Optical digital interconnects

[Rayn129]

I have been looking through many posts and am reading conflicting information about optical cables. I wish to utilize optical cables on some of my components. What length should an optical cable be?
Does brand name really matter?
Who makes the most reliable optical cables?
Any more information on the optical cable would be nice. I wish to understand more about it.

Adam

 

[JAD2]

Famous line in the Road Warrior comes to mind.

JUST WALK AWAY!!

Why, your going to hear what others believe to be true in which they talked themselves into. No basis to the argument, no scientific proof, what can be measured, your cant hear.
No name stuff, might not be very good, Phillips Brand, RCA and hoards of others are just fine!! You dont get what you pay for in cables!!!! You do then get what you believe when you spend!!!

 

[hemiram]

Good advice. How is a hunk of glass fiber is supposed to affect signals going through it?

I love reading the cable ads. Insanity!

 

[majorloser]

Unfortunately with some components you're given no choice as they only have optical digital outputs. Optical cable usually are more expensive than coax cable. For coax digital cable some good RG6 with RCA ends is all you need.

There are good deals on optical cables out there if you're willing to search.

Here's some 2 meter cables for $9.99 :

http://www.accessories4less.com/cgi-bin/item/HT181

 

[Rayn129]

Thanks guys, appreciate the help.

 

[tbewick]

Famous line in the Road Warrior comes to mind.

JUST WALK AWAY!!

Probably good advice .

I have been looking through many posts and am reading conflicting information about optical cables. I wish to utilize optical cables on some of my components. What length should an optical cable be?
Does brand name really matter?
Who makes the most reliable optical cables?
Any more information on the optical cable would be nice. I wish to understand more about it.

Generally you should use a short a length of cable as possible. Optical cables are more suited for use over longer distances than electrical ones.

Buying a well-known branded cable will probably get you a higher quality cable, but this shouldn't affect sound quality.

Belden are a good name in video cables and they probably make optical cables as well. QED are another well-known cable manufacturer.

I'd think that most optical cables nowadays are very reliable.

A large part of the science of optical cables revolves around glass chemistry. Developing and designing the 'recipe' for a glass suited for use in optical cables was a major technical breakthrough, particularly for the telecommunications industry. Polymers are also used instead of glass in the construction of optical cables. The Digital Interface Handbook by Francis Rumsey and John Watkinson has a few pages on optical cables.

 

[mmonaco27]

You should use optical cables if
a) you're running around a lot of electrical wires (light is uneffected by electromagnetic fields)

or b) if you're running long distances (I read somewhere that optical cables experience something like a 5% loss over 300 ft while copper cables 90%; this was comparing optical and cat5 for networking, but id assume the advantage is still true for optical audio cables)

or finally c) if an optical output is your only option for sound exceeding 2 channels

 

[Jack Hammer]

You may want to condsider using digital coax. I had problems with my optical cables coming loose on several occasions (I believe others have had issues also). IME, they don't have a solid connection. The coax plugs in like a rca and won't come loose. It also will send the same signal. For short runs (25ft?) their is no difference. I'll never use optical cables again, unless it is the only option for connection.

Jack

 

[markw]

I'll simplify it even more.

You may want to condsider using digital coax.

Actually, in many, many cases regular "analog" coax works as a digital interconnect. It does for me and a few buddies. you might want to try it and save few bucks.

 

[Vaughan Odendaa]

I have not been able to tell a difference between optical or coaxial cable. In theory, coaxial should give better performance but in practice, that isn't so, in my opinion.

--Sincerely,

 

[jonnythan]

I have not been able to tell a difference between optical or coaxial cable. In theory, coaxial should give better performance but in practice, that isn't so, in my opinion.

--Sincerely,

What theory would that be?

Does it transmit better bits or something?

 

[MDS]

The only possible theory as to why coax might be better than optical that I would give any merit is the idea that RCA connectors on coax cables make for a tighter fit that won't easily come loose, but I have both coax and optical connections and neither has ever come loose.

 

[Vaughan Odendaa]

In electrical terms, doesn't optical convert from electrical to light pulses and back to electrical, whereas coaxial converts electrical pulses to 0's and 1's ? So there is one less step in the signal chain to convert ?

It's not as if this extra step gives a perceivable loss in sound quality. As I said, I can't tell the difference between the two cables. I think coaxial is a better cable but not because it gives a better sound.

Construction wise, I think coaxial wins hands down.

--Sincerely,

 

[mtrycrafts]

In electrical terms, doesn't optical convert from electrical to light pulses and back to electrical, whereas coaxial converts electrical pulses to 0's and 1's ? So there is one less step in the signal chain to convert ?

It's not as if this extra step gives a perceivable loss in sound quality. As I said, I can't tell the difference between the two cables. I think coaxial is a better cable but not because it gives a better sound.

Construction wise, I think coaxial wins hands down.

--Sincerely,

The coax cable doesn't convert anything. It is already digital form.

The conversion for optical is similar. It converts the digital signal to light digital signal, not an issue at all. Digital is very robust unlike analog.

Coax can pick up noise and signal loss over long distances that can cause problems. Optical is immune to noise and has less loss over distance, one reason why cable companies are converting to optical.

 

[Vaughan Odendaa]

mtrycrafts, everything that I've heard and read is that optical has one more "step" to finish in order to convert to 0's and 1's. Is this not true ? Does optical not need an additional conversion in order to get to electrical compared to coaxial ?

I'm just asking.

--Sincerely,

 

[Vaughan Odendaa]

Isn't there a jitter issue with optical that is not prevalent with coaxial ?

--Sincerely,

 

[MDS]

Isn't there a jitter issue with optical that is not prevalent with coaxial ?

--Sincerely,

Jitter is a timing error and is inherent in any digital audio system but the amount is so small that it is entirely inaudible.

Yes. there is a conversion from electrical to optical and vice-versa. The transmitter has to convert the elecrical signal to light and the receiver has to convert the light back to electrical. That process takes a non-zero finite amount of time to accomplish and so could introduce jitter (it would be 'interface jitter') but again is so small that it is inaudible. Typical 'good' implementations have jitter on the order of 50 picoseconds (50 trillionths of a second) and there isn't one single golden-eared audiophile on the planet that can hear that difference.

 

[Vaughan Odendaa]

Thanks ! I just went to the Monster website and I was disappointed with the advice they were giving in the "learning" section. There, they claim that cables should all be the same length. Otherwise there will be timing issues, blah, blah, blah.

I think the biggest reason why I was disappointed is because I was seriously considering purchasing their display calibration software, but now I don't know whether it works or whether it's pure gimmick.

How can such a reputable manfacturer blatantly put out factually incorrect information on their website ? I mean, timing issues ? The signal is traveling at incredible speeds, and while there will be resistance, I simply do not believe that a couple extra meters could negatively affect the timing of the signal.

What do you think ?

--Sincerely,

 

[jonnythan]

Calibration software is way, way, way more important than expensive cables. It's one of the single best purchases you can make.

As for timing, think of it like this:
It'll take the electrical signal .000000003 seconds to travel one meter. Can you hear a .000000003 second delay?

 

[Vaughan Odendaa]

Yeah, I know what you are talking about. I'm just a little hesitant to buy this calibration software because of the fraudulent information posted on their site.

--Sincerely,