use digital audio cable (coax) for subwoofer line-level cable? - AVS Forum
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post #1 of 11 Old 11-26-2009, 10:05 PM - Thread Starter
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Hey folks,

I'm switching around my home theatre setup, and have a few extra high-pass RCA cables which I was previously using for digital audio (i.e. coax). Is it OK to use these as regular audio line-level cables?? I have a new subwoofer (powered) which I'll need an RCA cable for, and these old digital coax are the right length.

thanks!
EH
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post #2 of 11 Old 11-26-2009, 10:19 PM
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Yes it is a perfectly suitable cable for a subwoofer.
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post #3 of 11 Old 11-26-2009, 10:19 PM
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Quote:
Originally Posted by ehansen42 View Post

Hey folks,

I'm switching around my home theatre setup, and have a few extra high-pass RCA cables which I was previously using for digital audio (i.e. coax). Is it OK to use these as regular audio line-level cables?? I have a new subwoofer (powered) which I'll need an RCA cable for, and these old digital coax are the right length.

thanks!
EH

perfectly fine

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post #4 of 11 Old 11-27-2009, 05:41 AM - Thread Starter
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Excellent. Thanks for the responses.

When I bought these digital coax cables, they actually sold me hi-pass video cables saying that they were just about the same rating/impedience/etc, since regular RCA/audio was not suitable for digital coax. But I wonder why it is that you can't use a regular RCA/audio cable for digital coax, but you *can* use the digital coax cable for regular RCA audio...?
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post #5 of 11 Old 11-27-2009, 05:55 AM
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Quote:
Originally Posted by ehansen42 View Post

But I wonder why it is that you can't use a regular RCA/audio cable for digital coax, but you *can* use the digital coax cable for regular RCA audio...?

Education in electromagnetic theory is needed for a full understanding, but to try to put it simply:

Audio frequencies are much lower than RF frequencies. The electromagnetic wavelengths of audio frequencies are much longer than the lengths of the wires involved. As a result, you can transport audio signals over two separate wires with undetectable distortion.

In contrast, RF wavelengths are short compared to the lengths of the wires involved. Their cables have to be specially designed in order to avoid distortion of the signals. They're called "transmission lines." The cables have a center conductor surrounded by a cylindrical shield and have a characteristic impedance of 75 ohms.

Audio frequencies have no trouble traveling over transmission lines, but RF frequencies get seriously distorted if they are sent over separate wires.
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post #6 of 11 Old 11-27-2009, 06:52 AM - Thread Starter
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Selden, this was very helpful. Thank you!
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post #7 of 11 Old 11-27-2009, 07:01 AM
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ehansen42,

You're very welcome.

I should warn you that that discussions of the details of how much or little distortion is involved and whether or not it's audible invariably degenerate into shouting matches. A search of the forum will find many posts about cables.

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post #8 of 11 Old 11-27-2009, 07:10 AM
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Quote:
Originally Posted by ehansen42 View Post

Excellent. Thanks for the responses.

When I bought these digital coax cables, they actually sold me hi-pass video cables saying that they were just about the same rating/impedience/etc, since regular RCA/audio was not suitable for digital coax. But I wonder why it is that you can't use a regular RCA/audio cable for digital coax, but you *can* use the digital coax cable for regular RCA audio...?

Digital coax=composite video cable. They both have 75ohm impedance, and better shielding then regular RCA audio cable. Having said that you could use the flimsy RCA audio cable that comes with many audio devices, and use it as "digital coax", it will work just fine.

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post #9 of 11 Old 11-27-2009, 12:12 PM
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Years ago some audio old-timers decided to try using a wire coat hanger as a digital coax. They soldered RCA termination to both ends of the coat hanger.
There was no difference at all between the coat hanger and a reasonably priced "coaxial digital cable".
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post #10 of 11 Old 11-27-2009, 12:15 PM
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Originally Posted by spyboy View Post

Years ago some audio old-timers decided to try using a wire coat hanger as a digital coax. They soldered RCA termination to both ends of the coat hanger.
There was no difference at all between the coat hanger and a reasonably priced "coaxial digital cable".

Now you've stepped in it.

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post #11 of 11 Old 11-27-2009, 07:58 PM
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I never heard the term "high-pass RCA cables" before. I wonder what it means? From the point of view of a co-ax cable, audio is about as low-pass as it gets.

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