Optical Cable

[dinkeye]

Where should I get an optical cable. They are a rip off (like $50 or more) in big box stores. I am also in Canada which limits this. So where is the best place to get a decent cable for a decent price. Thanks guys.

[Sheep]

Where should I get an optical cable. They are a rip off (like $50 or more) in big box stores. I am also in Canada which limits this. So where is the best place to get a decent cable for a decent price. Thanks guys.

If you can wait, and wouldn't mind paying shipping charges, the optical cables from dayton on Parts Express would be a great buy.

This one (remove space)

http://www.parts express.com/pe/showdetl.cfm?&DID=7&Partnumber=180-945

Is all you will ever need.

SheepStar

[nibhaz]

Do have Radio Shacks up there in Canada? You should be able to find optical cables starting around 15 dollars.

[GlocksRock]

find someone on ebay who sells them and ships to canada. Even though they are generic no name cables, they work great, I've bought them before and had no trouble.

[Sheep]

Do have Radio Shacks up there in Canada? You should be able to find optical cables starting around 15 dollars.

We have "The Source's". All their cables are $29 or higher. I already checked. ;)

SheepStar

[bobbydigital]

Walmart can't get much cheaper

[markw]

Where should I get an optical cable. They are a rip off (like $50 or more) in big box stores. I am also in Canada which limits this. So where is the best place to get a decent cable for a decent price. Thanks guys.I take it coaxial isn't an option?

[dinkeye]

I prefer an optical connection versus coax.
I don't know why, is one better than the other?

[Francious70]

Not really.

[j_garcia]

I prefer coax to optical whenever possible. Far less likely that it will accidentally be knocked off due to a more solid connection with coax. I've had two installs that both called a day or two later complaining that they had lost their sound and both times it turned out to be the optical cable simply falling out of the cable box and satellite box. I've never had a problem with the cables falling out myself, I just prefer coax.

[patnshan]

I prefer an optical connection versus coax.
I don't know why, is one better than the other?


There are multiple articles discussing how sound quality is the same between digital coax and optical. I use coax for durability and because I got them for like $10 each on ebay. Works fine. Tried my buddy's optical and cannot tell the difference.

Pat

[Hi Ho]

I just optical and, if anything, the optical connectors are held on tighter than coax. If I turn my receiver around the optical cables stay tight but the coax cables easily slip off. There's no difference in sound but optical is more interesting with it's red light. :)

[Johnny Canuck]

I have tried both. With my Denon 3805 and 2910, i found the optical considerably better as the surround was wider compared to more forward with coaxial. Just what i heard. And I agree, the optical cable is a better connection. it does not come out unless you really pull it out. It "clicks" in, it does not just push in like a coaxial cable, therefore the suggestion that coaxial is a better connection is false..

I have a Monster optical cable (very good, but bought before I was educated) and tried the Bluejean optical cable.

I did not notice any difference on the cable box between the two but did notice a difference with my DVD player.

[rschleicher]

I think I paid 13 or 14 dollars (US) at Target for an optical cable made by GE. Works fine, although it does pull out easily from the back of both the receiver and my DVD player.

I have an optical link from my DVD player, but a coax cable from my HDTV cable box. That's just how the default inputs happened to be set-up/named on my receiver (a Yamaha).

[Hi Ho]

I have tried both. With my Denon 3805 and 2910, i found the optical considerably better as the surround was wider compared to more forward with coaxial. Just what i heard. And I agree, the optical cable is a better connection. it does not come out unless you really pull it out. It "clicks" in, it does not just push in like a coaxial cable, therefore the suggestion that coaxial is a better connection is false..
I'm not going to argue with you about what you heard but I'll bet it's really your mind playing tricks on you.

When a coax or optical cable is sending a Dolby Digital or DTS signal, they cannot alter the signal in the manner that you describe. It just can't happen. DD/DTS is a stream of bits that are decoded by the receiver. If the stream gets to the receiver, you will have sound and it will be the same whether you're using a coax or optical cable.

[Sheep]

I'm not going to argue with you about what you heard but I'll bet it's really your mind playing tricks on you.

When a coax or optical cable is sending a Dolby Digital or DTS signal, they cannot alter the signal in the manner that you describe. It just can't happen. DD/DTS is a stream of bits that are decoded by the receiver. If the stream gets to the receiver, you will have sound and it will be the same whether you're using a coax or optical cable.

Yep, the mind works in misterious ways. I though banana plugs made a difference. Boy, how stupid was I! :)

SheepStar

[Hi Ho]

Yep, the mind works in misterious ways. I though banana plugs made a difference. Boy, how stupid was I!
Not stupid, just wishfull. The brain *thinks* it is hearing/seeing a difference and therefore you do. If you spend a lot of money on something you want to notice a difference. If there is none, your brain makes one. :)

Once I *thought* I heard a difference when I put larger guage wire on my center speaker in an attempt to alieviate sibilance (at the recommendation of someont). I later figured out that it didn't do squat but at the time I sure thought it did. I didn't spend any money on it either.

[Takeereasy]

I use digital coax simply because they are cheaper. I've read that for really long runs optical has the advantage but that isn't a concern for myself at the moment. I have used both optical and coax in the past and I haven't noticed a difference in either. The connection made with coax cables has been super tight in all cases in my experence, and I've only ever had one loose optical and that was a cable I got for $6.

[markw]

I prefer an optical connection versus coax.Not a problem. I prefer vanilla to chocolate ice cream myself. That doesn't imply either is "better"

...is one better than the other?Performance wise in real world situations, no. For long runs with high levels of RFI/EMI, which is not a typical environment for home use, optical may have an advantage.

And, virtually any cheap interconnect with RCA cables will work well as a digital connection. You might be surprised at the money you can save with no sacrifice in quality.

[Johnny Canuck]

Probably right. I think lots of this talk on speaker cables and wires is all psychological.

[obscbyclouds]

There is the fact that coax cables can cause ground loops (i.e. 60hz hum). I had that problem with my dvd player and switched to optical. Optical cables cannot cause ground loops since it is not an electrical connection.

[j_garcia]

Ground loop isn't caused by the cable, it just transmits the problem from one piece of ungrounded equipment to your receiver. There are a few ways to easily fix this, but the use of an optical cable for this particular instance seems like an easy fix to remove the hum from the receiver. This breaks the connection between them, but did not remove the source of the hum at the DVD player.

[markw]

Ground loop isn't caused by the cable, it just transmits the problem from one piece of ungrounded equipment to your receiver. There are a few ways to easily fix this, but the use of an optical cable for this particular instance seems like an easy fix to remove the hum from the receiver. This breaks the connection between them, but did not remove the source of the hum at the DVD player.It can be a band-aid to cover up the symptoms of a pre-existing problem. Mind you, it doesn't fix the cause of the problem, only hide it.

[Nick250]

Not stupid, just wishfull. The brain *thinks* it is hearing/seeing a difference and therefore you do. If you spend a lot of money on something you want to notice a difference. If there is none, your brain makes one. :)

Once I *thought* I heard a difference when I put larger guage wire on my center speaker in an attempt to alieviate sibilance (at the recommendation of someont). I later figured out that it didn't do squat but at the time I sure thought it did. I didn't spend any money on it either.

The mind is a funny thing. As I mentioned in another thread my car always feels like it runs smoother, handles better and is faster after I have it washed.

[obscbyclouds]

Ground loop isn't caused by the cable, it just transmits the problem from one piece of ungrounded equipment to your receiver. There are a few ways to easily fix this, but the use of an optical cable for this particular instance seems like an easy fix to remove the hum from the receiver. This breaks the connection between them, but did not remove the source of the hum at the DVD player.

I was under the impression that this probably isn't dangerous. I live in an apartment, not sure if they'd rewire the outlets for me. Is this something i should further investigate?

[mtrycrafts]

I have tried both. With my Denon 3805 and 2910, i found the optical considerably better as the surround was wider compared to more forward with coaxial. .

For this to happen, the optical cable needs to unscramble the digital signals and alter the right data stream, in this case the surrounds. You think this is possible???

[tbewick]

It is probably worth spending money getting a decent quality optical cable. Not all signals sent down optical cables are digitally coded. An optical cable can, just like any other type of cable, act as a kind of filter. In poor optical cables, apparently this can (noticeably) reduce signal bandwidth (Sound on Sound magazine).

[markw]

Not all signals sent down optical cables are digitally coded. An optical cable can, just like any other type of cable, act as a kind of filter. I'm curious about this. Can you elaborate on what other types of signals they can pass or filter? ...and how it can filter them?

[tbewick]

Hi markw,

Optical cables can be used to send analogue signals - just like an RCA cable. I used to think that they were used for digitally coded signals exclusively, but apparently this isn't the case. Output from a DVD player would normally be DTS, Dolby Digital, or audio CD data, these all being digitally coded.

The fact that cables act as a kind of filter is, if I remember correctly, to do with the fact that no cable has infinite bandwidth. I read this a while back in 'An Introduction to Digital Audio', by John Watkinson, and I have forgotten the exact technical explanation. Of course, all cables will technically perform differently. The author gave more of an explanation for electrical signals than for optical signals. The technical explanations are the things talked about by cable manufacturers - the dielectric, shielding, etc. I'm sure no one disagrees that these are things you have to consider if you were to make a cable. Personally I make do with fairly cheap cables (RCA, toslink) apart from with video cables, where the cheapest cables usually perform poorly.

If using optical cable for digitally coded data, then the cable will still distort/filter the analogue signal, but the DAC receiving the digitally coded signal should be robust enough to reject such distortion.

If using the optical cable as a connection for output to, for example, a minidisc deck, then the data may be sent as a non-digitally coded signal, (e.g. FM radio recording through an optical out on an A/V receiver to a minidisc deck). The distortion of the signal by the optical cable will not be rejected because the signal is not digitally coded. Therefore the properties of the optical cable will be important, just as it is in a standard RCA audio cable. The optical cable has the advantage over an electrical cable of not picking up electrical noise.

[tbewick]

I looked this up on Wikipedia - apologies - I seem to be mistaken about the analogue over optical cable. I must have been thinking of something else. It's only used for digital data.

[markw]

And, this applies to the link between a DVD and a DAC exactly how?

The signal originates in a digital state, is passed in a digital state and, at the DAC is treated as a digital signal to be converted to analog.

Are you saying the cable "knows" what's a good digital signal and what's not and will pass only the good signal?

At worst it would be a steady on or off of the light source. Even if a totally bogus "signal" somehow made it into and through the optical cable, it would still be interpreted as a digital signal bu the DAC.

If it was of a duration long enough to exceed the buffer in the DAC, then some sort of sonic anomaly would occur, the same as if a bogus signal were passed via coax.

[MDS]

I looked this up on Wikipedia - apologies - I seem to be mistaken about the analogue over optical cable. I must have been thinking of something else. It's only used for digital data.

Mistaken for the case of optical, but not for coax. Any time you transmit digital data using an electrical connection, the signal is analog. The zeros and ones are modulated using any number of schemes, the most common of which is NRZ (Non Return to Zero) Look that up on Wikipedia. :)

[Tritonman]

I use a coat hanger.

oops...did i say that out loud? :)

[rumble]

I use a coat hanger.

oops...did i say that out loud? :)

That's ok, I use a special $500 coat hanger....

[mtrycrafts]

That's ok, I use a special $500 coat hanger....


You are so lucky to have that:) I could only modify one from the closet, free:D

[tbewick]

Hi markw

The quality of the cable will have some bearing on the amount of distortion added to the digitally coded signal. Remember that the signal itself is not digital, it is an analogue signal that has been digitally coded, and can be distorted like any other analogue signal. The fact that it's digitally coded should make the original information more resistant to the added distortion/noise.

The degree to which the digital system is effective in rejecting added distortion from the cable is shown in the way you can use a coathanger as a cable in S/PDIF and still get good results. I still think though that buying a decent quality optical cable is a good idea. The cheapest cables can sometimes be of very poor build quality.

As to your description of how the system works, I think it is maybe too simplistic. If things were that simple and distortion did not occur (thanks to signal quality etc.), there would be no need for error correction, phase-locked loops, self-clocking coded signals etc. in modern digital audio systems. It is to the credit of the channel technology and the coding system used in Toslink and S/PDIF that such distortion can be rejected.

[markw]

Actually, I beleieve that the optical cable is pure digital. It's the coax that rides on an analog carrier.

How far back do you want to take the signal? Yesm, it ws analog when the artists createdit but at some point early on it goes digital and eventually winds up on an aluminium disc. Said disc is then put in a player and read buy a laser and the read pits are shaped, smoothed and massaged so they are in ptetty good shape bbefore hitting that LED that sends the signal down the cable. And, when they arrive at the other end and go through the opto-coupler they again go through an error correction process. Any contribution by the optical cable is rendered useless.

but, I agree that a toslink (and coax as well) cable should have good, solid connectors since these are the bain of that media and it's worth paying a little more for solid construction. ...but there's a limit.

[tbewick]

I'm only making this point as it was something that the author of that book I referred to earlier stressed. The signal will be degraded by the cable and this would surely be true of optical cables as well. I'm not sure about the specifics of optical cable, but there will be physical and practical limitations as to the bandwidth and the distance you can send the data. This are issues with the how good the channel (Toslink) is, and naturally will be affected by the properties of the cable.

I understand what you are saying, that the LED is on/off, therefore it is digital. In the design of the Toslink though, there will probably be a light intensity threshold when the receiver decides whether the signal is on or off. The quality of the signal will, I'm guessing, fall off with distance, and therefore the 'sharpness' and quality of the signal will decline. This is surely a result of the analogue medium, where the glass can have an essentially infinite number of light intensities. I believe that this is in contrast to an electronic integrated circuit, where the 'signal' will be kept in good condition by reclocking.

I understand that this difference does seem very trivial, but presumably it is an important consideration in the design of channels, like Toslink, S/PDIF, USB etc.

[Hi Ho]

Over short runs, such "defects" introduced by a cable will be completely inaudible. Unless you are running 100+ feet of optical cable I'll bet there will be no audible difference between different "grades" of optical cables.

[AudioSeer]

I always pick coaxial because I see no need for the signal to go through the additional optical to digital conversion and add additional jitter in the process.

As long as you are using a good quality coax, RFI is a nonissue. Even though the difference is probably not audible, why pick the technology that is inferior on paper when the cost is the same. :)

[tbewick]

I haven't heard about jitter relating to Toslink. Most respectable sources (like Dolby, Audioholics) say that either S/PDIF or Toslink will work fine.

[MDS]

Jitter is inherent in any digital audio system but the levels are extremely small - on the order of picoseconds - that is trillionths of a second.

S/PDIF is the protocol used for both coax and optical connections. Any jitter or lack thereof will be the same for either type of connection. The reason people confuse s/pdif and toslink as being two different things is that the s/pdif spec was written first for electrical connections (coax) and includes the electrical parameters for the physical interface. Toslink is the physical interface for optical connections (as well as the name of the connector).

[ZoFo]

Lifatec was recomended by BlueJeans Cable who made all of my analog cables. They will build a Toslink cable to any length that you want and are very resonable, $12 for a 3ft Toslink if I remember correctly.

There fiber cables are very thin, no additional jacket is used. The connectors all have metal ferals and come in different colors, you can also get two Toslink cables molded together. They also make a "Armored" version where they cover the fiber with Romex and use aluminum connectors.

[xboxweasel]

I read that digital audio can transmit up to "x" channels of encoded audio (DTS, DD, DTS-ES, DD-EX) and 2 channels of non encoded audio (like from a CD player).

Can't remember what value x was. At least 7 though. :P

cheers.

[Davy9]

I go with optical just for one reason:

Coax consits of a conductor while optical doesn't. The conductor in the coax is susceptible to interference from other sources or cables. That being said, I don't know how much this really makes a difference, I just like to do what ever I can not to comprimise the end result.

Optical fibre is just a glass tube that carries a light signal. The quality of it is determined by the amount of inconsistencies in the glass itself, or the ability to produce the highest percentage of "perfect" reflections. The higher the quality, the less inconsistencies.

[Hi Ho]

The way I see it is this. An optical cable transmits 1's and 0's. That is, the light is either on or off. There is no in-between. Now, if you are getting a signal at all, that would mean you are getting a perfect signal. How can some light signals get through and some not? It there is anything getting through then it's all getting through. Is this not correct?

[tbewick]

This was the point of what I said in an earlier post - the Toslink/electrical digital signal IS analogue, and is therefore susceptible to distortion and noise as a signal that is analogue not digitally coded. The whole point of using digital coding (with error correction (redundancy), self-clocking, phase-locked loops etc.) is to make the signal resistant to this distortion and noise in a way that a non-digitally coded signal isn't. Resistance to noise and distortion is what digital audio is all about.

[markw]

...which was created by interperting and error checking/correcting the original ligjht signal that was reflected off of the DVD's surface.

IOW, it goes through two additional conversions when you use optical.

[MDS]

This was the point of what I said in an earlier post - the Toslink/electrical digital signal IS analogue, and is therefore susceptible to distortion and noise as a signal that is analogue not digitally coded.

You are a bit confused tbewick. It is 'digitally coded'. A stream of ones and zeros can be transmitted over a wire using any number of modulation schemes. It's the same principle as sending data over the wire between computers. It's the same principle used to send mpeg-2 data over the coax cable from the cable company for 'digital' cable. Just to make it even more interesting, your IR remote sends digital data via an analog infrared signal. RF remotes send digital data using analog radio frequency waves.

The signal is analog but has either fixed frequency or fixed amplitude (depending on the modulation used) but the DATA is digital.

[tbewick]

I'm just reciting from the book 'An Introduction To Digital Audio', by John Watkinson, Focal Press, which I read a while back. This is the technically correct way of describing how any digital channel works, like the Toslink interface. The transmission medium itself is analogue, and is susceptible to distortion and noise. Hi Ho said that 'if you receive a signal, it is perfect' - this is not true, it will have noise, distortion, and jitter. The original digital information can be obtained from this by interpreting all voltages/current/light intensity above a certain threshold to be 'on', and all below a certain value to be 'off'. Jitter is rejected and the signal correctly clocked by using a phase lock loop. The use of a coding scheme is essential in transmitting the digital data. How the digital information is reproduced correctly so that the cable becomes transparent is a subject of some detail.

Hi markw,

The distinction between when the data is analogue or not was not made by me. When digital data is sent over distances it is sent over a 'channel'. The design of channels is a separate subject from when digital data is kept in an electronic circuit.

[jonnythan]

I fully maintain that with digital, the signal is either there or it isn't.

If these interfaces were not capable of transmitting the exact same data, bit for bit, regardless of interference or whatever else, then the $4 18" SATA cable connecting my hard drive to my motherboard would be incapable of copying a 400MB file without numerous disk and transmission errors, and the $20 optical cable connecting my Cisco PIX router with the T3 line at my office would be incapable of coherently transmitting our internet traffic.

A $100 optical cable is not going to have ANY discernable difference from a $10 one. They are transmitting the exact same data, bit for bit. The entire idea of frequency response changing is ludicrous and belies a complete misunderstanding of digital data. With a CD sound source, you're going to have the exact same number of bits per second whether the CD contains total silence, a singer's voice, or a 100-piece symphony orchestra, and those bits are all 1's and 0's.

[tbewick]

'If these interfaces were not capable of transmitting the exact same data, bit for bit, regardless of interference or whatever else, then the $4 18" SATA cable connecting my hard drive to my motherboard would be incapable of copying a 400MB file without numerous disk and transmission errors, and the $20 optical cable connecting my Cisco PIX router with the T3 line at my office would be incapable of coherently transmitting our internet traffic.'

The reason why this is possible is because digital systems can reject distortion and noise, and this is not only because 'the signal is either there or it isn't'.

'The entire idea of frequency response changing is ludicrous and belies a complete misunderstanding of digital data.'

Again, this is a fundamental misunderstanding. Jitter could reduce the bandwidth of the audio as it has the effect of increasing the noise level. Personally I doubt whether jitter is very audible (at all), but as I say this is my personal opinion and is not based on anything I have read. Chris (WmAx) posted some time back a reference to a scientific journal which had a study into the audibility of jitter.

As for understanding digital audio, I am certainly no expert, and approach the subject as a layman, but I have read a book on the subject.

[MDS]

Jitter does not reduce the bandwidth of a signal. Jitter is a TIMING error. It's effect, were it significant, which it is not, would be to change the data due to incorrectly interpreting a 1 as a 0 or vice versa.

The simplest layman explanation I can give is to use something like PWM (Pulse Width Modulation) where the 'width' of the pulse determines a 1 or zero. Say a 20 usec pulse was defined as zero and a 50 usec pulse was defined as a 1. Now what is the receiver of the stream to do if it *thinks* it saw a 40 usec pulse? Was that supposed to be a zero but the pulse was too long or was it supposed to be a 1 but the pulse was too short? That is jitter, but of course we are talking about timing errors on the order of picoseconds and all the PLL and re-clocking circuitry mentioned takes care of it.

Optical cables can easily affect the data because the principle is different. The light pulses travel down the cable due to 'total internal reflection'. [Anyone remember 'The angle of reflection is equal to the angle of incidence'?] A kink or too tight a bend radius or worse a broken cable will totally disrupt the travel. It CAN happen, but unless the cable is broken, it doesn't happen in practice. Same with electrical connections - they CAN be susceptible to interference but in practice reject it just fine.

All this talk about jitter/rfi/emi is usually much ado about nothing in the short runs of typical ht cabling. Saying 'it either gets there or it doesn't' is actually close enough to the truth.

[tbewick]

I'm talking about the audible effect of jitter. Most of the fundamental concepts, like jitter, bit-depth, sampling etc. are quite easy to understand, but the effect of jitter in a real world system is very complex physically. How much jitter is tolerable has to be resolved using listening tests, objective and subjective. This is just like deciding how many bits you need or how many samples to take for the added distortion and noise (in sampling and quantisation) to be inaudible.

I would also say that commenting on the typical level of jitter (picoseconds) is meaningless unless you place that in the context of how much information you are sending. I would agree that such matters are trivial in regards to audible distortion but this is only based upon my own subjective observations.

Personally I like to understand the physical basis of most explanations, rather than just knowing 'digital is good'. This is probably the reason why people post threads asking whether optical is better than electrical digital etc. I would say it is more satisfactory to offer some technical explanation as well. Without having some physical understanding of the topic, it is very difficult to dispute the idea of needing to spend thousands on an expensive CD player, or of spending an excessive amount on cables. You can argue against these things using statistical explanations, like double-blind tests, but I believe some kind of physical explanation is also desirable.

[AudioSeer]

If these interfaces were not capable of transmitting the exact same data, bit for bit, regardless of interference or whatever else, then the $4 18" SATA cable connecting my hard drive to my motherboard would be incapable of copying a 400MB file without numerous disk and transmission errors, and the $20 optical cable connecting my Cisco PIX router with the T3 line at my office would be incapable of coherently transmitting our internet traffic.


Almost all digital communications like the ones you specify incorporate error correction to compensate for bit errors. The poorly designed S/PDIF interface does not to the best of my knowledge.

[tbewick]

The S/PDIF interface is quite similar to the professional AES/EBU interface, used in recording studios. This is a quote from Wikipedia:

'S/P-DIF is a consumer version of the standard known as AES/EBU; it provides small differences in the protocol and requires less expensive hardware.'

I've also heard criticism of Toslink on the Stereophile web site and on the Sound On Sound magazine web site. Sound On Sound said that bandwidth was reduced using Toslink. Stereophile said something about there being fundamental design problems in the interface. I would be interested to know what the audible effects of such poor design are in an objective (double-blind) test, which neither of these sources cited.

[tbewick]

Here's a quick diagram that I drew which hopefully shows more clearly what I was trying to explain earlier. The point I was trying to make was the importance of the digital system being able to reject distortion and noise, rather than being insusceptible to it.

[MDS]

I've also heard criticism of Toslink on the Stereophile web site and on the Sound On Sound magazine web site. Sound On Sound said that bandwidth was reduced using Toslink. Stereophile said something about there being fundamental design problems in the interface.

'Bandwidth' has two different meanings depending on whether you are talking about analog or digital. For analog, it is the highest frequency possible; for digital it is the amount of data it can carry over a given time period (the 'bitrate'). Sure the highest supported bitrate of s/pdif is lower than others but taking that quote out of context, one would assume that s/pdif somehow loses some of the information being transmitted. If you need to transmit 24/192 kHz uncompressed PCM, then it won't work, but that doesn't mean it 'reduces the bandwidth' - it's not like it will try and chop up the original data into smaller packets. It just doesn't work that way - it's not a packet switched network like tcp/ip.

That picture is nonsense. First, an optical connection has no analog component. The 'bits' are encoded using the same modulation schemes as electrical (coax) but they are pulses of light - not varying voltages or frequencies. I can transmit morse code 'digitally' by using a flashlight - short pulses for dots and longer pulses for dashes. That would be the equivalent of pulse width modulation. s/pdif uses bi-phase mark, which is slightly more complicated.

Everything can be 'susceptible' to problems, but they just don't occur over the short distances of HT cabling. You can build a null modem cable to transfer data from one computer to another using only 3 wires - receive, transmit, and ground. That wire would be susceptible to interference too and yet over the 3 feet it has to travel the number of errors encountered will be zero.

The Myths of Digital Audio are alive and well.

[tbewick]

All I can say is to refer you on to the book I read about digital audio, which was written by a respected author, and has received good reviews. If you were to engineer a system for sending digital audio over distances, then you would need to understand the properties of the cable and allow for distortion of the digital signal.

[MDS]

All I can say is that the book to which you refer as well as Principles of Digital Audio by Pohlmann are not a casual read (I've read them) and you have taken some simplistic, generalized statements and blown them out of proportion. Both are excellent books but require far more background in computer science, networking, and data communications to fully grasp.

[tbewick]

I did say that I thought the issue, which indeed I raised, was trivial earlier on, so I think it's slightly unfair saying that I've blown things out of proportion. In saying that, the diagram I drew I'm sure exaggerates the level of distortion a typical cable would introduce in a home hi-fi set up. My point was simply that such distortion is possible because of the cable, but can be rejected. This is unlike a signal that is not digitally coded.

[tbewick]

I have to hold my hand up over this one - you would probably get no significant distortion over the short lengths of optical cable involved in home theatre/hi-fi. So it is reasonable to say that you either get a perfect signal or not. I also doubt whether over long runs the signal would decay into a sine wave - this is probably only applies to electrical signals.

As for the book I read, it was the only one at the library which had anything about digital audio. It wasn't a particularly easy read.

[Hipnotic4]

This is totaly irrelavent but just wondering if they make any digital opt cables with a clear jacket?

[MDS]

tbewick,
Which Watkinson book did you read? The Art of Digital Audio or An Introduction to Digital Audio? The Art of Digital Audio is a bit more dense and similar to Principles of Digital Audio by Pohlman. Watkinson and Pohlman are probably the two best known authors on the subject.

If you really want your head to spin, pick up Digital Audio Processing by Doug Coulter. I admit that I didn't really follow alot of what he was saying in that book and I am familiar with the low level computer gorp.

A Programmer's Guide to Sound by Tim Kientzle (out of print) is alot easier to read. Digital Audio with Java by Craig Lindley is pretty good too. Although those two books show alot of code (which may be lost on non programmers) they both cover the basics in an approachable manner. Reading books like that first will make it easier to follow the more advanced books. If you started with The Art of Digital Audio, you jumped in head first!

Mastering Audio: The Art and Science by Bob Katz is a mix of technical and practical advice. He explains Jitter particularly well. He is a well known mastering engineer (mostly for his work with Steely Dan).

[jaxvon]

Mastering Audio: The Art and Science by Bob Katz is a mix of technical and practical advice. He explains Jitter particularly well. He is a well known mastering engineer (mostly for his work with Steely Dan).

I'll need to pick up some of these books. I have a correction though, the producer that did a lot of work with Steely Dan and Fagen was Gary Katz, not bob.

[Hipnotic4]

Nicee i gotta get some of those books 2

[tbewick]

Hi MDS,

I read the 'Introduction to Digital Audio' book. The book doen't offer much analysis of the explanations, so you could read it and leave without any idea how much you need to spend on equipment. I suppose such a book that did offer such information would be titled something like 'Practical Digital Audio'. Out of interest, seeing as this is such a regular sort of question, do you know of any links to sites that do proper physical tests comparing cables? This, to me, would offer a more rigorous coverage of the topic, rather than just going on the accepted principle of using short lengths of cable.

It's rather interesting with Bob Katz. I've seen his site, Digital Domain, and he seems to offer seemingly contradictory advice. For example, on an article about jitter, he initially seems to dismiss the importance of jitter, but then goes on to say how jitter can introduce (subjective) distortion on playback. Again, I think that his site, though interesting, doesn't really offer much practical advice. One of his conclusions is to buy a DAC that has high jitter reduction. I've never seen this sort of performance information on any CD player or digital receiver.

[WmAx]

1st thing: would a moderator please move this thread to the cables forum?

e.

It's rather interesting with Bob Katz. I've seen his site, Digital Domain, and he seems to offer seemingly contradictory advice. For example, on an article about jitter, he initially seems to dismiss the importance of jitter, but then goes on to say how jitter can introduce (subjective) distortion on playback.

On one part of his site, Katz also discusses analog audio and how it's audibly superior to most digital systems, going on about the subject with all sorts of typical audiophile subjective descriptions of sound. He may be a fine mastering engineer, but without supporting perceptual research to back up claims of audiblity, one can not take such claims seriously.

Katz is a mastering engineer; he may be referring to potential additive jitter in a long line of processes, if multiple AD/DA or non-master clock linked digital audio devices are used in conjunction with each other.

Based on the research I have read(I refer to blind test research using multiple test subjects, not the worthless joke whitepapers that are referencable from a site like stereophile), the amount of jitter-error to become audible in music playback is massive, relative to the amount induced by common digital electronics or cable transmission problems. To become audible on pure sine wave test tones, a very sensitive listener, under lab conditions, using headphones for maximum sensitivity, may detect 3 ns of jitter at just the right jitter frequency. This is worst case scenario, under un-realistic conditions, and this is a higher value than an average DAC(though some very poorly designed units with odd functionality/design may induce slightly more than this value) will produce. With music, using selections that contain isolated sections of instruments, to increase sensitivity, the most sensitive listener under the most sensitive conditions(headphones, etc.) could detect 20 ns in one instance.

Refer to an old thread which was concerning optical cable jitter, and in which I provided some result graphs of Dolby Labs research:

http://forums.audioholics.com/forums/showthread.php?t=4547

-Chris

[tbewick]

Thanks Chris for the link.

The Audioholics article on optical cable suggests that buying a good quality optical cable is worthwhile -

"The second concern, data error, is easier to understand - data arriving at the D/A converter is either missing or wrong. This would be very detrimental to sound quality and often results in loud popping noises or even muted silence. Data interpolation, the reconstruction of damaged data, would result in less obvious, but similarly compromising, effects on fidelity."

Is the necessity for data interpolation a common occurrence with Toslink connections? This contradicts the idea of having either a perfect signal or no signal at all. The book I read on digital audio said that in a properly working digital system, the need for data interpolation due to errors should be minimal.

"Today the TOSLINK optical interface has reached its sonic performance potential. What changed? There are three factors that draw the line separating mediocrity from excellence: purity of the optical conductor, clarity of the optical termination (lens), and flexibility without signal loss. When each of these parameters is optimized, and the interconnect is used with quality components, the TOSLINK connection is audibly indistinguishable from coaxial S/PDIF."

Wouldn't this mean that it's better value buying a cheap coaxial cable rather than shopping around for a high quality optical cable? The fact that a contributor to the article is a company that manufactures cables does lead to the feeling of possible bias.

[WmAx]

Wouldn't this mean that it's better value buying a cheap coaxial cable rather than shopping around for a high quality optical cable? The fact that a contributor to the article is a company that manufactures cables does lead to the feeling of possible bias.

Please refer to the jitter values claimed in said article concerning cheap optical cable. It's a bogus[unsubstantiated] claim that these have any relevance to audibility in a typical length distance connection.

-Chris

[markw]

Has someone here claimed to have heard the effects of jitter with either expensive or inexpensive toslink or coaxial cables? ...or is this simply arguing about the number of angels that can dance on the head of a pin.

If I read wick's last post, it basically says that when all is right with a toslink connection, which involves several parameters, it's just as good as a plain vanilla coaxial connection.

Again, what IS the point of this thread?

[jonnythan]

Has someone here claimed to have heard the effects of jitter with either expensive or inexpensive toslink or coaxial cables? ...or is this simply arguing about the number of angels that can dance on the head of a pin.

If I read wick's last post, it basically says that when all is right with a toslink connection, which involves several parameters, it's just as good as a plain vanilla coaxial connection.

Again, what IS the point of this thread?
The point, ultimately, in response to the original query, is that there is no difference between a $100 Monster Cable toslink cable and a $5 Cables For Less one.

[tbewick]

That's cleared it up for me. The only point that confused me was the possible need for data interpolation due to errors. I'm guessing that if there was something seriously wrong with the Toslink cable necessitating a lot of data interpolation, then clicks would give it away. Hopefully the rest of the time, data interpolation either isn't required or is so infrequent as to be inaudible. In other words, you get an effectively perfect signal or you don't get a signal at all.

[markw]

In other words, you get an effectively perfect signal or you don't get a signal at all.This is true for any cable, toslink or coaxial. I would think this was also made clear by the number of words expended in htis thread by now.