I know analog signals degrade over distance, but since HDMI is an all-digital signal, the digital signal stays intact right?

Wrong. A digital signal can and does degrade over distance-especially in copper cables that have similar electrical characteristics to their analog cousins. However, the fall-off in digital can be more sudden known as a “Cliff-effect”. In the simplest terms, the signal wave (square in this case) becomes degraded over distance due to the cables capacitance and lack of even and precision twists per inch. The result is a slowing and non-uniformity in the timing of the waves which causes them to become weaker, lose their shape. This can cause what is known as “jitter”.  An “eye pattern test” is used as the method for testing the cables ability to properly reproduce the signal over particular distances and at specified speeds.

I have read in some reputable electronics magazines and blogs that a cheap HDMI cable is just as good as an expensive HDMI cable. How can that be true based on the above?

You have to keep in mind is how the cable will be used as applications and conditions matter. For instance, those assertions are based on a very particular set of conditions such as (A) a very short length (3ft), (B) no cable stress i.e. repeated bending or disconnecting whatsoever, (C) the ability to easily access the cable if it fails and (D) and a standard 1080p signal.  In that “best case scenario”, yes, it is possible that most cables will work perfectly fine.

However, what is does not tell you is that all applications and conditions are not “best case scenarios”. For example, if you used a poorly made internet cable to go a longer distance, say 15-50ft, you could experience an entirely different outcome as distance is when the construction differences will become apparent. A poorly made HDMI cable can have jitter or fail completely, especially at longer lengths. 

Another primary consideration is environment. If your cables will be installed behind a wall (and those that are usually are longer than 3-6 ft), how much will it cost you if you have to replace it?

What if the cable will be disconnected and reconnected a lot as in educational or rental use? What is the ability of the connector mold and solder points to withstand that environment? How important will service and the warranty of the manufacturer be if you need support?

These are all questions you should ask yourself and decide to make the purchase that best suits YOU.

So what are examples of HDMI cable construction qualities that actually matter?

There are quite a few.  

1.) Accurate Twists and Connector Solder Process: Inaccurate twists and poorly performed soldering can dramatically affect the performance of an HDMI cable or cause it to fail. Inaccurate twists can cause jitter or cause a cable to fail and poor soldering at the connector can also cause impedance issues which will cause problems over longer distances.

2.) Gauge and Center Conductor: The gauge (size) of the center conductor(s) and the material (high purity tinned copper is best) from which it is made is one of the most primary features for the conductivity of any copper cable. While a digital signal can be somewhat re-constituted by the equalization circuit of a digital receiver, the gauge and center conductor still play an important role in bandwidth/speed capability and distance from one cable to another.  

3.) Quality Control: One thing often over looked in the cable discussion is quality control. Good quality control is essential and helps ensure consistent performance from one cable to the next-something which is especially important for Pro A/V and B2B customers as a system is only as good as its weakest link.

4.) Durability and Reliability:  This may not be as important to the average consumer but it is a primary consideration of Pro A/V customers. Jacket durability, bend radius and number of insertions to name a few are crucial and not always thought of when comparing. When a series of digital signage monitors, classrooms or an event stage is wired up, its show time again and again. The cables HAVE to work each and every time. Failure is not an option.    

All of these features add cost to a cable, however not $25, $50 or $100 dollars of cost. Ironically a very well known leading consumer brand does not publish its gauges. However, through examination we were able to determine it uses a small 30 gauge center conductor on almost all of its HDMI cables! (In contrast, Comprehensive does not even use gauges that small for our standard grade cables let alone “performance” cables.)This means not only are you being overcharged, you are not even getting a true performance product.

What features don’t matter?

24k Gold connectors: 24k gold connectors is a consumer trapping (Pro’s have always used nickel). 24k gold has little tangible benefit beyond corrosion resistance so unless you will be using near salt water, it’s not too big of a concern.

Braided Jackets: That net jacket looks kind of cool and interesting but does not provide any real value and is often used as a cosmetic to justify high prices.

What about so called “future proofing”?

Some retail manufacturers are using that term as a reason to charge outrageous prices for performance you don’t need. However technology capabilities and requirements are advancing at an extremely fast pace with 1080p and 3D now in our living rooms over just the past few years. So a cable that provides additional headroom could extend the life of that cable a few years which may be worth something to you-how much is up to you.   

So in the end, who is right, the expensive retail brands or the internet stores saying cable quality does not matter?”

Neither. That is because each camp has some truth in their argument but they approach the issue as an absolute which is not accurate and not fair to the consumer. The fact of the matter is the construction and the quality of an HDMI cable or any cable DOES matter-especially as you go beyond 3-6 ft-but that does not for a minute (a) justify the outrageous prices retail brands charge or (b) mean any internet cable from China is as good as a well built, quality cable from a legitimate brand.  

So how does Comprehensive solve this problem?

The reason Comprehensive has been so successful with Pro A/V customers (those that know cable and value very well) over the years is because we understand better than any other cable manufacturer the importance of balance. The need to provide a quality, reliable product at a great price has been our calling card since 1974 and it continues today in the digital world. We are definitely not the most inexpensive cable on the market, but no one provides more value or bang for the buck than Comprehensive.  We kindly encourage you to compare and see for yourself.   

 So What is the Take Away?

As with most products, construction does matter but not to the degree the retail brands would have you believe –especially for a very short length used in perfect conditions. On the other hand, not all applications are the same and construction and quality cannot be completely dismissed as internet stores would have you believe.

As with most things in life, the answer lies not in the extremes but in the middle. Use common sense, consider your application and the features that matter most to you.  We think when all things are considered, you will find Comprehensive HDMI cables to be of tremendous value and the sensible choice for most applications. 

As professional systems integrators know, cables may look very similar from the outside, but they can be completely different on the inside. Construction practices, materials used, quality control and many other factors both seen and unseen contribute to the performance and reliability of a cable. So we wanted to take you “under the jacket” to look at a basic cable construction so you can make an informed choice as to the cable type, quality level and brand that is right for you.

Basic Coax cable construction consists of the following:

Let’s take them each one by one:

Center Conductor: A good center conductor is made up of quality materials and a well sized gauge for the application. The center conductor is the primary conductor in the cable or each conductor. The size of the gauge and materials used will play a large role in the cables final performance. The center conductor itself can usually be solid or stranded. While solid has the best conductive properties, it is inflexible and more costly. Stranded conductors are actually a group of individual strands of copper which provide conductivity almost as good as solid construction while allowing much more flexibility and durability.

Gauge: The gauge indicated the size of the center conductor, the larger the gauge in general, the higher conductivity it will have. Why? Because the larger the gauge, the lower the resistance. The lower the resistance, the less signal loss a cable will have. The less signal loss a cable will have, the more signal that makes it to the display from the source. Be aware that although gauge size can be expressed universally (12 awg is larger than 18awg etc), the properties of a center conductor can actually vary somewhat depending on materials used and the construction process.

Materials: The material used for the construction of the center conductor can work with or against the gauge and greatly effect the performance of the cable. High purity tinned copper is the material of choice for most audio and video cables because of its well known conductive properties and flexibility which is important for cable durability. Some center conductors (like those used in many Comprehensive cables) use tinned copper which can last up to 10 times longer than non-tinned copper and enhances conductivity. Tinned copper also resists corrosion better than non-tinned copper.

Silver coated center conductors actually use a very thin coating of silver on top of a copper center conductor. This slightly improves the conductive properties of the cable (though not always in line with the prices retail brands charge). 

Oxygen Free Copper: Oxygen free copper is the purest copper available, often expressed as 99.9% pure and reduces oxidation and does slightly improve signal response. It also adds to the cost of the cable as well. 

Copper Clad Steel: One thing to watch out for is some internet stores and China importers have begun substituting a material known as copper coated steel for their center conductors. This is an inferior conductive material and is not suited for audio/video use. Copper clad steel has much poorer conductivity properties than true copper and does not perform nearly as well. It is used by some companies because it is much cheaper and significantly lowers the cost of the cable as a whole.

Dielectric:  The dielectric is the white material covering the center conductor under the shield(s). The dielectric acts as an insulator for the cable and determines the impedance of the cable. Most dielectrics are made of what is known as Foam Polyethylene or FPE. The density of the air injected into the dielectric plays a key role in the quality and consistency of the dielectric. Sometimes dielectrics will be made via a process known as Nitrogen Gas Injection. This process uses very small, dense nitrogen bubble distribution which can help to improve the uniformity and insulation qualities of the dielectric. While providing a modest increase in performance, it is often used by manufacturers in the consumer market as a tool to justify extremely high costs.   

Shield(s): The shield does as the name implies; it shields the center conductor to prevent it from picking up any extraneous electromagnetic or radio frequency noise which could disturb the signal you are trying to send. The shield also acts as a ground in the construction of the circuit. A cable can be made up of several different types of shields and can also have an outer shield as well as individual shields on particular wires or conductors. The four primary types of shielding are braided, spiral, foil and twisted. Generally, the larger the percentage of coverage the greater the shield’s effectiveness and all four shields have different properties for protection of your signal. Shields are usually measured in “percentage of coverage”. The higher the percentage the better the coverage (i.e. 90% is better than 60%). The percentage of coverage is critical to its shielding capabilities. Let’s explore the most familiar types of shielding:

Braided Shield: A braided shield is a woven braid of either aluminum or preferably copper that is extremely conductive and provides the best shielding of all types. The angle of the braid can also add to the overall coverage. Braided shields can be used alone or in conjunction with other shielding methods such as foil shields (more on that below). Copper braided shielding is highly effective and the percentage can increase the overall performance and price of a cable significantly. Typically a very well shielded cable is 85% braid or more.

Spiral or “Serve” Shield: A spiral shield is made up of individual strands of copper wound around the conductor(s) of a cable in a single direction. Spiral shields have excellent flexibility and are used most often on audio cables such as microphone cables for instance. However when the shielding flexes to accommodate cable bending, it can create gaps in coverage which can allow interference an entry door. The spiral shielding itself has a higher transfer impedance than braided shields and therefore are not as effective.

Foil Shield: Foil shields are very common because they are made of inexpensive Mylar backed aluminum with a drain wire and they provide 100% coverage. While they provide good coverage, they are not very flexible or durable. Foil shields are commonly used as an additional shield in conjunction with other shielding method for its coverage properties and ability to compliment a braided shield which works well at lower frequencies while foil is better at the higher end of the spectrum.

Multiple Shielding: You will see a lot of claims such as “Triple Shielded” but what does that really mean? Although the inference is that it is better than single shielding (and many times it is), as discussed above, you have to also be concerned about the type and quality of the shields being used, not just the quantity. That said, multiple shielding can be much more effective than say a single foil outer shield.

Twisted Pair: Although not a type of shield itself, the twisting of wires in what as known as twisted pair cable, more commonly referred to as Cat5 Cable, Cat6 Cable and even now Cat7. The difference in the cable is limited to only one factor, twists per foot. The more twists per foot the greater the amount of shielding per cable. Any of the above mentioned cables starting with the Cat5 would allow you to run power in the same jacket as signal and still avoid bleed over. Some twisted pair cable also uses a foil, spiral or braided shield in addition to the shielding provided by the twisting.

Cable Jacket: The primary role of the cable jacket is to provide protection for the inner materials of the cable. There are several types of jacket material used in cable construction some of the most common ones are:

PVC (Polyvinylchloride) This is the most common material due to it’s low cost and is rated for use in temperature ranges of -20C (-4 deg. F) to 80 deg. C (176 deg. F). 

Teflon has good electrical insulating properties as well as resistance to chemical splash and high heat conditions. The downside is Teflon is an expensive material and raises manufacturing costs. Teflon is rated for temperature ranges of -70 deg. C (-94 deg. F) to 200 deg. C (392 deg. F). LSZH (Low Smoke Zero Halogen) is a thermoplastic compound that reduces the amount of toxic and corrosive gases emitted during combustion. This is a good choice for cables that will be run in poorly ventilated areas, low smoke zero halogen is becoming very popular with military contractors. Typically rated for temperature ranges of -20 deg. C (-4 deg. F) to 80 deg. C (176 deg. F).

A “Plenum” jacket consists of high flame resistance properties that does not emit a toxic smoke when ignited, making it safer for in wall or in ceiling use. Most institutions and government buildings require the use of only plenum cabling. Plenum can be made from several materials such as Teflon and specially treated PVC. (Plenum tends not to be as flexible as PVC). Since there are different material used in each plenum jacket the temperature ranges vary per construction. There are many additional cable jackets for more specific uses that we will not go into here. Keep in mind, the more flexible the cable is overall which is partially dictated by the jacket, the more resilient and durable the cable will be when bending around corners or put under duress.

Impedance Matching: Most traditional A/V cables send and receive 75 ohm signals. As any audio-visual professional will tell you, this is important because of the characteristics of the cable are not within a very tight tolerance of 75 ohms (usually +/- 3 ohms maximum), the cable can actually cause signal reflections which can result in the “ghosting” of an image. This is another area of cable manufacturing that is often compromised when using inferior materials and can be an unintended result of poorly made import cables.

Strain Relief:

The strain relief on a cable is designed to absorb the stress of bending and pulling so as to avoid cracking or breaking away from the connector itself and keeping the solder points intact. The strain relief is typically a “molded collar” at the point where the cabling meets the connector. Strain relief can be measured in the number of “bends” it can withstand. Inferior strain relief is common cause of cable failure among inexpensive cable brands. Ironically some of the fanciest and most expensive home theater cables all use assembled connectors which look great but do not have the strain relief of their molded cousins.

Connectors: More than 50% of all cable failures happen at the connector. Either from bent pins because users impatiently push the connector in without lining up the cable properly or the cable is poorly made which causes a soldered connection within the connector to come loose so connectors matter. Connectors can be made of many different materials which can have an impact on the performance and durability of the cable overall. For instance, nickel over brass is one of the preferred connector materials because of its transmission properties and durability but it costs more. Many internet importers substitute this with what are called “die cast” connectors. It takes a sharp eye to spot.
 

Testing & Quality Control:One aspect often overlooked in the discussion of cable construction and manufacturing is Testing and Quality control. Like any product, cables are subject to the same production issues as any product (car recalls anyone?). The effort a cable manufacturer puts into quality control and testing is critical for performance, reliability and most importantly, customer satisfaction. Pro A/V professionals understand this all too well. They are often installing hundreds of displays in public places at a time. Downtime for them is more than missing the afternoon game…it’s catastrophic and costly. If a cable is working well today that is great but what about down the road? What about under stress? What about repeatedly connecting and disconnecting? Even for home users, once the cable is run through the wall and sometimes even terminated to a wall plate, it can be a costly inconvenience to have to swap a cable out.

To ensure a cable is properly manufactured and will last, there are many tests that need to be done.

The first and most common test is the continuity test.. A continuity test confirms that the signal is travelling from one end of the cable to the other end without intermittent problems. The next type of test is an attenuation test used to verify the bandwidth of a cable. There is a capacitance test to insure how much of the signal is being absorbed by the jacket material. An impedance test is required to verify the impedance going in the cable matches what is coming out of it, to insure the cable meets design specifications. There are several other tests required for different types of cables such as time delay, skew, durability, solder joint strength, dielectric withstanding voltage test, and a shielding effectiveness test. A bend test is done to test the strength of the strain relief. The final test is a quality control test which includes a visual inspection of the cable and a final continuity test as well as    a video test to confirm cable meets design specifications. All of these tests are included in what is called a “parametric test procedure”.

Cable Buying Guide

Since 1974, Comprehensive products were used exclusively by professional systems integrators, installers, I.T. departments, broadcasters and pro users. These customers are after all, video, audio or computer professionals and are pretty well versed as to what is important and what is hype when it comes to connectivity products.

However, in recent years, word of Comprehensive’s legendary reliability and value has started to leak out to the general consumer so we have more and more regular folks coming to our website and purchasing our products. Of course, most people are not connectivity experts and don’t have the time or the inclination to become one so we thought it would be helpful to provide some basic buying tips to sort out the mis-information out there (and there is a lot of it) and help you to make an informed decision.    

What Matters?

Application: The first and arguably most important consideration is how the cable will be used. Your application plays a large role in choosing the right performance grade of computer, audio or video cable. Is it a short run or a long run? Will the cable be under any stress? Will the cable be disconnected and reconnected many times or will it just sit there for years? If the cable fails will it bring down a major system or just be a minor nuisance?

For example, if the cable is exposed and you are going short distances (3-6ft) in a living room where the cable will remain untouched, there is no need to waste your money buying expensive “top-of-the-line” cables in most cases. A general purpose cable from a reputable source will almost always do the trick (providing it is well made and well shielded).

However if you are (a) going longer distances, (b) the cable will be under stress, (c) repeatedly connected and disconnected or (d) the cables will be used as part of a total system installation, you should consider a professional grade cable. Professional grade cables will usually use a large center conductor, better conductive materials, thicker jacketing, and heavy duty connector molds with high bend rates to provide better signal transmission over longer runs and increased durability. This is especially important in permanent installations where cables are not easily accessible.

Gauge: The gauge of the center conductor is an important factor. The larger the gauge, the lower the resistance and the better conductivity the cable will have. A larger gauge is typically better than a smaller gauge though represented backwards numerically. (For example, a 20 gauge cable is bigger than a 24 gauge and so on. However size alone is not enough as center conductor materials will play an important role as well. See below.    

Center Conductor Material:  In addition to gauge, the material the center conductor is made out of is critical. Pure copper has excellent conductive properties and tinned copper, which is a process where the copper strands are covered with a thin layer of tin, is up to 10 times more durable and has even better conductive properties.(It also costs more.) These are the materials found on most Comprehensive cables.

Shielding type and %:  A high percentage braided shield (85% or above) is far superior in blocking interference than a spiral shield or just an overall foil wrap. The density of high percentage braided shielding keeps the coverage consistent even when the cable is bent during use.

Molded Connectors with High Bend Rates: Choose molded connectors with a high bend rate from a reputable source. Inexpensive connector molds look very similar to the eye but they cannot withstand the strain of a stretched or repeatedly bent cable. This is one of the primary causes of cable failure. Well made molded connectors are a better choice than assembled connectors for long term durability as well. 

Reliability and Total Cost: As professionals know all too well, a cable that fails is no bargain, especially if there will be system downtime and then expensive labor costs to replace it. As stated above, keep your application in mind when making your purchasing decision.

Service: If you are a professional on a jobsite with an immediate need or connectivity issue or its 5:00 pm Friday and you need something delivered Saturday morning for a performance, premium service and experience becomes important very quickly. Comprehensive has the experience and the technical know-how to ensure the show goes on every time. We are also equally happy to help the home user figure out what they need and how to use it. 

What Doesn’t

24k Gold Connectors: Unless you will be using in extreme conditions where oxidation is a concern, there is no discernable difference. In the professional market, no one uses gold plated connectors.

Braided Jackets: They sure look nice and it is usually argued they protect the jacket. However in reality they have no real tangible benefit beyond helping manufacturers charge you more money for a better looking cable.

Hi-End Assembly Connectors: Fancy assembled connectors like those on expensive retail brands look nice but it is the materials used the durability and bend radius of the connector mold, the strength of the pins and the reliability of the solder points that are truly important.

Retail Brand Names: If you like giving your money away, this is a great way to do it. There is simply no justification for the prices that some of these retail brands charge. That is why professionals by and large would not be caught dead using over-priced retail brands.

Fancy Blister Packaging: Fancy “aero-dynamic” packaging looks nice and some have made an art of it, but it’s expensive, it is not green by anyone’s standards and it’s a waste of money. Also on a practical note, have you ever tried to open those darn clamshell packages?

What to Watch Out For:

Jargon without the Back-up: “Triple Shielding” for example sounds very impressive but means nothing without knowing what type of shielding they are using, the materials used and where/how it is applied. These are common techniques employed by internet stores and China brands to give the impression their cheaply made cable are an equivalent to legitimate brands.

Lack of Specifications: Many cable manufacturers and internet stores, including some of the major retail brands, do not publish the construction specifications at all! In fact one brand we all know uses a meager and flimsy 30 gauge cable for their so-called Ultimate 3ft HDMI Cable that sells for $200.00! The pro’s would never fall for that and either should you. 

Copper Clad Steel: This is a cheap copper substitute with inferior electrical qualities used by some well known internet stores and the China factories they purchase from. Be sure to ask for specifications in writing of the cable you are considering.

Application/Performance Chart

While it would be easy to ramble on about pin-counts and other connector specifics, sometimes a picture is worth a thousand words and in the case of connections, perhaps two thousand!

Allow me to introduce you to some very cool tools that make the complex very simple. 

1. 
    1. The Comprehensive Cable Consultant Tool shows the back end of common AV and computer equipment. Simply click the connection you are trying to wire and you are instantly taken to the cables you need.

1. 
   2. The Connection Assistant as the name implies allows you to de-mystify some of the most popular connection types in a quick and concise manner, browse products and get on with the important things in your life. Simply select the category and use the images and descriptions to zero in on the cable type you need. Click through and you are taken right to the available cables. Quick. Easy. Done.

Of course if you have any questions or need any help, our team of professionals are here to assist you. Simply start up a chat with us, email us at sales@comprehensivecable.com or call us Toll Free at 800-526-0242.