Product Review - AC Power Cord Comparison - June, 1999

Paul Knutson


Audiodyne Power Tap


Harmonic Technology Pro-AC II



Nordost El Dorado


Power Cord Comparison:

Audiodyne Power Tap, Harmonic Technology Pro-AC11 and Nordost El Dorado

In an audiophile's utopian world, power cords would not make a difference in the sound of a system.  Nor would interconnects, speaker cables or digital cables.  In this ideal world you could connect everything in your system with lamp cord that costs $.03/ft, and the sound would be perfect.  However, here in the harsh, cold, unrelenting real world of audio, all these various cables do make a difference (in my experience) - oftentimes significant. 

The notion that cables make a difference forces the audio and music lover to make some tough choices when assembling a system regarding how they will spend their money.  The goal (for most of us anyway) is to create the most musical enjoyment per dollar.  This becomes more difficult when some high performance cables cost as much (or more) than your CD player.  Hey, nobody said getting great sound was either simple or cheap.

In this review and comparison test, we're going to look at three specialty power cords.  "Ugh!" you moan, "not power cords".  Yes, power cords.  Specialty audio power cords always seem to generate a good debate.  If I were to rank the various types of audio cables in terms of the amount of controversy surrounding the effectiveness of each, the rankings would look like this (the top one has the most controversy, and the bottom one the least): 

1.      Power cords

2.      Digital cables

3.      Interconnects

4.      Speaker cables

If any of you spend time reading through the various Internet newsgroups like, no doubt you've read the threads that seem to start about every three months about the effectiveness of power cords in a high-resolution audio system.  Typically, these threads begin when a novice audiophile ("newbie") posts a simple question about whether a high-end power cord will improve the sound of his/her system.  Like clockwork, a certain group of know-everything, highly opinionated, self-appointed "Defenders of the Audio World" will post one message after another of "facts" (or attempted sarcasm) about how power cords cannot possibly make a difference.  Rarely do these posts talk about actually listening, but I guess that's beside the point, right?

Look back to the opening paragraph where I used the phrase "in my experience" when suggesting that the various types of audio cables all make a difference.  I chose this phrase carefully.   Yes, "in my experience" the right cable can help take a system to the point where you hurry home from work to listen, or skip a favorite TV show in favor of more music. On the other hand, the wrong cable, in the wrong location, can contribute to that annoying feeling where you instead want to turn the music off, leave the room, and read a book.  Every component and cable matters.  It's all about system integration, which is at once fun and frustrating.

I have no personal or professional agenda to force the cable issue or prove that power cables, in particular, can affect the sound of your system.  This is America, the Land of the Free, and every audio lover can think, say and hear exactly what they want.  The simple fact is that I, and a lot of my friends both in and out of the audio industry, also hear the difference that power cables make.  In fact, I've got three specialty power cords in my possession right now, and yes, each sounds different in my system connected to various components.  If you are absolutely convinced I'm full of it and that there is no way, scientifically or otherwise, that power cords can impact the sound of a system, then close this review and move on to another that interests you.  If, however, you are curious about what's out there in state-of-the-art audio power cords and how they sound, then read on.

Do I sound like a grumpy audio reviewer?  I hope not.  This hobby is supposed to be fun, so I'll step down from my soapbox now and move along to the good stuff. 

The Contenders

Ladies and gentlemen, the Contenders are . . .

In the red corner, the Audiodyne Powertap ($125/6 ft.) and in the green corner, it's the Harmonic Technology Pro-AC11 ($180/2 meter) and finally in the blue corner, the Nordost El Dorado ($600/2 meter). It's a triangular boxing ring, what can I say? 

These cables spent considerable time (a minimum of 4 months) in my system connecting a variety of components.  Switching between each as I saw fit, the cables alternated between my CD transport, D-to-A converter, and tube preamplifier.  I couldn't use the cables on my power amp since I built it using a captive power cord that was hard-wired to the power transformers within the amp.

All three of these contenders are well constructed, and there were no mechanical problems with any during the review period.  These power cords held up through many cycles of connect/disconnect, likely more than most consumers will ever put them through.

Two of the cables, the Audiodyne and Harmonic Technology, look very similar with a traditional black mesh jacket. The Nordost on the other hand, looks positively radical for a power cord with a sky blue two-wire weave that is not covered by a jacket. 

Each cable is sufficiently flexible to route conveniently in most systems.  The Audiodyne and Harmonic Technology have a moderate amount of stiffness, enough to hold a basic shape from point A to point B.  Meanwhile, the Nordost is positively flaccid and can be routed about as easily as string.  I point out these facts because you should always keep power cords as far away as possible from other cables - speaker, digital or analog interconnects.  You can run power cords right next to each other or even cross them one on top of the other, but for the least noise and interference with your delicate music signal keep power cords away from other cables!

The connectors at both ends of the power cords, male and female, are high quality in each instance.  Good IEC connectors maintain a positive connection with AC power, thereby keeping voltage drop to a minimum, which is important for optimal performance.  You don't want your power cords to be wiggly and loose within the socket or at the component.  Along those same lines, if your wall socket is old, broken, or if the blade tension is simply not there, I urge you to hire an electrician to replace the socket with a new one from Hubbell, Eagle, or Audiodyne.  If you absolutely, positively know what you are doing, and know how to shut off the main power to your building, this is something that you can do yourself.  However, if you have any questions about what to do, or lack confidence in your ability to do it, leave the wall socket alone and hire someone to replace it for you.  A good AC socket is a big plus for audio performance, but it's not worth dying for!

I'll refer you to the website of these companies for expanded construction details on each cord.  There you will find additional  information to this review. However, I will touch on a few of the features that are either unique or innovative with each Contender.

Beginning in alphabetical order, the Audiodyne Powertap features 10-gauge, silver-coated OFC/6N purity conductors, an air-core carrier, and an EMI-Trap for EMI-RFI noise reduction.  Another unique feature is the use of non-corrosive nickel blades on the wall plug as opposed to brass.

The Harmonic Technology Pro-AC11 CL-3 utilizes the 11-gauge, Single CrystalTM  (OCC) 6N purity copper that is at the heart of all Harmonic Technology cable designs that use copper as the conductor.  In fact, the Pro-AC11 is based on the Pro-11 speaker cable, with added shielding and insulation said to eliminate and reject RFI noise.  The version of the Pro-AC11 that I am reviewing uses a Hubbell male plug that is available for a $10 additional charge over the base model (and I recommend you spend the $10).

Nordost's El Dorado is basically similar in construction to the highly-praised Nordost Quattro Fil analog audio interconnect, but of course the conductors are radically different in size.  The El Dorado uses 10 silver-plated 7N-purity OFC conductors, suspended in a monofilament design and wound in a twisted pair.  The conductors are bonded with Nordost's own Teflon extrusion process.  Additionally, the positive and negative leads are further isolated from each other by a dual-layer shield to improve isolation.

The Battle

Your first reaction to this power cord comparison may be "not fair!" based on the price discrepancy between the most expensive contender, the Nordost at $600/2 meter, and the least expensive, the Audiodyne at $125/6 ft.  In response I'll simply say, "point well-taken".  Yes, there is a big price difference, but if you look beyond that fact for a moment and read on it will become apparent that each of these cords has a lot to offer, regardless of price.

As a preface to my listening impressions, I want to say, and I can't stress this enough, that where you use a particular cord has a big influence on how the cord performs in a given system.  This realization meant that forming accurate sonic impressions of each cord took a long, long time, moving each contender from component to component, taking listening notes at each stop, only to find that the cord is doing something completely different on this piece of gear than the last.  Oh well, such is the life of an audio reviewer . . . 

A quick description of the review process I followed may be helpful: as mentioned earlier, there were three components used in the comparison, namely my CD player, DAC, and preamp.  In addition to the three cords being reviewed, I also had on hand three generic, stock power cords (the kind that the manufacturer would typically supply with the component).  Here is what I did during my listening tests:

            Step 1: Generic cord on each component (yuck!)

            Step 2: Inserted one Contender and left generic cords on other two components.

            Step 3: Moved Contender from component to component, generic cords remained on others.

            Step 4: Inserted new contender and went back to Step 2, repeat Step 3.

            Step 5: All three Contenders installed and moved randomly from component to component.

            Step 6: I vowed to myself to get a life when this comparison test is done.

The Results

First, and this has to be stated clearly, the sonic differences between any of the three Contenders and the stock, generic cords were laughably obvious.  You absolutely cannot go wrong with any of these power cords as a replacement for a stock power cord.  There, with that out of the way, the $64,000 question remains "which is best?"

The Nordost El Dorado is the best overall performer (and, yes, the most expensive).  I couldn't find an instance where its insertion into the system, on any component, didn't bring about wonderful, positive changes in sound.  You want vital, live, crunching dynamics?  Try the Nordost on your preamp or DAC.  This baby absolutely slammed when compared to the stock cords on hand.  While the improvement in dynamics over the Audiodyne and Harmonic Technology cords was not as pronounced as the improvement over the stock cords, yes, the Nordost was still the most dynamic-sounding of the three Contenders.  What about space?  Acoustic space, to me, is that sense of instruments and voices in their original recording venue laid bare before you, top-to-bottom and side-to-side.  With the Nordost, I felt like I was getting everything that my system was capable of delivering in terms of space.  The stock cords positively deflated the sense of space and reigned in the soundstage.  The other two Contenders were good in the re-creation of space, with the Harmonic Technology holding a slight edge over the Audiodyne in this regard.  In the end, the Nordost made its best attributes most evident when used on my tube preamp.  With both the DAC and CD transport, the Nordost was also wonderful, but not quite as noticeably so as when connected to my preamp. 

In a tight match, the Harmonic Technology AC-11 CL3 edged out the Audiodyne Powertap for second place overall.  Now is a good time to mention that the version of the Audiodyne Powertap I was auditioning has been replaced in the Audiodyne lineup by the Powertap Reference, which retails for the $125/6 ft. price I've listed in this review.  The normal Powertap is no longer available.  My assumption is that the Audiodyne Powertap Reference is even better than the cable reviewed here, but not having heard it personally, that is only my assumption. 

The Harmonic Technology AC-11 was the equal of the Nordost in terms of high-frequency air, detail, and delicacy.  It was quiet, quiet, quiet.  With the AC-11 installed, music sprang forth from a much blacker sonic background than with the stock cords, and again, about the same in this regard as the Nordost, followed closely by the Audiodyne.  Transparency and timbre were perhaps the areas most improved by the Harmonic Technology AC-11.  Music sounded very organized and coherent with it installed, dramatically more so than with the stock cords and equal to or more so than the other Contenders as well.  This transparency and truth of timbre added a sense of wholeness and a breathy, rounded quality to well-recorded vocals, especially female, that was captivating.  In the end, the Harmonic Technology AC-11 ended up strutting its stuff most effectively on the CD transport.  On the preamp, it just didn't quite match the dynamics of the Nordost, and on the DAC, I felt like the lowest bass notes were perhaps a bit truncated compared to the Audiodyne. Therefore, the CD transport was the AC-11's new home.

Finally, and without any sense of defeat, the bargain-priced Audiodyne Powertap rounds out the pack.  This cord was a big improvement over the stock power cords in all categories, except perhaps the highest treble, where I thought things got a little soft with the Audiodyne.  Trust me, this minor attenuation was not a downfall in all instances (some music needs a little treble "buffering"), but I just didn't feel it was accurate.  Maybe the EMI filter on the Audiodyne contributed to this effect, I don't know.  That small drawback aside, there was one area where none of the power cords, Nordost and Harmonic Technology included, could match the Audiodyne, and that is bass impact.  There was simply more and deeper bass with the Audiodyne installed than any other.  This bass impact was a wild ride on material that relies on a strong bass line to propel the music forward - lots of techno, dance music like the Propellerheads and Orgy, as well as a lot of hard-bop jazz from Mingus and the Coltrane of that era.  I thought the Nordost and Harmonic Technology cables equaled or exceeded the Audiodyne in bass tonality, the sense of bass notes having separate, distinct pitch, but again, none had the sheer bass weight and impact as the Audiodyne.  Installed on the preamp, I felt that the Audiodyne brought the music in a little, at least compared to the Nordost, and therefore I tried other locations.  The CD transport was perhaps not the place to demonstrate the bass qualities of the Audiodyne either.  Therefore, it was the DAC where the Audiodyne found its home and continues to perform exceptionally well. 


As announced above, the Nordost El Dorado was the all-around best performer of the bunch.  It did virtually everything right and nothing truly wrong.  Time after time, on any of the three components, my pre-conceived notions of the sonic improvements that a power cord could deliver were re-defined by the El Dorado.  Yes, it is also the most expensive power cord in this review by more than three times over the Harmonic Technology and more again than the Audiodyne.  Is it worth it?  In my humble opinion, yes, it is.  I can't tell you what to do with your money, but if you have it, and you want the best power cord these ears have heard, then by all means go for it.  Your own ears will thank you.  On an absolute value scale, was the Nordost more than three times better than the Harmonic Technology?  No.  I'm sure you realize by now that retail pricing, especially in the world of high-end audio, doesn't work that way.  You pay quite a bit more to squeeze that last 10% or so of performance out of your system.  The scales are definitely off in this regard, but that's the way it goes.

Even though the Harmonic Technology and Audiodyne didn't top the Nordost in ultimate performance, you could still construct a solid argument that they offer better value to the cost-conscious audio consumer.  Each cord has a long list of unique attributes, sometimes when compared to the other Contenders, but always compared to the stock cords.  The Harmonic Technology cable, in particular, strikes me as a great overall value, giving it up to the Nordost only in the areas of dynamic contrast and soundstaging.   The Audiodyne, at its wonderfully affordable price of $125/6 ft. is a genuine steal compared to much of the rest of the high-end power cord world, none of which were covered in this review, but many of which I've had in (and quickly out) of my system over the past three years. 

If you have stock power cords on your high-end components, do yourself a favor and give one of these cords a try.  Find a good dealer that will let you experiment with a Nordost or Harmonic Technology cable for yourself (Harmonic Technology also deals directly).  Audiodyne sells only over the Internet and will back up their products with a 30-day, no-risk audition.  How can you go wrong?

This battle of power cord Contenders was both enlightening and a lot of fun (in an audio-reviewer sort of way).  There will certainly be others.  In the meantime, I'm off to get that life I promised myself during Step 6.

Paul Knutson

Manufacturers' Response:

Dear Paul, thanks for including our power cord in your survey. Not many reviewers want to take on such a difficult and time consuming comparison test! We're happy that you felt our cord is one of the better values at any price and is within 90% of the Nordost, a cable several times more expensive than ours. Our goal was to bring the highest levels of transparency and clarity to the average audiophile, as you found, yet not break his wallet at the same time. I'm glad you agree with our company's goal and our results ! Best regards, Albert Von Schweikert, Director of Marketing, Harmonic Technology

Paul: Thank you very much for your informative review. Our current Powertap Reference power cord features PTFE Teflon insulated 6N OFC silver coated wire. This has improved the high frequency extension of the cable. The EMI-Traps are offered as an option (not included with the cord). The EMI-Traps are recommended when the cord is used on digital electronics. The net effect is similar to a shielded power cord. In our customer surveys we have learned that the "bass impact" was most noticeable when the cord was used on power amplifiers. Tom Swenson, Audiodyne

Copyright 1999 Secrets of Home Theater & High Fidelity
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