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New member Username: FletcherdunnPost Number: 2 Registered: Oct-04 | This is actually a cable question, but I haven't gotten an answer on the cable forum, so I'll ask it here. My question is specifically about DVI cables, but I suppose it could also apply to digital audio cables. Let's say I get a relatively cheap DVI cable ($40), and I hook it from my HD cable box to my TV. Assume that I don't see any glaring problems in the signal. So I assume that since there aren't any glaring problems, then the cable must be transmitting the signal from point A to point B 100% properly, correct? So the question then becomes - what additional benefit could I possibly get from a more expensive cable? (Example - the monster version costs $100 retail, although I've seen it cheaper online.) And ignore the emotional benefit of "Ohh - look at the shiny cable". I'm talking abotu improvement in signal quality. It's a digital signal. Either it gets from point A to point B properly ot ir doesn't. If a portion of the signal doesn't arrive properly - then you have *major* glitches in your picture. I see this occasionally when the digital signal from my cable company to my HD box screws up - there are noticable "crud" int he picture - you don't have to be a purist to notice it. That's the whole point of doing things digitally in the first palce, right? If you receive a copy at all, then you know that you copy is PERFECT and there is no generation loss. Two comparisons of other digital transmissions: Ethernet networking cable. If you have a bad physical connection, sometimes packets are not carried correctly. But you don't get a corrupted file - the network detects this and resends the packet. Thus *speed* may suffer but *quality* does not. You still get a perfect copy, if you manage to get anything at all. A better analogy might be a digital cell phone conversation. If the physical connection is bad, packets are dropped. This results in gaps or stuttering in the conversation. This could be considered a "loss in quality" but actually it's just a total loss of signal - just a very small portion of the signal. This is analagous to the "crud" that I see every now and then on my TV. For the purposes of my question, let's assume that there are no obvious efects in my picture, and so no "packets" are being dropped. My assumption is that if there are no obvious defects, then I'm getting a 100% perfect transmission on the cable. Is this assumption correct? I can understand in some situations (for example, a long cable), using a poor cable could degrade the quality of the physical connection enough to cause packets to drop. So in this case, cable quality is important. So cable quality might matter for speaker cables or for a front projector, where the cables are usually longer. So - for digital cables - if there are no glaring problems, then you couldn't possibly get any benefit from a "higher quality" cable. Right? Can anybody justify spending $100 for the 6' monster cable??? There's got to be something I'm missing here, or else people buying these cables don't understand what digital is all about! |
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Anonymous | my 2 cents on cables. physical stores hike the prices since they know many people don't go online to buy where comparable products are less than half the price. now, all else being equal, the more expensive the cable the better. reasons include better shielding, allows more bits per second, and better end connections. electro magnetic waves wreak havoc on poorly insulated cables. some don't allow the full mega bits per second for hi def. and cheaper cables have hex crimp connections that corrupt the signal. if you have no glaring problems you can always benefit from a higher quality cable- but the value of diminishing returns becomes so small that the extra money spent is not worth the small increase in quality (that many people cannot even see anyway). it is impossible for any data to be sent 100% properly (one reason, all electrical current has resistance that is turned into heat resulting in a loss of efficiency)but a quality cable's job is to be efficient enough so that we cannot detect a loss of data. |
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New member Username: FletcherdunnPost Number: 3 Registered: Oct-04 | >it is impossible for any data to be sent >100% properly (one reason, all >electrical current has resistance >that is turned into heat resulting in >a loss of efficiency)but a quality >cable's job is to be efficient enough >so that we cannot detect a loss of data But if it's "impossible for any data to be sent 100% properly" then how come I can send a file over a network and get an *exact* copy at the destination? With digital, it IS possible to get an *exact* transmission, with no generation loss - that's the whole point of doing things digitally. I can send that same file over a network 200 times and I will still have a *perfect* copy. No matter how crappy the cables are. >if you have no glaring problems you can >always benefit from a higher quality cable- My questions is - what exactly is the benefit of a higher quality cable? If there are no glaring problems with my cable, then I must have received a perfect copy, right? So what could possibly be better than perfect? |
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Anonymous | we are not talking of a static bit file such as a digital photo at exactly 1.2 mb but of variable bit rates. say your dvd has mpeg-2 that compresses the data to 3.5mbs. you are seeing a picture with much of the data left out but your eyes cannot detect this. a cheaper cable passes even less but there will not be video "crud" and only video philes can tell the difference. now up the bit rate to hi def about 19mbs. many cables cannot pass this fully but you will still see a great picture without glitches. the higher quality the cable the more bits per second resulting in better video quality. you will always benefit from a higher quality cable but there comes a point that the increased quality is small compared to the large increase in price. the point myself and others are trying to make is don't spend a fortune on cables if your eyes cannot see the difference. if your $40 dvi cable looks the same as $150 cable then stick with the less expensive one. same for audio. buy a cable that can pass 448kbs if using dolby dig. and stop at the point where your ear cannot detect better quality. better cables have better shielding from electromagnetic interference that can become a problem from all the cables from one's home theater gear. take a digital meter and you can read inductance coming through any cable (especially household wiring). digital transmission is unlike an analog wave form that degrades over distance but the reception of the bit stream is never perfect. missing bits are not the same as a degraded signal. the rest of the bits still hold exact values but much of the missing values a human eye and ear cannot detect anyways. that's why mp3 is a popular encoding format. it does not degrade the audio signal but removes bits whose information for the most part will not be detected by the human ear. |
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New member Username: FletcherdunnPost Number: 4 Registered: Oct-04 | I downloaded and read the DVI technical specification last night. Two things about how DVI works: * There is no error detection or correction. * The signal carries a flat uncompressed digital image. (So the comments regarding variable bit rate, cheaper cables passing "less", etc are not accurate.) Because there is no error detection, a bogus bit can go through undetected. Comparisons with ethernet are not really appropriate - there are no "dropped packets" in DVI. Since the image is uncompressed, a bogus bit would result in a slight degredation in quality on that one pixel lasting only one frame - not like if there was a bogus bit in an MPEG stream. Thus in theory a faulty cable could generate a degredation in picture quality without creating any glaring error on the screen. However - I think that this is unlikely in practice for two reasons: 1.) Unlike an analog signal, a slight degredation in physical signal quality doesn't cause an error. The signal on the wire would have to be misread *completely* in order to generate an error - in other words, because the receiver only has to decide if the signal is low or high (0 or 1) then there is a relatively large margin of error on each wire. With analog (for example - component input), a slight fluctuation actually causes a change in the effective "value" of the signal, but with digital, a slight fluctuation is effectively ignored. 2.) Since DVI was designed primarily for computer displays with very high resolution, HDTV is a relatively low bandwidth load compared to what even a single-link DVI system was designed to handle. So - I think a cheap HDTV DVI cable is perfectly fine for almost everybody. Basically what My Anonymous has been saying - although I wasn't satisfiued with that explanation. Of course, I may get my cable in the mail and hook it up and find that I'm totally wrong! But I want to understand the theory, not just say "better cables mean better picture." |
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Anonymous | i'll make one last attemp to explain the theory using a different analogy. think of your dvi cable as a water hose. now increase the pressure in your hose. a cheap garden hose will leak at every connection. the better the hose the tighter the seal. cables are the same way except you cannot completely seal the connections. pulling one amp of current means 6.25x10to the 18th power of electrons pass a given point every second. every connection has electrons escaping. the cheaper the cable the more are lost. also, the insulation surrounding the conducter lets electricity escape as well. the cheaper the insulation the more escapes. use a basic digital volt meter and ground one end and touch the insulation (not the conducter) and you will see what i mean. now lets move to another item in your home theater gear to observe more loss. the splitter. the numbers on the splitter are important to separate the cheap from the good. you'll see the frequency range and insertion loss. you have hi def so yours operates above 900mhz (say you have up to 2 ghz for the widest bandwith giving the best picture). but, you notice the other number, say 4.0dB. this insertion loss is incurred when a signal passes from the input to any of the outputs. you lose 4.0 dB (on a good splitter) on every output and nothing can prevent this! say you have your cable to a set top box and it outputs dvi to your tv. insertion loss! cannot be prevented. the new cablecard tv's have even lower insertion loss because the cable goes directly to the tv resulting in a slightly better picture. but loss nonetheless. a cheap quality dvi creates more loss and the best quality the least loss. so a cheap quality dvi cable is not fine. there are several sites (bettercables.com, etc) that sell quality cables at a fair price. your tech specs are not on the cable but on the dvi standard. a huge difference. dvd is a standard but does not mean a $29 player will be just as good as a $1000 denon. my point is the theory states better quality cables give a better picture all else being equal but stop when your eye and ear cannot detect an improvement for the increased cost. if you wish more elaboration on the theory i will let these other fine ladies and gentlemen take over. but it sounds like you found a good cable online and you may be very happy with it |
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xvxvxvx Unregistered guest | "my point is the theory states better quality cables give a better picture all else being equal but stop when your eye and ear cannot detect an improvement for the increased cost. if you wish more elaboration on the theory i will let these other fine ladies and gentlemen take over. but it sounds like you found a good cable online and you may be very happy with it " This must be where I come in. Your theory is all wet. Any loss in a digital cable is impercitible because it does not exist. A digital one is still a digital one likewise is a digital zero. It is either on or off, the amplitude does not matter even a little bit. It is either there and you have a perfect picture or it is not and you have no picture, no in between, no snow, nada. xvxvxvx |
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Anonymous | hmmm. kids these days. "the amplitude does not matter even a little bit. It is either there and you have a perfect picture or it is not and you have no picture" with your permission i would like to post this for the wire gang at work. i'm not debating the virtues of a digital cable but this sense of "perfect" is quite hillarious especially the belief that bandwidth size does not matter. amplitude is not bandwidth. amplitude is the measure from the average to it's hi-low point while bandwith encompasses the range of frequencies. mr. xv, i suggest a basic course in electricity. then you may comprehend the effects of a digital audio or video signal passed through different conduits. loss exists in analog and digital. don't fret. one day you will understand |
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Ben Q Unregistered guest | Let me give my dealings with digital. Had a Samsung,used dvi, got cruddy black contrast levels I could not change.(Returned it for other reasons). Switched to component, got beautiful picture. There, debate is over. |
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xvxvxvx Unregistered guest | "mr. xv, i suggest a basic course in electricity. then you may comprehend the effects of a digital audio or video signal passed through different conduits. loss exists in analog and digital. don't fret. one day you will understand" You are an obtuse one aren't you? I have a MSEE so I understand bandwidth, amplitude, analog and digital. As I wrote earlier your initial post is pure bunk. Any and I repeat any DVI cable will suffice with no degradation of signal. Your wire gang has no clue if they agree with you. Digital is either there or it is not as seen on your TV screen. The perfect picture is in reference to an analog signal where you may see a partial or snowy picture. The digital pic will be a perfect representaion of what is being sent at the other end of the 6 foot cable. If you see pixelezation or other anomalies they are not caused by the cable but by the source. You know this very well or at least you should so quit being so obnoxious and admit you are full of it. xvxvxvx |
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Believer Unregistered guest | Hey xv: Don't get tweaked! I happen to believe both of you. You're absolutely correct in saying that if the 1's and 0's are present from A to B(no glaring problems) then the copy is perfect. So, if the cheaper cable can get it done then it's done. However, what's it made of? How is it put together? The quality in materials and workmanship do play a role, eventually. It's possible that a breakdown could occur, probably at the connectors, but maybe through induction. The cable could carry an unwanted current if the shielding is inferior. Here is a portion of my posting on another thread for your entertainment. "As for cables, well, everybody has their own story to tell. I've seen the Monster cut open. It's impressive! Unlike any gold and silver shielded cable I've ever seen. Let's face it...it's about moving electrons down a wire with low resistance and no other signals interfering with it. Gold and silver are best. Stranded conductor and double braided shielding is best. You get what you pay for. Name aside, just make sure your getting what you pay for. I've recently witnessed a lightning strike first hand. It blew the siding off the house and entered the attic, traveled the electrical and phone wiring throughout the house looking for ground. It blew out all phones, a Honeywell Central Air system, two treadmills, two computers, a server, a monitor, a printer, and a cable modem. However, the projection tv, all video and audio components, and the sat box were saved by an HTX2000 Monster Surge Protector and Monster cables. I'm not with Wendys, (Monster) , but I did stay at a Holiday in Express last night." |
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Bronze Member Username: VindslPost Number: 90 Registered: Jul-04 | LoL! If you want to get picky, I might mention that 'true digital' can only be transmitted via optical interconnects, e.g. fiber optics. The term 'digital' gets tossed around a lot these days; for instance, 'digital' watches. There isn't one damn thing that's 'digital' about them. Even analog watches have numbers on their face[s]. Hello?!?!?! Then there's 'digital' phones. You cannot transmit 'true digital' signals through the air. It has to ride on a radio carrier signal. So, you have digital to analog conversion and modulation/demodulation taking place of both ends of the connection. And, so it goes with TV sets, blah, blah, blah. This isn't rocket science. It's mostly marketing hype... Having said that, there is nothing wrong with Monster Cables. However, they are a high mark-up, high profit item for retailers. So, if you don't mind getting bent over the counter at the checkout stand, go for it. Or, you can get one here: http://www.walmart.com/catalog/product.gsp?product_id=2625067&cat=163399&type=19 &dept=3944&path=0%3A3944%3A3964%3A163399 If you wanna go the cheapskate route, go to Walmart. Gemini makes a nice DVI cable for Philips. The quality is okay, and the price is right. You can get it here: http://www.walmart.com/catalog/product.gsp?product_id=2625067&cat=163399&type=19 &dept=3944&path=0%3A3944%3A3964%3A163399 Take your choice! I sincerely doubt you will detect a difference in PQ... |
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Believer Unregistered guest | I agree with VinDSL. Don't buy a Monster cable for a monster price. Buy a quality cable for a discount price online. He's right, you really won't see a difference in a digital picture. What about the picture. What channel will you be watching when you do a comparison. What is the quality of the camera that is capturing the image or their cables or their processing equipment. Garbage in...garbage out, be it digital or analog. |
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xvxvxvx Unregistered guest | "LoL! If you want to get picky, I might mention that 'true digital' can only be transmitted via optical interconnects, e.g. fiber optics. " So you are telling me you are using an analog computer huh? No fibre optics in your PC is there? You are confused about digital signal transmission (including the digital watch and cellphone examples) although I did enjoy the rest of your entertaining post. xvxvxvx |
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Bronze Member Username: VindslPost Number: 92 Registered: Jul-04 | I am simply saying that there is confusion in the terminology. This web site is NOT unique in that respect. The term 'digital' is universally misapplied to the point of being almost useless. 'True' digital signal transmission involves using pulse code modulation, time division multiplexing, yada, yada, and yada. When ppl talk about 'digital' televisions, they actually are referring to 'digital' to analog conversion, and vice-versa. This, of course, has nothing to do with this topic, so let's not hijack the thread. This 'guy' wants to know if there is a difference in cables. |
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Anonymous | xv, you have an msee if it stands for 'making silly erroneous elenchus' it's refreshing to see believer and vindsl understand mr. dunn's question on cable differences rather than your misrepresentation of a digital signal. did you sleep through class on fiber optic transmission? on cable shielding relating to elec.mag. interference? your contribution to this thread lies not with useful constructive information but with guffaws at your postings on the coffee room bulletin board |
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xvxvxvx Unregistered guest | "xv, you have an msee if it stands for 'making silly erroneous elenchus' it's refreshing to see believer and vindsl understand mr. dunn's question on cable differences rather than your misrepresentation of a digital signal. did you sleep through class on fiber optic transmission? on cable shielding relating to elec.mag. interference? your contribution to this thread lies not with useful constructive information but with guffaws at your postings on the coffee room bulletin board" This from another idiot with no useful input. Please elaborate where I am incorrect. Oh, you can't? No surprise at all. xvxvxvx |