[mythtv-users] optical vs coax (was My Ultimate Mythtv?)

Per Åge Sørvik peraage at leneogperaage.com
Thu Sep 18 09:58:07 EDT 2003


Jarod C. Wilson wrote:

> On Wednesday, Sep 17, 2003, at 03:42 US/Pacific, Per Åge Sørvik wrote:
>
>>> I can definitely see the argument that a signal having to be 
>>> translated from one medium to another and back is bound to have a 
>>> wee bit more loss of signal than one that never needs translation 
>>> during transport.
>>
>>
>> This kind of conversion doesn't really have a loss in the form of 
>> "loss of data" at all, as in different sound quality. 1 is 1, and 0 
>> is 0. Som audophiles will probably start talking about jitter or 
>> something though.
>
>
> It isn't always 1 is 1, 0 is 0. Sometimes it is 0.9 is 1, 0.2 is 0, 
> and 0.6 may have been intended to be 0, but comes out 1. Highly 
> unlikely, unless something is very wrong, but bit-flipping is still 
> possible on a digital signal.

Yes, but then you are talking about an error situation. My point here is 
that conversion from electrical to optical isn't a lossy operation in 
itself, as was implied in your original statement ("is bound to have a 
wee bit more loss of signal"). BTW, the signal that goes out on the coax 
cable also goes through a translation, albeit not a change of physical 
media.

>
>>>> On the other hand, optical cables are immune to electrical noise.
>>>
>>>
>>> Good point. The superiority of coax over optical argument does 
>>> assume you have high-quality coax cables that are well-shielded. 
>>> Optical might be better if you have an issue with lots of electrical 
>>> interference. Optical also has the advantage of being able to span 
>>> much greater distances, so if you want to put your stereo 500" away, 
>>> you can... :)
>>>
>> That depends on the quality of the optical cable (attenuation)
>
>
> But of course.
>
>> and the fact that toslink probably is multimode fiber, not singlemode.
>
>
> Not sure.

Well, I'm pretty sure, but I'm to lazy to check it out :)

>
>> I really don't think the normal optical consumer cables can cover 
>> very large distances (more tha a few meters). Haven't teset it 
>> though. I have testet some 20m shielded coax, that worked just fine.
>
>
> Hm. I was extrapolating from 100BaseTX versus 100BaseFX, but then I'm 
> not seeing many very long optical toslink cables on the site of the 
> dealer I use for cabling... Perhaps you are correct.

I guess the case of availabilty of high quality long optical cables for 
toslink is what keeps them out of use. High quality coax cables are  
much more readily available.

-- 

peraage



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