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post #1 of 20 Old 08-10-2017, 12:15 AM - Thread Starter
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Digital coaxial cable question

Is there anything special about these cables, or can I use one of the RCA cables I have? I have composite cables, red/white audio cables, component cables, etc.


Thanks.
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post #2 of 20 Old 08-10-2017, 03:03 AM
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Video component cables are supposed to be 75 ohm so you can use them for coaxial digital connections. For short distances you could probably get away with any cable with RCA connectors.
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post #3 of 20 Old 08-10-2017, 05:05 AM
 
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In very long runs cables with lower capacitance than typical audio cables may be beneficial, but we're talking 50 feet or more. Besides, most cables labeled as digital are the same as those labeled as analog, the only difference being the latter are paired, while the former may be priced higher for no reason other than being labeled as digital interconnects. As is the case with all audio cables ignore the hype.
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post #4 of 20 Old 08-10-2017, 05:54 AM
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Post Fact ≠ Hype

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Originally Posted by Bill Fitzmaurice View Post
In very long runs cables with lower capacitance than typical audio cables may be beneficial, but we're talking 50 feet or more. Besides, most cables labeled as digital are the same as those labeled as analog, the only difference being the latter are paired, while the former may be priced higher for no reason other than being labeled as digital interconnects.
It is possible that some analog cables are simply labeled as digital and sold at a higher price. What SHOULD be happening is cables that are labeled as digital should be using a dielectric material that has a lower capacitance.

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As is the case with all audio cables ignore the hype.
The need for lower capacitance cables when working with digital audio is not hype. It is true that you can GET AWAY with using cheap cable designed for analog use over short distances as digital audio cable. Just because you can do something does not mean that you should, nor does it mean that the claim to the contrary is hype.
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post #5 of 20 Old 08-10-2017, 07:34 AM
 
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What SHOULD be happening is cables that are labeled as digital should be using a dielectric material that has a lower capacitance.
Not if the capacitance of an analog cable is low enough. At typical interconnect lengths it would be the rare analog interconnect that had too high a capacitance to function perfectly well at digital frequencies.

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The need for lower capacitance cables when working with digital audio is not hype.
That need is totally dependent on the cable length. As for what constitutes hype, this is a prime example:
http://www.audioquest.com/seventy-five-ohm/carbon

They tout all sorts of falsehoods, yet make no mention at all of capacitance.
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post #6 of 20 Old 08-10-2017, 08:06 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
In very long runs cables with lower capacitance than typical audio cables may be beneficial, but we're talking 50 feet or more. Besides, most cables labeled as digital are the same as those labeled as analog, the only difference being the latter are paired, while the former may be priced higher for no reason other than being labeled as digital interconnects. As is the case with all audio cables ignore the hype.
Thank for this info!

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post #7 of 20 Old 08-10-2017, 10:59 AM - Thread Starter
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Thanks guys. I want to buy a new Blu-ray player to hook up to my old receiver, and I don't feel like waiting for a cable to be shipped. Or pay $15 at Best Buy for one.

I only need a 6' cable. Would I be best off using one of my yellow/red/white cables, or one of my component cables? It will probably only be temporary anyway. If the player works with my old receiver, I will order one from Monoprice.
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post #8 of 20 Old 08-10-2017, 11:20 AM
 
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At 6 feet it probably makes no difference, nor would it make sense IMO to order another one. The main advantage at that length in not using a paired or triplet cable is reduction in cable clutter.
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post #9 of 20 Old 08-10-2017, 01:54 PM - Thread Starter
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post #10 of 20 Old 08-13-2017, 07:02 AM
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Exclamation Ha!

Quote:
Originally Posted by Bill Fitzmaurice View Post
As for what constitutes hype, this is a prime example:
http://www.audioquest.com/seventy-five-ohm/carbon

They tout all sorts of falsehoods, yet make no mention at all of capacitance.
…the speed of digital communication is important. Most visibly, “speed” is about transferring large files as quickly as possible, or carrying enough data for HD video. For Digital Coax audio “speed” is critical not because of how-much how-fast, but because time relationships within a digital stream are critical to the reconstruction of the analog waveform that brings information, music and joy to our ears. Time-based damage (jitter) to this information within the data package makes the sound small and flat instead of 3D, harsh and foggy instead of smooth and clear.


Amazing . Jitter can affect sound, though speed does not affect jitter. Speed is not determined by the cable. Speed is determined by the rate at which the transmitting device outputs data. Jitter is created when the transmitting device does not send each bit/packet of data at the specified (constant) rate. Jitter is defined as variations in the timing of when some data was received versus when it should have been received.

Solid conductors eliminate strand-interaction distortion and reduce jitter. Solid silver-plated conductors are excellent for very high-frequency applications. These signals, being such a high frequency, travel almost exclusively on the surface of the conductor.

Strand-interaction distortion ? Please. While the skin effect, alluded to in that quote, is real, I am skeptical that it exists at digital audio frequencies. If we were talking about 12-G SDI cables, it would be a different conversation.
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post #11 of 20 Old 08-14-2017, 08:24 AM
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Quote:
Originally Posted by Chief Technician View Post
It is possible that some analog cables are simply labeled as digital and sold at a higher price. What SHOULD be happening is cables that are labeled as digital should be using a dielectric material that has a lower capacitance.

The need for lower capacitance cables when working with digital audio is not hype. It is true that you can GET AWAY with using cheap cable designed for analog use over short distances as digital audio cable. Just because you can do something does not mean that you should, nor does it mean that the claim to the contrary is hype.
Dielectric materials don't have capacitance by themselves. These materials are used to construct capacitors, which do have capacitance.

https://en.wikipedia.org/wiki/Capacitor

Cables are analog, The digital data is encoded in analog waveforms. Transferring digital data that is encoded in an analog waveform, puts requirements on the analog cable, as well as the terminations and associated electronics, that vary depending on the characteristics of the data.
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post #12 of 20 Old 08-14-2017, 08:32 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
Not if the capacitance of an analog cable is low enough. At typical interconnect lengths it would be the rare analog interconnect that had too high a capacitance to function perfectly well at digital frequencies.

That need is totally dependent on the cable length. As for what constitutes hype, this is a prime example:
http://www.audioquest.com/seventy-five-ohm/carbon

They tout all sorts of falsehoods, yet make no mention at all of capacitance.
Just a side question: you seem to have a particular dislike for Audioquest among the legion of companies that sell overpriced cables based on questionable claims. Any particular reason for that dislike? There seem to be companies that sell cables that are even more overpriced.
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post #13 of 20 Old 08-14-2017, 08:32 AM
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Specifications for AES cables are 110 ohms, 75 ohms for S/PDIF.

I use the correct cable and connectors for digital audio. You can get them for reasonable prices from Blue Jeans Cables or Redco.

http://www.bluejeanscable.com/store/...udio/index.htm

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post #14 of 20 Old 08-14-2017, 12:41 PM
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Quote:
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Would I be best off using one of my yellow/red/white cables, or one of my component cables?
The yellow cable of the composite set or any of the 3 of the component set would be best. Whichever is easiest to strip apart and down to a single cable for the run.

"All men are frauds. The only difference between them is that some admit it. I myself deny it."
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post #15 of 20 Old 08-14-2017, 04:58 PM
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Quote:
Originally Posted by bigguyca View Post
Just a side question: you seem to have a particular dislike for Audioquest among the legion of companies that sell overpriced cables based on questionable claims. Any particular reason for that dislike? There seem to be companies that sell cables that are even more overpriced.
Of course I cannot speak for Bill but it seems Audioquest is pushed more than other high end cables around here.
No data to support this just an observation though.
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post #16 of 20 Old 08-14-2017, 09:17 PM - Thread Starter
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Originally Posted by sivadselim View Post
The yellow cable of the composite set or any of the 3 of the component set would be best. Whichever is easiest to strip apart and down to a single cable for the run.
I wound up using one of the red audio cables I had from Monoprice, and so far so good.
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post #17 of 20 Old 08-15-2017, 06:33 AM
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Post Point Noted

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Dielectric materials don't have capacitance by themselves. These materials are used to construct capacitors, which do have capacitance.
Point noted.
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post #18 of 20 Old 08-15-2017, 10:59 PM
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The most important characteristic of a (long) SPDIF cable is that it is 75ohms impedance. SPDIF running at 48K is essentially NTSC video bandwidth. 3.072 mbs, which requires at least a 6mhz -3db point. At these frequencies any cable becomes a transmission line that must be impedance matched. Otherwise reflections result and with a digital signal, once they reach the 50% signal voltage, you will induce errors.

Now all that said for a simple 6 foot connection between a DVD player and a receiver, any old analog audio cable will probably work just fine. The effects of impedance mismatch and capacitance as outlined earlier are cumulative with cable length. At short enough distances that can be ignored. Now how about an old analog cable for 6 feet at 192khz? That might be a problem!

While it's a good idea to use a 75ohm cable for SPDIF, don't get caught up in the 75ohm connector BS you read about in audiophile magazines! Connector impedance is not relevant at any standard digital audio sampling rate. The physical length of the connector is too short to have any detrimental effect. Note that in the days of analog NTSC video, BNC connectors and patch bays were 50ohms using 75ohm cable. It simply didn't matter at 6 to10mhz and the RF industry did require 50ohm connectors so that's what was widely stocked.

Now when digital video came about in the 1990s at 143 and 270mbs, the connector length now became a factor and 75ohm BNC connectors were highly recommended. When HDSDI came about at 1.5gbs and now higher, precision 75ohm connectors are a requirement.

But again for digital audio, there is no need for precision 75ohm connectors, RCA or BNC.

P.S. 75ohm RCA connectors are an oxymoron! Yes Canare makes them but IMO, anybody worried about connector impedance should not be using an RCA connector in the first place!
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post #19 of 20 Old 08-21-2017, 04:23 AM
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Coaxial versus straight wire...

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post #20 of 20 Old 08-21-2017, 10:58 AM
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Coaxial versus straight wire...
??? Coax is wire!
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