Digital Audio Cables: Wire or Optical

I am trying to connect my CD/DVD player to my processor. My basic question is: Should I use the RCA digital wire interconnect or an optical cable for the audio? What is truly the difference? What is everyone experiences and/or suggestions?

Go with the coaxial cable. This gives you much better sound.
Go with the coax cable (this is a "no brainer"...I wish all choices were this easy!) I assume that by optical, you are referring to Toslink and NOT AT&T glass! Happy Tunes!
Definitely Wire/Coax cable.
I beg to differ: why not toslink?
As long as you keep your equipment in its place and are not prone to moving connected components thereby inadvertently pulling/loosening the connecting wires - toslink is a better choice. From my recollection- everytime a "high-end" review has criticised toslink their argument has been that it is not a "secure" connection - cable tends to pull-out. That is because these people keep pulling/pushing their components. Infact, if one was to consider the imperviousness of toslink to RF or AC interference due to running close to power cords , this alone makes it superior to coaxial. Coaxial digital can easily pick-up interference from power cords. Bottom line- if you intend to SUSPEND or TOW/PULL compnents then use a coaxial with its supertight connection. Else go with the toslink. BTW, I also feel that part of the reason for reviewers/manufacturers to tout coaxial digital is because they can keep going upscale with "esoteric" shielding etc and basically delude the public into buying their so-called "improved" designs. Whereas in glass or optical - no such improvement is required and shielding is a non-issue.
The reason that wire is superior to toslink is that there is a lot more "unnecessary" work taking place with the toslink. As such, there is more room for signal loss and degradation.

The signal on a disc starts off as digital. When using a Toslink, it must be converted to an optical signal at the transport. It is then fed optically to the DAC. The Dac receives the optical signal and must convert it back to digital. Once it completes the optical to digital conversion, it is then converted from digital down to analogue. This can be summed up as DODAC, which would stand for Digital Optical Digital Analogue Conversion.

Using wire, you start off as digital. Leave the transport as digital. Arrive at the DAC as digital and is then converted to analogue. This is simply called a DAC process because it is Digital Analogue Convesion.

As you can see, involving optical in the digital chain adds two unnecessary steps. Which one do you think is closer to the "shortest path" and has the potential fo the "purest signal" ??? Sean
To add to Sean's explaination, toslink is an excellent connection in THEORY. Problem exist on the receiving end of the DAC whre the optical receiver cannot cope with the bandwith and speed of the optical transmitter on the transport end causing a time delay in converting the optical signal to electrical.

This time delay or rather time error is what causes jitter. ST glass is another story much better than the Toslink.
Genesis168 wrote: "Problem exist on the receiving end of the DAC whre the optical receiver cannot cope with the bandwith and speed of the optical transmitter on the transport end causing a time delay in converting the optical signal to electrical."

Are you saying that the optical transmitter in a Toslink-based audio system is sending data too fast ("bandwidth and speed") for the receiver to process correctly? If so, do you have anything which supports this explanation?
Firstly, bandwith of TOSLINK is only 6 MHz. ST glass optical is between 50-150 MHz and electrical coax is 500 MHz.

I am not saying that the transmitter is sending the signal too fast. Rather when receiving the signal and CONVERTING it to electrical signal has a back log in doing so (takes time to do so). Transmitting will be at light speed. Receiving too at light speed but the conversion to electrical is where the problem is. Jitter is the timing error for this..we're talking micro secs to miliseconds

AT&T ST optical has far wider bandwidth therefore will better handle the signal at the receiving/conversion side.

I have read this somewhere but at this moment cannot remember where. Specs. on bandwidth is taken from "Guide to High End Audio.

Hope this helps.
In Response to Sean's comment:
Regarding additional two steps - are you saying that with coax signal starts as digital and stays digital? My impression is that it starts as digital and is then converted to some form of electrical (??) and the reverse occurs at the other end. Thus- in theory timing errors can creep into coax transmission thereby leading to jitter. And supposedly this jitter can be even MORE EXTREME than in case of toslink since the potential of RFI/EMF susceptibility of coax can be very damaging to the signal! This possibly again negates the "so called" superiority of coax over toslink. As for bandwidth, I doubt if that is even a restrictive factor. There is enough bandwidth for current signal specs.
Sean is right. Output from transport is electrical digital and stays that way until it reaches the DAC chip then converted to analog inside the chip.

If you use toslink, optical signal when input into the receiver on the DAC has to be converted to electric digital before it goes into the DAC chip hence the extra step.

On the transport side, the laser pickup DOES NOT output the optical signal. Signal from laser pickup is converted to electrical then sent to the optical LED to light up the TOSLINK cable.

Yes, coax has it's own problems with the RFI and grounding which the TOSLINK does not have.

Ultimately, it is up to you the listener to use whatever cable you think sounds better to your ears.
With no real attempt to clarify all of the confusion, please keep in mind that the bandwidth limitations stated are those of the "typical" transmitters/receivers usually found in consumer equipment at the time the information source was written. The optical cables are capable of far greater bandwidths with commercial grade lasers or even higher quality, current technology opto-converters. Single-mode fiber has transferred near terra-bit data rates in specialized experiments. The typical negative associated with Toslink is the poor connector pair mating. Any misalignment will result in signal loss, but also signal reflection. Toslink's plastic shells allow too much play between the connector mating. Also, multi-mode fiber is used in most Toslink cables. (Actually, I'm not aware of any Toslink using single-mode fiber, but I haven't taken a survey of all manufacturers. The Toslink shells that I'm familiar with are designed for the larger diameter multi-mode fiber.) Multi-mode uses a "reflective boundary" characteristic to propogate the signal down the fiber. This will induce additional jitter. Of course, until your equipment is completely thermally stabilized, the timing source will produce far greater levels of jitter.

Conversely, ST-type connectors typically use ceramic that is precision ground to achieve much better tip alignment. Also, single-mode fiber inherently should minimize any timing error due to the cable. However, the quality of the glass thread used in single-mode can vary. The specifications would suggest that there should be no practicle difference, but how often do we hear differences in copper cables. Just something I thought I'd toss out to further muddy the waters. In both cases, the quality of the tip polishing is very important to maximize signal transfer.

As for opto-electrical conversion time, this should be irrelevant. Jitter is the relative timing error between the leading and falling edges of the serial digital data or clock, either of a single bit or from one bit to the next. As long as the conversion time is constant, there will be no increase in jitter. Reclocking of the received data from the FIFOs is very common in digital circuitry to reduce timing errors. Extreme accuracy crystals are available, though expensive. Phase lock loops (PLL) are also routinely used to minimize clocking variations.

I guess what I'm trying to get across is that you should be careful not to be too quick to blame a particular type of cable system as much as the quality of the components used within the equipment to implement that cabling system.
Enjoy the music.
Response to Genesis168 and Sean:
Is it possible you are confusing two different types of electrical signals and lumping them into "electrical digital" ? My impression is that signal from pick-up/laser is some form of "pulse-wave electrical" [is this electrical digital?] and then gets converted to a different kind[voltage?]. Anyway - I do not recollect much about this now- too many years have passed. In lieu of that I will make this my last post on this topic. The final point I wish to make is that one should refrain from making blanket statements like "coax is better" OR "coax is superior to optical" since there are a whole lot of other parameters involved (see post by Jcbtubes). My fear/feeling is that a majority of users jump on the coax bandwagon just because it tends to be driven by the reviewers/manufacturers who both have their own axes to grind in this matter. Cheers.
I think that digital signals are PCM ( pulse code modulated ) but i'm not sure. Never really paid a lot of attention to how they did this, only the results. Either way, they are "modulating" or "super-imposing" the digital data stream onto an rf based signal. If i remember correctly, i think that this signal is somewhere around 3 to 4 MHz or so. As such, coax is still a pretty efficient conductor at that range and should work quite well.

You do bring up a good point though that i had forgotten about. There actually has to be another stage that we've overlooked. Obviously, laser is a light based energy. As such, the signal has to start off as optical and is then converted to digital. At this point, the data can be extracted / seperated between the optical laser signal and the digital data that was superimposed on that light stream. From there it can be sent from transport to dac via the rf based coaxial jack or via optical on a toslink jack. Obviously, there must be technical problems ( probably scientific limitations ) with trying to leave the signal optical from the transport and then directly it at the DAC directly. This would drastically simplify things if possible.

After thinking about all of this, it is no wonder that it has taken us 20 years to get good sound out of redbook players. While i do believe we started off with something that was not well thought out to begin with, there is obviously a LOT going on within these players. As such, i see a lot of room for error and the necessary refinement that takes place when you have such errors.

Maybe we should be grateful for what we have and be glad that technology is working to our benefit. Then again, if they would have simply started off with a higher sampling rate to begin with ..... : ) Sean
Genesis -

The bandwidth of Toslink is at least 6Mbits/sec, assuming that you have your transport and DAC within shouting distance of each other. Note that as Jcbtubes said, plastic fiber links (including Toslink) can run much faster. The datastream for CD runs under 1.5Mbits/sec.

If you prefer coax to Toslink, no problem. If you're looking for a technical reason that would make coax superior in audio applications, bandwidth isn't it.
I had the same question after I had used an optical link for a number of months. I went to a coaxial link recently and did an A/B comparision. The audio is more realistic on the coax. The sound went from just musical notes to the reproduction of the musical experience. The soundstage presence was missing on the optical. I'll not go back to optical.
Hi Lbietz2001,
I had the opposite reaction. I once tried a $200 "highly touted" coax digital cable (only 1m lenght) and felt that the music lost its charm. The experience (diluted) was there but the "notes" were lacking. Instead of "musical notes" I heard dome kind of "noise", "harshness" and other sounds which were not in original signal. My friend brought his mega bucks transport along with his $500 coax digital cable and we sat down for some serious A/B comparisons. Imagine his shock! He was completely blown away by my rig using a cheaper $100 optical cable. Next day he put his coax digital for sale. I will NEVER go back to coax digital again- its a sucker product. Cheers
Upgrade1394, what is comprised of your system, if I may ask? I was curious as to why Toslink sounds better for you as I too find Toslink to sound better. You said you are using a $100.00 version. I originally started with a $50.00 Audioquest and upgraded to a little more expensive one from DH Labs and there was an improvement. I have not researched all the Toslink models, but with the connection being of key importance, you could spend probably upwards of $200-400.00 for some fancy Toslink models,but is there a limit as to how good the cable can sound ? in other words, a point of diminishing return.Thanks for your feedback.
Hi Sherod,
I have the Sony XA7ES and used a AQ toslink. The coax was some fancy Kimber Kable model. Speakers are the ML SL3 powered by (hold steady) Parasound HCA1000A! Owners of SL3- try this combo out but biwire the speakers, I am using Straightwire Rhapsody cables. Unbeleivable performance by the Parasound/SL3 combo - blows away other esoteric amps upto the $2000 range.
My friend used a Classe transport and DAC and some real fancy "silver" coax digital. Rest of setup was mine. Oh- the preamp was the Sony TAP-9000 (NOTE: TAP, not TAE) which by the way is a superb simple 2-3 source analog line only pre-amp. Hope this helps out prospective buyers of toslink cables and current owners of Martin Logan SL3's. Cheers.
Oops- my dac is the Parasound DAC-1500.