Multimedia myths exposed.

[Malpine Walis]

What follows here is a repost of my sticky over on OCF but lightly edited to bring it up to date. I hope that it will save people some cash that can be used to spend on better hardware.


OK, this is going to be a round-up of some of the common (or even less common) myths that are out there so that people can learn what to avoid. Let's face it, home theater can be a very expensive hobby for some of us and it would be best if we could avoid some of the common traps that are out there.

Don't get me wrong, if you want a thousand dollar TV or in this case a monitor as the tuner will be a separate component, feel free to go out and buy one. Just remember that the ones that they do not sell at that price today will be selling for $289.95 in three or four years simply because they do not want to pay someone to haul them off to a landfill.

So with that in mind, let's start this list. Post away and see if we can work together to save some money.

You do not need monster brand cables.


As a working musician, I swear by monster products. The “no questions asked” replacement thing has saved my bacon a few times. However, home theater systems are not in the same category. They get plugged in once and sit behind your gear, never to be touched again until you change your gear around.


Monster cable costs twice as much but performs exactly the same as cheap cables from an outfit like http://www.bluejeanscable.com/

No, you do not need gold plated connectors.

Sure, they look nice but you are going to plug them in where they will not be seen. Does anyone really think that the signal is somehow going to go through three feet of copper and then be magically up-converted at the cable end by a bit of gold foil that is just thick enough to notice?

Green magic marker does not make CDs sound better.

This one has been floating around since CDs first came out and you would think that after all this time, people would have learned but it still rears it's ugly head from time to time. It is really only a joke that some of the more experienced people foisted off on some anonymous noob twenty-five years ago but in reality, there is just no science behind the idea. It is bunk. However, it is bunk that somehow took hold and led a few manufacturers to label some green magic markers as being specially prepared for use on CDs and selling them to the unwary for $25.00 each. They are the exact same magic markers that you can buy for $4.00 a dozen at Staples or Office Max.

You cannot restore data to greater fidelity than the source file.

Any device the promises this amazing feat is a gimmick to sell hardware and does not really work as advertised. This is nowhere more true than with lossy compression formats such as MP3. When the data is gone it is gone. As well to try to restore the stereo channel data after a file has been converted to mono (not that many people do that but even so...). When the data is gone it is gone. Then too, even with formats such as FLAC the same would apply as you cannot just add data that is not to be found in the source.

While we are on this point, it also bears noting that “studio quality” is a mini myth in itself. Little enough music is recorded in a single take for that to even be possible. Most of what you see is recorded over time in a multi-session environment and layered by the recording engineers in post production. Thus you cannot make what does not really exist.

Oxygen free cable is about fake prestige. Not about superior performance.

While it is true that copper with quite a lot of oxygen would make for poor wiring (thus no company would ever intentionally produce “enhanced oxygen wire”), removing the little bit of oxygen that will occur in nature does not actually improve electrical conductivity. For brevity, I will skip the physics lesson but even if you did have high oxygen content, it would not affect the electrical properties of copper sufficiently to make a noticeable difference.


Perhaps it does bear mentioning what oxygen actually does to copper. It makes it not bend. Obviously, this would not be an optimal condition for your wires but the effect really does not show up until you get to a fairly high level of oxygen in your copper.

You do not need the latest and greatest of hardware.

One does not need to be a rocket scientist to know that the more capable hardware will do more stuff. However, if you are looking to save some money, you can get a perfectly acceptable build with less expensive components.

Alternatively, you can get a build from older components that you want to reuse to save even more money. Obviously, the lower your processor speed the more likely you are to find something that is just not up to what you wanted to do. However, it happens that there are some people who are using 500 MHz processors and getting decent if minimal results.

There is no such thing as digital wire/cable.

There is such a thing as wire/cable and manufacturers will, on request, provide a spec sheet for anything that they make. Such spec sheets will include data on known physical properties of the product such as wire gage, dielectric constant and isolation at different frequencies. However, digital readiness is not a property of wire/cable and no spec sheet will mention the matter.

One property that does bear consideration is the “bend radius” of different types of coax cable. Basically, that would be how tightly you can bend a loop of such cable without causing the shielding to “open up”. Exceeding this specification can cause spurious signals to get into your signal path. Apart from that, all products are basically similar.

Joint Stereo is neither good nor bad.

As always, the devil is in the details and there is no exception here. Joint stereo is one name for a few different coding schemes ands they all have their uses. They also have some poor implementations and some better implementations.

Intensity coding is a form of lossy compression that should be used when ripping to low bit rates and the consequently smaller file sizes that they generate. Matrix coding has much less loss of data but results in larger files so is better for intermediate bit rates. Two channel stereo is still probably better when ripping at the highest bit rates as that tends to preserve the original data on a CD.

Oddly enough, if you are recording from vinyl (which some audiophiles still insist it the best form of recording as it is the original analog stream), there is really nothing to be gained by the use of a full stereo rip as the stereo image is made with Matrix coding anyway. The Sum (mid) channel is recorded horizontally in the groove and the difference (side) channel is recorded vertically in the same groove.

[Neuromancer]

Nice write up Malp

Never saw this at OCF somehow

Question about the digital wire myth you discuss.

I was told that as long as it is 75 Ohm coax, it is fine for digital audio. IE, all those yellow RCA cables that we got with our ATI cards over the last 10 years .

I never tried running a regualr Red or white RCA cable to the Coax out on my board, is it true that the red/white is NOT 75 Ohm coax than?

[Archer]

The Monster cables in most cases may not be necessary but over extreme distances I have noticed that heavier wire seems to carry a signal a longer distance but there again this is extreme cases only. Just thought I would point that out.

[Malpine Walis]

Nice write up Malp

Never saw this at OCF somehow

Thanks dude. For reference, the original is in a subforum from display and sound.

Question about the digital wire myth you discuss.

I was told that as long as it is 75 Ohm coax, it is fine for digital audio. IE, all those yellow RCA cables that we got with our ATI cards over the last 10 years .

I never tried running a regualr Red or white RCA cable to the Coax out on my board, is it true that the red/white is NOT 75 Ohm coax than?

OK, I have not heard that one before. However, it has all the basic elements of myth to it.


Seriously, 75 ohms is just a quantity. About the same as 16 penguins is a quantity. However, if I told you that you needed to use 16 penguin cables for a specific application, would you want to know what I meant by penguins in relation to a chunk of cable?


Ohms refers to the tendency of a piece of wire to reduce the level of a signal over it's length. Specifically, what matters is the ohm-meters of the cable. Since the great quantity of such cables are sold in 1 meter length, it is somewhat understandable for manufacturers to shorten the term a bit.


On the other hand, if your specific setup required you to use a two meter cable it would likely have a total impedance (what ohms is actually measuring) of 150 ohms. Unless, of course, the manufacturer was nice enough to use 37.5 ohm-meter wire that is but I don't know of a company that does that. In any case, if the product exists, it is probably boutique cable for the people who don't mind paying silly prices for gear.


Honestly, 150 ohms is a trivially small number for fairly short cable runs. Where it will matter is when you get to the 10+meter runs for speaker wire. When you do that, you are going to get involved in other complications. However, for brevity, I will cover those issues in another post.

[Neuromancer]

Ah cool. Never knew what the Ohm referred to, despite having just built my 5th HD TV antenna and needing a Balun to convert from 300 Ohm twin lead to 75 Ohm coax.

I will just continue using the video cable wire though since thanks to ATI I have a lot more of them than I do audio RCA cables

Some day though I will try it out and see if it makes any difference.

[slugbug]

I laugh when salesmen at the local Electronics store try to push Monster cables by telling me they'll make my home theater sound 100% better

These are the same guys who tell you Bose make the best Home Theater gear No highs? No lows? it must be Bose

[Archer]

If you have super human hearing Bose can reproduce the sounds only dog's can hear. I buy all my cables at Big Lot's. $18 10' HDMI 1.2 cable is what I am talking about

[Neuromancer]

monoprice.com for cables is where I shop. I just find a decent gauge wire for my purpose and go from there

[Malpine Walis]

The Monster cables in most cases may not be necessary but over extreme distances I have noticed that heavier wire seems to carry a signal a longer distance but there again this is extreme cases only. Just thought I would point that out.

OK, I took a while to get back to this one. Even so, it is likely to be correct but the devil will be in the details. If a manufacturer wanted to sell cables for 5x as much, adding a thicker layer of rubber sheathing (cheap) would also make a heavy cable without providing the benefit of a well engineered cable. Such is the stuff that I would like to see people avoid.


As it happens, there are two ways to make a thick cable that could do well for a long run. Neither relates to thick the insulation is. So yah, it is really not a good idea to go with the idea that a thick cable tells any useful information.


The center conductor of a coax cable carries all of the signal and a thicker bit of wire will carry a signal a rather longer distance with less signal loss. I will skip the physics lesson here but I will note that the matter is not actually relevant for audio connections.


Seriously, your fast as “crap through a goose” cable internet connection goes through wire that is not really much thicker than the wire that carries my “good enough for youtube” DSL connection. So yah, while it plays a role here, the center conductor for your cable line ultimately goes all the way back to your ISP a dozen or so miles away from you with no real problem.


What really makes a long cable run work well is the shielding layers. Your signal does not “leak out of” the center conductor in any meaningful way. However, noise from the environment can “leak into” your cable and the shielding is what determines how that happens. Basically, shielding that is engineered for the specific situation is where you should put your money.


Since home audio cable is not usually marketed based on the engineering, you can usually ignore any claim to the contrary. Most HTPC users can ignore matters. For long runs of speaker cable, your best performance would not be buying cable because it is thick but rather because it has good engineering behind it.


If you are willing to go to the trouble to make your own cables, I would suggest that you ignore most claims on cable for runs under a few yards. For actual speaker runs, if you use RG58U cable, you can place your speakers a mile from the source with no noise getting into your signal.

As a musician, I do have to deal with such considerations. My Peavey Millennium 5 BXP bass guitar has great sound but it picks up noise from fluorescent lights. If I am playing in a place with that action, I have to play an instrument that is wired to avoid that issue.

Also, if you ever manage to chop a bit of monster cable, you will see that what is inside it is not really any better than what is in the cheap stuff. Really, matters like the brand or the thickness of a cable do not tell you anything worth paying attention to. Reading the manufacturing codes that are imprinted down the length of the cable will tell you how it will perform in a given situation. Good luck getting to that info on a cable that is packaged in so much plastic that you can't get it open without scissors.

[Archer]

Perhaps I was a little vague as I was speaking of output cable not signal cable. As to a digital signal, that is diffrent than what I was speaking of. I have given up on RCA and opt for 16 or 14GA wire for all runs over 50'. And soldering is better than any pop or screw in connector you can buy. Going with high quality connections in extreme conditions (outdoor) is a must if soldering is not an option.

[invalid_character]

Seriously, 75 ohms is just a quantity. About the same as 16 penguins is a quantity. However, if I told you that you needed to use 16 penguin cables for a specific application, would you want to know what I meant by penguins in relation to a chunk of cable?

Ohms refers to the tendency of a piece of wire to reduce the level of a signal over it's length. Specifically, what matters is the ohm-meters of the cable. Since the great quantity of such cables are sold in 1 meter length, it is somewhat understandable for manufacturers to shorten the term a bit.

On the other hand, if your specific setup required you to use a two meter cable it would likely have a total impedance (what ohms is actually measuring) of 150 ohms. Unless, of course, the manufacturer was nice enough to use 37.5 ohm-meter wire that is but I don't know of a company that does that. In any case, if the product exists, it is probably boutique cable for the people who don't mind paying silly prices for gear.

Honestly, 150 ohms is a trivially small number for fairly short cable runs. Where it will matter is when you get to the 10+meter runs for speaker wire. When you do that, you are going to get involved in other complications. However, for brevity, I will cover those issues in another post.

-----------------------------------

I just ran into this post and wanted to provide some clarification. Sources of info are listed at the end of the post.
I noted above the definition of 75 Ohm cable as the resistance/meter of cable, and that's not correct. As the detail below shows, that designation refers to the impedance due to to the insulation between the inner and outer conductors of a co-ax cable (regular cables with 2 conductors side-by-side like speaker wire have no such designation.) This number is important for impedance-matching purposes to minimize distortion (i.e. a pre-amp to an amp) and to form an electrically "transparent" link between a transmitter and its antenna.

Also as the post below shows, there is some validity to a cable being called "digital-ready" when speaking of a meeting a particular bandwidth for data (baseband) transmission, although as Malpine justly states, this has been a boon for marketeers and snake-oil salesmen. I would refer you to http://www.epanorama.net/links/wire_av.html as a good source for audio-video wiring information.

The requirements for audio are adequate shield (to fend off interference along the way) and proper cable to suit the termination (balanced, unbalanced, etc.). Because audio is sent by voltage, if you use cable with high capacitance over very long distance, the capacitance of the cable forms an R-C network with the output impedance of the source (also the input impedance of the destination has some effect on this, but typically very small). This results in allow-pass (high rolloff) "filter". The higher the equipment impedance and larger cable capacitance, more rolloff. High output impedance (typically up to several kilo-ohms) is feature in many consumer audio equipment, and this limits the distance you can carry the signal without noticeable high frequency attenuation. Consumer audio equipments with lower output impedance and professional audio equipment (always low impendance output, usually 50-600 ohms) will happily run 10-30 meters of cable without noticeable loss (professional devices with balances connections runs up to 100-300 meters are not uncommon). Audio lines are generally not impedance-matched. Practically speaking, electrical engineering transmission line theory does not apply to real world audio lines that carry analog audio signals. To carry audio signals without interference use something with proper shield, at least 85% coverage braided, but preferably 100% coverage foil shield with braid.
For balanced audio a proper shielded twisted pair cable (like "professional microphone cable") is best. Typical this type of microphone cable has around 70-150 ohm/km resistance on conductors, typically around 50-70 pF capacitance between the conductors and around 90-130 pF capacitance from conductor to shield.

As Malpine correctly states, most "special" audio wire is bunk, including oxy-free, micro-strand, etc. etc. basically because that the frequencies that audio falls into are low (compared with data and broadband signals in the kHz and mHz ranges) and so all the fancy-schmantzy stuff in this post about co-ax cable just does not come into play. Key to good wire is low overall resistance (<5% of speaker resistance) but this is easy to get by just using heavy-gauge wire. Nothing fancy or magic about that. Only if you have some really weird interference problems would you need to go to shielded wire. See http://www.roger-russell.com/wire/wire.htm for an excellent discussion of speaker wire and how to select/design it in.

Also, see http://www.rane.com/note110.html for an excellent discussion of ground loops and how they are often the most common and preventable cause of interference and hum in audio/video systems.

Introduction to coaxial cables

A coaxial cable is one that consists of two conductors that share a common axis. The inner conductor is typically a straight wire, either solid or stranded and the outer conductor is typically a shield that might be braided or a foil.
Coaxial cable is a cable type used to carry radio signals, video signals, measurement signals and data signals. Coaxial cables exists because we can't run open-wire line near metallic objects (such as ducting) or bury it. We trade signal loss for convenience and flexibility. Coaxial cable consists of an insulated center conductor which is covered with a shield. The signal is carried between the cable shield and the center conductor. This arrangement give quite good shielding against noise from outside cable, keeps the signal well inside the cable and keeps cable characteristics stable.
Coaxial cables and systems connected to them are not ideal. There is always some signal radiating from coaxial cable. Hence, the outer conductor also functions as a shield to reduce coupling of the signal into adjacent wiring. More shield coverage means less radiation of energy (but it does not necessarily mean less signal attenuation).
Coaxial cable are typically characterized with the impedance and cable loss. The length has nothing to do with a coaxial cable impedance. Characteristic impedance is determined by the size and spacing of the conductors and the type of dielectric used between them. For ordinary coaxial cable used at reasonable frequency, the characteristic impedance depends on the dimensions of the inner and outer conductors. The characteristic impedance of a cable (Zo) is determined by the formula 138 log b/a, where b represents the inside diameter of the outer conductor (read: shield or braid), and a represents the outside diameter of the inner conductor.

The dielectric of a coaxial cable serves but one purpose - to maintain physical support and a constant spacing between the inner conductor and the outer shield. In terms of efficiency, there is no better dielectric material than air. In most practical cables cable companies use a variety of hydrocarbon-based materials such as polystyrene, polypropylenes, polyolefins and other synthetics to maintain structural integrity.
Sometimes coaxial cables are used also for carrying low frequency signals, like audio signals or measurement device signals. In audio applications especially the coaxial cable impedance does not matter much (it is a high frequency property of cable). Generally coaxial has a certain amount of capacitance (50 pF/foot is typical) and a certain amount of inductance. But it has very little resistance.

A cable with a matched termination resistance at the other end appears in all respects resistive, no matter whether it is an inch long or a mile. The capacitance is not relevant except insofar as it affects the impedance, already accounted for. In fact, there is no electrical measurement you could make, at just the end of the cable, that could distinguish a 75 Ohm (ideal) cable with a 75 Ohm load on the far end from that same load without intervening cable. Given that the line is teminated with a proper 75 ohm load (and if it's not, it damn well should be!), the load is 75 ohms resistive, and the lumped capacitance of the cable is irrelevant. Same applies to other impedance cables also when terminated to their nominal impedance.

There exists an effect that the characteristic impedance of a cable changes with frequency. If this frequency-dependent change in impedance is large enough, the cable will be impedance-matched to the load and source at some frequencies, and mismatched at others. Characteristic impedance is not the only detail in cable. However there is another effect that can cause loss of detail -- fast-risetime signals. [This may impact the ability of a particular cable to handle digital signals above a certain frequency - My Edit] There is such a thing as frequency-dependent losses in the cable. There is also a property of controlled impedance cables known as dispersion, where different frequencies travel at slightly different velocities and with slightly different loss.

Most common coaxial cable impedances in use in various applications are 50 ohms and 75 ohms. 50 ohms cable is used in radio transmitter antenna connections, many measurement devices and in data communications (Ethernet). 75 ohms coaxial cable is used to carry video signals, TV antenna signals and digital audio signals. There are also other impedances in use in some special applications (for example 93 ohms). It is possible to build cables at other impedances, but those mentioned earlier are the standard ones that are easy to get. It is usually no point in trying to get something very little different for some marginal benefit, because standard cables are easy to get, cheap and generally very good. Different impedances have different characteristics. For maximum power handling, somewhere between 30 and 44 Ohms is the optimum. Impedance somewhere around 77 Ohms gives the lowest loss in a dielectric filled line. 93 Ohms cable gives low capacitance per foot. It is practically very hard to find any coaxial cables with impedance much higher than that.
Here is a quick overview of common coaxial cable impedances and their main uses:

• 50 ohms: 50 ohms coaxial cable is very widely used with radio transmitter applications. It is used here because it matches nicely to many common transmitter antenna types, can quite easily handle high transmitter power and is traditionally used in this type of applications (transmitters are generally matched to 50 ohms impedance). In addition to this 50 ohm coaxial cable can be found on coaxial Ethernet networks, electronics laboratory interconnection (foe example high frequency oscilloscope probe cables) and high frequency digital applications (for example ECL and PECL logic matches nicely to 50 ohms cable). Commonly used 50 Ohm constructions include RG-8 and RG-58.
• 60 Ohms: Europe chose 60 ohms for radio applications around 1950s. It was used in both transmitting applications and antenna networks. The use of this cable has been pretty much phased out, and nowadays RF system in Europe use either 50 ohms or 75 ohms cable depending on the application.
• 75 ohms: The characteristic impedance 75 ohms is an international standard, based on optimizing the design of long distance coaxial cables. 75 ohms video cable is the coaxial cable type widely used in video, audio and telecommunications applications. Generally all baseband video applications that use coaxial cable (both analogue and digital) are matched for 75 ohm impedance cable. Also RF video signal systems like antenna signal distribution networks in houses and cable TV systems are built from 75 ohms coaxial cable (those applications use very low loss cable types). In audio world digital audio (S/PDIF and coaxial AES/EBU) uses 75 ohms coaxial cable, as well as radio receiver connections at home and in car. In addition to this some telecom applications (for example some E1 links) use 75 ohms coaxial cable. 75 Ohms is the telecommunications standard, because in a dielectric filled line, somewhere around 77 Ohms gives the lowest loss. For 75 Ohm use common cables are RG-6, RG-11 and RG-59.
• 93 Ohms: This is not much used nowadays. 93 ohms was once used for short runs such as the connection between computers and their monitors because of low capacitance per foot which would reduce the loading on circuits and allow longer cable runs. In addition this was used in some digital communication systems (IBM 3270 terminal networks) and some early LAN systems.

Essential properties of coaxial cables are their characteristic impedance and its regularity, their attenuation as well as their behavior concerning the electrical separation of cable and environment, i.e. their screening efficiency. In applications where the cable is used to supply voltage for active components in the cabling system, the DC resistance has significance. Also the cable velocity information is needed on some applications. The coaxial cable velocity of propagation is defined by the velocity of the dielectric. It is expressed in percents of speed of light.

http://www.epanorama.net/documents/w...coaxcable.html

[spooony]

Getting a soundcard for gaming in windows 7 these days due to the reason you Receiver don't support features like Eax etc is also a myth. Ms abandoned the dx half finished.

[spooony]

If you have super human hearing Bose can reproduce the sounds only dog's can hear. I buy all my cables at Big Lot's. $18 10' HDMI 1.2 cable is what I am talking about

So you can hear caps whistle aswell?