Many experiments have been done using valid statistical methods to see if a subject is doing better than guessing about things like a selected playing card. Results are inconclusive. However, if one scientist could find the MECHANISM for psychic power, perhaps some kind of electrical wave traveling between people's brains, all the sceptics would be converted.

So too about power cords. The reason to look for the electrical characteristics responsible for sonic characteristics is to fix the problem. Thousand dollar power cords may not the the best solution.

Of course the 115VAC power lines also carry some HF modulation...simple table radios often use their power cord as the FM antenna. It's doubtful that any such HF would get through the power transformer impedance, and if it did it would be shunted to ground by the power supply capacitors. What's the impedance of 20,000 mfd at 20KC? Ziltch. If this isn't enough, put some ferrite beads on the power input wires.

If your digital electronics GENERATES noise that propogates through shared power lines to other components you need a better digital electronics design. Fix the problem at the source. (Frankly, if I were digital noise I would travel by the signal interconnections).

What is a "closed mind". I think it is one that dogmaticly argues for some point of view as an article of FAITH rather than as a result of LOGIC. For some, I guess, audio is a religion.
Psychic powers do not equal--nor have anything to do with--mind reading. If my mother read you the cards you'd be surprised. I, on the other hand, don't have that specific gift. I can sense the present and my surroundings very well...sometimes "too well".

And yes, power cords have an effect. Whether you can notice it or not depends on your hearing and your system. I hold the view that as power delivery/noise control improves, expensive power cords are not needed. They could actually be deleterious by acting as filters and limiting extension.
I suppose it would be totally out of bounds at this point to say that I have gone beyond AC power cords, and found that even in straight flat DC power, I can hear differences in the types of chemical compositions of the batteries being used. Not only does the wire matter, but whether there is a Ni-Cad, Lead Acid, Alkaline, or whatever kind of battery being used. I use DC power for most of my system, and have experimented with different battery types, and believe me, they are audibly different. So, is 12v simply 12v, or is there a difference?

Science is to be used to explain why things happen, not to be used to say that they can't happen because the scientist can't measure them. A real scientist would expand his study and abilities to find out why there is a sonic difference, and not stand on previous ideas that cannot explain the phenomenon. Science is learning, not the refusal to learn.
Viridian - the point is that if you cannot measure anything, then your mind may be playing trick on you or you have not gotten to the root-cause of the sonic change. At least if there are measurements that coincide with sonic changes, then theories as to why the changes happen are more feasible. It provides some basis for explanation.
Batteries, like AC power sources have impedance. Some batteries will have lower internal impedance than others. Some will work well during transient current demands and others will not work as well to provide the transient current. There is no surprise here.
But Twl, what about the cases where science CAN explain things, but audiophiles refuse to acknowledge that an explanation exists? I'm alternately amused and offended by people who want to lecture me about what science SHOULD do, while refusing to accept what it has already done.
Bomarc, I have no problem with science explaining things. I like that. What I repeatedly hear, though, is that either there is no scientific reason for cables sounding different, or that we are all imagining it, or both. If there is some other scientific reason that you are alluding to, I am all ears. I have no quarrel with anyone who can show that there is some difference in inductance or capacitance or whatever, and if that is verifiable and useful, then I am all for it. I only say that I hear differences and am willing to use the product that sounds best to me. If I can gain information that will help me to make decisions in bettering my system, I will welcome that. However, I do feel frustrated, as you seem to be. I am frequently under attack for believing something that I can hear making an improvement in my system. Personally, I really don't care if there is some kind of magic dust in there or something. All I care about is that it makes my system sound better. To me, technology is a means to an end, and not an end unto itself. I don't make cables, I listen to them in my system. The details can be up to the manufacturers. What I want is a good sounding system. And whatever it takes to do that, is what I want.

While we frequently disagree on this subject on this forum, I have no quarrel with you personally. I would like to reach some kind of common ground that we could agree on, and maybe that would yield some good. I have a very simple goal, and that is a good sounding system. I assembled a variety of things that sounded good to me, and that is what counted for me. If technical-type people want to boil all the nuts and bolts down to some kind of essence that will help us all understand and decide, that's great. The only part that irritates me is the part where people tell me I can't hear something that I clearly hear, and claim that some "fact" means that I can't be hearing it. If I am misunderstanding your position, then I apologize. It is also frustrating to be on this side, and commonly be told that I am in some sort of "delusion world".
Fair enough, Twl. First of all, let me say that you are not under attack, and that I think you should be free to decide on whatever products you want to buy based on whatever comparisons you choose to make.

Second, let's be clear about what science is, and is not. No one claims it to be the final truth. It is no more than the best explanation for something, based on everything we know to date.

Third, there are a number of different sciences at play here. Yes there's electrical engineering, and the physics that underlies it. There's also biology (since part of your "system" is your ears) and experimental psychology, which is also a science and operates under the same empirical rules as physics.

I don't know enough EE to say for certain that power cords can never affect the sound. I suspect, but cannot prove, that when they do, there is probably something wrong somewhere else in the system, since it's not terribly difficult or expensive to build a power supply that can handle the normal quirks of residential electric service.

No one claims that, "If we can't measure it, it must be your imagination." But the tendency of people to hear differences between things which are demonstrably identical is a scientifically validated phenomenon. So if you compare two power cords (without the kinds of scientific controls that those who study human hearing use) and conclude that they sound different, the best you can say scientifically is that there MIGHT be an electrical reason, or you MIGHT be falling victim to this "placebo effect."

Of course, the more plausible the electrical explanation you have for something, the less likely it's the placebo effect. The lack of a good electrical explanation (absent, say, some known problem with a power supply) is what leads some of us to suspect that the placebo effect is at work here.

Finally, let me say that "falling victim to the placebo effect" is not a bad thing. It's normal, and no one is immune. (Including me. I once witnessed a demonstration of the infamous green pen effect, and damned if I didn't hear a difference. But under the circumstances in which I heard it, the placebo effect--or a judicious nudge of the volume knob by the salesman who was doing the demonstration--was the most plausible explanation.)

I don't expect you to agree with everything I've written here, so I suppose we'll just have to agree to disagree. But I hope I've made it a little clearer where I and some others are coming from, and maybe that'll help keep the sniping to a minimum, which is something we can all agree on.
Eldartford: Many of your suggestions are valid and are exactly what should be done by those designing / building the gear to begin with. As such, i would have to say that we are probably on the same page / line of thinking, but our actual experiences differ.

Besides that, the ESR of some capacitors at 20 KHz will be MUCH higher than you think it is. Regardless, the ESR doesn't really matter to RFI since the caps are in parallel with the power supply and the RFI can "ride right over the top" of them. You acknowledge this in your post when you mention digital gear "pumping signal" back into the AC lines. After all, such a signal would have had to have either been radiating into all of the circuitry in the box and using the power cord as a feedline OR the circuitry was actually modulating the power supply and feeding signal back into the AC system. Both are distinct possibilities and realities and i think that you know this. That's why i want YOU to experiment on your own and see for yourself just how "under-designed" most of this "high end" gear really is.

Theory aside, your first hand experience will probably change your mind about things. I'm not saying that you will become a power cord convert, but that you may better understand why some people talk about actually hearing sonic differences. The approach that you mentioned i.e. better filtering and design of the power supply, is the right approach in my mind. Reducing the potential for RFI and other "pollution" entering the gear through the use of more technically advanced yet reasonably priced power cords can only help the situation though. Sean
Okay Bomarc. I'm on the same page now. Thanks for your point of view.
Twl: As Audioengr mentioned, some batteries will be better for this than others. As a side note, this is the reason why some car stereo enthusiasts employ LARGE filter caps very near their amps. The caps themselves can discharge and supply power faster than the battery sitting very near it can. This is due to differences in the internal resistance of the devices themselves. While some caps may be worse than some batteries, caution must be used when selecting such a cap. Very careful selection of batteries and placing them very near the device drawing the current may negate the need for any support components such as caps, etc..

I'm curious as to whether or not you've ever tried anything like this ? The main things that i'd look for if you did was greater bass impact with greater punch / clarity on peaks. Sean
Sean, I'm currently using a large capacity lead acid automotive battery with 650 cold cranking amps, located about 24 inches from my amplifier. I have the terminals directly connected to the power input barrier strip on the amp, with 12ga OFC copper stranded wire.

I have not tried any capacitors on the power connections as of yet, but the idea has crossed my mind. I was thinking that since my amp only draws 3.1 amps @ 12vdc at rated power, I figured that the 650 cold cranking amp capacity of the battery could handle that. From my listening observations, this amp really has some balls in the bottom end and dynamics, even though that may sound comical with only a 2 watt SET 45 amp. But it really is true. This amp has alot of punch, and it makes those Lowthers stand right up and get with it.

Another thing that I have done, is to use a separate battery for each of my components, so that there is no modulation of the power supply of one component by the draws of the other. This seems to make a difference. Individual power supplies take the idea of "dedicated AC lines" further into the isolation of each components power supply totally from the others. I like the effect of it. It's clean.

I'm still working on doing whatever I can think of to ensure the cleanest, unencumbered power to my components as I can possibly do. I think that the flat DC, with no intermodulation between components, full isolation, and high current availability has improved my sound.
Sean...OK, here is a test that will be easy to do.

1. Get 2 monoblock power amps (I have a pair of Kenwood LO7Ms which should suffice).

2. Get 2 "super" power cords. (The Kenwoods will need modification to use them. The original cords are, I admit, crummy. Strange for such a well made piece of equipment. (Maybe they properly designed the power supply!)

3. Using the super cords, play the same music signal into both amplifiers. Adjust gain so as to minimize the voltage difference between the HI outputs of the two amps. If everything was perfect this voltage would be zero.

4. Record the voltage. If possible I will use a 100sps bench type precision A/D. With this type of data I can make plots and even perform Fourier analysis of the signal.

5. Now, replace one power cord with a "crummy" one.

6. Repeat the test procedure.

If the differential signal is the same as before, the "crummy" power cord has no effect. Note that while this test procedure does not involve subjective evaluation of sound, it does examine the amplifier audio output that drives the speaker, which is closer to a listening test than measurements of power supply voltages.

Now...what should I use as the "super" power cord. Please suggest wire type and configuration(s). Any other comments/suggestions are welcome.
When performing this test, are you driving speakers or dummy loads ? If you are using speakers and performing the tests simultaneously, my guess is that the speakers would have to be phenomenally well matched in order to do this. So well matched that i don't think it could be achieved without great time and expense.

As far as using dummy loads go, they will not "modulate" the power supplies like the signal being fed into a speaker would. Nor would they provide the reactance necessarily to simulate the actual conditions that the output stage has to deal with during normal use.

I would like to know what you intend to use as a test signal, the amplitude of signal that you intend to drive the amplifier up to and if the amps will be connected to the same identical unfiltered power source ?

I bring all of this up as these specific amps are very load sensitive ( vary their frequency response / output characteristics as impedance is changed ) and their distortion characteristics vary drastically as frequency rises. As such, using some type of wideband or sweeping tone that is varied in amplitude with a reactive dynamic load attached should REALLY produce some interesting results. I would LOVE to have some computer assisted test equipment that was capable of performing such a test. This is the kind of testing that could REALLY advance the SOTA of audio gear. That is, if one knew how to interpret the data provided and manipulate the circuitry to correct for the flaws detected.

If you are talking about doing a "null test" where equal but opposite signals are fed into each amp and calibrated to produce a "zero beat", you would have to do a baseline run with "stock" cords first and then with one of the cords replaced or modified. I'm sure that BOTH tests ( stock and modified cords ) would provide very sufficient "nulling" ( at least -60 dB ) for the scientist in you. The question is, if there are measurable differences in "nulling", would the differences be audible on a finely tuned system with a good "listener" at the helm ???

If you really want to do this correctly, you'll have to perform a baseline on the amplifier prior to cord modification and then afterwards. That is, unless the two amps measure and respond to signals in identical manner. They would need to do this regardless of load, frequency or amplitude of signal. Relying on two "similarly constructed" mass produced amplifiers of antique vintage to provide identical levels of lab grade reproduction would be asking a bit much in my book. Sean
My question would be that after performing a test like described above, and having the possible result of no measurable difference, but they still sound different, what do you do then? Do you conclude that the testing methods are flawed, or that your hearing perception is flawed? This is what this subject really comes down to, isn't it?

My position is that if you want to spend the evening running test signals through your power cords into an analyzer, pick the one that measures best. If you want to spend the evening listening to music, pick the one that sounds the best. I really think that this simple approach is the best one.
Tom hits the nail right on the head. Of course measurements have validity, but nothing can take the place of listening as a yardstick of sound quality.
sean and others...

1. About the A/D. Of course I meant 100K samples/second.

2. The amp load will be Magnepan MG1.6 speakers, 4ohms ,and with impedance characteristics like a dummy load. (Of course I will listen, but that is not part of my test plan).

3. The input signal will be real music, of various spectral characteristics. I find that real music works best for most things like setting speaker levels, and subwoofer gain and phase.

4. I thought that my initial setup measurements using two super cords provided the reference for comparison. Of course I could do it with the original cords as well.

5. Some of you guys didn't understand the objective of my test. I am not (at this time) evaluating audio quality. I am testing to see if the electrical signal applied to the speaker changes in any way when the power cord is replaced. If it does, then listening tests would be in order. (And I will apoligize to all those I have offended). Viridian..I agree with you about listening being the best test of sonic quality, but I just don't want to fool myself, which is easy to do. If there is no change, listening tests might be fun but can prove nothing).
My speakers only "know" about what comes in to them as an electrical signal from the power amp. Maybe your speakers have psychic powers and can discern the type of power cord in use. That's too far out for me.

6. By the way, when I said that the original power cords were "crummy" I really meant it. They don't even have a 3prong (grounded) plug...but maybe that was by design. I will need to try the super cord with and without ground.

7. The Kenwood LO7Ms may be old, but they were top rated by T.A.S and Stereophile. They are comparable to the best available today. (Besides they are what I have on hand. If you have Krells, or the like, feel free to use my procedure).

8. One procedural detail...I will make the electrical hookup such that I can switch cords without shutting down power, or interrupting the signal measurement process.

9. Hey this could be a money-maker! If I find a power cord effect I can sell the data to power cord manufacturers. If not, they can pay me to keep it under wraps.

10. Finally...(for now)...how about some suggestions about the design of the super power cord(s).
TWL wrote: "I'm currently using a large capacity lead acid automotive battery with 650 cold cranking amps, located about 24 inches from my amplifier. I have the terminals directly connected to the power input barrier strip on the amp, with 12ga OFC copper stranded wire."

24 inches of ANY wire represents a large inductive impedance. You need what is referred to as "decoupling caps", which essentially decouple the power source from the load by providing local energy storage. This means low ESR (equivalent series resistance) capacitors located as close as possible to the load. And a combination of HF caps (.01 UFd to .1 UFd) and some swamping caps (1 UFd to 100 Ufd) are needed to supply current at a broad frequency of transient currents. It would not hurt to have even a 1000Ufd close-by as well.
You may not be able to measure what you hear. Depends on the noise floor of your sampling oscilloscope. You MUST use differential probing technique for this to avoid ground-loop noise as well. This is not a trivial measurement.

You would be better off to measure the voltage drop (scope capture) across the power cord when transient music passages are being played. IF two cords have different voltages, this means that more current is getting to the amp with one than the other. If the cords didn't matter, then the currents should be identical.
Following Audioengr's comments, especially since i know what he's getting at, i would suggest a cable of very low inductance against a "typical" zip style power cord of adequate gauge. Using the "crummy" stock cord as a reference should work fine since the manufacturer thought that it would more than suffice at the time of design / sale. The engineers there obviously took into account such things as current draw and thought that it should be "plenty good enough". At least, according to theory.

If the "fancy" cord was of a high capacitance nature, all the better ( in my book ). The directions on how to make a very basic cord that offers good performance and is suitable for this specific installation is what follows. It should by no means considered my idea of "the ultimate" power cord or a power cord with universal application. It is however, a good starting point for someone that wants a good cord for pennies on the dollar : )

If using this for an amp, look for a cable that uses four 16 gauge ( at least ) or preferably four 14 gauge individually insulated conductors. These should be arranged with two conductors stacked on top of the other two. Since your amp does not use a "ground" per se, this should be easy for you to work with since you don't need to add an extra wire for an external ground.

The internal wiring should use staggered polarities as we go around in a circle i.e. hot, neutral, hot, neutral. Not only should the polarities be staggered to reduce inductance, lower EM radiation, reduce the susceptability of RFI, etc.., all four conductors should have a spiral twist to them. This rotates the wires within the main jacket so as to never have them running in a straight line. Hence, we end up with what is called a "spiral wrapped star quad" arrangement.

While looking for a cord of this nature, i would see if i could find one that used as little dielectric insulation material between conductors as possible. Obvously, you have to take into consideration safety factors in terms of rated voltage and current and remembering that the cord itself will be bending / flexing, but finding a suitable candidate should not be tough. Once you've found such a design, terminate it with good quality connectors and have at it.

As to my comments about the Kenwood L-O7M's, the "review" that i have on their bigger brother ( L-09M ) was not very complimentary at all. Then again, these amps probably "measure" quite well as far as "standard test procedures" go. Given the similarities between the two models of similar design and vintage and the more reliable than TAS or Stereophile ( at least as far as i'm concerned ) comments that i read, that is what i based my comments on. None the less, am amp is an amp and the results will speak for themselves.

One other thing though. You will need to be able to feed the amps a mono signal. Then again, i'm sure that you knew that : ) Sean

PS... we all know that it is the sound that counts. By properly conducting tests and applying the knowledge derived from those tests, we can work towards making more consistent and reliable products that DO sound better. In the past, coming up with the right tests has been the problem, but we are slowly learning more and more as we do more testing. As such, scientific testing CAN be a means to an end if applied in that manner OR it can help to explain how we arrived at the end when broken down and reverse engineered.
well, in my system power cords certainle made a difference on my CD player, but none whatsoever on the power amp...i went by trusting my ears...the CD player made in France had some problems with the stock power cord (including a dim display)...after replacing the power cord, the CD layer seems to be just fine and the display is nice and bright...now, on the amp was a different story...i couldn't detect any change in the sound at all...i even tried a test with some of my friends...we took turns to replace the power cord on the fly while the music was playing...you can do that safely if your amp (has to be SS not tubes!!!!) has a good power supply...we had the stock power cord and another one that costs $500/6 ft...someone was switching back and forth between the two while the music was playing and we couldn't detect any change in sound...what was even more surprising was that the amp played just fine for 4-5 seconds even without power cord...was running from its own capacitors without a change in the sound...well, that was pretty conclusive for me that the power cord have absolutely no influence on audio gear that has a well designed power supply...
again, just a personal experience...
sean...Thanks for the design spec on the power cord. Based on your suggestion,I intend to use so called "high temperature" wire (intended for range hoods and oil burners) which has very thin insulation. It is readily available. I could use magnet wire, with super-thin enamel insulation, but that would probably be going too far. Three questions...

1. How do I keep the wires "stacked" as I twist them? Does it really matter as long as all four get twisted together?

2. How many twists per foot? (I won't pull your leg about whether the twists are clockwise or counterclockwise).

3. Would not three pairs be as good or better than 2 pairs? I might do this if I can't get #14 wire.

I disagree with audioengr about difficulty of making measurements across bridged amps. Been there, done that. Also, the greater voltage drop in a wimpy power cord does not translate into degraded sound provided that the power supply is robust. As Iasi notes, most power amps play on for several seconds even if you pull the plug completely. I shifted the focus of my investigation from the DC power to the amplifier output signal in answer to those who claim to hear things that can't be measured. The amp output is as close to the sound as we can get without subjective judgements about subtle effects (if any).

As to power cord effect on a CD player...I can try that too. Frankly a CD player draws so little current at such a uniform level that it's even harder to see how a power cord could have an effect. If the display was dim with the old cord it really must have been defective. But then again, this is French engineering. Did you ever work on a Renault?

Regarding Kenwood LO7M...I thought that the LO9M was the lower power unit. The TAS and Stereophile reviews that I recall were before those mags took advertising, and the reviews were credible. My personal review is that these amps, within their 150 watt (8 ohm) power rating, sound darned good.
"Also, the greater voltage drop in a wimpy power cord does not translate into degraded sound provided that the power supply is robust."

So, show me one amp which has a "robust" power supply. I have never run across an amp yet that did not benefit from a low-inductance power cord, except those that have inductors already in series for filtering (bad idea IMO).

Seans guidance on the power cord construction is very good. The star-quad achieves the lowest inductance. Multiples of them will be very effective.

I would be wary about using "high-temperature" wire. The copper in these is usually sub-standard for audio purposes, as is alarm, telephone and control wire. Find a good Alpha or Belden hook-up wire with pTFE insulation.
Iasi - what type of power amp do you have? Does it have an AC input filter?
Audioengr.... OK. Where do I buy #14 hookup wire?

By the way, why does the power cord have to be "audio quality"? It only has to pass 60Hz. Besides, audio is AC, and the power gets rectified, so any "audio" characteristics of the AC get lost.
I have no idea if it had an AC input filter...the amp that I tried the experiment on was Innersound ESL amp into a pair of Innersound Isis speakers...I wanted to see for how long will the speakers play if I remove the power cord from the back of the amp...it went with no problems for about 10 seconds...the sound faded away in about 15 seconds...
I'm going to agree with Eldartford.
The whole power cord marketing scheme is smoke and mirrors.
You're invited over to my house to prove me wrong.
I live in an Akron, Ohio suburb with nice clean power at, most of the time, 60Hz with a nice looking sine wave.
Eldartford: Forget about buying parts, doing the assembly, twisting the wires, etc... There are PLENTY of mass produced cables like this on the market that you can buy for a few bucks.

Hbarrel: Glad to hear that you've got good power where you are at. You must be one of the few in the country.

My business is located in a small rural town. Until i called the local electric company and kept raising hell with them, i was experiencing severe voltage sag, massive amounts of distortion, etc... While the AC was never "good", it had continued to get worse and had finally reached a point that i was beginning to have major problems. Since i have test equipment hooked up and pay attention to the AC and how the equipment runs, i was the first to notice the problems in the area. When i talked to the other tenants in the building, they said that they were not having any noticeable problems.

Within a week, several computers went belly-up in other businesses and other problems started developing. After a half dozen more phone calls to the power company from me and other tenants beginning to call, the utility company came out and re-examined the system again. As it turns out, the pole transformer was VERY old and was not up to spec. That probably explained the voltage swings from 118 volts down to 104 - 106 in the middle of the day. Once they changed the transformer, voltage hovers at about 120 - 122 and is rock solid. There is still distortion of the 59.9 Hz sine wave, but it is FAR superior to what i was getting before.

At my house, which is inside of a highly populated City, my voltage stays pretty steady at about 123 volts. If it is REALLY hot out in the summer with every air conditioner in the city turned on, i'm down to about 118 volts or so. Regardless of the fact that we have a steady supply of power, the 59.9 Hz sine wave is always distorted. While this does clean up quite noticeably at appr 1 - 2 AM, it is still not as clean as one would think.

For the record Hbarrel, you should try looking at your AC line with a spectrum analyzer. I'm near certain it isn't as "clean" as you think it is.

As to your comments about AC cords, i've already stated that much of what these filters / line conditioners / power cords are doing is nothing more than band-aiding poorly designed gear. Nothing more, nothing less. Sean
sean....Aw shucks. I am just beginning to get interested in this PC thing. Since the original Kenwood PC are so "crummy" I won't be wasting my time replacing them, and I will do it with multiconductor configuration that you suggest. I checked out listings for power cords, (I need 2) and it seems that your idea of a few bucks is different from mine.

If I can figure out how to send you an attachment (test plan with diagrams) with EMail I will doi it.

Thanks for your constructive comments.
Eldartford - you can buy hookup wire at: alliedelec.com

Copper quality matters, whether it's power IC's or speaker cables.
Iasi - I have had the Innersound ESL amp in my system for a couple of weeks. I know the design of this amp (by Coda Technologies) - no negative global feedback, strictly class A/B and lots of protection fuses etc.. - however, you have to be careful about removing IC's before it's fully discharged. My power cords definitely made a difference with this amp. Maybe you have not tried the right power cord yet.
Hbarrel - I will not be driving from Oregon to Akron, sorry. BTW - Power cord effectiveness has little to do with how clean the power is.... See my FAQ page at: