Film-Tech Forum ARCHIVE: Optical vs Coaxial Digital Inputs

This is topic Optical vs Coaxial Digital Inputs in forum The Afterlife at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=12;t=000132

Posted by Joe Redifer (Member # 3) on 04-12-2003, 02:58 AM:

OK what's the deal here? Why does TOS-link optical even exist? You'd think coaxial connectors would be MUCH cheaper to include on any DVD player and/or receiver. The cables are certainly much cheaper. You can use any standard RCA cable. You can even route several digital signals through a cheap video switcher from Radio Shack to one digital input on the receiver. Cheap and good. But the cables for the optical TOS-link are expensive, fragile, and just stupid. I see no reason whatsoever for it to exist. If you want more bandwidth, go with Firewire. But for current home theater, coaxial just kicks ass.

People probably just see the shiny red light and think "Oooo look at the pretty light! That's for the sound! How space age! I am in the digital age now! I am cool. I am with it. I am space age. But I am still a moron!"

Posted by Michael Schaffer (Member # 1204) on 04-12-2003, 06:43 AM:

The optical connections are less easily disturbed by electrical interference and are also more effective for long cable connections. However, I agree that for a home setup they are not really necessary. It is more a professional thing for sound studios.

Posted by Darryl Spicer (Member # 711) on 04-12-2003, 10:16 AM:

to be honest there is really not much difference between the two. one thing is certain you do not want to pinch a tos link cable it will screw it up.

Posted by Bobby Henderson (Member # 840) on 04-12-2003, 11:46 AM:

On the bright side, prices have come down some on optical cables. They typically used to cost $30 or more, but lately I've seen them running $15 or less in many stores. Still not as cheap as coaxial.

Posted by John Anastasio (Member # 607) on 04-20-2003, 06:45 AM:

Michael's right on about cable length. The more bandwidth you try to cram into a piece of coax, the more capacitance and line loss become an issue. I can get a baseband video signal to go a few hundred feet using RG-11 cable as thick as your thumb, and that's only with using specially equalized amps. Even so, there's always the problem of noise. I regularly use fiberoptic cable to feed video, audio AND data all together in one line for thousands of feet with no noise problems. Granted, it might be a bit of overkill for the home, where signals only go a few feet, but then so is 12 gauge monster cable for speakers only ten feet from an amp...and people LOVE that stuff. You'll see a lot more home components using digital interfaces in the future...and optical is just a simpler way to do it.

Posted by Jim Spohn (Member # 1547) on 04-30-2003, 02:59 PM:

Not only does the fiber-optic eleminate the potential noise problem, but ground loops are a thing of the past with fiber.

Posted by Steve Guttag (Member # 268) on 05-13-2003, 10:53 AM:

Congrats Jim...you win the prize. The TOSLINK cable is the cleanest way to connect two pieces of equipment that may or may not have good grounding techniques. Many consumer pieces of equipment only have two-pronged plugs and no good ground...others have all three prongs and a grounded chassis and maybe signal ground (reference or return). With a TOSLINK (optical) cable one doesn't electrically connect the two pieces of equipment. Most people do not understand grounds (techs, consumers and manufacturers included). With a TOSLINK cable, you don't really have to.

In the digital audio world...the ranking is AES-id (coax 75-Ohms) for long runs (hundreds of feet), AES (2-cond shield 110-Ohm cable), Optical and S/PDIF coax (RCA) are strictly consumer. The consumer coax should also be 75-Ohm cable. Most consumers, like Joe here, probably just take any RCA-RCA cable they have laying about and glory be it works...then again it is only going about 12-feet or less. Impedance mismatches are not going to be an issue there.

Steve