What’s special about ‘digital coax’?

[TrevorD]

If I remember correctly toslink was designed for maximum 24/96. Even if you could send more on the media, I don't know of any audio device that will do so.

I have an HDMI to Audio extractor that can send out up to 24/192 over toslink.

 

[TrevorD]

It's a good thing none of that makes any audible difference whatsoever.

It might make a BIT --see what i did there?

 

[weesch]

Yes, a "digital" audio (or video) cable will have 75-ohm nominal impedance by design. In practice, it is far cheaper for companies to buy 75-ohm cable in bulk and use it for audio, video, and digital audio cables. And most coaxial audio interconnects are of such a size that they are about 75 ohms anyway. Thus, the differences among interconnect cables tend to be more about shielding and wire gauge (larger wire, lower gauge, means lower loss) than impedance (which does not matter for audio signals).

As for "improvement", who knows. A large-gauge interconnect with foil or 100% braid that is 75 ohms but marketed for "audio" signals may work better than a cheap, small, poorly-shielded video RF/digital cable. And vice-versa. Look around, ask questions, and buy a decent cable from a decent manufacturer (which usually means one that does a good job mounting the connectors). Such cables often cost <$10 for a 1-m pair.

hi !
yes I use old television antenna cable (75 ohms) for the spdif connections between a 01v96 my pulsar 2 sound card and my berhinger src 24/96 converter
I solder it on male rca plugs!
and it works perfectly!

 

[mansr]

Has anyone measured the things you describe as changing the output of the DAC?

Not to my knowledge. I have, however, measured the waveform entering the DAC, and the tiny wiggles caused by cable reflections are no concern. Here's the scope image again:

 

[DonH56]

Oh, good to know, thanks. I thought that having a continuous stream, as long as the signal is digital 0/1 will be always as the source will deliver, not a question of clarity.

In this case, only a measurement test will tell how ‘clear’ is the sound, comparing a Coax with a Toslink.

Virtually all DACs today recover the signal and clock using asynchronous techniques that isolate the DAC's output from any input jitter (short of actual signal loss). There is no reduction of "clarity" until you lose the signal, then there will be drop-outs (silence and/or glitches/noise in the sound). Coax or TOSLINK.

 

[Blumlein 88]

Optical to Coaxial converters introduce jitter?

Can they introduce jitter? I can't find any research on this. There are plenty of cheap ones on ebay and I'd like to have one for the rare occasion I'd need one.

www.audiosciencereview.com

Here is a post where I measured the output of a DAC fed via toslink and then coax using the device for the digital signal. Looks like no difference to me. In the post above it you see a JA measurement of the eye pattern. Again shows no difference like the scope graph from mansr.

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Here is one I had on file. Red is coax and green is Toslink. Tact RCS2.0 for the DAC. Essentially no difference. This shows from 10 khz to 14 khz.

Here is a close in view +/- 20 hz of 12,000 hz. One coax and one Toslink.

 

[Beave]

Great. The thing to look for is clarity, since jitter is adding noise. Pops or clicks would be extreme. It would have to be really bad Toslink connector or completely mismatched coax.

Jitter would also have to be "really bad" (or, really, really, really bad) in order to be audible.

 

[Beave]

It might make a BIT --see what i did there?

I almost started my initial reply with "None of that will make a bit of difference," but I decided against it.

 

[tmtomh]

My anecdotal and totally unscientific $.02: A few years ago I decided to get new speaker cables and component interconnects. The reason was simply that it had been about 15 years or more years since I'd installed the existing ones, and that seemed like a long enough time to justify replacing them just for the possibility of wear and tear. I went with BlueJeans and while I had all the necessary stuff in my shopping cart I figured why not throw in a digital coax cable just to see? I'd never transmitted digital via coax before.

I plugged in the cable and it worked perfectly.

Then just for the heck of it, I swapped out the new digital coax cable and swapped in one of the old, no-name RCA cables that I had been using as a component interconnect for 15 years and had just removed from my analog chain. It worked perfectly too.

I had no regrets about the BlueJeans cable because it was cheap, didn't add to the shipping cost of my cable order, and the stress-relief sleeves connecting the plugs to the cable were 10x more robust than on my old RCA cables.

But in terms of transmitting the digital signal, it made no difference. It just worked with the purpose-made cable, and it just worked with the crappy old one.

 

[Momotaro]

It might make a BIT --see what i did there?

This thread hasn't touched on the essentials of optimal digital cable design. We've seen both flat and hollow-core in speaker cables. Digital interconnects require combination of flat (for the 1s) and hollow (for the 0s). High-end audiophile cables are subtly shaped by artisans to match the precise font. Argument still rages over the relative merits of serif vs sans-serif. There's no standing still on this. Every time (for example) Apple changes their system font, MacBook Pro users (to say nothing of iOS) must replace those cables to stay ahead of the inevitable distortion issues.

 

[dpturner]

Hey guys,
Hope this is the correct forum for this post. About a year ago my elderly parents started experiencing lost TV stations and weak signals. They live in a single family home in the Chicago suburbs and at the time, had a huge rooftop antenna, which worked perfect for about 30 years. The issue started when the Chicago market started making changes to their transmitters, but I think that was just a coincidence.

Early this spring we removed the old antenna, which had a couple missing elements, and replaced it with a new one from either Winegard or Channel Master. We also replaced the antenna coaxial cabling in the attic with new RG6 from Mediabridge. Lastly we replaced the splitter in the attic with a Leviton passive 8 way splitter, which feeds four leads to the four TV's in the house, and added a Channel Master antenna preamp to the base of the antenna which is connected to the balun.

In spite of all this, they only get 11 weak TV stations in the Chicago market, which should have over 50 when the antenna is pointed towards downtown Chicago. They are about 25 miles away from the transmitters and they should have a great signal. I'm wondering if anyone can think of any trouble shooting tips or maybe how to measure the signal strength going through the coaxial cable. I've been messing with this all summer trying to figure out what the problem is and am about out of ideas. Thanks

didn't all broadcast tv in the US switch to digital a few years ago? making the traditional rooftop antenna obsolete?

 

[Beave]

didn't all broadcast tv in the US switch to digital a few years ago? making the traditional rooftop antenna obsolete?

Yes, all broadcast TV in the US switched to digital, but a traditional rooftop antenna is not at all obolete. They're still the best way to pick up off-air channels.