I can only add that this is exactly what I eventually first found way back in the Elgar/Purcell/Verona days. BTW this is why subjective listening to just brief switching in an a/b style test probably won’t reveal much.
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Cheers guy’s
I know i will probably end up with the clock, but will be interesting to see if i miss it now it’s gone, as i had it about a month i guess.
But i feel it’s vivaldi clock or nothing.
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I understand @PAR 's post above, and if I were to summarize, I would write: “if you have a multi-box system, an external clock does a much better job keeping everything in sync than just the DAC’s clock which can only work with the bits once they get to the DAC.”
I question only this statement:
As the VCXO units in both the Vivaldi DAC and the Vivaldi clock are the same, I’m not sure that this is the case.
More generally, there is no technical reason why the clocking mechanism in the Vivaldi Clock needs to be the same as the Vivaldi DAC. It could be higher accuracy. I note that Esoteric (in the Esoteric G-01X) has licenced the SRS technology in its master grade clock and that unit now has rubidium-quality accuracy (i.e., errors per billion: “within +/- 0.05 ppb”), which is over 3 orders of magnitude more accurate than the current Vivaldi (i.e., “typically +/- 0.1 errors per million”).
I have not had the chance to listen to either unit and therefore can’t comment on sonic results/improvements.
@PAR Yes I use one frequency on the Clock 1 input (NB and DAC) and the other on Clock 2. Both units know/sense which is which and switch accordingly. This was actually one of the big surprises when going to the Vivaldi DAC, locking is so much faster than any previous dCS DAC, or for that matter any other DAC I had.
@Anupc I am not sure if it’s actually the same VCXO used. Those come in different qualities with different phase noise specifications. As with the Scarlatti clock it looks from the pictures I’ve seen as these clocks are inside an enclosure (black) within the unit/on the mainboard. I think dCS mean that they use VCXOs throughout and no OCXO. Calibrating all clocks to the unit temperature is something dCS has been doing since the beginning, allowing them to squeeze a lot more performance/linearity out of ‘standard’ VCXO crystals. Perhaps the Vivaldi clock also gets a lot more time in the special climate chamber compared to the other units?
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From what I read on rubidium clocks, their long term stability might be very high, but that is not what we need in audio. Low phase noise is more important, as is care in design of the circuit.
There’s a LOT to read on clocking in audio. An additional one has some excellent info from the dCSers themselves:
…where in particular @James talks about a reference clock and a master clock being better served by different technical approaches. I won’t keep writing here…no need for me to fail to add value and be an additional “clocking in audio” source 
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If this is the case, while I understand your concern, I believe a lot of the magic happens in the surrounding components which appear clever enough to adjust the clock signal.
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I’ll admit I considered other options before choosing the Rossini Master Clock and came to the same conclusion
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Correct and agreed.
A previous thread from Andrew (at dCS) allowed that an additional 10MHz reference clock could results in sonic improvements to the already outstanding dCS Vivaldi Clock. A number of folks on this forum have implemented this solution.
My point is, why need both? It seems that if dCS followed the path of Esoteric, one could have the Vivaldi DAC with a “very good” internal clock, and Vivaldi stand-alone Clock with an even higher accuracy clock AND the other “magic”, outputting 44 and 48, dither, etc…
Then, at the highest end, you don’t need two clocks.
I don’t know for a fact as I’ve never opened-up my Vivaldi Clock to take a peek, but I believe it’s the same, but as mentioned elsewhere, everything else around it, including the temperature sensors, the control board firmware, etc. is unique to the Clock.
Thats true, but there are Rubidium clocks with both long term stability and low phase noise. I believe that’s exactly why the SRS PERF10 is suitable as a 10MHz reference clock for dCS Masters, whereas something like Mutec Ref10 is less so.
Ps: @August by the way, you might want to read-up on the link Ben posted above. Specifically posts from James about dCS’ 10MHz Reference Clocking needs being quite different from (other) DAC systems where low phase-noise is more important.
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I’ve read that since, thanks. Seems in line with the PLL-explanations of Grimm.
Reading the whole thread did leave me wondering why @PaleRider never got back on what the Kronos did for him or if he left it in his system. Is this that rabbithole you were talking about Greg 
?
It is 
Another way to look at this would be that if we did this, having a higher quality VCXO inside the Vivaldi Clock than inside the Vivaldi DAC, we would knowingly be putting a lower quality clocking source inside the Vivaldi DAC than we could, for no reason other than to make the Vivaldi Clock a more appealing upgrade.
The Vivaldi DAC, whether as part of a full Vivaldi system or on its own, should be the best performing version we can make, so it should not have hardware that is in any way compromised.
We have been working with our crystal supplier for 25+ years with a huge amount of collaboration between them and dCS to get to the point where the crystals we use are, we believe, of the highest quality available anywhere in the world. That has been the output of decades of work, moreso than simply choosing a more or less expensive component from an electronics catalogue.
On a separate note, to give some background to what I talk about when it comes to clocking and jitter, this paper by Julian Dunn discusses:
- The difference between intrinsic and interface jitter (why phase noise is only one very specific element of clock performance)
- Intersymbol interference (one part of why using a Vivaldi Clock increases sound quality even when it uses the same VCXOs as the Vivaldi DAC)
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Sorry for any ambiguity. I have several times expressed my extreme satisfaction with the system. I don’t pretend for a femtosecond to have performed an objective comparison, but I have twice done a Pete-style comparison of 2-3 weeks with/without. I am quite satisfied, to the point where, when it came time to downsize and consolidate my headphone listening system, I chose to sell the MSB Select II. I believe I would have reached that conclusion without the Kronos, but that’s a probability, not a certainty.
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Thanks James.
Agreed.
Sorry, I didn’t read all threads yet, glad you like it.
There are at least two asymptotes that figure regularly in my life, August.
One of them is the “my system is perfect and I’ll stop now” asymptote.
The other the “I’ve read all the system clocking threads” asymptote. There’s always another one. You’ve just not found it yet 
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No worries August. One of the most delightful things about this community is the tremendous amount of information shared, often in new and different contexts. It can be difficult to explore a topic completely.
The warren has many tunnels.
So to try and get my head round this, and for me, and my set up.
I have the apex vivaldi dac, and upsampler.
I run the upsampler from the clock out on the dac to the clock in on the upsampler.
I believe this then this means they are both locked to the dac’s clock.
The vivaldi clock in the dac, and clock are the same.
I take it the upsampler has a clock, and is this the same as the one in the dac.
By locking them together i get slightly better results than not locking them together.
So adding a vivaldi clock to my set up, brings in a 3rd clock, the same quality as the other 2.
This 3rd clock now somehow makes it even better, how exactly does that work.
I can see that a separate box, power supply could be beneficial, but find it hard to really see the benefit from doing what i am doing now, by just locking the upsampler to the dac.
I can see the added benefit if you then add the transport to it all.
I haven’t really had time to listen since my clock went back to the dealer, so i may find i am missing what the clock does, but for now just trying to get my head round it all, as this clock / re clocking is certainly a strange one.
I know i have asked alot off questions, and may not get all the answers.
Cheers dunc
Thanks for taking the time to reply to this thread and share dCS’s perspective James.
I’d like to very politely and respectfully explore this statement:
If dCS allows that a master 10 MHz clock can be added and further increase the Vivaldi’s performance, isn’t this logically very similar?
Why not have a dCS product that eliminates the need/temptation to add another clock by another manufacturer? As Greg jocularly put it, paraphrasing: “Well, there is that plug in the back…”
And if so, then wouldn’t the logical place to house this performance upgrade be the external Vivaldi Clock?
(My initial answer to my own question was: “There has to be some limit to a product’s performance, given price and market size.” But the SRS Perf10, for example, only costs ~$4k retail (and therefore ~$2-3k wholesale) and so I have ruled this reason out… )
Thank you
You’re more than welcome to - by no means is there anything going on “under the hood” that we wouldn’t want to talk about, and thus far there hasn’t been a question I have asked the engineers that they haven’t had a very well considered (like 30+ years well considered) answer for. Personally, I love this sort of discussion 
I do see where you are coming from here, though bringing it back to the Vivaldi Clock and DAC comparison for a moment, consider that we are using the highest quality VCXOs we can possibly get our hands on. If we were to differentiate the quality of the VCXO used in the Vivaldi Clock and DAC, that would mean we would have to use a lesser VCXO inside the DAC. That’s just not how we do things - the Lina DAC uses the same VCXOs as the Vivaldi Clock. We don’t compromise on hardware for any of our products.
The benefit of the Vivaldi Clock isn’t in the specification compared to the Vivaldi DAC, it is from performing the master clocking for the system external to all the busy stuff going on inside the DAC, Transport, Upsampler, streamer and so on, which makes it perform better with the same hardware spec. The regularity of the word clock signal being sent by the Vivaldi Clock removes intersymbol interference from being a problem, each connected device doesn’t have to work at pulling sync pulses out from AES or SPDIF signals (which is difficult to do), and so forth.
The 10MHz input on the Vivaldi Clock is by no means a statement by dCS saying that you have to use it to get the best out of the system. The reality is that the vast majority of 10MHz clocks on the market will not provide an audible benefit to the system. Such a 10MHz clock would be inherently very jittery by audio standards, and actually making use of a 10MHz signal for audio purposes is pretty hard (ASRC naturally adds jitter).
The fact of the matter with the 10MHz input is that it is in place because we can do it, and there do exist some devices (such as that Greg has found, devices on the more esoteric and exotic side of things) which will improve the long term accuracy of the Vivaldi Clock. However, this can only be done and is only considered by us as a viable option because we have a really really good PLL that can actually make something useable from what is, quite frankly, a very jittery 10MHz signal coming from an atomic clock.
To make sure I understand, is the suggestion here to place an atomic 10MHz source inside the Vivaldi Clock and then to remove the 10MHz input as an option for the user?
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