Source equipment must be locked to the same master clock as the DAC. If this source does not have a clock input (like a TV), then Audio Sync will be used, and not the clock.
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Erno I understand the synchronisation point that you are making drawn from the dCS user manual but I think it could be misinterpreted. Surely the reception of data by the DAC involves buffering ? And then, if you have a wordclock, the data timed out of the buffer would use that clock which offers increased stability over the inbuilt one, the latter being referenced to it? Not synchronisation of the two components but nevertheless still giving an advantage.
Although using Network and USB does not involve Audio Synch being asymmetric interfaces (where the DAC is timing the source’s output) again surely the more stable system clock would provide an advantage?
Otherwise, as so few home audio components offer BNC wordclock inputs, effectively only those using a dCS disc transport would derive any advantage from the external clock which I do not think is the case.
Pete, this is how I understand it:
Without a Master Clock:
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the system is set up to lock to the clock generated by the source (Audio sync Mode)
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or in Master Mode
a) for only asynchronous Network and USB1 or USB2 input. The DAC uses its own internal clock to control the internal DAC and regulate delivery of data packets. In this situation, the DAC is acting as the source device.
b) in Master Mode using the AES or SPDIF inputs, the DAC again uses its internal clock to control the DAC and outputs a clock signal at the Word Clock Output, and this one MUST be connected to the source’s word clock input. If the AES and SPDIF source cannot be clocked by the Master Clock, the synch is only through the audio signal of the source, i.e. the DAC extracts the clock from the data stream of the source.
With a Master Clock (Word Clock 1-2 Auto Mode):
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the system is set up to re-lock to the Master Clock (only asynchronous Network and USB1 or USB2 input)
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or, for AES and SPDIF, the system is set up to re-lock to the Master Clock only if the AES or SPDIF source is also locked to the same Master Clock. For the Rossini Master Clock, this can only be 1 source at the time, and only with 44.1kHz. The Vivaldi Clock has more outputs, also at 48kHz.
Again, if the AES and SPDIF source cannot be clocked by the Master Clock, the synch is only through the audio signal of the source, i.e. the DAC extracts the clock from the data stream of the source.
However the audio signal got clocked, the clocked bits are buffered in memory immediately prior to playback.
the difference is so great?
If you don’t mind, could you describe the differences in more detail?
The important bit as I understand it is that when a dCS system clock is used the internal clock of the DAC is referenced to it - a bit like using an external rubidium reference clock with the Vivaldi clock.
This means that not only is the system clock functional for synchronisation between components in the circumstances cited by you but it is otherwise in all circumstances providing a more stable reference to the internal DAC clock .
Correct. I have just re-read this:
I couldn’t say it any better than this:
The Bartók is the most expensive piece of gear to grace my audio rack. Late in the review period, I got to wondering: the Bartók must surely be far into the diminishing-returns region of the price-performance curve. How much better could its bigger brother, the Rossini, really be?
Any hopes I had that the Rossini’s advantage would be subtle and small were dashed within the first few seconds of the opening title track. Instead, my jaw dropped. Remember how I said comparisons were cruel? Well, the same Bartók I was praising for its dynamics and physicality earlier now sounded positively skeletal compared to the Rossini! The sheer realism of the instruments was eye-opening. Nowhere was this more evident than on the percussion. The level to which the Rossini conveyed the weight, the volume, and the texture of the djembe drums was remarkable. Later in the track, when the guitars kick in to create a veritable wall of sound, that wall was darn near impenetrable with the Rossini!
If you’ve ever heard a live cello, you know the weight and physicality the instrument conveys, the incredible detail and texture as the bow strokes the strings, and the satisfying bass of pizzicato notes. The Rossini came close to that live experience.
I was flabbergasted to hear the magnitude of improvement that still exists between the $15k Bartók and the $24k Rossini, and the fact that it was clearly audible in my system.
From: https://audiophilestyle.com/ca/reviews/dcs-bartok-review-r849/
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Thank you!
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I have Bartok and I still don’t try to compare it with Rossini or OMG Vivaldi. I know the outcome, but I still have no money for Rossini+ level.
But this does not prevent me from comparing my Bartok with DACs from other brands. Within reason, of course.
If you like your Bartok, just don’t compare it to dCS DACs in the lineup above.
And read this forum less 
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Well I switched to the optical input and the screen says it’s using W2. Thought it would fail to lock and mute. That’s my impression from the manual.
The manual says that if you lock the SPDIF (optical) input to a Master Clock, without locking the source to the same Master Clock, you will experience periodic clicks, dropouts, noises or distortion on the output.
The W2 icon indicates a video signal, or at least a 48kHz, is coming in.
Did you experience one of the anomalies described above?
At some point in August, my wife approached me and said “I saw you wrote a check for $x from the joint account to some ‘stereo place’. What is that about?” Luckily I had the foresight to redirect the conversation to mansplaining how Alibaba is incredibly undervalued, Wall Street doesn’t understand, and eventually I’ll be proven right. As supporting evidence I pointed out how I bought Amazon at $6. To which she replied “Yes and, if I recall correctly, you sold at $120. What’s it at now?”
Communicating relative value of hifi is impossible and I’m just more comfortable focusing on my personal failings as a market timer. In this way we both win. I am not put in a position requiring even considering if it actually is a legitimate value. While she can subtly suggest this is probably a terrible decision. Conversation ended with her saying “Okay just wanted to make sure it wasn’t, you know, a mistake or fraud.”
Last night it occurred to me that the large brown box with a dCS label sitting in the middle of the room for past two weeks would soon result in questions like “what is this”, “why is it here”, and ultimately “if it’s so important why haven’t you opened it?” Realizing Alibaba hit several new multi year lows on Friday, thought it best to open the clock and install it.
Installed the clock with one “audiophile” bnc cable for 44.1 and a “commercial grade” bnc for 48. Will at some point officially switch to “Auto Wordclock” sync mode.
No. It sounded fine. I guess the dac doesn’t know the source isn’t locked to the same clock so the W2 makes sense.
I think that you may need to distinguish between auto ( Wordclock1-2 Auto) and " Audio" synch. Auto basically only automatically switches between the 44.1kHz base clock and the 48kHz base clock clock in accordance with the incoming data . Synchronisation per se is a related but somewhat different animal and, beyond just selecting the correct frequency, relates to e.g. 2 nominally identical timing cycles running on different machines ( e.g. CD transport and DAC or TV and DAC) so that each starts and concludes at the same point in time (i.e. are synchronised). If the cycles start at different points in time this may eventually result in glitches as the cycles drift further apart over time. However this synchronisation cannot be done where the machines cannot share the same reference clock for example because one or both does (do) not have wordclock inputs. So in order to avoid potential glitches the clock embedded in the source’s AES3 interface ( which includes S/Pdif) is used to “time” the DAC ( “Audio” synch).
I found that hard to explain so I hope my attempt is adequate.
Meant that I’m leaving it in master mode for the time being. The optical input is set to audio.
I did try W2 mode and it worked fine. I also tried W1 mode and it… worked fine. This makes zero sense. All four modes work fine with the 48khz optical stream. The manual says it shouldn’t be able to lock and would mute. Not sure what is going on.
I don’t think that it will necessarily mute with the incorrect clock input. The manual only says that it “may” fail to lock and mute. Wordclock is not synchronising TV with the DAC as the TV does not have a wordclock input. In brief it works because with Audio synch you are not then using the wordclock for synchronisation. As I mentioned above the wordclock will however be providing a more stable reference to the DAC’s internal clock. With other synch settings selected you will probably get sound but it may be some time before you start to notice glitches as it depends on how far out of synch the TV is with the DAC.
One thing worth double checking anyway is that you have the Rossini clock correctly connected to the Rossini DAC. It is very easy to mix up the ins and outs 
.
Wait… if I select the 41.1khz wordclock how can any stream of 48khz data play successfully?
It all depends upon what you call “successfully”. It will play but the timing of the processing will be incorrect. Therefore the reconstructed waveform will be incorrect. In effect you will have a bad case of jitter. It may even sound OK or at least passable to you .
Just to check I am playing a 16/48 source but using the wrong 16/44.1 clock ( Vivaldi clock Group 1). It still plays and the sound is not all that bad. Just somewhat rougher (my subjective impression). No doubt if I carried on then in due course I might find glitches occurring.
How can the stream be converted 14% slower and not sound completely distorted? Doesn’t the dac clock time the transmission of the 16/24 bit words into the dac? If I’m telling the dac that the current stream is 44.1khz then it should convert exactly 44,100 words/second. If the song is recorded at 48khz then processing @ 44.1khz should be incredibly noticeable.
Sounds like the dac determines the appropriate sample rate from the stream itself and the external clock simply regulates the internal clock…
Wait… maybe I should put the 44.1 clock signal into the 48khz input. It’s possible the dac just disregards the W1 clock input for a 48khz stream because it knows it’s wrong but might think the w2 44.1 signal is accurate because it’s supposed to be 48khz. That might be a better test.
At this point I can’t figure out how to verify the clock is working within its specification…
Okay y’all I figured it out. Instead if not locking or muting or producing terrible sound, the dac reverts to Master mode when the incorrect clock signal is selected. Unfortunately the Mosaic app does not reflect the actual mode just the selected mode. The app says Wordclock 1 on a 192khz stream but the display indicate master mode.
Problem solved.
Note that while the malfunctions mentioned can occur, it is not a given.
For example, if you connect a GeerFab D.BOB breakout box, you have to set the clock mode for the input to A or you will get a constant stream of clicks along with the audio.
However, I have a DISH Network Hopper 3 that I use to watch TV and send audio channels to my Rossini, I have it set to Auto W1-W2, and it works perfectly locked to W2 - the only time I have heard a click is when changing channels.
Sometimes you get lucky and the clocks just line up.
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