Question about Cables-- sorry if this is the wrong thread!

martyj19

· #4 · Dec 20, 2005

Quote:

Originally Posted by Xayd
the difference is 120 dollars and 1 cent, that's it.

there's no difference in cables when you're talking about digital signals. the same 1s and 0s that get pushed out of point A end up as 1s and 0s in point B.

This is a little oversimplified. There is some good reading courtesy of Blue Jeans that may shed light. http://www.bluejeanscable.com/articles/

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tdavis21484

· #5 · Dec 20, 2005

Quote:

Originally Posted by Xayd
the difference is 120 dollars and 1 cent, that's it.

there's no difference in cables when you're talking about digital signals. the same 1s and 0s that get pushed out of point A end up as 1s and 0s in point B.

And a Corvette is exactly the same as a Geo Metro, you still wind up getting where you're going.

$130 is too high - well made cables can be found for less. A poorly constructed cable can cause signal dropouts and "sparklies" or missing pixels of information on the screen. Being that digital signals are so hardy anyway, it's not common, but it's worth putting the money into a well-shielded and well constructed cable. Just not necessarily a $130 one. Some people don't feel comfortable hooking up their $10,000 plasma with a $25 cable.

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Xayd

· #6 · Dec 20, 2005

Quote:

Originally Posted by martyj19
This is a little oversimplified. There is some good reading courtesy of Blue Jeans that may shed light. http://www.bluejeanscable.com/articles/

is it?

from their own section on digital cables...

Quote:

Second, a digital signal, because of the way its information is contained, can be quite robust. While the signal will always degrade to some degree in the cable, if the receiving circuit can actually reconstitute the original bitstream, reception of the signal will be, in the end analysis, perfect. No matter how much jitter, how much rounding of the shoulders of the square wave, or how much noise, if the bitstream is accurately reconstituted at the receiving end, the result is as though there'd been no degradation of signal at all.

which is of course true. digital is either "it works or it doesn't". there is no benefit from one cable to another, assuming both cables "work" to begin with.

unless someone wants to suggest that there is some grand conspiracy on the part of radio shack to sell 12 dollar HDMI cables that don't work, in order to promote the sale of more expensive HDMI cables, I think the results of two working cables will be pretty much identical, by my calculations

.

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business-spice

· #7 · Dec 20, 2005

With all the talk of cables I need someone to explain something to me, I just am not understanding the fact that your digital signal runs 50' lets say from your Direct TV dish on your roof down to your receiver using RG6 line and then you use a $130 HDMI cable to connect 4 feet of cable from your receiver to your plasma, I just don't follow that. Can someone explain why the 50' of RG6 doesn't matter but 4' of $120 HDMI does? Is it b/c it is after the receiver? Can you use anythign better than RG6 when running the cable from the dish to the receiver or would it really not make a difference ..... how much does a 75 foot HDMI cable cost?

(j/k)

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martyj19

· #8 · Dec 20, 2005

The result of two easy runs will be identical. Longer runs or presence of EMI with poor shielding may affect the signal. While you can have a stable one or zero in a latch or a memory cell, it is not the case on a cable that the bits you put in is necessarily what you recover. I fully agree with you that usually it doesn't matter.

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Xayd

· #9 · Dec 20, 2005

Quote:

Originally Posted by tdavis21484
And a Corvette is exactly the same as a Geo Metro, you still wind up getting where you're going.

...

Some people don't feel comfortable hooking up their $10,000 plasma with a $25 cable.

yes, you illustrate the point perfectly. the same person who is impressed by an expensive car, for instance, for no other reason than its price, looks to spend an outrageous amount of money on a 10 dollar cable to brag about how much he spent on his gear. and not only will he spend it, but he will defend spending it even with the fact that there is no difference in cable A and cable B slapping him in the face. when all else fails he'll demand to know how much everyone else spent on their audio/video gear, in a futile attempt to demonstrate that his is better and he can hear and see more than they can so they aren't worthy of judging him. there are a million such threads in the speaker and receiver forums, go look, they're great entertainment

.

unless you are running the cable an abnormally long distance, digital cables don't matter. if you get dropouts on a short-run connection then obviously, your cable falls under the "broken" category instead of the "not broken" category. return cable to radio shack, get another 10 dollar cable that's not broken, problem solved.

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K

kal275

Discussion Starter · #10 · Dec 21, 2005

Thanks for all your help.

We ended up returning the Monster cable (which I convinced my husband was a rip-off) and ordering from pacific cable, which has gotten good reviews elsewhere in the forums.

For other newsbies who have the same or similar question, there are a few good links about cables in the Plasma FAQ (which I should have looked at first!)

Thanks again!

-Kristen

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mmdieter

· #11 · Dec 21, 2005

I would like to know if there is any reason i shouldn't use my monster cables that are 1 video (yellow) and 2 audio, as my component video. It seems like cables are cables, so there would be no reason I couldn't just use the cables i have intead of buying new component cables.

thanks

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mfan

· #12 · Dec 21, 2005

Quote:

Originally Posted by business-spice
With all the talk of cables I need someone to explain something to me, I just am not understanding the fact that your digital signal runs 50' lets say from your Direct TV dish on your roof down to your receiver using RG6 line and then you use a $130 HDMI cable to connect 4 feet of cable from your receiver to your plasma, I just don't follow that. Can someone explain why the 50' of RG6 doesn't matter but 4' of $120 HDMI does? Is it b/c it is after the receiver? Can you use anythign better than RG6 when running the cable from the dish to the receiver or would it really not make a difference ..... how much does a 75 foot HDMI cable cost?

(j/k)

Check out this article... http://www.bluejeanscable.com/articles/rg6.htm

Quote:

Originally Posted by mmdieter
I would like to know if there is any reason i shouldn't use my monster cables that are 1 video (yellow) and 2 audio, as my component video. It seems like cables are cables, so there would be no reason I couldn't just use the cables i have intead of buying new component cables.

thanks

Here's one on component... http://www.bluejeanscable.com/articl...videocable.htm

Courtesy of martyj19...

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BillyMc

· #13 · Dec 21, 2005

This thread seems as appropriate as any to pose this question:

Previously, I was running component cables from my STB (SA 8300) to my plasma and the picture quality with both HD/digital channels and SD/analog channels were great. I recently picked up an HDMI cable and while the picture and sound on HD/digital channels seems to be a little better, the SD/analog channels are barely watchable. Is this normal?

To me, it would make sense that running an analog signal thru a digital cable may result in decreased PQ.

If true, does anyone know if one can hook up the SA8300 to the TV thru multiple inputs concurrently (i.e., run both HDMI and component and switch to the HDMI input when watching HD/digital, then switch to the component input when watching SD.)???

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Elantec

· #14 · Dec 22, 2005

Quote:

To me, it would make sense that running an analog signal thru a digital cable may result in decreased PQ.

You're not running an analog signal through a 'digital' cable. It is a digital signal, representing an analog signal. There is no such thing as a digital cable.

Digital signals 'represent' analog information. A digital signal on a cable is a cintinuously varying voltage, which is, by definition, analog.

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BillyMc

· #15 · Dec 22, 2005

Thank you for that lesson on semantics and cluing me in on the correct argot of cable technology, however, that reply did very little to answer my question.

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Elantec

· #16 · Dec 22, 2005

What was your question?

Why such a bad attitude?

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martyj19

· #17 · Dec 22, 2005

The only thing special about a "digital" signal is that we arbitrarily define certain voltage levels to mean 1 and certain voltage levels to mean 0. We sample these levels in synchrony with a clock to derive the successive bits of the signal being transmitted. An example of a workable system would be (and I am dating myself somewhat here)

1 is any voltage between 2.0 and 5

0 is any voltage between 0 and 0.8

So there is a considerable latitude for error in the signal, because as long as the voltages are somewhere in the desired range, we can exactly recover the 1's and 0's. Contrast this with an analog signal, where the voltage level *is* the value, and nearby electrical interference, or whatever, changes the value that is recovered.

The problem in a digital signal comes when the signal is stretched by the inductance and capacitance of a cable so that it gets out of phase with the clock ("jitter"), or is smacked by a burst of electrical interference, or is interfered with by reflections, or whatever. In this case we may have a voltage that is between 0.8 and 2.0, so is not either 1 or 0, or is valid but comes at the wrong time. This is how you can have a bit error and why analog signal distortion can't be totally ignored in the digital world.

----

As to why your SD looks worse over HDMI, double check your cable box setup and if it is correct, I guess you can blame it on the analog to digital conversion in the SA8300. Maybe someone who has an SA8300 will comment. You should be able to hook up all the outputs you want between the cable box and TV and switch inputs to select them.

As to whether you can use a yellow-red-white in place of a red-green-blue, yes. I do vaguely remember that the red-white are supposed to be 50 ohm and the yellow is 75, but even if that's true, which I am not sure of, my guess is that consumer grade cables are identical except for the color of the plastic.

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BillyMc

· #18 · Dec 22, 2005

No bad attitude here.

To me, it seemed that you completely disregarded the whole point of my post to focus on one rather irrelevant sentence in which I used some incorrect terms in order either to prove your knowledge on the subject or completely belittle my lack of. Perhaps you were trying to answer and I just didnt understand.

If you re-read my post, the questions are pretty apparent--look for the ????

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boyce89976

· #19 · Dec 22, 2005

Quote:

Originally Posted by Xayd
is it?

from their own section on digital cables...

Quote:

Second, a digital signal, because of the way its information is contained, can be quite robust. While the signal will always degrade to some degree in the cable, if the receiving circuit can actually reconstitute the original bitstream, reception of the signal will be, in the end analysis, perfect. No matter how much jitter, how much rounding of the shoulders of the square wave, or how much noise, if the bitstream is accurately reconstituted at the receiving end, the result is as though there'd been no degradation of signal at all.

which is of course true. digital is either "it works or it doesn't". there is no benefit from one cable to another, assuming both cables "work" to begin with.

I think you took that out of context. Here's the paragraph immediately preceding the one you posted...

Quote:

First, a digital signal, because of its sharp transitions, is highly subject to degradation in its waveform; those sharp transitions are equivalent to a long--indeed, an infinite--series of harmonics of the base frequency, and the higher the frequency of the signal, the more transmission line effects, such as the characteristic impedance of the cable, and resulting signal reflections ("return loss") come into play. This means that while the signal may originate as a square wave, it never quite arrives as one. Depending on the characteristic impedance of the cable, the capacitance of the cable, and the impedance match between the source and load devices, the corners of the square wave will round off to a greater or lesser degree, and the "flat" portions of the wave will become uneven as well. This makes it harder for the receiving circuit to accurately identify the transitions and thereby clock the incoming signal (causing the phenomenon known as "jitter"). The more degradation in the signal, the harder it is for the receiving device to accurately measure the content of the bitstream.

When you put the two together, a cheap cable may in fact make it more difficult for the receiving device to accurately reconstitute the signal.

Both analog and digital signals are electric waves (sine and square) and are subject to degradation due to the influences of the cable, or from outside sources. Both represent degradation in different ways, and the most common for digital is complete loss of signal. So, to the extent a $130 cable has better shielding, consistent impedence, and so on, the more accurate the reproduction of the signal on the receiving end... analog OR digital.

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