Optical versus Coax

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:19 pm

Which is better for audio, Optical or Coax?

Mark

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:19 pm

We had the same discussion on the TIPS list and this was the result plus some additions. Toslink is an inferior connection to coax. There is another element called jitter. In audiophile circles coax is considered the more precise connection provided you use the correct wire and connectors. 75 ohm DVD video cable works great.

digital is digital only in the digital domain. The products of jitter do not seem to appear until you actually decode the signal into analog. It changes the sonic signature of the D/A convertor. This is why you can digitally record something and have a better sound quality due to the player having less system jitter during playback. Jitter errors can also be introduced by the CD itself.

In the end don't sweat it because few even setup the speakers and viewing position correctly anyway which means so much more than this issue. I use toslink also for my HDTV receiver. Home Theater is not what drives me as much as two channel audio. In this case I would use coax and if possible use "AT&T glass" optical connectors (very unpopular so coax is king). This is also why I wanted a 75 ohm digital coax out on the receiver - just in case.

If you can hear the difference between Dolby Digital and DTS then you might be able to hear the difference between toslink and coax. (The point here is the ability to hear a difference and not to make some sort of comparison between connections and encoding processes)

Richard F. Fisher

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:20 pm

Richard,

Have you done an A-B and can you hear the difference?

ToddK

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:20 pm

Yes

Richard

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:21 pm

Richard,

In summary:
- Toslink is inferior.
- You can hear the difference.
- Don't sweat the differences.
- You use Toslink for HDTV.

I think understand now. Thanks for the insite.

ToddK

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:22 pm

Coax probably provides a more direct path, eliminating the fiber-optic conversion on each end. Not a biggie - the datastream is recovered with no errors with a good interconnect. Optical fiber has no EMI or noise coupling concerns and a smaller, light-weight cable. Less chance of signal distortion over longer cable lengths with optical. But if equipment only a few feet apart either one is fine. I use optical, but have had problems with the connectors being easier to break than with coax.

EMC Guy

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:24 pm

In terms of what you hear, coaxial audio and optical audio are perfectly identical.

Ken - KQ6QV

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:25 pm

Ken,

In terms of what you hear, coaxial audio and optical audio are perfectly identical.

thought so too, and even did an A/B. I've got both outputs on my DVD player and I configured two inputs on my receiver so that I was able to switch back and forth quickly.

Other posters have disagreed. Back in September, one said:
"Toslink is an inferior connection to coax. There is another element called jitter. In audiophile circles..."

Maybe the DVD was not an adequate sound source, but it's probably my equipment or my ears.

a

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:25 pm

That was me.

I can't find the thread. The quick version is most any connection can be used to transfer bits provided you are recording those bits to another medium. If you are listening to that stream then the jitter products of your connection could affect the final D/A conversion process. Audiophiles have prefered coax, 75 ohm cable and connectors just like video, always over toslink due to potential jitter issues with AT&T Glass being the best but seen only on some hi-end products.

Bottom line is don't make a big deal out of it. Try both if you want to play. If you hear a difference then go with the coax. If you don't then move on.

Richard F. Fisher

HDTV Forum · Post by **HDTV Forum** » Tue Jun 22, 2004 3:26 pm

Dan, I agree with you regarding the following:

The interference caused by a digital coax cable is not distinguishable by the average human ear.

The digital audio itself won't be affected by interference. What was going through my mind was that digital data is inherently noisier than analog and the noise is spread over wider frequencies (digital will always appear as noise to another unrelated system). If it leaks off a poorly constructed shielded cable it could get into other analog video/audio cables and degrade the SNR. You might hear some hiss in the sound or interference in the picture. I doubt if it's a serious concern, but when people say that noise on power cords affects things, this digital coax is even a worse source of noise in a system. Just make sure a good cable is used.

emc guy