Is the orange colored s/pdif digital coaxial cable a scam - AVS Forum
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post #1 of 17 Old 11-21-2012, 10:38 AM - Thread Starter
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I have read that this cable is nothing more than a standard rca cable that is orange instead of white, red,
Just because it is labelled spdif coax digital, (evertyhing else being equal, you are out 2 or 3 times the prices?

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post #2 of 17 Old 11-21-2012, 11:14 AM
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Hi Pleh4help,

Coloring it orange is a good idea. Charging much more for it would be a scam. A little-bit more might be justified, because of economies of scale, but I would bet that there is no difference, electrically.
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post #3 of 17 Old 11-21-2012, 11:59 AM
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Aren't coax cables for SPDIF typically 75 Ohm? Which I think is different than your typical RCA cable.

http://en.wikipedia.org/wiki/RCA_connector
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post #4 of 17 Old 11-21-2012, 12:27 PM
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Quote:
Originally Posted by pleh4help View Post

I have read that this cable is nothing more than a standard rca cable that is orange instead of white, red,
Just because it is labelled spdif coax digital, (evertyhing else being equal, you are out 2 or 3 times the prices?

Some of the cheaper white and red ones aren't up to spec for some things a 75ohm cable can do. Yellow video cables usually are, though.

Monoprice sells a standard non-color coded cable as a digital coax, subwoofer, and composite video:

http://www.monoprice.com/products/subdepartment.asp?c_id=102&cp_id=10236

But you can get a similarly priced cable from other outlets that are color coded, if that's what you want:

http://www.tartancable.com/digital-audio-cables/index.htm

The color coding is just to assist in connections and tracing signal paths, nothing special about it. Orange is the industry standard for digital coax (much like purple = subwoofer, red = analog right channel, white = analog left channel, etc.)

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post #5 of 17 Old 11-21-2012, 12:34 PM
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Quote:
Originally Posted by designmule View Post

Aren't coax cables for SPDIF typically 75 Ohm? Which I think is different than your typical RCA cable.

http://en.wikipedia.org/wiki/RCA_connector

Characteristic impedance doesn't matter until a cable is more than 1/8 of a wavelength long, at the highest frequency transmitted.

A typical 44 KHz SP/DIF output is coupled through a transformer that is effectively a low pass filter at about 12 MHz, to meet FCC Part 15 rules. IOW any SPDIF cable under 10 feet is totally in the "impedance doesn't matter" category. For mild impedance mismatches such as 2:1, multiply that length by 5 or more.
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post #6 of 17 Old 11-21-2012, 12:53 PM - Thread Starter
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Thanks everyone,
I will return my 3 feet/30$ cable & will use one of the better 5 or 6 feet rca that I already have a boatload of.

My setup:
TV: Samsung plasma 59" pn59d550, DVR: Cisco 8642HD, HTPC: Acer Aspire E1-570,
Peachtree audio DAC-iT, Logitech Harmony 650 remote, Logitech MediaBoard Pro Bluetooth k/b
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post #7 of 17 Old 11-21-2012, 02:27 PM
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Quote:
Originally Posted by arnyk View Post

Characteristic impedance doesn't matter until a cable is more than 1/8 of a wavelength long, at the highest frequency transmitted.
And, of course, the manufacturers know this. I don't believe they even bother to control the impedance when molding short cables.
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post #8 of 17 Old 11-21-2012, 02:46 PM
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Quote:
Originally Posted by pleh4help View Post

Thanks everyone,
I will return my 3 feet/30$ cable & will use one of the better 5 or 6 feet rca that I already have a boatload of.


Last time I looked I saw an orange SPDIF cable at Amazon for $5 each. I use a yellow video cable for my SPDIF coax connection.
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post #9 of 17 Old 11-21-2012, 10:01 PM
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Quote:
Originally Posted by MarkHotchkiss View Post

And, of course, the manufacturers know this
I wouldn't be surprised if some of the Chinese manufacturers hadn't a clue.
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I don't believe they even bother to control the impedance when molding short cables.
That's a good bet, long one's too...

And of course, the authors of the S/PIDF specification probably knew going in that there is no such thing as a 75 ohm RCA plug.

Anything less than a significant fraction of a wavelength doesn't act as a transmission line and doesn't need tightly controlled impedance.
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post #10 of 17 Old 11-22-2012, 06:06 AM
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I used on a philips DVD player (can't remember the type, but it was one with a'phile creds) a regular RCA cable for SPDIF to a behringer src and it would not transmit the signal, or when with dropouts. Switched to a Blue Jeans audio 75 ohm cable and no more problems - cable length was 6'.
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post #11 of 17 Old 11-22-2012, 06:47 AM
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Quote:
Originally Posted by MarkHotchkiss View Post

Quote:
Originally Posted by arnyk View Post

Characteristic impedance doesn't matter until a cable is more than 1/8 of a wavelength long, at the highest frequency transmitted.
And, of course, the manufacturers know this. I don't believe they even bother to control the impedance when molding short cables.

Exactly. I do suspect that if a cable is billed as being a video or digital audio cable, the actual wire part has a characteristic impedance of something like 75 ohms.

At digital audio data sample frequencies, the reflections due to impedance mismatch across RCA or BNC connectors are moot.

One can learn a lot about this sort of thing if you play around with high resolution video signals, such as one of the pieces of coax in a RGB monitor cable running at 2048 x 1080 x 60. The signal frequencies are easily 10 times what you would see with digital audio, and any reflections in the cable will show up as fringing around the picture on the monitor.

The gold standard for this sort of thing is 75 ohm coax and impedance-matched BNC connectors. Generally, sleazing off to RCA connectors has no visible effects, even at like 10 times the frequency of a digital audio signal. However, maybe 6 inches or more of badly impedance-mismatched line, such as might be found in a cheap video switch, can cause visible effects. Multiply that by 10 as a guide to what it takes to possibly cause problems with digital audio. Most DACs are far more tolerant of dirty signals than video monitors.
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post #12 of 17 Old 11-22-2012, 06:52 AM
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Quote:
Originally Posted by kraut View Post

I used on a philips DVD player (can't remember the type, but it was one with a'phile creds) a regular RCA cable for SPDIF to a behringer src and it would not transmit the signal, or when with dropouts. Switched to a Blue Jeans audio 75 ohm cable and no more problems - cable length was 6'.

YMMV. I'm a bad boy ;-)

I use cheap thin RCA cable with yellow plugs to drive the SPDIF inputs of both an AVR (speakers) and a digital processor (headphones) hooked in parallel for stereo PCM from my TV with no audible problems, drop outs, or anything else. Just clean sound. I soldered the cables into a Y about 3 feet from the source, with each leg of the Y about 3 feet long.
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post #13 of 17 Old 11-22-2012, 01:37 PM
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Quote:
Originally Posted by Colm View Post

And of course, the authors of the S/PIDF specification probably knew going in that there is no such thing as a 75 ohm RCA plug.

Well Canare does make one. Of course unless the jack you are plugging it into is also true 75ohm impedance it really doesn't make any difference. Then you have to consider internal wiring including long PC board traces. So yes, for SPDIF and any AES signal, connector impedance is a non issue.

I think Canare makes them because even in the professional arena there are non-technical people that can be fooled into buying then.

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post #14 of 17 Old 11-22-2012, 05:10 PM
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Among the players I used (micromega, pioneer, diy based on cd rom drive, denon) the philips was the only one I had the problem with regular rca cable into a sample rate converter.
(I used the latter one as a sort of digital preamp to convert/pass through all signals to 44.1/16 bit into to a deq and a dcx 2496 by behringer)
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post #15 of 17 Old 10-23-2013, 12:59 AM
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Hate to necro this thread, but economies of scale would merit a reduction in cost to produce, usually doing the opposite of what you said in terms of price for the consumer as a result.

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post #16 of 17 Old 10-23-2013, 01:08 AM
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Grave digging a thread to argue semantics.
Your first post none the less!
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post #17 of 17 Old 10-23-2013, 01:29 AM
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Hi Nicholas,
Quote:
Originally Posted by Nicholas Koa View Post

Hate to necro this thread, but economies of scale would merit a reduction in cost to produce, usually doing the opposite of what you said in terms of price for the consumer as a result.
You misunderstood the point: An orange cable would need to cost more because an orange cable would not have the economy of scale to make it competitive with normal RCA cables. How many orange RCA cables do you see around?

Maybe I should have said "the lack of economies of scale".
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