Clocking & Multiple Devices

I don’t want to start an argument and I am not trolling, but I want to inquire about the benefits of external clocking of a single device with an excellent internal clock. I assume we would all agree that Rossini has an excellent internal clock already. There are technical articles that insist that the use of an external clock with its associated cables,(no matter how good) on a single device—as opposed to clocking multiple devices—will actually introduce more jitter into the digital signal. This would strike me as sub-optimal, no matter how good one’s ears think that more jitter might sound. Is anyone aware of technical reasons why the use of an external clock should improve the already high-quality clock in Rossini? FWIW, when I demo’ed Rossini with and without the Clock, I consistently selected the Clock combo as preferable, and it’s what I have on order. [I also noticed in a recent piece about EMM, that Meitner is described as “disdainful” of those that advocate the use of external clocks; this sounded like a shot across dCS’s bow].

This leads me to a second question: is anyone here using their Clock to control more than just a DAC? I am a network audio guy, and there aren’t many servers/streamers with word clock inputs that I know of, though Aurender comes to mind.

Thanks for any input.

Yes it is an debatable topic for sure, just hope that you’ll gain more from the external clock than you loose in timing and phase jitter that occurs on the way. -1 + 1 = 0
You can masseur this in different ways so i think our human ears/brain detects certain artifacts, and maybe the bad ones are more covered than the great ones in this case.

One interesting example about master clocks aspects is the new Auralic G2 DAC + G2 Master clock have dun it in a different way, where they can completely turn off and and go pass through the master clock inside the G2 DAC using I2s connector that is connected directly inside on the dac board, and will then only use the separate clock as the default master clock to prevent insert any timing error, reflections or jitter etc etc benefits. It also meaning that you can just change the separate master clock when it comes a new better one, and not be in the hands of the internal master clock’s capabilities that sets the bar on how correct it can time your dac.

I think this is the way to go, and that we will see this in the next gen of dCS products if the separate clocks will still be in the spotlight a few years untill.

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Thanks Fredrik for this thoughtful and informative reply. Interesting approach by Auralic.

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That question is gong to cover just about all who run a complete dCS multibox system. So, yes, my clock is connected to DAC, transport and Network Bridge.

Does it make a positive difference? A few years ago when I was running a 4 box Paganini stack I found myself without the clock whilst it was returned to the factory for the Clock 2 upgrade. After a couple of days without it I decided to just listen to LPs until the clock was returned. Its absence was that profound.

Meitner is a competitor to dCS so anything he says must be taken with that in mind. After all it is pretty simple to test. Just use the clock then remove it and see what you think. I am unable to see any difference between Auralic and dCS’ approach as advised by Beolab. You can always change the separate master clock in a dCS system for a better one. And the dCS clocks have improved over time, I have owned one from all three generations.

Thanks Pete. I should have thought of that multi box arrangement when I asked the question. And your other points make perfect sense. As for differences with and without the Clock, my ears have already heard those.

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I think the main difference between Auralic’s G2 DAC-Master clocking approach versus dCS’ approach is Auralic’s elimination of the clock-input Phase-Locked-Loops on the DAC. Auralic is not the first vendor to attempt such proprietary work-around against the supposed weakness of PLLs. However, couple of things to keep in mind;

(1) PLLs are quite efficient and very well understood. They can operate well into the GHz range without any real challenges. In the Telecom space where clock synchronisation is even more critical, PLLs are standard practice among network elements BITS inputs and operate in the parts-per-billion (ppb) accuracy range on a daily basis without any problems. Audio application in comparison is peanuts.

(2) DAC manufacturers who don’t like PLLs typically complain about it adding low-frequency jitter to the reconstructed clock, obviously if the circuits are not designed properly. So, to mitigate that they just eliminate external clock inputs on the DAC, so no need for PLLs at all. And they use other techniques to keep everything in sync, for example, with very high-frequency sampling of the incoming digital bitstreams (via an ADC) at each of the digital inputs and then reconstructing the buffered bitstream within the DAC, thus maintaining a single clock domain. DAC vendors like Chord, MSB, EMM, Wadax, Berkeley, Trinity, etc., use similar techniques, and just focus on sourcing and designing-in the best internal clock as close to the analog-conversion stage as possible. Even lower-end DAC manufacturers like PS Audio do this.

(3) At the end of the day, the final measured performance of the overall system will prove which technique works best. I don’t think anyone has proven one way or another which is better, but we all know how well dCS measures, safe to say among the best in the industry if not the best :wink:

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The idea of adding a synchronous clock used in Audio for a network streamer or Ethernet switch is, in my view, pretty ludicrous, because (a) the clocks for the streamer/switch operate at totally different frequencies, and (b) the IP/Ethernet packets flowing out of the streamer/switch is asynchronous in nature which requires reassembly at the end-point, which is within the DAC domain anyway!

That said, within the professional space, there are technologies in-place designed to keep audio system components in sync; standards such as AES67 has synchronisation as a key aspect of Audio-over-IP streaming, and uses an existing industry standard; IEEE 1588 Precision Time Protocol (PTP) - which uses packets embedded within the TCP/IP stream to maintain sync, not an external clock interface port. And in the Telecom space there is an Ethernet switch clock synchronisation standard; ITU-T G.8261 designed to keep networks in-sync end-to-end for multiple applications. Those Ethernet switches are typically a lot more expensive than run-of-the-mill Enterprise or consumer grade Ethernet switches.

Net net, it’s complicated :grin:

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Greg, I have owned the entry level dCS gear, so I never had a chance to listen to the improvements that an external clock can make. Having noticed your enquiries at AS about EMM, I find going the USB route will be opening a can of worms, and a straight connection from Nucleus to EMM won’t be optimal, whereas a network connection to the dCS Ros is the right way to go. One can argue that a decent endpoint such as the Sonore Sig Rendu SE can mitigate things, but that’s a very pricey approach, (plus an additional component) since it was the top tier component reviewed.

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I think you have miss read my post as usual Pete :slight_smile:

The difference is that you go past the Master clock inside the DAC on the Auralic design.

It can be bettered with a descent external clock, but it can’t go pass the Master clock in the current dCS design, it can only make the pll clock more accurate.

Well put, Anupc.

Kelvin, I completely agree. I generally loathe USB, and try to avoid it when I can (yeah, I know, follow the SQ, wherever it leads, but with USB, there is so much to overcome). I am a thoroughly confirmed network audio guy, and it’s one of the attractions of the dCS line for me. In fairness, EMM have a reasonably priced streamer box, but even when connected with their proprietary EMMLink, it has certain limitations that, well, make it less decent.

Correct, the external clock in a dCS system does not replace the internal clock in a dCS unit, such as a Rossini DAC; the external clock instead acts as a reference for the DACs on-board clock to work to.

With that in mind, you want to isolate your reference clock from any kind of possible interference. This includes electronic noise, power rail variations, temperature variations and physical vibrations. All of these factors can influence a clock’s performance.

Think about everything a DAC, Upsampler or Transport has to do. They’re pretty big jobs all things considered, with lots going on simultaneously inside each unit. This will generate heat (from things like the amps), small variations on the power rails, and potentially very small amounts of crosstalk between components.

While we do an awful lot of high-level engineering to minimise the effects of these factors in these units, an external clock naturally has much less to do. It has a power supply that is not feeding amps, transports, processors etc., so the power fed to the crystals in a standalone clock is cleaner, they have more stable temperatures, less physical vibrations and no DAC boards, amps etc. inside the same box.

This isn’t to say the on-board clocks in a Rossini DAC for example aren’t already very good, they still have to be (as ultimately they are the clocks controlling the audio). But, feeding them a stable reference clock from a unit which does not need to worry about the external factors above will be, well, better! It’s essentially like removing all of these external factors from the clock inside every DAC, Upsampler and Transport connected to the external clock.

In a perfect world the clock inside let’s say a Rossini would live in a little vacuum with perfect power, heat and physical stability. In that case, an external reference clock wouldn’t make sense. Unfortunately though, you cannot cheat physics.

In practical listening I would wager most people who have experienced a dCS system with an external clock would agree this gives a very high level of performance. Subjecting the clock to external factors for the sake of not having a PLL to our ears is not the way to go! Besides this, the PLL (which as Anupchas touched on) is a very well known, understood and optimised bit of tech. We also do some clever stuff with ours to minimise jitter on the incoming master clock signal.

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I currently have a Aurender 20Wse clocked to the Rossini external clock. The Aurender, without clocking, sounds phenomenal. With clocking, the improvement is subtle…

Thanks. What were your comparison configurations with the W20SE, how does it deliver music to the Rossini, how do you control music selection (Aurender app?), and what would you say are the improvements you hear?

The W20SE feeds Rosinni via dual AES/EBU XLR outputs. Yes, I control the music with the Aurender app. Like I said, the improvements of clocking the W20SE were subtle. If I had to say, I’d point to slight improvement in separation and soundstage depth.

I have a Rossini with its clock and audiophile (not the stock) bnc cabling, along with the associated mega audio components/cables/headphones/speakers

I have to be honest and say that I hear absolutely no difference with the clock in use (with or without its dither feature) or not in use–in my case, I spent $7500 for no apparent difference in the musical sound or presentation

my opinion, for what it’s worth

You originally wrote that the Aurender sounds “phenomenal,” and I was curious as to “compared to what?” What were you using before the W20SE, and what competitors did you consider/evaluate against it? TIA!

Thanks for sharing that. I suspect that this is more than a little disappointing for you. When I auditioned Rossini, I was actually surprised how much of a difference the Clock made.

Prior to the Aurender I was using a highly modified macmini with Uptone Audio JS2 power supply, running os on SD card, minimal processes etc… bridged to Rossini. I was also using the SOtM ethernet switch, which was clocked by MUTEC REF10.

I agree Greg. When the first consumer dCS wordclock was released ( the Verona, sometime in the early part of this century) one was brought to me for a couple of days audition. Like diken 1957 I didn’t think it made a lot of difference and returned it. A couple of years went by and I had an opportunity to use one again. This time a metaphorical lightbulb illuminated above my head. So that’s what it does!

I think the reason that I didn’t get it first time around is that I was listening for the wrong thing in a typically audiophile manner; Is the bass better? Is there more detail? That’s not what the wordclocks do. It affects the overall presentation of the music ( not so much the sound per se) making it somehow more flexible, smoother, less trapped by the medium and closer to what we experience in live performance. I remember John Atkinson’s review of the Verona back then in Stereophile. He could measure the difference with it in circuit but found it difficult to find suitable words to describe the audible change. I will have to paraphrase his actual words but it was something like , the dCS stack sounds authoritative without the Verona. The Verona adds magnificence. Yep.

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