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struts
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Q for JA: Toslink vs Coax

John,

Purchase of a Sonos system as a Christmas present to self and the subsequent liberation of my entire iTunes library through my big-rig (however did we manage before?) is causing the first major audio relapse I have suffered since the birth of one baby led to the boxing and storage of all the others.

B.C. (before children) I was an avid reader of Stereophile and HFN/RR and one thing I clearly recall is that Toslink was very much regarded as the red-haired child of digital interface standards. The conventional wisdom, if I recall, was ST, then Coax and if all else fails, Toslink.

However, I noticed in your reviews of both the SB3 and the Sonos system that you used Toslink to connect to your Levinson DAC. What, as J-10 used to say, is the hoopy-scoopy? Both units support S/PDIF over coax and I'm sure you had suitable cables on hand. Was this a sound quality choice or one of convenience? I notice that the Toslink cable you are using is pretty high-end (I believe it costs about $500) but haven't seen any reviews, in Stereophile or elsewhere (in fact I don't think there are any Toslink cable reviews in your online archives!?). Is that part of the picture here or just a red herring?

A related question. Your comment

Quote:

I was hard-pressed to hear much of a difference between the Levinson driven by the ZP80 receiving Apple Lossless Compressed or AIF files, and the original CDs from which I had ripped the tracks, as played back by the Class
struts
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Re: Q for JA: Toslink vs Coax

No reply from JA which is a shame, but I guess he like many of us has a day job too. Just in case anybody else is wondering about the same questions I wanted to share a couple of interesting pieces I found:

On Toslink vs RCA see this comparison over at sixmoons.com. Very interesting reading indeed. The take-out is that RCA is not inherently better than Toslink and that a good Toslink cable can sound every bit as good (and sometimes at considerably less cost) as a good RCA. In some cases, even better. I am horrified and ashamed that in these enlightened times I should have been harboring such outmoded and, frankly, downright cablist prejudices. I repent, I have seen the light!

On streamed audio vs silver disc see this paper over at wavelengthaudio.com. I'll let Gordon Rankin provide his own summary: "A Computer will always be better than even the most expensive transport, just from the virtue of an endless supply of software. When was the last time you receive a software update for your expensive transport?". Of course, you may dismiss this as the rantings of just another deranged Mac fetishist, especially if you have just shelled out (ahem) 27 large for your Zanden 200 Premium, however I would recommend that you at least read the PDF linked above; he presents a pretty compelling case.

I found both the above articles very interesting but as always, in the final analysis you have to trust your own ears. Happily I will soon be in a position to test both theses myself. Stay tuned.

Elk
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Re: Q for JA: Toslink vs Coax

My understanding is that TosLink can sound as good as S/PDIF if the TosLink cable itself is of good quality with good termination lenses and the transmitter and receiver of the equipment it is connected to are well designed.

However, I believe it is easy and cheap to include a poor quality but functional optical out in a unit and that this is why there are ubiquitous. S/PDIF is more expensive to implement but also easier to do correctly. Lesser quality TosLink cables also must be kept as straight as possible, once curved there can be a significant transmission loss.

Accordingly, I expect that what you will find is that optical is as good as coax when the equipment is of good quality and reasonable care was taken implementing each.

I, for one, am very interested to read what you learn in your testing. I know that you have a reclocking unit. Please try listening without it in place as well in your testing. I suspect that it will remedy much of the problems with TosLink and make a meaningful comparison of the formats that much harder.

struts
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Re: Q for JA: Toslink vs Coax


Quote:
I would recommend that you at least read the PDF linked above; he presents a pretty compelling case.

Apologies, the wrong reference (I plead sleep deprivation). The compelling case I was referring to is woven into the text of Art Dudley's review of the Wavelength Brick (Listening #33, 'phile Sep 2005). The PDF referenced above contains practical advice on putting together an audiophile digital media server (i.e. computer + disk) for under $1250.

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Re: Q for JA: Toslink vs Coax


Quote:
Please try listening without it in place as well in your testing.

I certainly will! The Purcell is 'on approval' so I will be listening hard before throwing money away on such a chronically obsolete piece of kit. I want to test its effect both as a jitter-buster (on Toslink and RCA) as well as determine any incremental benefits of up-sampling to 24/96.

I used to have a dCS stack back before children (B.C.), initially an early Purcell/Delius driven by a Meridian 500 transport and later the full Verdi/Purcell/Elgar Plus/Verona "four-pack" with upsampling to DSD, so I am quite familiar with the Purcell and its 'magical' qualities. However it remains to be seen how it will fare in the strange company of the Sonos/Boulder combo!


Quote:
I suspect that it will remedy much of the problems with TosLink and make a meaningful comparison of the formats that much harder.

Well I guess that's the theory. If the data stream is bit-perfect then the timebase (and variations therein) is the only other variable, right? And even then it is only relevant at the transition points to/from the analogue domain, nowhere in between. That, to my understanding, is the theoretical beauty of the digital domain, everything else is just abstracted away.

The two main strategies to secure a stable timebase seem to be:

  • Smooth any variations in the embedded wordclock using PLL(s), which as far as I understand it act as 'digital flywheels', or some similar strategy
  • Send the wordclock separately over a wired or optical link

The latter is not an option for me since neither the Sonos nor the Boulder can act as or slave to a master clock.

As an aside I have not seen any comparisons anywhere of the sound quality of the Transporter used with/without its wordclock input. This is despite (or maybe because) afaik at $2000 it is about the cheapest digital source that can accept a separate word clock. Please let me know if you stumble across anything.

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Re: Q for JA: Toslink vs Coax


Quote:
No reply from JA which is a shame, but I guess he like many of us has a day job too.

My apologies for the tardy response. I missed it the first time; my thanks to Stephen Mejias for alerting me to the second posting.

I used the Toslink connection in my review because I was suspicious of the switching power supply possibly injecting RF noise into the common ground shared by the DAC when it was connected by coax. I therefore used a high-quality Toslink to make sure that the grounds were isolated.

John Atkinson
Editor, Stereophile

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Re: Q for JA: Toslink vs Coax


Quote:
And even then it [timebase variations]is only relevant at the transition points to/from the analogue domain, nowhere in between. That, to my understanding, is the theoretical beauty of the digital domain, everything else is just abstracted away.

Exceedingly well, and somewhat poetically, stated.


Quote:
As an aside I have not seen any comparisons anywhere of the sound quality of the Transporter used with/without its wordclock input. This is despite (or maybe because) afaik at $2000 it is about the cheapest digital source that can accept a separate word clock. Please let me know if you stumble across anything.

My hope is that driving the Transporter with a separate word clock makes no difference whatsoever. A properly designed DAC with good jitter rejection capabilities should not provide better sound when so driven.

However, some disagree. I recall quite a heated discussion between Dan Lavry and Bob Katz with Max Gutnik of Apogee (maker of the Big Ben) on this point. Lavry and Katz pointed out that a good DAC can address word clock variations by reclocking, etc. My conclusion at the end was that driving a group of ADC's and DAC's with a single word clock (such as in a studio) makes great sense to synch them (this prevents random clicks) but that a separate wordclock makes no improvement when driving a good DAC. This has been my experience as well.

Using a separate word clock can improve sound in some circumstances however. Users of TacT equipment have found that placing a Big Ben prior to their digital room correction preamps, and again prior to their digital amps, can improve the sound. This makes sense as TacT equipment is silly sensitive to jitter and has poor jitter rejection. (Conceptually this has always bothered me a great deal as the whole appeal to TacT equipment is its ability to operate in the digital realm, something that it however does poorly.)

John, thanks for the explanatory note. This makes sense.

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Re: Q for JA: Toslink vs Coax


Quote:
A properly designed DAC with good jitter rejection capabilities should not provide better sound when so driven.

I can't comment with any authority on the merits of the theoretical arguments here, only to say that in my own experience:

  • slaving the dCS Verdi to the Elgar Plus did make for quite a noticeable improvement in sound quality (although I can't remember the details of the nature of the improvement as I only tested without long enough to compare and then went with the slaved configuration from then on)
  • slaving both to the Verona made a further but very subtle improvement. I do remember describing that difference to a disbelieving audiophile friend at the time ("it does WHAT???") as akin to the difference a really good mains cleaner makes, similar in nature but far more subtle. In a less painstakingly optimized room/system the same improvement could undoubtedly have been had more cheaply any of a hundred ways and I remember almost deciding to give it a miss. However, I rarely pass up an opportunity to invest and true to form this turned out not to be one of those rare instances.

You may also enjoy, as I did, the sixmoons.com review of the Zanden 200P. Quite a lot of attention is devoted to the clock interface (both in the product and the review).

By the way, it's a sure sign you're going off the deep end when even your audiophile buddies think you're barking mad (I feel your pain, Mikey!). Happily children arrived just in time to bring me back down to earth.

Elk
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Re: Q for JA: Toslink vs Coax

Thank you for posting both your experience and for the link! They each make great reading.

struts
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Re: Q for JA: Toslink vs Coax

Elk,

If you enjoyed that you will surely also enjoy the sixmoons.com review of the Shun Mook Mpingo disc, written with a wry humour I found irresistable. If you've ever dabbled in "Shun Mookery" yourself I expect you will find yourself "resonating sympathetically".

In general I have found sixmoons.com both illuminating and entertaining. I only came across it recently when a review there was linked in one of the Swedish forums. They cover a quite different slice of the high-end to 'phile (there seems to be little overlap) and have their own style which is distinctly different but usually hugely entertaining.

When I first started reading 'phile about twenty years ago it was for my money the de facto guardian of the high-end as well as the magazine that set the benchmark on review quality. Now I would have to say that it has serious competition. Watch out JA! Objects in the mirror may be closer than they appear..

struts
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Re: Q for JA: Toslink vs Coax

Sorry to keep bombarding you with links but there's more on separate wordclocks in the sixmoons.com review of the Esoteric P-03, G-03, D-0s triple-stack. You may also find their coverage of the Red Wine-modded Olive Musica of interest.

By the way, do you get the impression we're the last two people in the bar here? I expect the guy with the floor polisher will start chasing us out any minute.

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Re: Q for JA: Toslink vs Coax


Quote:
By the way, do you get the impression we're the last two people in the bar here? I expect the guy with the floor polisher will start chasing us out any minute.

Indeed. Many of the links are quite quiet. Unfortunate as their are some superbly articulate knowledgable people on this forum.

The Shun Mook review is hysterically fun! Thanks.

I have seriously considered sending in my Olive to Vinnie to mod. In addition to doing good work he is an extremely nice guy that I hope is doing well designing and modifying equipment.

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