Idiot’s guide to clocks

Can anyone please explain in simple terms what is involved in adding a clock to my Bartok. I,e
What does the clock do? How is the clock connected? Can any dcs clock be used? What are the sonic results?
Many thanks.

Hi John,

Adding an external Master Clock to your Bartók allows the unit to keep much better “digital time”. For good quality audio, you need the right sample at the right time. The quality of DAC is what makes the right sample, and the quality of the Clock is what makes it at the right time.

While any dCS Clock could be used with the Bartók, bearing in mind the software and hardware improvements we have made over the years you would definitely see the biggest performance increase to the system with a current generation clock, the most popular pairing being the Rossini Clock. In the case of either a Rossini or Vivaldi Clock, you would connect two BNC cables between the clock and the Bartók, to it’s Word Clock Inputs.

The sonic benefits you would hear from adding a Master Clock to your system would be that the clarity of the sound stage (where an instrument or part of the music is left to right but also where it is placed in the mix front to back) is greatly improved, the width of the soundstage becomes much bigger and the ability for the speakers to simply disappear takes a huge jump. It really isn’t a subtle difference, and I would absolutely recommend if you have the option of trying one out for a demo, go for it.


The Bartok already has a very good clock built in. However an external clock can provide improved accuracy and stability thus lowering jitter. When using a multi box system such as a Vivaldi stack a system clock ensures that all of the components are running synchronously.

In theory any dCS clock can be connected to the Bartok via BNC terminated 75 ohm coaxial cables. However as the dCS clocks have improved in performance over the years it may be ( though I haven’t tried) that e.g. the Rossini clock performs better than some of its historic predecessors such as the Verona etc. Further the older dCS clocks used a single connection for both 44.1 and 48 kHz based sources. The current dCS range requires dual connection. I am guessing that use of a legacy dCS clock would require manual resetting when the frequency base changes. Maybe someone from dCS has a view in this?

What do you get sonically? There are a few comments on this posted here over the past couple of weeks. Basically do not expect to hear improvements in typical audiophile terms e.g better bass, more detail etc. What happens IMO is the sound will be substantially more natural and substantially less fatiguing ( even if you do not think it fatiguing now :slightly_smiling_face:).

It took me a while to appreciate the benefits of using a system clock ( back in the Verdi\Purcell\Verona\Elgar days) and subsequently I could not imagine being without one.

BTW, with reference to one of your earlier questions, a recent review of the Network Bridge also touches on the order files play in when using an Innuos server:


Correct. Legacy clocks such as the Verona or Scarlatti only output one clock frequency at a time, so you would need to manually change the clock frequency when going between content base rates (going from playing a 44.1kHz track to a 48kHz tarck for example).

The Rossini and Vivaldi Clocks output the two different base frequencies on the separate outputs, so no need to manually switch, the Bartók will just use whichever one is needed for the content.

1 Like

Many thanks to all.

In addition to what has been said, some of the greatest improvements a master clock makes are not easy to describe in HiFi terminology: it’s very much about that elusive goal that one isn’t listening to reproduced music, but the thing itself. Music sounds more immediate, more realistic. I’m experiencing even less fatigue. Be sure that when you demo a clock to leave it on in your system for as long as possible versus going back and forth sampling songs. The improvement adding a master clock may not be subtle, but you’ll sorely miss it once it’s gone.

Greetings from Switzerland, David.

1 Like

Yes indeed :+1:

1 Like

Like butter from grass fed cows. The better you clock, the more real it gets.


I am also new to clocks so excuse my possible neophyte obvious question here. James noted that you hook up 2 cables from the Rossini clock to the Bartok.

It looks like the Rossini clock has 3 BNC clock outputs only “wordclock outputs”, that presumably run to the “wordclock in” 1 and 2 on the Bartok. In my admittedly remedial understanding (mostly from reading this rather helpful DCS forum) there would have to be bidirectional transfer of information. This is how the clock was described in another forum thread by DCS’s James Cook (same one as in this thread) – His comment below is in reference to a question on possibility of a master clock introducing jitter, but explains succinctly how the Rossini clock works:

“This would only be true if the clock signal being sent from the Master Clock was being used to actually clock the DAC. It isn’t - it is being used as a reference to synchronise the DAC’s own internal clock to. Whether any jitter on this interface is passed onto the DAC comes down to how the PLL inside the DAC is configured.”

So, the Rossini clock it is serving as a reference to synchronize the internal DAC clock I would think you would want data information to flow both ways - otherwise wouldn’t it simply be driving the internal Bartok clock?

Sorry if I am not explaining my question well - In other words, does the Rossini external clock need to sample or test if you will what the internal DAC clock is doing to “correct” it - it doesn’t seem like it is simply pushing out a stable clock signal based on what James said - in that the Bartock is using the Rossini clock as a “reference”–Thus to the neophyte learner here, it seems more like the two are communicating so that the internal clock can reference the external one and correct any errors?

If information is simply flowing unidirectionally from the Rossini clock to the Bartok how does that work then?

How can it work for ethernet input for example when using Roon as a source off a Roon Nucleus or Mac PC running Roon?

Thanks, in advance, for my learning
Happy holidays and best of health to all

I’m sure dCS will be able to fill in more details, but (as I understand it) the clocks inside the dCS DAC are constantly being ‘nudged’ in the correct direction by the external clock. The external clock doesn’t know what’s going on inside the DAC, it’s simply providing two reference signals that the internal clocks will stay in sync with.

Technologically, I suspect the DAC uses a Phase Locked Loop (PLL) to measure the difference between the internal and internal clocks and keep the internal clock locked closely to the external one. The ‘bidirectional communication’ you asked about is handled (within the DAC) using this circuit, it doesn’t need to send its own clock signal back to the master clock.


Spot on on all counts :smile:

1 Like

I will give you a very simplified explanation:

A good clock helps keep jitter down. It is not about super-precise frequency but about that frequency being as stable as possible. However, not all jitter is the same:

1- Very high frequency jitter, on the order of megahertz, is generally not audible and not that bad - unless it causes signal errors, but this is never the case with decent clocks these days.

2- Low frequency jitter is audible because it can alter the frequency a signal is reproduced: This is sometimes called “phase stability”, “phase drift”, or “phase noise”. Consider your fast clock slowly drifting frequency between a low and a high value, back and forth. For example, imagine this drift happens 100 times a second (ie a phase noise of 100Hz). If you play a 2KHz tone, what you will see out of the DAC’s analog output is that 2KHz tone with side bands at 2.1KHz and 1.9KHz. I should add that the frequency position of the side bands is given by the drift frequency whereas the “size” of the side bands is given by how large that fundamental frequency shift is.

A clock with a very low phase noise, ie very low low-frequency jitter, is what the dCS clocks provide. An additional very important benefit of an external clock is that it can clock the entire chain of components in sync. So for example adding a transport and clocking it with the same clock avoids all the pitfalls of the SPDIF/AES interface in regards to clock recovery.

I should add something about dithering: Dithering adds jitter to the clock signal, but the frequency of that jitter is very high. What that does is ensure the PLL (Phase Locked Loop) follower in the DAC clock stays tightly locked with the incoming signal from the clock. When the “locked” frequency is very close, the ability of the PLL to “lock” is reduced, and dithering essentially “shakes it a bit so it latches”. But as I explained above, given the frequency is very high, it does not have phase noise effects which are bad for sound quality.


Thanks - but if USB and Ethernet have no timing issues (from James post on clocking) how does the external clock help with this in particular. I understand how it would help with an external transport, but if using the Bartok as a streamer with Ethernet, and a media player (Aurender N10) pushing USB, how does the Rossini clock help?

Does the Bartok internal clock occasionally drift due to electromagnetic and other interference, and the external clock, serving as a reference, helps that Bartock internal clock become that much more accurate??

It clearly notes in the Bartok manual that the Rossini clock can only be used for the USB and ethernet inputs, so how is the Rossini Clock helpful in a Bartok based system without a transport, given the lack of timing errors with USB audio and Ethernet interfaces?


USB and Ethernet have no timing issues because they put information in a buffer and the DAC can talk back to the source and say “slow down” “speed up” and in the Ethernet case “resend that packet”. By the way, the USB Audio protocol does NOT have error correction, so it is not guaranteed to be error-free.

SPDIF is different because there is no flow control: The DAC cannot tell the source “slow down” or “speed up” so it has to sync with the source. There are many implementations that use a buffer and reclock, but those are not really kosher as that buffer can either run out or fill up if the two clocks (source and DAC) have very different frequencies.

A DAC always needs a clock - that’s how bits are converted to analog audio. That clock needs to be stable. The most important aspect of this stability is that the frequency of conversion does not drift around. What the external clock does is provide a frequency that is very stable and has very low drift.