The Great Audio Cable Mystery
Audio cables. What dare we say? There are few subjects in the realm of audio reproduction that illicit more controversy - that’s for sure. Dismissing the skeptics that only know what they “think,” those of us that have experienced their differences KNOW that they are real.
So… there must be something going on. Exactly what that “something” is even we here at Aether Audio aren’t certain, but we’re pretty convinced that, once again, at least part of the phenomenon has something to do with the issue of Phase Noise.
— Continued —
Whatever the mechanisms - and there are many candidates - we can all agree that cable effects are (generally speaking) fairly subtle. Then again, that’s not always the case. On occasion many of us have heard what can only be described as rather dramatic sonic differences having been produced by various makes and formulations of Audio Interconnect, Loudspeaker and AC Power cables.
Before we get too deep into the weeds though, a little background regarding the numerous factors that affect cable performance would seem to be in order. Real quick-like, below is a fairly comprehensive list of parameters, with some that are fairly well known and accepted, and others not so much.
* Characteristic Impedance
* Eddy Current Formation
Insulation Dielectric Parameters:
* Dielectric Constant
* Dielectric Absorption
* Dielectric Hysteresis Effects
Construction Geometry Parameters:
* Single Strand Conductors
* Multi-strand Conductors
* Conductor Spacing
* Conductor Twisting
* Conductor Weaving
* Parallel Run Conductors
* Twisted Run Conductors
* Round Wire Conductors
* Litz Wire Conductors
* Flat Ribbon Conductors
Conductor Metallurgy Parameters:
* Conductor Equivalent Wire Gauge
* Conductor Material
* Conductor Purity
* Single Metal or Alloy
* Conductor Plating
* Amorphous Metal? (i.e., no crystalline structure)
* Liquid Metal Conductor? (e.g. Mercury)
We realize that somebody is surely bound to note that we left something out of the above list, but you need to understand that it really doesn’t matter. Our main point here is to show you just how complex the subject of cable construction can be, what with so many variables being involved. Sadly, academic electrical engineering would have us believe that among them all it is only electrical resistance that matters, and even then not very much.
That “philosophy” is mostly rooted in the fact that engineers are able to accurately predict and measure the effects of virtually all of the variables listed above, and as a consequence hold that view because their effects are very small in amplitude and/or only manifest at extremely high radio frequencies beyond human hearing. Their “oversight” though is that their view is based on a rather simplistic type of “first order analysis” of those effects, and therefore fail to consider the results of their interactions with the electrical circuits that the cables are connected to.
While we could debate the matter in greater detail, there is one variable in the list above that there is little to debate because there is virtually no data to go by either way. We’re talking about the effects those variables associated with above “Metallurgy” section.
When we get to those the engineers out there will tell you that about all they can measure or even predict is what the electrical resistance of a given conductor will be. Well, if the surface area of the conductor is known, because of “Skin Effect” we can also include its high frequency bandwidth too. Other than those though, assuming the bulk resistances and surface areas of two different conductors are the same… then acaademic engineering would tell us that they are the SAME - at least as far as their electrical = sonic performance is concerned.
!!! NOT !!!
Following that logic, the skeptical engineers out there would try and tell us that given the wire gauges, surface areas, conductor spacing, insulation - you name it - of all conductors are adjusted such that their predicted electrical performance would be exactly the same, that a 20-foot pair of speaker cables made from the alloy Inconel 600 are going to sound IDENTICAL to a pair made from 99.999% pure Silver.
So we’re really supposed to believe that - right? Never mind the fact that Inconel 600 exhibits a bulk resistance that is “only” 64 times greater than that of pure Silver? That means if you start with Silver wires of a given diameter and then adjust the electrical resistance of the Inconel wires to match, the Inconel wire diameter needs to be 8 TIMES LARGER!!!
Then let’s go a step further and repeat the above scenario, but this time replace the Inconel with plastic tubes filled with ordinary Salt Water that are sealed and fitted with some Silver connectors at each end. Hey, Salt Water will conduct electricity just fine, and if you dissolve enough salt you can get the electrical resistance down pretty darn low too. Gee, we wonder how those two would compare to the Silver?
DUH - Common Sense tells you that there is bound to be some sonic difference between the Silver and the other two. Exactly what those may be, who knows? Something tells us though that the Silver would probably sound just a wee-bit better than either the Inconel or the Salt Water. Whaddaya wanna bet? We’re not ready to bet the farm, but then again we don’t even buy lottery tickets. Nevertheless, if our lives depended on achieving the best sound possible by having to select from those three options, you can be darn certain that we’re going with the Silver first every time.
Well, let us make one possible exception to the above. We are pretty certain the Inconel wouldn’t be so good because we are well familiar with metals and alloys regarding their properties of crystalline grain structure, impurities and other such things. But the Salt Water is unique in numerous was compared to any metal. It’s ability to conduct electrical current has to do with salt ions (sodium & chlorine) an the fact that they are free to move around in the liquid water. We’ll touch on that subject more later, but for now we’ll just say that because of those unique qualities we might not be too surprised to find that cables made from Salt Water actually sound good after all.
Anyway, sorry to get carried away, but sometimes you have to go to extremes to make your point. Different metals (and other conductive materials) sound different - period, and after all this we’d be happy to hear from any engineers out there that can reasonably argue that the Inconel (forget the Salt Water for now) cables are going to sound the same as the Silver in the hypothetical examples above. Oh, and if you’re out there, don’t bother trying to use the old “resistance is the same” argument because anybody with a thinking brain KNOWS that within the boundaries of such extremes there HAS TO BE other variables involved besides just simple resistance.
For the rest of you good folks out there, we rest our case. Again, for ya'll the above was little more an exercise in superfluous rhetoric because you already know better. Therefore, now all we have to do is “pin the tail on the Phase Noise donkey” to make the point we have been trying to get at from the beginning. Toward that effort we’re gonna do a flip-flop for a moment here and give the academic engineering crowd some credit after all. To their defense, we have to admit that the sonic differences we are referring two are, at minimum, extremely difficult to measure with conventional laboratory test gear - even very good and expensive gear. It can be done, but the established tests most everyone in the audio industry uses are not designed to detect it.
The Case for Active
As an example, just trying to ACCURATELY measure noise down to -120 dB will set you back over $10,000 for the analysis gear you’ll need. Oh, and there isn’t an audio cable in existence that will exhibit ANY form of “self-noise” anywhere near as high in magnitude as -120 dB. Electrical circuits? No question there because in the case of active amplifier circuitry, getting noise levels down below -100 dB can be a bit of a challenge, let alone down to -120 dB.
In fact, the above actually helps to make our point, because Phase Noise cannot be heard like traditional noise whatsoever. That’s because Phase Noise is a type of “time modulation” wherein an audio (or other) signal varies up and down randomly in FREQUENCY (not amplitude) by extremely small amounts, and often very quickly. As stated earlier, this behavior is exactly the same thing as jitter in digital systems, but more difficult to measure. That’s because the effective “sample” rate of an analog signal is so incredibly high.
“Huh… sample rate? Analog signals are not ‘sampled.’ Sampling is a digital process, so how can there be a sample-rate associated with an analog signal? This sounds like pseudo-science hogwash.”
Sorry. Go do some research regarding the basics of Quantum Theory. Specifically, check out the subject of the "Planck Constant" and you’ll discover that TIME itself is “quantized,” meaning that there is an absolute “minimum” amount of time that can exist. In fact, that amount is called “Planck Time,” which then transforms to the Planck Frequency. Therefore, we would then say that the sampling frequency of an analog signal would be equal to the Planck Frequency, which turns out to be 2.95 X 10^43 Hz. That said, digital audio has quite a ways to go yet to compete with analog when it comes to high resolution sampling!!!
The upshot is that EVERYTHING IS DIGITAL, with the sample-rate of the universe being the Planck Frequency. Therefore EVERYTHING EXHIBITS JITTER, which is nothing more than a type of “Frequency Modulation,” and is very similar in behavior to the “suppressed carrier” modulation technique employed in common FM radio technology.
Conversely, traditional “noise” that you can easily hear (usually in the form of “hiss”) is something that we are all familiar with. Specifically, all forms of common noise are a type of Amplitude Modulation, which again is akin to a suppressed carrier technique used in AM radio transmissions. When one considers that limiting these more common forms of noise can alone be difficult enough to do, and that the results thereof can at least be easily heard, it only makes sense that something as obscure and difficult to measure as Phase Noise would go relatively “overlooked” by the audio engineering community.
Actually, the only reason it is even being considered at all these days is because it shows up as jitter in digital systems, and the main reason for that is that because digital encoding involves timing circuits and square waves. Jitter is fairly easy to detect if the bandwidth of your oscilloscope is wide enough. That, and the fact that these days digital storage oscilloscopes are fairly common, which makes capturing and analyzing signal events that vary in time much easier to perform. Even then though there have been some very expensive Digital-to-Analog Converters (DACs) in the not too distant past that were shown to exhibit fairly high levels of jitter, yet they still received good reviews for their sonic performance in the audio market press.
So What Does
To make this simpler we’ll put it another way: “What does Frequency Modulation (FM) sound like?” On a macro-scale you’ve most certainly heard it before if you have ever listened to pretty much any kind of music. FM in an extreme case that is yet quite common is the same thing as the “Vibrato Effect” that musicians employ. Another common example is the “Wow & Flutter” associated with analog record and tape playback equipment. In most such cases vibrato, wow and flutter are all rather pronounced effects and can be easily heard, but at the extreme low levels we are discussing, obviously not so much.
Then again, maybe Phase-Noise/Distortion is actually easier to hear than anybody has ever realized. We already know that human hearing is rather insensitive to amplitude (volume) variations. Proof of that can be easily seen in the case of loudspeaker performance, wherein variations in their output levels vs. frequency can be rather extreme, and yet numerous (and often expensive) models that exhibit such large variations are still often held in high regard by many audio enthusiasts.
Conversely, there is now evidence suggesting that human hearing is far more sensitive to variations in frequency or “pitch” than had been previously thought. For a rather comprehensive overview, check out the following “Temporal envelope and fine structure” article from Wikipedia. In particular, scroll down and read the section titled “Role in speech and music perception,” paying particular attention to the factor called “TNFp.”
Aside from the scientific evidence suggesting that human hearing can be extremely sensitive to very small variations in pitch, we also have a more obvious example in the form of certain people that exhibit what is commonly referred to as “Perfect” or “Absolute Pitch.” In light of this fact, we would ask: “So were are the people that have the ability to accurately identify absolute levels of amplitude (volume)?” We’ve searched and can’t find any references for such an ability anywhere, but it is well known and almost a common fact that many individuals have Perfect Pitch.
Hmm… so does the above tell us anything? Well, it’s certainly not “proof” per see, but these facts are highly suggestive that there is good reason to believe that humans CAN detect very slight variations in frequency, which is the definition of Phase Noise.
OK, when it comes to audio systems, what would Phase Noise sound like? Seeing that the effect is usually very small in even the worst cases, we wouldn’t expect that a person would actually be able to hear any type of “vibrato” or other similar obvious effect. Rather, we would expect a type of “blurring” effect - similar to that of a photograph taken with a camera in which the lens had been adjusted ever so slightly out of focus.
We would expect a “softening of sharp edges” with respect to musical harmonics at high frequencies (i.e., a form of “dullness” or loss of high frequency content), and a partial loss of information due to the blurring of fine details at the lower end of the dynamic range (i.e., at low volume levels). These effects would also manifest in a reduction of sound stage and imaging, such that the illusion of “3-D Space” has been somewhat compromised. Then in the reverse condition wherein Phase Noise has been significantly removed from the system, the “lifting of a veil” or “looking trough a window that has just been cleaned” would be the kinds of observations we would expect.
Now, does the above sound familiar? We thought so. How many cable formulations make claims to the very same effects? MOST ALL OF THEM!!! The question then becomes…
So What is Going On With Audio Cables?
Some years back before we developed the Smith Cell, we had come to realize that cable differences were a real phenomenon. That alone was a major revelation because before that time our professional work experience and associations had caused us to adopt the same academic line of thinking (all cables sound the same) regarding the subject that we now oppose and are working to disprove.
We held that view for a long time though, until one day when we clearly heard the simple reversal of a pair of audio Interconnect Cables completely transform the sound of OUR own loudspeakers in a customer’s system. That was our “come to Jesus moment” and we had to REPENT!!! We were snickering in mockery of the “foolish man” under our breath at first, but afterwards we were sure glad we hadn’t laughed out loud at the guy that was suggesting the Interconnect Cables between the preamp and power amp had been installed BACKWARDS (DUH - stupid man. Don’t you know AC signals are not directional?!) and that they needed to be switched end-to-end in order to correct the problem. Then he did and…Wow!!!… a total transformation! OK, all “opinions” be DAMNED -
!!! EXPERIENCE IS REALITY !!!
Anyway, not being given to “mysticism” or other a-causal effects, but rather, that we live in a “Causal Universe,” we are therefore convinced that there must be a reason or cause for everything that happens and/or is observed. Consequently, back then (just as now) we believed that:
If for no other reason than due to their shear numbers, Audiophiles that hear differences in audio cables are not all suffering from mass delusion.
Given #1 above is true, then there MUST be some scientifically identifiable reason for their observations.
Given #2 above is true, if the answer to the question is “knowable,” then we’re smart enough to at least understand the problem, regardless of whether or not we can discover exactly what its cause may be.
Given #3 above is true, then were just dumb enough to not know we’re not smart enough to be making an effort to succinctly identify such a complex problem and/or discover a solution to it, so we went ahead and tried… and maybe we just HAVE :-)
As a result of those initial efforts, our research ultimately led to the writing of the following White Paper titled, “Sub-Debye Phase Distortion - A New Source of Audio Band Distortion.”
Now, before the engineers and scientists out there start bellyaching that the above paper “proves nothing,” that “correlation is not causation” and that the paper is not even of proper scientific structure, etc., hold your tongue for a moment and don’t get your frick’n panties all in a wad. The fact is, that paper was never written with those intentions and we KNOW full-well that correlation is not causation.
Please understand, our ONLY intent EVER was to wave a red flag to say, “Hey, take look over here. Maybe something is going on with this?” - so as to maybe inspire others that DO have the means and the expensive laboratory gear to check further into it. Other than that, we realize that in our little “hypothesis” that we may just be totally full of $#*+! OK, are you feeling better now? Then go grab a beer or whatever trips your trigger, chill-out and then let’s move on.
Anyway, after that we developed our “Smith Cell” device (amp-to-loudspeaker version), checked it out and found that in a few cases it made a HUGE improvement in system performance. Then in most cases it made an appreciable improvement, while in a handful only a very slight improvement or none at all. The rest is history and so here we are.
Some time has passed since those days and we’ve recently started taking a second look at the cable issue regarding just what really may be going on. We’re certain it has to do with Phase Noise because basically, there is nothing else left to be discovered - unless we’re talking extremely exotic stuff like Dark Energy or Scalar Waves, etc., and we highly doubt that’s the case. Whether there are any such related issues involved or not though, “Occam’s Razor” directs us to look at the more obvious causes first, and Phase Noise is a well established phenomenon that has never really been fully investigated to this point, so we’re going with that - at least for now :-)
That said, we are now wondering if audio cables are not actually acting so much as “sources” of Phase Noise, but rather acting as “filters” thereof to one degree or another? Logic suggests that the dominant sources of Active Phase-Noise/Distortion will be electrical circuits and their underlying components, at least in comparison to simpler structures such as passive metal (or other) wires, conductors, etc.
In light of that fact we’re beginning to wonder if maybe the conductor metallurgy and it’s internal structures (crystalline grain size, geometry, impurities, etc.) along with such factors as their Specific Heat/Debye Temperature, etc. all work together to affect how well they are able to reduce the amount of Active Phase-Noise/Distortion that passes from the source, through them, and on to the load that they are connected to.
As a little “thought experiment” to illustrate our point, consider for a moment the case of manufacturing a wire of some type that is constructed from a bundles of modern “carbon fiber nano-tubes” of continuous length and all laid parallel to one another. Seeing that they exhibit an electrical resistance that is claimed to be 1,000 time lower than that of Copper AND they confine electrons such that they follow the tube and are not free to wander about like they are able to do in common metals, we ask the following question:
“Would such a cable act like a type of filter to reduce the transmission of noise artifacts? If not, would they at least reduce the likelihood of exacerbating the levels of any existing noise?
Those questions are a simple paraphrase of the concepts and claims already being made for OHNO cast “Continuous-crystal” Copper and Silver cables, and their advocates all but swear on “bended knee” that type of conductor is the best sounding there is to be had - period.
Finally, regarding the carbon nano-tube idea we must admit that we aren’t exactly the first to think of such a thing. In fact, for a number of years now there has been an electronic device designer that goes by the first name of “Jack” that offers a range of audio accessory products he claims are based on the very same thing — carbon nano-tubes. He also claims the devices “purify” the audio signal by blocking or filtering out “Quantum Background Noise.” His devices are relatively small and can be connected to the ends of speaker cables or located in series with the signal at other locations within the audio chain. In fact, his devices have had fairly widespread appeal for many years now in the niche audiophile market, and to the point that even a few electronics manufacturers now install them inside their product during manufacturing.
In light of the above, it seems that assuming those devices actually work, then maybe we’re correct and that it is Phase-Noise/Distortion of some form and/or from some source or another that has been hiding among our beloved audio signals all along and working to reduce overall system fidelity. It’s also likely, based on the claims of the above unnamed manufacturer, that we’re not exactly the first to think so… which to be clear, we are not and never were making any such claims that we are the first to begin with.
Taking things a step further in that regard, the unnamed vendor above might be the one that actually deserves the credit for being the first to identify the issue and developing a product to try and remedy it. That’s all fine with us. Actually, because of that he would be considered our competitor because we make similar claims for our “Smith Cell”/Vortex Filter technology devices.
Hey, the more the merrier - right"? Besides, we tried his devices several times and heard virtually no difference in performance… and that was when they were substituted for and installed in the exact same systems where our Vortex Filters had previously made a substantial improvement. So… “Caveat Emptor” and much happy listening! :-)