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Video Cable in place coaxial audio cable


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7 replies to this topic

#1 of 8 OFFLINE   Peter-Ts

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Posted January 27 2003 - 05:50 PM

Is it possible for me to use a high quality video cable to replace my ordinary coaxial audio cable (connecting my DVD to my receiver)? It seem to work and i can't really notice any difference in loss of audio.

Is there any negative effects on doing so? What's the main difference between the two cables anyway?

#2 of 8 OFFLINE   Allan Jayne

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Posted January 28 2003 - 12:54 AM

The video cable is overkill for audio and the only negative effect is the cost.

Video cables need a much greater frequency response (sometimes expressed as bandwidth), upwards of 30 megahertz for HDTV. Video cables also must have what is referred to as 75 ohm impedance, which can be proven only with laboratory equipment.

Generally you can't tell the difference just by looking and comparing. The primary intrinsic difference is the kind of plastic lining between the center conductor and surrounding coaxial braid or shield.

Video hints:
http://members.aol.c...ynejr/video.htm
.

#3 of 8 OFFLINE   Eric Samonte

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Posted January 28 2003 - 12:58 AM

Any cable should work fine actually. I remember back in 1998, someone here even used hanger wire.....

#4 of 8 OFFLINE   Bob McElfresh

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Posted January 28 2003 - 02:37 AM

Quote:
..my ordinary coaxial audio cable

I think he is talking about the Coaxial-Digital cable: One cable that carries all the audio from your DVD player to your receiver?

If so, then YES. A video cable is exactly what the designers had in mind for this connection. Some cable companies took their ordinary $15 video cable, put the word "Digital" on the package and started charging $50+ to the unsuspecting public.

Here are the rules:

- Video cables MUST be made with something called "75 ohm coax".

- Audio cables can be made with any of the popular types: 50/75/110/300 ohms.

- The coaxial-digital cable must be a ... (say it all with me) "75 ohm coaxial cable".

Some people have used an audio cable and claim it works. They got lucky because their spair cable happened to be made with 75 ohm coax.

Others have used an AUDIO cable by mistake and it appears to work. But then they noticed sound drop-outs every few minutes. (It varies from every minute on one system to once every 15 minutes on another).

Hope this helps.

#5 of 8 OFFLINE   Iver

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Posted January 28 2003 - 06:58 AM

It's a digital connection, meaning what's passed down the cable is two voltages (two voltage levels, that is), one representing zero and the other representing the numeral one.

That would probably explain why a regular audio cable works. The cable is just passing the two voltages, not really a job that requires a high-performance piece of wire.

#6 of 8 OFFLINE   JeremyFr

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Posted January 28 2003 - 10:27 AM

I at one point used 12 foot RCA-RCA speaker cable that worked fine when I had my computer hooked up coax digital out to my reciever at the time. have used many different cables in the past and never had problems, but nowadays I've got everything connected via optical.
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#7 of 8 OFFLINE   Bob McElfresh

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Posted January 28 2003 - 02:38 PM

Quote:
That would probably explain why a regular audio cable works. The cable is just passing the two voltages, not really a job that requires a high-performance piece of wire.

The signal gets there fine even with the wrong impedence cable.

The problem is reflections.

Imagine you are at the street in front of your house and you need to walk to the front porch. The cable is the sidewalk between the two.

If the sidewalk exactly matches the height of the street->porch, you dont stumble. If the sidewalk is higher/lower than your porch, it's more likely you/or someone else/ will stub their toe or stumble on the un-even surface.

With the wrong impedence cable, some of the sharp zero-one transitions will 'stumble'. That is they will reflect back into the cable, bounce back, then back again.

If this was an analog video feed, you would see a 'ghost' outline caused by the reflected signal. With a digital signal, the data gets messed up.

The current generation of Dolby will catch the messed up data and go silent until it gets some data it does recognize.

#8 of 8 OFFLINE   Zbigniew

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Posted January 28 2003 - 03:51 PM

To answer original question:

Yes, you can.

For longer runs between rooms/floors, use decent RG-6 cable.. from Home Despot, or if you do not feel like doing it yourself, give Brad from BetterCables a call.

Now I must admit - I forgot to run coax down to my office in the basement. Instead, I am using a nice long run of Cat5 :-).

My M-audio card has no troubles with locking on signal; Denon 3300 worked as well. Only Sony 595 was sometimes dropping signal...

Good luck,

_zjt





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