News To Me: Optical Inferior to Coax: Except Glass...

Arthur S · 08-21-2005, 02:38 PM

A serious player on another Forum said that optical is inferior to coax because it has to go through another process.

The discussion then went on to say that if you use an optical cable that is made of real glass strands (as opposed to the ordinary plastic strands), optical is as good as coax.

This is all news to me.

What do you think?

Thanks

Phil A · 08-21-2005, 03:49 PM

This has been covered many times and there's probably somehing about it here: http://www.hometheaterforum.com/htfo...hreadid=120328

Do a search. Dolby Digital signals are delivered in packets so I'd be hard pressed to think that there really can be much if any in the way of differences. With 2 channel PCM on a CD, optical cables can induce more jitter but are not prone to RFI or EMI like a coax cable. So the answer might not be the same for every situation.

Kevin C Brown · 08-21-2005, 05:08 PM

I have come across similar arguments:

1) Coax is better because it does have higher bandwidth (data rate capacity).

2) Coax is better because optical has extra conversions (optical to electrical to optical to electrical), and is therefore more likely to have higher induced jitter.

3) No RF/EMI interference for optical. (But coax is 75 ohm shielded coaxial cable, anyway.)

I have used both with no complaints, but I always default to coax if I have a choice.

JeremyErwin · 08-21-2005, 06:55 PM

Using optical is often the simplest way to eliminate ground loops

Phil A · 08-21-2005, 10:04 PM

The issue was discussed in these 2 threads and many others:

http://www.hometheaterforum.com/htfo...hreadid=218245

http://www.hometheaterforum.com/htfo...hreadid=213566

**HTF Ads**

Chu Gai · 08-22-2005, 12:35 AM

A serious player on another Forum said that optical is inferior to coax because it has to go through another process.
So what? Does the serious player understand that the data on CD's is interleaved to begin with and needs to be reconstructed before it gets processed by the DAC? If there are bad conversions you'll have data loss that can't be reconstructed and then have dropouts. What you will find though between the two flavors though is that levels might be different and that in itself can lead to perceived sound quality differences. I'm sure such a serious player has taken the time to measure the output levels using test tones and a VOM, right?

The discussion then went on to say that if you use an optical cable that is made of real glass strands (as opposed to the ordinary plastic strands), optical is as good as coax.
There are less attenuation losses with glass as opposed to plastic, but that's only an issue if you're running very long lengths. Glass, though, does give you bragging rights. Comparatively inexpensive glass toslink can be found at MCM.

This is all news to me.

What do you think?
Use the type of connection that best meets your needs or potentially addresses a problem. The serious player probably needs to go out and laid more often. Maybe it'll clean out his ears.

John Garcia · 08-22-2005, 12:53 AM

I prefer coax simply because I know it's not going to get knocked out of the socket.

Kevin C Brown · 08-22-2005, 02:19 AM

It won't get "broken" either. Coax cables are much more robust than optical. One other problem with optical, is that you can get dust in the connectors which can kill the signal.

Good point about ground loops.

But more than likely, if you have a ground loop from cable TV or a satellite connected up wrong, changing just the connection from the DVD player to the receiver or pre/pro isn't going to fix the problem.

Lewis Besze · 08-22-2005, 06:07 AM

I keep hearing about how the the coax is more robust and has tighter connection.
I don't see how that makes any difference to most people at all.Unless you move equipments in and out like a reviewer from it's place therefore unplug things often, or just like to play with your cable like a lasso[sp?], it shouldn't make any difference how beefed up the connection or the cable is.

Cees Alons · 08-22-2005, 07:55 AM

Millions of yards of optical fiber connections are used in offices, across the country, buried beneath your streets, etc. for the Internet as well as cable transmissions.

What do you think? They are all inferior?

Truth is: fiber connections between AV-modules are so short, as compared to all other professional use, that the chance of losing even one packet of data is virtually zero. This includes the conversion to and from light. Glass or plastic.

When used for digital audio, they're electronically at least as good as coax. And I wonder about mechanically. Sure glass can break. But so can metal strands and soldered connections.

Cees

PS: Do I count as a "serious player" on this here forum?

C.

John Garcia · 08-22-2005, 10:08 AM

It depends on the quality of the connectors on the end of the cables. I've used optical cables that just don't "click" into their little socket and have had them pop out too easily when just moving the HD box slightly. Yes, it only happens when you move the unit, but that's still not good enough for me.