Thank you for the thorough explanation @James. The above were exactly some of the details I was trying to understand and now do. Greatly appreciated!
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Very late and tangential into this fascinating debate (not all of which I completely grasp with my limited digital tech awareness), I acquired an external Vivaldi Clock even though it cannot link with my built-in Meridian active speaker DACs. However I do input music via CD from my Oppo 205 and hi-res albums from an Innuos server into the Vivaldi Upsampler (replacing a previous Network Bridge) and I have noticed sharper transients and depth to the soundstage (in a good recording) although it is incremental. I am assuming my findings link with James’ explanation. I would be interested to know if this is the case and not an example of the ‘emperor’s new clothes’!
Graham
Note that a clock is not a clock, if you will.
dCS’ clocks output 44.1 KHz and 48 KHz clock signals as TTL square wave outputs.
So if you are going to sync your external device with a dCS clock or a dCS device with a third party clock it’s important to find out which clock frequencies and modes the master clock can generate and which the recipients expect.
For example, the Jay’s Audio CDT3-MK3 Transport only accepts a 10 MHz clock in, so it could not be clocked by any dCS clock.
However the VIvaldi Clock can accept the signal of a 10 MHz clock as a reference clock to which its generated clocks will be locked.
It sounds even more insane than most things in high-end audio, but I know people who have their Vivaldi or Esoteric master clocks locked to a 10 MHz clock generated by a GPS receiver.
I’m also surprised no one in the audio community is yet offering a device with a chip scale atomic clock, unless they’re less accurate than the current offerings:
CSAC SA65 Chip-Scale Atomic Clock
They’re not as expensive as you might think.
Thanks for the further guidance which is sadly way beyond my understanding. I am not at the cutting edge of (or even close to!) anything remotely to do with digital technology. Taking advice from my dealer who further referred to dCS, I am working on the basis that the dCS Clock will link and is compatible with their Vivaldi Upsampler. I am hoping there will be additional benefits incorporating this particular Clock with inputs from a disc player and music NAS outputting from the Upsampler to a stereo pair of active speakers (where individual DACs are obviously found). Those cannot be externally clocked as I understand it.
Apologies if this all sounds very simplistic but I was always more comfortable with analogue technology back in my youth! Graham
I was wondering what the life span of a dCS clock is before its inaccuracy renders it more harmful than good?
Welcome to the dCS community, Mark.
This will help you a bit further:
and
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Talk about the perfect illustration that sanity is a relative concept, especially in this hobby. 
My dealer carries cables, equipment racks, and a host of “accessories” that cost more than my GNSS clock.
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Exactly.
The beauty of a personal hobby is we each get to decide for ourselves. Some of us geek out on clocking, some on cables, some would prefer a Bartok with full Nordost Odin over a Vivaldi with subpar cabling. Who are “we” to judge? 
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Of course no offense meant Greg.
Certainly to an outsider it looks nuts, but so is the idea that clock cables can make an audible difference, yet they very much do.
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Gosh Bill, none taken! That’s why the little winky emoji. More than once, I have found genuine mirth in my and others’ “selection of obsession.”
I am willing to believe that’s possible, But I have yet to read or hear an engineering explanation for why, other than compliance to standard. Shortly before my Vivaldi went in for its upgrade, I spent weeks comparing some very expensive clock cables, which are enthusiastically reviewed here and elsewhere. These weren’t demos. I paid nearly $10k for a full loom. Zero audible difference—“better” or “worse,” whatever those two terms might mean; simply no difference—in my system.
As you have suggested in other threads, sometimes the only way to find out is to try out. I did and, while I will gladly acknowledge that there might well be a cable out there that could make a difference in my system, I’ve given that possibility about as much trial-and-error time out of what remains on my actuarial table as I am willing. 
Time to remain in the joy of just listening.
On a separate and unrelated note, while I was waiting to retrieve my Vivaldi Apex, I was fortunate to have as a fallback the Sonore Optical Rendu feeding the Legacy Wavelet directly through USB. The Wavelet is a very good DAC in its own right, but it’s no Vivaldi. Having the Apex back is noticeably so much better, but I acknowledge that my brain and ears are probably making more of a comparison with the Sonore/Wavelet combo than they are capable of accurately comparing the pre-Apex Vivaldi. 
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Hi,
Do you mean that between the pre apex and the apex you couldn’t swear that there is an audible improvement of the sound quality ?
I mean exactly that. Too much time and too many intervening factors. While I have zero doubt that it is better, there is no demonstrably credible way to prove it.
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This is a great thread - I have learned a lot.
I am new to external clocks. I have a Bartok and just found a DCS Rossini clock at a nice price on a trade-in from a non-DCS dealer. The clock comes with no cables.
I use an Aurender N10 via AES and also Roon via ethernet.
I own a1.5m 75Ohm Nordost Valhalla cable with BNC terminations that I am presently not using. I assume any good quality 75ohm cable will be sufficient for the Rossini clock, so was thinking of just buying a 2nd Valhalla cable and then using these 2 cables for the Rossini clock to Bartock - is this reasonable, or is there a special cable specifically designed for external clocks that I should be using? (I realize there is some controversy on quality of clocking cables, but since this should be a fairly high quality cable, I was more inquiring if any standard 75ohm BNC digital cable would work, thus allowing me to use the cable I already own and thus buy one rather than 2 new cables or whether it needed to be some special cable designed for external clocks.
2nd question -
much has been made of Ethernet switches and having ones that re-clock that signal (Nordost has Qnet that has an internal clock and SOTM has a nice product with optional internal or external clock) -In anticipation of the Rossini clock, I was reading the Bartok manual on this (again it’s all new to me) - My understanding is I can clock either the USB or ethernet (Not both), so I figured I’d get more bang for my buck by re-clocking the ethernet signal than using Aurnder with USB – Is that reasonable logic? and is so, if I set it to re-clock the ethernet, than is it pointless to consider a specialized network switch that re-clocks the ethernet signal?
Sorry - there is a fair bit of meat on that bone, thanks for any thoughts. I figure this was a better place for the question rather than creating a new forum thread??
Thanks
Best of health
Happy Holidays to all
Not sure if the clock will do anything when using the Aurender N10, as it has no clock connections.
When using the Bartok as a streamer you will have the advantage of the Rossini clock.
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You can certainly use the Valhala cable for the clock connections. The 75 ohm spec is the main requirement for dCS clock cables, so you’re good.
Might also be worth trying two normal pro-grade BNC cables before buying another Valhalla as well to see if the expense is worth it in this application. You can A/B since you only need one clock cable at a time.
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Blaven, with respect to your 2nd question, all Ethernet Switches operate at an internal frequency of 25MHz, and have nothing to do with Audio clocks at all (either base redbook rates, or 10MHz reference clocks). Additionally, Ethernet being an asynchronous packet-based technology with very robust error correction at multiple layers, their internal clocks don’t need to be very precise at all. Which is why even the cheapest Ethernet switch can provide totally error-free operation for years in any normal home.
As far as the regular Music streaming services and protocols (e.g. DLNA/UPnP/Roon/RAAT etc.) are concerned, adding additional clocking to consumer Ethernet switches does absolutely nothing. Unfortunately theres just so much misinformation out there on the ‘net which only serves to feed an audiophile’s imagination. I highly recommend that you read dCS’ series of technical articles (by James Cook), and specifically the one about asynchronous sources in relation to clocking and jitter.
Enjoy 
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Thanks all!
so, as usual, more information can lead to more questions
Not sure if the clock will do anything when using the Aurender N10, as it has no clock connections.
When using the Bartok as a streamer you will have the advantage of the Rossini clock.
Like the Aurender unit, the incoming ethernet signal also has no clock connections - so then how does it work for anything?
It does not seem, in the recommended hookup in the Bartok or Rossini cloick manual, that any input cable is being connected to the clock.
I am admittedly VERY new to external clocks yet thirst for knowledge on how stuff works. I would understand it better if for example the digital source were connected the Rossini clock, that than reclocked the signal - thus ethernet input in the clock, USB, AES etc, etc - but it looks like there are only 3 “wordclock outputs” and no inputs.
So I guess where I am confused is how the clock works - or how it could work for the ethernet, but not the Aurender N10 I have. I realize James above said it was being used as a reference for the Bartok internal clock, but then wouldn’t that necessitate bidirectional flow of data between the DAC and Rossini Clock?? or, how can the Bartock reference the precision crystal in the Rossini clock if it cannot communicate with it?
Sorry if I did a bad job explaining, but hopefully that makes sense.
Thanks for your help
happy holidays and best of health
By all means I am not a clock expert, but where I hear a Rossini clock really working is when an Aurender N20/N30SA is connected to the Rossini clock (with extra USB dongle to switch between 44/48 sample rates), when powering off the clock in a system like that the soundstage collapses.
If I understand correctly the Rossini clock will work between the internal streamer and DAC in the Bartok, but with the N10 it’s not doing that
At the PHYsical layer, Ethernet is similar to S/PDIF in that it’s a serial digital bitstream that carries both data and associated clock. And just like S/PDIF, the Ethernet PHY Transceiver at the receiving-end typically synchronises to the incoming bitstream via Phase Locked Loops (PLL) and extracts the associated data.
However, unlike S/PDIF which is a continuous synchronous bitstream with no mechanism for correction, Ethernet is bursty self-contained frames with an 8-byte preamble at the start of each frame designed to (a) wake-up the receiver, (b) re-synchronise the receiver to the incoming bitstream, and (c) signify the start of the Ethernet frame. While at the end of each Ethernet frame is a 4-byte error-check sequence which the receiver uses to detect transmission errors and discard errored frames in order for the upper layers to request the data to be resent.
I highly recommend slowly re-reading James’ pieces on Clocking, start here;
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