Toslink Quality

I can understand how sound quality could differ in solid core interconnects but does it really make a difference in brand when selecting digital cables (i.e. No name, Monster, PureAV, and a slew of others)?

I wouldn't recommend over-spending in this category. You just need well made cables. For optical, I'd be hard pressed to change from Outlaw's PDO for any application where the 1.8-meter length is sufficient. For coaxial, I've got one Outlaw PSC and one Blue Jeans digital audio - both are good quality, reliable cables.

I've been recently researching this area myself. It's been the subject of fairly passionate debate. There's one school of thought, which is "bits is bits" and neither the cable type (toslink vs. coax) nor brand should make much difference.

The other school of thought is do not use toslink if you can avoid it and get a good coax cable that has a true 75 ohm RCA connector. The reasons? From what I can gather: (1) the connection on toslink is not as good as coax; (2) toslink is more prone to jitter; and (3) coax has a wider bandwith. There's also something about the inherent weakness of toslink converting light as the input signal, but I can't remember the particulars of the argument to do it justice.

Anyway, I haven't done any A/B comparisons of the two. However, I am currently upgrading cables throughout my system and plan to make a length of coax and compare it to the toslink I am currently using on my Oppo DVD player. If your a DIY-type, the digital cable made by DH labs (D-75) with their 75 ohm RCA connectors can be had pretty cheap online. (BTW, I do not work for or have any affiliation with said company.)

I plan to order this combo soon and will report back my results if anyone's interested. Be forewarned, I'm the same guy who heard differences between my stock power cord and an aftermarket brand.

I've read that the jitter issue with toslink is the same as that with the coax, in that the S/PDIF interface itself uses its own clock signal, separate from the clock signal coming off of the source, causing some "confusion". The result, from what I've gathered, is less apparent than the tic-tic sounds caused by jitter from a d/a. However, if you read this article by Bob Katz, it says that almost all jitter is subtle at best.

Flying in the face of audio idolatry, I suggest buying a relatively cheap, well-shielded coax cable, since they're overall cheaper than the optical. Radio Shack is usually fine, so is making your own from RG59, although if name brands appeal, you can find many used audiophile RCA video cables on ebay very cheap.

One more bit of information about toslink, should you go that route, is to use a glass-based cable. I found this post on audioasylum.com that summarizes the issue much better than I can:

"Early Toslink cables were poorly designed. They used plastic insides that often developed cracks and caused problems for the fiberoptic light. This raised its head as increased jitter in the signal and many heard this effect on the sound. Thus, cheap Toslink (and all Toslink in the end) got the reputation of a poor connector. As time went on, as it always seems to do, Toslink fiberoptic cable was manufactured along the lines of the ST (AT&T) fiber cable. High-End cable companies offered Toslink connectors manufactured with glass on the inside that was more robust and began polishing the ends (the connectors). Voila, better sound for Toslink. As for coax digital cable, the materials and design have just as much an effect as Toslink materials and design. A great deal of the sound depends on how well the interconnected components are grounded. Which is better? Technically, the coax has a higher bandwidth than Toslink and this is a benefit. The ideal coax connection is better than the ideal Toslink connection. But, when do we have ideal when dealing with electricity (or light for that matter). You need to try each in your system and decide for yourself."

I wonder if that remains true or if it is over-reacting to older problems - glass fiber cables are still pretty rare (and pricey), but good optical cables are available from a number of sources that still use plastics of various types which avoid the problems described in the Audio Asylum post. Of course, I've been dealign with design requirements driven by over-reactions to old problems a lot this week, so I may be a bit biased...

Could be.

I don't know much about what's out there in the way of toslink, but I did come across this glass cable from Sound Professionals that seems reasonable ($50 per meter): http://www.soundprofessionals.com/cgi-bin/gold/item/SP-TOC-99HQ

And here's a review from an audioasylum poster that really seemed to like it: http://www.audioasylum.com/audio/general/messages/233584.html

$50/meter for optical is not an unreasonable price, but it's still a fair bit more than the $20 for Outlaw's very nice 1.8-meter PDO and $14 for a 3-foot Blue Jeans optical (both of which use some form of plasic optical fiber). I also find myself wondering why an optical cable would be directional, as mentioned in the Audio Asylum review - there's no grounding that I'm aware of in light transmission.

Good point. There was also nothing I read on Sound Professionals' product description that would indicate it was directional.

Another cable I stumbled acorss with a bit more searching is this one: http://www.worldofcables.com/oscatalog/CreateHTMLPagesItem/45456.htm

Apparently, it has more strands than the Sound Professionals cable and is a bit less - $38.99 per meter. Frankly, at those sorts of prices, it would be interesting to do a shootout of a good coax-based cable, like the DH Labs D-75, and a glass-based coax like the Sonic Wave.

I may do just that. The winner would go on my DVD audio out and the loser could feed my CATV audio connection.

Oops. I meant to type "glass-based toslink."

Digital Jitter is not caused by the physical properties of the cable (i.e., glass vs plastic). If the quality of the cable were to affect the signal at all, it would be an all-or-nothing issue - the signal either is there or it's not, basically a data error. This would manifest itself inaudibly as dropouts in sound. Digital jitter in S/PDIF would manifest itself audibly in the music.

The jitter introduced by the S/PDIF connection is a result of the signal itself, which is produced by a combination of the source signal and the signal introduced by the S/PDIF hardware at the source end.

In other words, an expensive ST-type glass toslink cable wouldn't solve jitter issues.

That seems to be at odds with a lot of technical analysis on the subject. The interface between the transport and the DAC is one chain in which jitter can be induced -- whether that interface is toslink or coax. Hence the terms "cable-induced" or "line-induced jitter" that have become part of the digital audio lexicon.

One resource I came across that seems to be devoted to this topic is: http://www.jitter.de/english/what.html

A more lengthy white paper entitled "Towards Common Specifications for Digitial Audio Interface Jitter" is also available as a PDF on that site: http://www.jitter.de/pdfextern/towards.pdf

Not exactly my type of reading mind you, but may be useful for tech-heads out there.

One more thing, just based on the empirical evidence that is out there, if the type and quality of the interface were unimportant, why do Wadia, Theta, Audio Note and other high-end DAC makers consider it in their designs? For example, Wadia and Audionote devote most of their digital inputs to either glass toslink or coax. I would have to assume that the guys who are at the cutting edge of digital music reproduction would not place much emphasis on the interface if it did not have an impact on performance.

We're actually in agreement, in fact the link you gave has the following:

It's important to note that S/PDIF/Toslink, transmit the same signal, which incorporates the jitter-inducing added clock signal. ST transmits a different signal. You'll note from Wadia's site that their glass inputs are ST inputs, while their Toslink are plastic. IIRC glass is part of the ST spec (to accommodate wider bandwidth), so using the interface requires it.

I'm not trying to argue here, just noting there is a difference between the signal interface (or transmission format) and the physical interface when referring to jitter. This can cause a lot of confusion when laypersons like me get involved, and semantics can keep my point from being clear. I hope I have been able to clarify a little bit better.

Kind of goes past my pay grade after that. I'll raise a beer to the subject on Sunday and drink to all of our digital interfaces being error free

No argument inferred. I have enjoyed the discussion. Thanks for taking the time to read through all that stuff and wade through the techno-speak.

I may still try an A/B comparison between the cables I mentioned earlier. For starters, I'm updating cables anyway; and second, this thread has piqued my interest!

Jim, I love your setup. Your photos actually inspired me to get my HT going in my basement. I have the Salamander triple. Now I have to consider the paint (everything is white) and couch and reclining chairs. What is the name and manufacturer of both the tan and brown wall color in your room? I think it looks fantastic.

Thanks for the kind words, Aaron. If I remember correctly, the tan is a Behr color that I had color matched to Benjamin Moore. It is in their matte finish, which is bascially a flat formulated for stain resistance and easier clean up than traditional flat.

The dark brown is a paint line called C2 that was carried by my Benjamin Moore dealer. The color is osso bucco. Finish is eggshell. At the risk of sounding like HGTV, C2 uses more colorants than other manufacurers, so you'll notice they have colors that are much deeper and richer than their competitors.

Both paints were latex.

Oops. Forgot, to mention the Behr color was "Classic Taupe."

Videodrome,

Thanks for your response. The dark brown color sounds delicious. I love braised veal shanks. Now I'm worried that if I paint with that color, I will be perpetually hungry. Thanks as well for the color for the walls.

Aaron

I use the Outlaw PDO with my Ps2 and love it!