An XLR Cable is Just a Cable, Right? The discovery of electricity has dramatically changed our lives, with the wonders of modern science surrounding us everywhere—the light bulb, the electric motor, radio waves. Who would want to be without them? Audio engineers, for one, because all of the above are potential sources of audio pollution that can affect our pristine signal, as it travels between source and destination. Refrigerator motors, light dimmers, radio transmitters, Wi- Fi, etc., can all cause unwanted noise in audio. Of course, the proposition is absurd, since without electricity there wouldn’t be audio engineers and cables, to begin with. However, the point is that what benefits us one way can easily be detrimental in another situation. There are multiple points at which a signal can degrade in an audio system, but often the first culprit is a microphone cable. Why the microphone cable? Attach a microphone to one end and plug the other end into a preamp and you have sound, right? Yes, except that the cheap cable you just bought at the discount store is providing your vocal with an accompaniment featuring a local taxi dispatcher’s instructions, along with some nice 6. Might be what you want if you’re into avant- garde recording, but otherwise those are some serious problems. You run out to the local music store and buy a really expensive cable and suddenly all of those issues are gone—or perhaps not. So, did you spend your money wisely? Despite cables being ubiquitous, information that helps the typical purchaser make competent decisions about a cable’s performance is hard to come by. Mostly, manufacturers tend to rely on marketing rather than hard facts to promote their cables. Cat 6 Ethernet Cables Monoprice, Inc. MonoPrice.com) specializes in the wholesale distribution of world class cable assemblies for home theater, PC. ZEROboot Series Cat6 24AWG UTP Ethernet Network Patch Cable. Cat6/5e network or ethernet cable quality is a little understood but big problem. We dive into why 80% of cables fail to meet spec and what you can do you ensure you are buying good network cable. Home Resources Buying Guides MiscellaneousAudio Cable Buying Guide. Audio Cable Buying Guide. DIY Shielded RCA Interconnect Cables. This project is a guide to build your own simple high quality RCA interconnect cables for your Hi-Fi audio system. Good quality indoor 23awg cat6 utp cable with high speed,US $ 10 - 98 / Roll, Guangdong, China (Mainland), OEM/BLG, UTP CAT6.Source from Shenzhen BLG Digital Network Co., Ltd. Low noise, oxygen- free copper, and gold- plated contacts are all notable features, but they don’t really tell you why a given feature will work, or in what scenario. And sometimes, unfortunately, the manufacturer misstates facts that only confuse. This article aims to dispel the hype, while examining what constitutes a good, balanced microphone cable. A balanced microphone cable consists of three main components—the conductors (internal wires, or cores), which carry the signal; the shielding, which helps protect the integrity of the information passing through the conductors; and in the case of a microphone cable, three- pronged connectors (XLR) that allow connection of the cable at either end. All three need to work together to ensure proper functioning of the cable, especially with increased lengths, as distance provides additional opportunity to increase electromagnetic and other noise interference. So, what is it in particular that makes a microphone cable susceptible to noise interference? Microphones generally operate at very low voltages, with the output requiring a relatively hefty amount of amplification applied to it before the signal can successfully travel on its way through an audio system, at line level. When the signal arrives at the preamp, any noise that has infiltrated the cable becomes greatly amplified along with the original signal. Using a good, balanced cable helps to eliminate the problem. The solution starts with the signal generated by the microphone capsule being sent over two wires, with one side inverted by 1. A differential input amplifier at the receiving end re- inverts and then combines the two signals. Since any interference entering the cable during transmission will appear equally in both conductors, the induced noise is now inverted and therefore cancelled (phased) out, leaving the original signal intact. Additionally, the original signal is slightly strengthened by the recombination of the two sides, thus helping to compensate for any reduction in signal strength that occurs on a long cable run. However, it should be noted that any noise inherent in the signal, from say, a noisy microphone, will not benefit from this process. Having defined the basic operation of a balanced cable, let’s look in detail at each component. Although it is not customary to give away the plot, let me state that the shield is the most important factor in a cable. But it makes sense to start the discussion from inside out, so let’s begin with the conductor, the part that carries the audio signal. Copper has been the material of choice for conductors for well over a century, because it has the greatest electrical conductivity of all non- precious metals. Normally, the stronger a metal is, the less pliable. Copper is unique in that it combines strength with high pliability. It is resistant to the effects of corrosion, which normally weaken other metals and impair their conductivity, and copper is easy to solder, allowing for durable connections. Generic Balanced Cable. The use of oxygen- free copper in cables is contentious. There are “levels” of oxygen- free copper, with 9. OFC (Oxygen Free Copper) being the purest form. Certain audiophiles insist their cabling meets this highest standard of purity. However, in reality the difference between the grades is negligible for most audio applications. The purest copper is required only for extreme scientific situations such as the manufacture of semiconductors, or for use in particle accelerators, etc. Use of such copper in audio is expensive and unnecessary. For audio applications OF (Oxygen Free) and the most common ETP (Electrolytic- Tough- Pitch) copper will meet the needs of audio applications. Audio cables generally use a stranded conductor as opposed to a solid cable. While the latter is cheaper to produce, a solid conductor is more rigid and prone to breaking when flexed. Obviously, microphone cables need flexibility, and a stranded conductor provides that. And if damage to a strand does occur, the whole conductor does not cease functioning. Also, in certain circumstances the stranded conductor can include a higher “volume” of copper than a solid one, aiding in the transmission of the signal. The downside is that termination of the stranded conductor is slightly more finicky, and if the strands aren’t wound tightly enough, the conductor will have a higher resistance, which in turn will require greater electrical energy to maintain the same flow. As noted, a balanced cable needs at least two conductors (cores), with the majority of cables belonging to this category. Generally, the cores vary in thickness between 2. AWG (American Wire Gauge), with the smaller number being thicker in diameter. Here, the compromise is between a manageable overall thickness of the cable, as applied to its flexibility and level of conductivity. Some cables feature four cores (two pairs) and are often referred to as quad cables. Four- core cables are more expensive, but in extremely “noisy” environments or where cables run unavoidably parallel to power cables, they can provide at least 2. B or more of common- mode noise reduction when compared to two- core cables. However, care should be exercised as not all these cables are constructed equally, with some cheaper varieties simply having four parallel cores wrapped in the cable jacket, which can introduce more problems than they solve. To be effective, the four cores need to be wound tightly around each other to achieve the additional noise cancellation that such a configuration provides. Four Core Cable. Now let’s look at cable shielding. This is where a cable will stand up or fall down. You can have all the OF copper you want, with millions of strands, but if the signal traveling down the cable is compromised with noise, then it is next to useless. To this end, there are multiple layers of protection that address the basic forms of electrical interference, and we will discuss those as we travel through the various layers of a complete cable. It should be noted that not all cables have the same kinds and levels of protection, and most of that comes down to price. The first order of things is to isolate the two (or four) cores from each other, and not just for the obvious reason that wires that touch will short each other out. Any current travelling down a wire will generate a magnetic field, and the resulting EMI (Electromagnetic Interference) introduces noise in an adjacent conductor. In this case a layer of insulation is applied over each core to contain the magnetic field. These days, polyethylene (PE) is used, since it provides better insulation over the PVC found in earlier cables. Although not a 1. Some cables then add a layer of conductive (modified) PVC on top to do the opposite, that is drain off any EMI that might be trying to enter the conductors from outside. The other form of protection that is common to all cables is a metal- based shield, usually copper but sometimes TAC (Tin Plated Copper), and in the case of foil, an aluminum laminate. This is the third leg of a balanced cable, and is connected to ground via the third pin of the XLR connector. A foil shield provides excellent coverage and is very effective when radio frequency (RF) interference is present. It is also lighter and cheaper to produce, but the down side is that it is far easier to damage when flexed, is more difficult to terminate, and should only be used in fixed installations, or as an absolute last resort. The other type of shield is a braid, an interwoven mesh of bare or tinned copper wires, which is much easier to terminate. TAC braiding is more expensive than regular copper, but the tin coating aids in preventing oxidation of the copper and improves wear. The type of braiding also comes into play. Because copper possesses higher conductivity than aluminum and the braid has a larger mass, it is more effective as a shield. It doesn’t provide absolute coverage due to the unavoidable presence of small gaps in the braid, but given that for stationary cable 7. However, it will add bulk and cost to a cable. Copper Spiral Braid. A spiral shield utilizes helical, wrapped strands for up to 9. Some manufacturers implement dual- spiral shielding where each core gets its own shield.
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October 2016
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