<font color='#000000'>See my responses in CAPS.
This is a critique of the article by Steve DellaSala, "Component Video Cables - The Definitive Guide" at the Audioholics website:
http://www.audioholics.com/techtip....les.php
This article has been praised by some as "great", and touted as the last word on video cable issues. Well, I read it, and noticed a lot of questionable portions in the article. I quote some of these, and respond here in this post. Note that I have not necessarily picked out all the problem spots, just some that I have found to be sticking out more than others.
QUESTIONABLE TO YOU AND YOUR SO CALLED KNOWLEDGE BASE.
All of this post constitutes my own personal opinion, and is based on my understanding of cable issues.
NOTICE HIS DISCLAIMER OF "OWN PERSONAL OPITION" NOT BASED ON ENGINEERING TRUTHS BUT MORE CONVOLUTED HALF TRUTHS SPREAD BETTER THAN NOOTHER THAN MR. RISCH.
Section 1.0, toward the end
[ There are a number of concepts and misconceptions about component video cables that will be addressed in this article, many of which will be proved or disproved mathematically. ]
Only, he does not show the math for a great many of the things he writes about, instead, he states it as if it were a given. Some of the math is only indirectly related to the subject at hand, or may be totally irrelevant.
THE MATH WAS USED AS A REFERENCE TO ENGINEERING EXPLAINATIONS. I AM NOT SURE HOW YOU CAN CLAIM THAT THE MATH EQUATIONS HAVE NO RELLIVANCE.
Section 1.1, toward the end
[ Cable lengths less than 30 meters have no effect of overall impedance. ]
This is not necessarily true, and in any case, is contradicted later in the article.
THIS CAN BE MISINTERPRETED AS IT IS A FUNCTION OF FREQUENCY THAT WILL DETERMINE THIS SO I CAN SEE SOME OF YOUR CONCERN HERE.
Also, he goes into characteristic impedance formula's for infinitely long cables (Section 1.2), but have already stated they are not relevant.
?
WHERE DID HE STATE THEY WERE NOT RELEVANT? I BELIEVE HE STATED THAT MOST VIDEO CABLE RUNS ARE SHORTER THAN 30FT FOR MOST PEOPLES SYSTEM. THESE LISTED EQUATIONS ARE ALL FACTUAL, RELEVANT AND BASED ON REAL ENGINEERING PRINCIPLES, NOT SNAKE OIL.
The whole impedance section is confusing and self-contradictory.
I CAN SEE HOW YOU WOULD HAVE A PROBLEM WITH IT. THERE IS NO MAGIC HERE, JUST FACTUAL DATA.
Sec. 2.0
[ Furthermore, strand jumping is another made up term used by manufacturers to justify using less expensive
solid conductor wire for their cable assemblies, as discussed in Section 3.1.1. ]
I am not aware of any manufacturer that uses strand jumping in extolling the virtues of their video cables.
TRUE, THERE ARE LESS FALLACIES AND MARKETING TATICS USED IN VIDEO CABLE MARKETING. THIS IS PARTLY TO DO WITH THE FACT THAT VIDEO IS NOT SUBJECTIVE. IT IS BASED ON STANDARDS (NTSC, ETC) AND THUS EVERY PARAMETER THAT CAN BE MEASURED OR SEEN CAN BE EXPLAINED TECHNICALLY. SOUND IS MORE SUBJECTIVE, LESS STANDARDS ARE IN PLACE FOR QUANTIFYING SOUND, AND THUS MORE MARKETING CLAIMS CAN BE MADE AGAINST THEM. THIS IS CLEARLY EVIDENT WITH SUCH FALLACIES AS STRAND JUMPING, CABLE BREAK IN, ELEVATORS, ETC. THIS WAS THE POINT I BELIEVE THE AUTHOR WAS TRYING TO MAKE.
With this in mind, I find it odd that this would be mentioned in an article on video cables, if none of the manufacturer's make any such claims.
AGAIN SEE MY RESPONSE ABOVE.
Strand jumping has been brought up for analog audio IC's by a few manufacturer's, but not very many.
SHOW ME ONE MANUFACTURER OTHER THAN AN AUDIO CABLE ONE THAT MENTIONS THIS. SHOW ME ONE CREDIBLE ENGINEERING TEXT BOOK THAN METIONS THIS.
HOW COULD STRAND JUMPING HAPPEN?
IF YOU HAVE A CABLE CARRYING THE SAME SIGNAL ON ADJACENT STRANDS, HOW WILL IT JUMP? ALL OF THE STRANDS ARE CARRYING RELATIVELY THE SAME POTENTIAL, THEY HAVE NO REASON TO JUMP. ALSO, JUMPING AN OXIDE AND AIR GAP IS FAR MORE RESISTIVE THAN TO JUST CONTINUE THE PATH DOWN THE CABLE. SINCE ELECTRICITY TRAVELS THE PATH OF LEAST RESISTANCE, IT WILL NOT JUMP. NEXT I AM SURE YOU WILL TELL US THIS STRAND JUMPING LEADS TO SIGNAL RETIFICATION. HOW CAN A LINEAR ELEMENT CAUSE SUCH A NON LINEARITY? ONLY IN JONS WORLD, OR THE WORLD OF AUDIOQUEST, OR FANTASY WORLD. PERHAPS THEY ARE THE SAME WORLD?
Also, this is the first place that mention is made of "solid wire costs less to manufacture than stranded wire" for video cables. This is so mis-guided and ill-informed, I can not begin to make any sense of it.
While there may be a very slight premium to use stranded wires in a coaxial cable, the cost difference would be SO slight as to defy any logical reason to base a design on that cost factor, the mere fact of having a custom cable made would completely obviate any reasons for doing so, virtually no significant cost difference for solid vs. stranded once we are talking about custom cables.
I AGREE WITH YOU HERE. I DON'T SEE MUCH OF A COST DIFFERENCE BETWEEN THE TWO FOR ONE INDIVIDUAL CABLE. BUT THINK OF IT ON A MUCH LARGER SCALE. A CABLE SUPPLIER SUPPLYING WIRES TO MULTIPLE MANUFACTURERS CAN SAVE ALOT OF MONEY IF THEY SELL EACH COMPANY ON THE CHEAPER ALTERNATIVE. THERE MAY BE SOME TRUTH HERE.
See: "The Cost of High End Audio Cables"
http://www.AudioAsylum.com/audio/cables/messages/34038.html
for a bit of an explanation on this.
Additionally, I have spoken with more than one RF engineer who was adamant that solid wires made for better coaxial cables for RF purposes, as the stranded wires could "spread" when the cable was flexed, and move within the insulation, and a solid wire would not do that as much. They also preferred a solid insulator to a foamed one for the same reasons. I doubt that it would be as much of an issue for the really stiff foamed insulation's, such as foamed FEP teflon, not nearly as soft as foamed PE, etc.
EITHER WIRE WILL WORK WELL FOR VIDEO APPLICATIONS IN QUESTION, AND ESPECIALLY WELL FOR AUDIO FREQUENCIES. THE OVERALL CONSTRUCTION OF THE WIRE IS OF MORE IMPORTANCE.
See:
http://www.gepco.com/whatsnew/pr_050102_HDfoamcoax.htm
for an article on making Hi-Definition coaxial cable for HDTV.
Note that the article was published in "Broadcast Engineering" magazine.
This web site says that solid wire coax has less losses than stranded wire coax:
http://tcns.thaicom.net/RF/Coax.asp
THIS IS TOO GENERAL OF A STATEMENT. EQUIVALENT GAUGE STRANDED WIRE WILL HAVE LESS AC RESISTIVE LOSSES (SKIN EFFECT) THAN EQUIVALENT GAUGE SOLID CORE WIRE BECAUSE THE OVERAL SURFACE AREA OF THE STRANDED WIRE IS GREATER.
SEC 2.1
[ ....or a poorly made component video cables are used that are not true 75-ohm, the lower impedance value of these cables can result in a loss of video signal do to a mismatch in impedance. ]
This statement is not precise enough to be able to comment on very much, except that it gets repeated in other forms later on. Impedance mismatches will not cause an overall level drop, nor will they cause a loss of the video signal as a whole. What an impedance mismatch WILL do, is to cause partial signal reflections that bounce back down the line. Some if this is ALWAYS going on in any RCA plug based video cable, so it is really a matter of degree. Proper impedance cables can help minimize the amount and severity of these reflections, but will not eliminate them. More on this later.
OH OK SO I GUESS RETURN LOSS (WHICH IS A FUNCTION OF IMPEDANCE) IS NOT IMPORTANT FOR SIGNAL INTEGRITY. I GUESS YOU SHOULD TELL MICROWAVE ENGINEERS TO STOP DESIGNING IMPEDANCE TRANSFORMERS TO COMPENSATE FOR IMPEDANCE MISMATCHES DOWN THEIR TRANSMISSION LINES SINCE THERE WILL BE NO RESULTANT POWER LOSS FROM ALL THE REFLECTION. EVERYONE THROW YOUR SMITH CHARTS AWAY. QUARTER WAVE WHAT?
THE TRUTH:
IF THE STANDING WAVE RATIO (1+PO)/(1-PO) IS NOT UNITY, THUS NOT PERFECT IMPEDANCE MATCH, THE DRIVING POINT IMPEDANCE OF A LINE IN GENERAL IS COMPLEX VALUE DEPENDING ON THE LENGTH OF THE LINE. THE LARGER THE VALUE OF SWR THE MORE RESULTANT POWER LOSS.
SEC 2.3
[ Mismatched impedance is one of the most common and most frequently experienced sources of signal degradation. This phenomenon occurs when a 75-ohm signal encounters different impedances through its signal path, usually on the order of 35-ohm or 50-ohm for Home Theater applications. It can occur in video cables that do not use true 75-ohm RCA connectors, .... ]
Well, that would be great, except that there is no such thing as a true 75 ohm RCA phono connector! More on this later, in response to section 3.5
HMM SO I GUESS YOU CAN'T DESIGN A 75 OHM CONNECT BY A FUNCTION OF DIAMETERS GIVEN IN THE AUTHORS EQUATION. I SUPPOSE THAT ENGINEERING PRICIPLE THAT HAS BEEN USED FOR OVER A CENTURY IS FLAWED. THANKS FOR SHARING THAT WITH US JON.
Also in section 2.3, we are lead through a series of equations, but what he fails to point out completely when discussing the equations, is that the signal losses due to reflections will tend to occur ONLY at certain frequencies related to the effective electrical length of the cable, and will NOT affect ALL frequencies the same. It is entirely possible that for a short cable (2M or less), NONE of the frequencies carried by a video signal would be affected by any of the reflections, unless they bounced back and forth many times.
HUH? DOES IT MATTER? LOSS AT ANY RELIVANT FREQUENCIES WITHIN THE VIDEO BANDWIDTH IS NOT A GOOD THING. DOES HE REALLY NEED TO SPELL EVERYTHING OUT TO YOU?
In order for this to occur, there would have to be impedance discontinuities at both ends of the video cable, and they would have to be fairly severe at both ends.
HOW DO YOU QUANTIFY THIS? DOES IT HAVE TO BE MORE SEVERE THAN THE RESULTANT LOSS YOU CLAIM BY STRAND JUMPING? WILL IT HAVE LESS OF AN IMPACT THAT IF YOU ELEVATED YOUR CABLES OFF THE FLOOR? OR WAIT, WILL IT IMPACT LESS THAN CABLE BREAK IN?
PLEASE QUANTIFY ALL OF THOSE AND SHOW US YOUR MEASUREMENTS AND CALCULATIONS. THEN SUBMIT THEM TO AES AND LETS SEE WHAT HAPPENS.
SEC 2.4
[ Skin effect is sound engineering phenomenon that can be defined mathematically, however as outlined in the following examples, it has minimal effects at low frequencies within the range of audio and video cables. ]
This section is also written in a very confused manner.
First, we are lead to believe that skin effect has no consequence, yet, in the first side bar "Pursuing the Truth", we are told that: "When a copper conductor is plated with pure silver with a thickness of 50 microns, 92% of the current density will be in the silver. Since silver has a 10% gain in conductance compared to copper, a copper wire plated with silver will have less signal loss especially at longer lengths, thus minimizing skin effect."
So which is it? Can skin effect be ignored, or it is a factor, and silver plating will reduce it? He seems to be saying both things.
HMM I SUPPOSE I CAN SEE HOW THE WORDING HERE CAN BE CONFUSING.
Later on in this section, he talks about the increase in AC resistance that skin effect causes, and later the power loss from skin effect.
However, these two kinds of losses are not the only effects that result from the skin effect, phase shift also occurs, and skin effect is responsible for forcing the current out toward the surface of the wire, even at audio frequencies, much less video. So skin effect DOES make the surface of the wire more important than the rest of the wire, and the condition of the surface of the wire, in terms of impurities, or poor metallic crystal structure, are going to have a potential effect. None of these aspects is even considered or brought up.
THATS BECAUSE THE SO CALLED "IMPURITIES" THAT YOU MENTION ARE NOT SIGNIFICANT. IF THEY WERE, THEN WHY DO COMPANIES THAT DESIGN ULTRA HIGH EXPENSIVE AND ACCURATE TEST EQUIPMENT USE NORMAL COPPER COAX CABLES FOR THEIR EQUIPMENT? HIGH POWER RF APPLICATIONS, THE SAME THING. NOBODY USES MAGICAL SILVER WIRE OTHER THAN SO CALLED EXOTIC SPEAKER CABLE VENDORS. JUST HOW PURE IS THEIR WIRE? HAS ANYONE MEASURED IT?
Finally, it is said that the frequency ranges of video (and audio, once again, trying to squeeze in a subject that is not the avowed topic of the article) is not subject to skin effect.
Well, at 20 kHz, the skin depth for copper is 0.46 mm, or about 5/64's of an inch. The diameter of a 19 ga wire would have this depth at the center of the wire, and while this kind of assumption is often made for what size wire will be "free" from skin effect, it is just another way of providing a benchmark for comparison. Most folks who have worked with audio cables find that a 19 ga. wire has problems, and that smaller diameter wires are needed to avoid audible problems, whether they are due to the skin effect, or other issues.
IS THIS BASED ON OBJECTIVE MEASUREMENTS AND LISTENING? OH WAIT, YOU DON'T BELIEVE IN DBT. YOU CANNOT PROMOTE MAGIC WITHOUT FAITH.
One can certainly see that there will be some significant skin effect at video frequencies for any reasonable size of coax center wire, even RG-59 types with a 20 or 22 ga. center wire.
SURE AND THE AUTHOR STATES SEVERAL TECHNIQUES TO MINIMIZE THIS. HE NEVER STATED THAT SKIN EFFECT IS IRRELEVANT AT VIDEO FREQUENCIES. IN FACT IF YOU PICK UP ANY ENGINEERING BOOK THAT TALKS ABOUT SKIN EFFECT,THEY DON'T EVEN CONSIDER IT UNTIL AT LEAST 50 KHZ OR MORE.
End of SEC 2.4
[ Pursuing the Truth: Most cable vendors use multi stranded wire as opposed to solid core conductor. Multi Stranded wire actually helps to reduce skin effect since the combination of strands act as a larger surface area then an equivalent gauge solid core conductor. ]
The amount of increased surface area for a stranded wire is NOT that much greater, as the skin effect will still manifest on the stranded wire bundle AS A WHOLE. The individual wires WILL NOT each act independently unless they are BOTH individually insulated, AND woven in and out. This kind of wire is called Litz wire. I know of no vendor that uses a Litz wire for the center wire.
ACTUALLY THE STRANDED WIRE WITHOUT INSULATION ON EACH STRAND IS STILL CONSIDERED LITZ WIRE AND YES THE SURFACE AREA IS GREATER. PICK UP A POWER RF BOOK AND YOU CAN READ MORE ON THIS.
The only increase in surface area that a stranded wire has is due to the extra area of the rounded outside edges
of the stranded bundle. This is not a huge increase in surface area, since the skin effect is still pushing the current out toward the surface of the bundle as a whole.
You might see a 10-15% increase in conductivity for skin frequencies, due to stranded wires vs. a solid wire of the exact same overall diameter as the stranded bundle.
Yet again, what is the big deal if skin effect is not an issue in the first place? Either it IS relevant, and stranded vs. solid and silver plating vs. bare copper are then relevant, OR they are a moot point.
Doesn't this sound exactly like the very snake-oil they rankle about? Touting certain features (stranded wires, and silver plating) as relevant, even though they say in the same breath, that it doesn't really matter according to the calculations?
AGAIN, THEY DONT MATTER FOR AUDIO, THEY START MATTERING FOR VIDEO. YOU LOVE TO TWIST WORDS DONT YOU JON?
BTW, as for "Most cable vendors use multi stranded wire...", I am not sure this is actually true for video cables, it certainly may be for audio cables. However, this article was supposed to be about video cables.
SEC 2.4, 3rd "Pursuing the Truth" sidebar, 3rd section, where they talk about terminating the cable.
The pictures at the bottom of the 3rd page in the article (
http://www.audioholics.com/techtip....s_3.php )
are used as examples of a "good" solder connection, and a bad solder connection.
In my experience, what constitutes a good solder connection for RF is a nice smooth, even solder profile, with no sudden discontinuities. The wire or braid solder joint surface should smoothly "flow" into the connector termination, with no kinks or sudden bends or large blobs of solder.
Based on that criteria, the cable on the right is not so bad, it could be improved on, but it makes no really awful mistakes. It may look superficially less than tidy, but the main concepts regarding solder joints for RF that I am talking about have not been badly violated.
No, it is not good to melt the insulation, but when we are already in the region of the termination, the exact spacing is not being maintained anyway, so this is being rather anal about the subject.
I note with interest, after all the talk about impedance matching, and proper soldering technique, they use as an example of a "good" RCA plug, one that has a built-in impedance discontinuity. Note the half open inner barrel section, where the area for soldering the center wire is open. This section is a different diameter than the rest of the barrel, and so, MUST present a different impedance than the rest of the barrel. So much for being truly concerned with all of the details.
SEC 3.1
[ For component video cables, the conductor is usually made with stranded wire for improved flexibility and increased surface area. ]
We have already dealt with the "increased surface area" myth promoted in this article. But there is an even bigger gaffe to come:
[ The use of different materials for the primary conductor becomes apparent with video cables above 10 meters, as signal losses increases due to conductor resistance. ]
Increased conductor resistance is not really the primary reason for losses in a coaxial cable at RF frequencies.
As was pointed out earlier, RF tends to travel on the surface of the conductor, and so, the absolute gauge of the wire has little to do with these types of losses.
While the video signal is not, strictly speaking, RF energy, it will not have the kinds of signal losses due to sheer cable resistance that is implied here.
Then again, according to this article, all we have to do is silver plate the wire, and no more fuss!
Much of the loss in a coaxial cable at RF frequencies is due to dielectric losses, and a superior quality dielectric will minimize these losses.
So what about baseband video signals that are not RF?
Just as a point of information, the losses for a 100 feet of high performance cable at 10 MHz are: for an RG-59 (with a 22 ga. center wire) are 0.9 dB, for an RG-6 (18 ga. center wire) the losses are 0.7 dB, and for an RG-11 (14 ga. center wire) the losses are 0.5 dB.
This compares similar construction and materials, so as to eliminate as many variables as possible, except center wire ga.
These are very small differences in signal losses, and the actual materials and construction can often make more of a difference than the wire gauge. RG part numbers are not that specific, see:
http://www.AudioAsylum.com/audio/cables/messages/25155.html
In the "Pursuing the Truth" sidebar:
[ Consequently, cryogenically freezing the cable does not slow down or prevent oxidation either (unless it remains in the frozen state). The process itself only produces a temporarily cold cable. Once the cable is warmed, it is the same cable it was before being ‘frozen.’ ]
While this may or may not be true for the oxygen free aspect, most of the folks who cryogenically treat the cables do not necessarily do so to improve the oxygen free content of the cables, rather, they are doing it to try and improve the crystalline structure of the metallic conductors. Metallurgy has shown that some sort of an effect does take place in many instances when a metal is cryogenically treated, so to say that nothing has changed is a bit much to be saying without any further qualification.
GIVE ME A BREAK. YOU ARE DEALING WITH SOMETHING SO INSIGNIFICANT AND SO FAR BELOW THE NOISE FLOOR AND THRESHOLD OF HUMAN HEARING. THE INDORSEMENT OF SUCH A FALLACY IS FAR MORE MISLEADING THAN ANY TECHNICAL ERRORS IN THE ARTICLE IN QUESTION.
I have never seen any claims about cryo treatment being for the purpose of improving or maintaining the oxygen free aspect of the copper conductors. This would seem to be a red herring brought up to discredit cryo treatment without actually discussing the relevant issues associated with cryo.
THERE ARE NO RELEVANT ISSUES, PENDING YOUR SANITY.
SEC 3.1.1
"Pursuing the Truth" sidebar,
[ Be forewarned that some cable manufacturers use a solid conductor primarily for cost purposes. Through their clever marketing schemes, they use made up terms such as, "Strand Jumping". By using this made up term, they attempt to justify the use of less expensive coaxial cable for their component video cable assembly, ... ]
I have already dealt with the cost bugaboo, so now let us address the strand jumping issue here.
Skin effect, you remember, that non-issue effect that was reduced by stranded wire (false) and silver plating (somewhat)? Well, if the current in the wire, the actual electron flow IS the current, is forced toward the outside of the wire, then what happens when a stranded wire is not perfectly aligned all along the length of the stranded bundle? Some of the strands will be on the outside, and then end up on the inside of the bundle.
In order for that strand of copper that was carrying the HF currents while on the surface to follow the skin effect current density profile, it HAS to "hand-off" to a strand that is nearer the surface of the stranded wire bundle. The eddy currents that have formed and that are responsible for the skin effect in the first place, will cause this to occur. So skin effect WILL be instrumental in promoting some amount of "strand jumping" .
The various forms of stranding geometry as shown in the article will reduce the possibility of strand jumping, because if a given strand does not wander in and out of the overall bundle, but maintains it's place within the bundle, then there is less of an amount of skin effect current density differences to provide the impetus for any strand jumping to occur.
However, that does not completely eliminate all possibility of strand jumping, nor does it render the reason for it (skin effect) an inconsequential effect.
HMM SOUNDS LIKE ALOT OF BLACK MAGIC AND SNAKE OIL TO ME. HOW COME I NEVER HEARD OF SUCH CONCRETE ENGINEERING THEORY IN MY 6 YEARS OF ENGINEERING SCHOOL. PERHAPS THIS TOPIC IS TOO COMPLEX AND THUS RESERVED FOR A FEW CABLE VENDORS TO WRITE ABOUT ON THEIR WEBSITES. LETS JUST MAKE SURE THAT EVERYONE IS SELLING THE EXACT SAME STORY SO IT SOUNDS LEGIT. OK? GOOD.
SEC 3.1.1
[ Resistance values of cables becomes significant in lengths well over 2-meters. If you are installing a custom Home Theater System and must run lengths of coaxial cable that greatly exceed 2-meters, component video cables made from higher gauge wire are typically recommended as they will have a lower resistance and therefore, will minimize video signal loss. ]
Well, now we are getting confused again. First, it was anything over 30 M, and I would argue about that.
But I can not possibly see how anything over 2M (about 6 feet), is going to need a huge RG-11 coax to avoid video signal losses! Totally off the wall, and inconsistent with earlier statements as well.
After pooh-poohing a 0.047 dB power loss due to skin effect, he is now saying that an amplitude loss of 0.04 dB (from RG-11 down to RG-59 for a 10 foot length at 10 MHz) is significant? Again, not consistent criteria here.
SEC 3.1.2
[ The grounding diameter is not related to the ohm
rating since in theory the ground does not carry a current. What is important is the ground shields ability to complete the circuit, protect the conductor to minimize signal leakage and shield the assembly from EMI. ]
Whoa! The coax braid does not carry a current? But in the very same section, he says that the braid completes the circuit! Well, which is it?
OK I CAN SAY THIS SECTION IS WORDED A BIT CONFUSING AND MISLEADING. THE AUTHOR SHOULD GO BACK AND MAKE CORRECTIONS HERE.
I can tell you, the 'shield' braid is the ground return, and does indeed carry current and complete the circuit.
See:
http://www.AudioAsylum.com/audio/cables/messages/503.html
for more on this.
SEC 3.1.2
[ By using two 95% copper braids, the amount of copper is substantially increased and the resistance therefore decreased, thus reducing the chance of current flow and noise in the cable. ]
Whoa ! Again! Reducing resistance does not reduce the current flow, in fact, it reduces the voltage potential between two video components by lowering the resistance, which actually increases current flow in the braid.
SEC 3.3
Under the dielectric section, he fails to mention that teflon also comes in a gas-injected/foamed formula, and would have dielectric constants as low or lower than GI/foamed PE, all other things being equal.
[ As seen by their constants, neither Nylon (4.0 to 4.6) or PVC (3.0 to 8.0) make effective dielectrics for any cable length, yet they are still used by some component video cable Manufacturers due to their low cost. ]
In so far as I know, no one currently uses PVC (or nylon) for the dielectric in a video cable. PVC has not been in general use as an insulator in a coaxial cable for many years, and it would indeed be a travesty if someone used it for video cables. I am personally not fond of it for audio use either.
However, the implication is that some vendor out there IS using PVC, when in fact, this does not seem to be the case.
SEC 3.4
[ This method also preserves the diameter ratio of the dielectric and conductor at the end of the cable where it has been cut and soldered onto the connector housing, thus preserving the 75-ohm impedance of the cable/connector combination from tip-to-tip. ]
As has already been commented on, this is not the case, the portion of the RCA plug inner barrel that is cut-out for access to the center pin changed the diameter of the plug along half of the plug for that length. Why this is ignored, when much is made of smaller issues, is a mystery.
SEC 3.5, bottom of page 5
[ It turns out that the RCA connector on the left has the correct diameter ratios to create a 75-ohm connection, where as the one on the right is adequate for a 50-ohm connection such as that found in audio signals. ]
Whoa! This would be funny if it weren't stated in an entirely serious manner. Apparently, the writer has swallowed some manufacturer's hype about "true 75 ohm RCA plugs", which is ironic given that the avowed purpose of the article is to provide solid information about video cables, rather than to parrot what has been hyped.
Bottom line: no matter what the RCA plug itself is doing, the female RCA jack is not 75 ohms impedance. Period. End of discussion.
Even if, by some miracle, the RCA plug itself could be made to be a 'true' 75 ohm impedance, which I am not convinced that it can be (nor are quite a few knowledgeable RF folks and engineers), then it would still be a moot point since the RCA female jack is not a 75 ohms Z.
YEST, BUT IF YOU LOOK AT A SCHEMATIC FROM SOME TVS OR OTHER VIDEO PRODUCTS, YOU WILL NOTICE A SERIES 25-30 OHM RESISTOR INLINE WITH THE RCA CONNECTOR. THIS IS TO HELP WITH IMPEDANCE MATCHING WITHIN FREQUENCIES RELEVANT TO LUMPED ELEMENTS.
Yes, the RCA plug on the right will be slightly worse than the one on the left, as it does have a "constriction" in the overall diameter of the barrel to center pin, as shown. This is not necessarily a show stopper, or a huge problem. After all, as we have seen earlier, the plug shown as being of a 75 ohm impedance, has an impedance discontinuity due tothe differing diameter of the inner barrel where it is cut out for access to the center pin.
So these RCA plug related impedance discontinuities are more a matter of dgree, rather than any sort of absolute.
[ That being the case, only a few component video cables actually have true 75-ohm RCA connectors since very few exist. ]
In point of fact, no real 75 ohm impedance RCA plugs exist. Much has been made of a certain brand of plugs that do everything they can to promote this myth, but if the claims and wording of this brand of plug is examined closely, one will find that words and phrasing like "75 ohm coaxial cable compatible", or "impedance-matched" or they make reference to a VSWR measurement, but they really never come out and SAY that the plugs are actually endowed with a 75 ohm impedance, nor do they mention if the plugs were measured for VSWR when actually plugged into a female RCA jack!
SEC 3.7 Jackets and Sheaths
This section is very confused, as so much is misstated for the subject line.
[ The disadvantage of PVC (as a jacket material) is its overall stiffness and lack of flexibility. ]
That's my parenthetical insert.
PVC, with the addition of the proper type and amount of plasticizers, is one of the THE most flexible jacket materials, and is often the only choice if cable flexibility is needed.
[ Polyurethane is restricted to use in jackets only, due to its poor dielectric properties. ]
While I am not fond of PU's dielectric properties, and do not recommend it be used as an insulator, especially for coaxial cables, it IS used as a coating on lots of magnet wire, and so, IS used as an insulator, contrary to what this article says. As a matter of fact, I am not aware of too many cable jackets that use PU either, when PVC is cheaper.
[ Polyethylene is the compound most widely used in coaxial and low capacitance cables due to its fine electrical properties. ]
This is true from a center insulator (dielectric) standpoint, but has little relevance for use as a jacket material. In point of fact, PE is seldom used as a jacket material, due to cost and stiffness.
[ Nylon has a very low coefficient of friction, making it a good choice for use in high flex applications. ]
While this is true for certain types of wiring, such as THHN type wires, run inside conduits for AC power, nylon is hardly ever used as a jacket material for coaxial cables, as it is too stiff, and would tend to encourage kinking of the inner dielectric, compromising the impedance of the cable.
This whole section looks like it was lifted right out of some cable manufacturer's web site, only, it was in the section on INSULATORS, not jackets. Sheesh!
SEC 4.0
[ Based on the lengthy discussions in each section, marketing schemes such as the misuse of the term skin effect and the entirely made up term known as ‘strand jumping’ were found to have little to no effect on cable performance. ]
This is not exactly the case, as I have already pointed out, and while SOME equations and "math" were presented, they do not definitively show that what he states is some sort of inherent mathematical truth.
Aside from contradicting himself on skin efect, and whether or not it needs to be addressed (is stranded wires and silver plated NEEDED, or not?), he does not address the other aspects of skin effect issues.
This includes the very reasons that strand jumping may occur, which is going to be skin effect driven.
Given that only some of the issues were discussed, how is it that skin effect and strand jumping "were found to have little to no effect on cable performance" ? Found by whom?
[ Don’t be fooled by to good to be true marketing claims that are abundant when considering the multitude of cables on the market. ]
Including claims about true 75 ohm RCA plugs, stranded wires being significantly superior to solid wires, and silver plating being needed for video cables?
Summary and Comment
The general tone of the article is one of an adversarial one towards cable vendors, as if they were out to try and "trick you" or cheat you with techno-bull, but the article itself has obviously accepted without reservation certain specific vendor's 'techno-bull', and proposes some of this as the gospel truth.
You are told that solid wires are used because they are cheap, not really the case, and in fact, it may be that a solid wire is actually superior for video/RF use.
You are told that some video cable vendors are selling you strand jumping, when I do not know of any vendor doing this.
AUDIOQUEST, STEALTH AUDIO CABLES, AUDIENCE-AV, JON RISCH DIY, NORDOST ALL PROMOTE STRAND JUMPING.
You are told that some vendors provide "true 75 ohm" RCA plugs, in contrast to other vendors, when in fact, it is highly unlikely that there are ANY "true 75 ohm" RCA plugs", and even if there were, it is a moot point due to absolutely NO "true 75 ohm" RCA JACKS!
You are told that silver plating is desirable, even though it will not matter. (Silver plating costs money)
You are told to look at solder joints, without the whole story of what to look for.
Frankly, I think that such an article, pretending to be the last word on the technical aspects of video cables, does the video enthusiast a disservice, because some poor fool is going to believe the contents, and run out and buy a silver plated, stranded center wire, RG-11 sized cable with special non-impedance consistent RCA plugs.
The ironic part is, this highly sophisticated super duper video cable may or may not perform any better than other video cables, how can anyone tell for sure from all the 'technical' information in this article?
JON YOU MADE SOME GOOD POINTS ABOUT THIS ARTICLE, HOWEVER YOU MADE MANY MISLEADING AND UN TRUE ONES. I THINK THE ARTICLE ON A WHOLE IS GOOD. DOES IT NEED WORK? YES. IS IT PERFECT? NO. HOWEVER, AT LEAST ITS INTENT IS GENUINE. ITS CONTENT IS NOT POLARIZED. IT TEACHES BASIC CONCEPTS. IT DOESNT PROMOTE FALLACIES SUCH AS THE ONES FOUND ON YOUR WEBSITE.
BOTTOM LINE, THIS IS MY 1ST AND FINAL DEBATE ABOUT THIS ARTICLE WITH YOU. I DON'T KNOW HOW YOU FIND THE TIME TO DEBATE AND NITPICK IN SUCH LENGTH AS YOU ALWAYS DO. IF I MAY SUGGEST, FIND OTHER AVENUES TO MAKE YOU FEEL GOOD ABOUT YOURSELF. GET ON AN EXERCISE PROGRAM, FIND A MATE, GO FISHING, DO SOMETHING. I CANT BELIEVE HOW YOU DELIBERATELY GO ON ALL OF THE POULAR AUDIO WEBSITES WITH YOUR SO CALLED TEACHINGS AND SLANDER AGAINST ANY ARTICLE POSTED ON AUDIOHOLICS ABOUT CABLES.
YOU ARE A TECHNICALLY COMPETENT PERSON. WHY DO YOU MIX TECHNICAL INFORMATION WITH FALLACIES? WHAT MOTIVATION DO YOU HAVE? WHAT GAIN DO YOU GET BY SPREADING SUCH DISSERVICE? I HOPE YOU SLEEP WELL AT NIGHT.
NIGHFLY!
Jon Risch</font>
