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life before HDMI digital connections whats better

587 Views 7 Replies 6 Participants Last post by Worf, Feb 23, 2014

gearheadslife

Discussion Starter · Feb 20, 2014

Like the title says, before HDMI most equipment had optical toslink and coax of the 2 what one is better for pure dynamic range and not changing the data (compressing it, if it even does that )

Some of my gear has both of these, some only have one (coax) those with both I have the choice of what one to use.. providing the new a/vr has enough of that type inputs..

2) is there really any difference in the cable make up of a coax digital patch cable, and a good rca patch cable..??

and if so.. what??

I ask this for a few reasons , 1) I have a bunch of good rca patch cables and 2) while working on running wires through wall and had the whole works unhooks , wife put all the cables in one box.. and I can't tell by eye what one is a rca patch or coax.. is there a way to tell.. the coax ones I have are monster cable(yes I know, now. but in the late 90's I didn't and paid for the "better" cables)

and when I say paid for. I mean paid through the nose buying them at the hifi store.. unlike today that you can get good cables for tons less..

Thanks for any insight..

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commsysman

· #2 · Feb 20, 2014

A digital coaxial connection carries a radio-frequency signal, and requires a 72-ohm cable type to transmit it without an impedance mismatch, which will corrupt the signal.

The circuits that transmit and receive the coaxial digital signal have a 72 ohm impedance.

An ordinary RCA interconnect cable does not normally use a 72-ohm cable type, and should not be used. It will cause big problems.

Ordinary audio signals are low-frequency, and impedance matching is not an issue.

RG-59 and RG-6 are the 72-ohm cable types that are usually used, so that marking, one or the other, should be on the cable.

If you are in doubt about what you have, buy the Monoprice Digital coaxial cables, part # 2680 or 2681.

They both are made with RG-6 cable, have gold plated RCA plugs, and cost less than $5 each.

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arnyk

· #3 · Feb 20, 2014

Quote:
Originally Posted by gearheadslife /t/1518884/life-before-hdmi-digital-connections-whats-better#post_24383505

Like the title says, before HDMI most equipment had optical toslink and coax .

Yup, been there done that and kept the T-shirt.

Under ideal conditions there is no audible difference. I prefer optical because it can't possibly add grounding problems.TV sets are inherently electrically noisy (less so since we quit fooling with CRTs but still...) and electrically isolating them from the audio signal world can be a problem solver.

Quote:
of the 2 what one is better for pure dynamic range and not changing the data (compressing it, if it even does that )

The digital signal on toslink and coax is bit-identical. Inside the box they come from the same circuits and go to the same circuits aside from the line drivers.

Quote:
Some of my gear has both of these, some only have one (coax) those with both I have the choice of what one to use.. providing the new a/vr has enough of that type inputs..

Yup, but compared to HDMI they are both way down on bandwidth and don't help you with your video interconnection problems.

Quote:
2) is there really any difference in the cable make up of a coax digital patch cable, and a good rca patch cable..??and if so.. what??

There generally is a construction difference between audio and digital cables but in a great many applications they can be interchanged without any audible or even measurable differences at all. Using coax cables for audio works. In the relatively short lengths in home systems, the fact that coax and audio cables have different characteristic impedance is a moot point - it takes 50 foot + cables for the difference to be apparent.

Please note that not all of the latest-greatest A/V fomats can squeeze through coax or toslink, and that HDMI gets you a superior digital video connection and that it also vastly simplifies installation.

Quote:
I ask this for a few reasons , 1) I have a bunch of good rca patch cables and 2) while working on running wires through wall and had the whole works unhooks , wife put all the cables in one box.. and I can't tell by eye what one is a rca patch or coax.. is there a way to tell..

Video cables are often stiffer and/or larger in diameter. Sometimes the text that may be printed on the cable can help.

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jontyrees

· #4 · Feb 20, 2014

Quote:
Originally Posted by arnyk /t/1518884/life-before-hdmi-digital-connections-whats-better#post_24384167

Yup, but compared to HDMI they are both way down on bandwidth.

Would it be fair to say that the actual cable is not the limiting factor in Toslink (probably coax too), but the transmitter and receiver at either end of it (the pitcher and catcher, if you like). A strand of fiber should be capable of carrying an enormous amount of data. If you've ever seen the fiber cable connecting a big data center to a national fiber broadband network, it's pretty amazing - just a little thin strand.

One thing I preferred about digital coax and toslink, RCAs, component video, was the almost total lack of issues with boards going bad, handshake issues, CEC control ghosts in the machine, etc. The convenience and ability to carry the latest greatest audio and video is nice, but hdmi is so buggy.

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arnyk

· #5 · Feb 20, 2014

Quote:
Originally Posted by jontyrees /t/1518884/life-before-hdmi-digital-connections-whats-better#post_24384240

Quote:
Originally Posted by arnyk /t/1518884/life-before-hdmi-digital-connections-whats-better#post_24384167

Yup, but compared to HDMI they are both way down on bandwidth.

Click to expand...

Would it be fair to say that the actual cable is not the limiting factor in Toslink (probably coax too), but the transmitter and receiver at either end of it (the pitcher and catcher, if you like).

Absolutely so. About the only thing that better transmitters and receivers can't overcome is a totally broken data path. ;-)

Quote:
A strand of fiber should be capable of carrying an enormous amount of data. If you've ever seen the fiber cable connecting a big data center to a national fiber broadband network, it's pretty amazing - just a little thin strand.

Again, agreed.

Quote:
One thing I preferred about digital coax and toslink, RCAs, component video, was the almost total lack of issues with boards going bad, handshake issues, CEC control ghosts in the machine, etc. The convenience and ability to carry the latest greatest audio and video is nice, but hdmi is so buggy.

The current problem with HDMI is partially inherent and partially just new technology. The inherent problem with HDMI is that it is based on a direct metallic connection with no effective built in electrical isolation that is anywhere near as effective as optical or transformers. Optical will isolate megavolts and a direct hit by lightening. Transformer isolation is usually good for about 3 KV. The rest is just about working the bugs out of new technology, much of which would be there no matter what the actual physical connection was.

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budwich

· #6 · Feb 20, 2014

I think that you might find that a coax "feed" is more stable than an optical one.... of course, commercial communication systems use glass and a few other things, but plastic optical connections do seemed to be "less stable" than the equivalent coax links... at least that's my read.

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gearheadslife

Discussion Starter · #7 · Feb 22, 2014

thanks, guys.. I have 8 optical cables.. I'll look for the RG59/RG6 on my rca ended cables to see if I can fine the ones that are coax.. as the older monster rca's are singles,meaning not connected together like most patch cables are..

the sony had upscaling.. and hope to use that to record the vcr tapes to dvd.. will see.. hope to have it set up today.. the shelves are now dry.. so after doctors I'll screw the roller draws for the laptop server control and the one for the turntable and then put all the gear in the cab and re arrange it a few times. then wire the patch cables and be good to go..

also got a neat leviton (part#1755)3 switch in one..

so I can wire 120v outlets into cabinet and shut off the computer/etc when not in use and the antenna both that draw power with the wall warts..

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Worf

· #8 · Feb 23, 2014

Quote:
Originally Posted by arnyk /t/1518884/life-before-hdmi-digital-connections-whats-better#post_24385533

The current problem with HDMI is partially inherent and partially just new technology. The inherent problem with HDMI is that it is based on a direct metallic connection with no effective built in electrical isolation that is anywhere near as effective as optical or transformers. Optical will isolate megavolts and a direct hit by lightening. Transformer isolation is usually good for about 3 KV. The rest is just about working the bugs out of new technology, much of which would be there no matter what the actual physical connection was.

It's less about new technology and more about how HDMI is a much more complex specification. And how it allows for a wide variety of source,sink and repeater capabilities. It scales a video signal from QVGA all the way to cinema 4K, an audio signal from piss poor 8kHz mono to 12 channel 192kHz 24 bits. And inherent in all this is a set of things that should happen and thongs that are vague. So people have to guess what something really means. And there are plenty of parts that the software doesn't expect, or cases where one person interprets something differently, or expects something that doesn't happen.

Heck, even someone as simple as the EDID is really quite complex, having evolved as a way to describe analog monitors from the 90s to handling resolutions and timings that were not even imagined 10 years ago.

I know, I actually have to deal with it.

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