[cededone]

Which is the better cable connection ? I tried to use forum search engine as I'm sure this question has been answered but no luck. I've used the toslink(optical) cable in my current set up with no problem. I'm setting up another H/T set up with Panny RP 91. I'm reading that coax is much better to use that toslink even though they both pass through digital signals. Help with advise in the right direction. thanks

 

[Glen Graham]

You've asked a question that has been hotly debated many times; perhaps the search engine is having issues since the forums were just re-arranged last week.


In any event, here is what you will find:


Group 1:

co-ax is better because of various deeply faithful reasons, people claim they can hear a difference. No real scientific proof. A belief, like a religion.


Group 2:

Digital is digital. 1's and 0's are just that - and an error in transmission is a flaw, thus cannot happen. Science.


Group 1 disputes Group 2, by claiming that optical is more susceptable to various corruption, and that all transmissions have errors, but coax have less


Group 2 will counter with: errors are unacceptable, and any hard-core geek Q/A tester would fail any cable that had ANY errors. Period.


Group 1 counters with "co-ax sounds warmer".


Group 2 replies: How can 1's and 0's sound "warm" or "cold"???? Either the cable 100% correctly passes the right digital sequence... or it does not. Period.


At which point, Group 1 usually replies that the optical plug is less reliable, they fall out, etc.


Then, the argument degenerates into bashing, and sometimes attacks even get personal.





Bottom line? If you believe you can hear a difference, then it matters to you. If you don't, go with what works out easiest. If you can use both, try both. See if you can hear a difference. If you believe you can, then buy what you believe.


Sorry to be vague, but it is a huge can of worms!

 

[Ratman]

Glen...

You gave the perfect answer! That's exactly what gets tossed around...

 

[cededone]

Thanks for the reply. I've only used optical in the pass since someone else did the set up. This time around I may try coax and see if it makes a difference.

 

[spidey07]

Group 3 - People that actually design digital communication circuits and will continually refute the notion that "digital is digial". It is NOT 1s and 0s, but an analog waveform interpreted as on or off. Science.

 

[bpape]

I guess I am in group 2.5.


REAL optical is a much better medium. However, TOSLINK is not REAL optical. The only advantage to this is elimination of ground loops and hum. If you have this, there are other problems in your system. Most of the TOSLINK connections are crap. The fiber is a plastic derivitive and is not faithful to the original signal.


Now, if you want to talk ATT standard (ST) optical connections, then optical is the way to go. Otherwise, stay with coax. Even good network cable techs have approximately a 5% cable scrap rate when making optical cabling due to the exact nature of the beast.


As for the 1s and 0s, I agree with Spidey. Yes. It is only light. BUT!!!!! what is interpretted is when the light gets there and its intensity at said measuring point. If you have ANY, and I mean ANY kind of reflection in the cable (flaw in the cable), sharp bends, non perfectly square ends, you will bounce light around in the cable and corrupt the signal.


Think about stray light off a front projection screen. Same thing. Hey, would you spend a ton of money on a great front PJ and then build the hushbox lens using plexiglass from home depot or would you get optical grade glass? This is the difference between most TOSLINK cables and real fibre optical communications cabling.

 

[Ratman]

...and the beat goes on!

 

[JeffGrimes]

I agree with the connections issue. I received a cheap Toslink with my DVD player....Junk! Would always fall out...When connected, hoever, perfect signal...


Coax, like an RCA connector, is not as prone (although loose RCA connectors do exist)...


As an engineer, I'll take the science...Quality of the sound is MUCH more related the DAC/ADC used to facilitate/interpret the signal on BOTH sides of the cable...A higher quality (you define quality, whether it be accuracy, "warmth, etc") DVD/Pre-AMP will give you better results, regardless of the cable used...


COAX is prone to EMI, but a decent (note, NOT HIGH QUALITY) shielded cable will suffice for more than the most "dirty" of runs.


Your best bet...Buy a decent exapmple of both cables...use your significant other (or other bored friend) to help you with an Blind A/B test...If you can't tell the difference...Go for the more reliable connector...COAX...


Caveat: More expensive Toslink cables and better quality receivers have "snaps" that actually work really well, insuring a quality Optical connection...My experience, though minimal...Coax tends to run cheaper...

 

[avguygeorge]

I think for HT;toslinc is fine. It's when you get into megabuck 2 ch reproduction--- you will find none of those dacs even have a toslinc in.--- Geo.

 

[jheoaustin]

Did anybody mentioned jitter difference between Coax and TOS? It seems nobody did. There may be group 4 talking about jitter. Optical transmission is not very good, and especially MOST TOS cables or transceivers have relative low bandwidth, resulting in high jitter.

 

[John Kotches]

Jaehoon,


The highest bandwidth possible by the defined specifications is two channels of 24/96K, which is under 5megabits/second. This isn't anywhere near "high bandwidth".


If TOSLink uses NRZI to pass 1s and 0s (don't recall the details on that) your maximum modulation (all 1s) is under 10megabits/second.


I just don't agree with you on the bandwidth limitations.


I prefer Coax for the robustness of the connector, otherwise, I have yet to hear an audible difference between the two.


Regards,

 

[jheoaustin]

John,


I am not sure if I put it in right way. Let me try again.

Lower bandwidth makes the analog wavefrom of S/PDIF strweam farther from ideal square wave. Resulting waveform will look more like some pre/post ringing happening on the ideal squre wave. That ringing and round edge(even worse) could impact the threshold-crossing points. This will cause the PLL at S/PDIF receiver to recover more jittery clock.


I am still unsure what you disagree with me on bandwidth limitation???

Maybe I cannot read between the lines?

 

[John Kotches]

Jaehoon,


This isn't an analog waveform we are reproducing, and the square wave analogy is not valid when discussing a TOSLink connection.


The phase change is on/off transitions, not square wave modulation. The highest number of transitions (even assuming an all 1s signal, which is pretty bogus) is

Regards,

 

[Ratman]

I think what is being said is that assuming the finite amount of data transmitted on a media type and considering the finite bandwidth that media is capable of carrying, it's a moot point. As long as the quality of the transport (copper/fiber) and the connection(s) meets or exceeds the standard for transmission of that data, there should be no audible difference.

 

[jheoaustin]

John,


I am sorry, but that is not an analogy, and whatever form the signal is in optical channel, eventually, it's converted to electrical form, and subject to jitter due to the limited bandwidth, even though the degradation and caused jitter may not be big enough to be noticeable.

 

[Colm]

Just a comment on internal reflections with TOSlink. They exist with coax as well. You will get them if the load impedance is not exactly matched to the characteristic impedance of the cable. And you will get them because of inconsistencies in the cable imparted during manufacture and use. IIRC Belden states that its manufacturing tolerances hold impedance within 3% anywhere within the cable, and that the best that could be practically achieved would be .5% Basically, at any point in the cable where there is a mismatch, you will get a reflection. The greater the mismatch, the greater the reflection. Also, coax has capacitance, which has some effect on the waveform.

 

[GotNoRice]

I use Toslink on my laserdisc player and Coax on my DVD player and they both sound fine.


This is using the cheapest toslink cable I could find, which was still a whopping $15 for a 3' segment at radioshack!

 

[AndreYew]

jheoaustin is correct about bandwidth, and it doesn't matter whether it's carried optically (converted to electric signals) or electrically --- bandwidth is bandwidth. If Toslink has 10 MHz of bandwidth, there is no way it is ever going to carry 20 MHz of information.


Further, his point is not the bandwidth in bits of the signal being carried, but sufficient bandwidth to maintain sufficient signal integrity so that those bits may be recognized and be used as a clock reference (stupid, but it's how it's done), because most DACs have relatively unsophisticated receivers, so many transports compensate by outputting ridiculously fast waveforms. Ideally from an EMI perspective, the link should carry the lowest bandwidth transmission possible with maximal jitter so that emissions noise is spread out and low, but since most DACs are pretty bad about receiving anything short of perfect signals, this isn't really an option. Of course, this EMI emissions thing is for galvanic connections, such as coax, and not for Toslink.


Another advantage not mentioned for Toslink is that there are no galvanic ground loops with Toslink. There've been measurements done years ago that show a marked decrease in jitter effects at the analog output of the DAC when a Toslink connection was used instead of the coax connection. This effect depends on how badly the DAC is designed, and unfortunately is better for worse DACs. I believe the device in question was the Theta TLC, a supposed jitter buster, which unfortunately did not separate its input coax ground from its output coax ground, so using its Toslink input and coax output resulted in lower jitter. Brilliant ... not.


--Andre

 

[LexMan]

Above all listen for yourself. But to throw my .02 in, Toslink can sound indistinguishable from coax if it is glass fiber.


Plastic Toslink can pose a problem for certain systems due to many things, increased jitter through refraction,( blurring of the square wave), poor clarity of the plastic which results in over all poor transmission of the signal.(High Signal Loss)


I had a Onkyo receiver and when I switched from a plastic Toslink cable to a glass fiber, it was the biggest difference a cable has ever made to the over all sound that I have heard. When I got my Lexicon, the Lexicon captured the digital signal no matter what I feed it.


So I would say a cheap coax wouldn't sound much better than cheap/plastic Toslink cable and the same for more expensive versions of both. And it also depends on your system.


And to those who feel since its digital its perfect, Stereophile/Widescreen Review did a lot of articles in past years where CD/DVD players were not reproducing 16 bit sound. The early DVD players were sighted with poor CD quality which was due partly to their inability to reproduce 16 bit sound. I believe it was Widescreen that sited most early DVD players were only abe to reproduce 12-14 bit sound. The only one that came close, the sony 7000 at just over 15. So if your machine ain't able to get the signal correct to the cable, its really moot as to which cable you're using.

 

[jheoaustin]

Even though the cable is a glass fibre one, the transceiver at players or receivers are mostly not as good. Does anybody know any TOS Tx/Rx which has as high bandwidth as glass fibre cables?