Importance of Clock Cables

Well the rossini clock has been here for a week. Sometimes i thinks oh yes and other times not so much. The overall impression so far is that it brings an effortlessness to the music, i think i shall give it a few more days running in to try and get a good understanding of what’s it doing then disconnect it it and run like that for a few days. Sometimes it’s more telling going backwards!

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Understood. I had a similar experience way back when the very first wordclock came out ( the Verona):

I must say I have never heard any significant differences when I remove the clock from my Vivaldi set-up.

As I mention in my linked thread above I think this partly has to do with exactly what you are expecting to hear. I also think that as it affects things like the naturalness of the musical delivery its benefits may not be apparent with some genres e.g. EDM or other wholly synthesised music which have no external existence to use as a comparison.

I can only say that whilst I could not “get” the use of a wordclock initially I now find not using it so diminishing that I prefer not to listen at all. Still, we all have different aspects of sound or music that are of prime importance to us.

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Pete, your reply chimes very much with my experience so far. As i said, sometimes i think Yes! this is something else, other times meh! So far it seems very much to be music dependent. But i have been told that it can take quite sometime for the to really settle and “open up”. So far more positives then negatives with the promise of a lot more to come.

I’ve mentioned elsewhere that when I auditioned my Rossini Player without the Rossini Clock, it did not exceed the sound quality of my Wadia S7i and I never would have purchased it.

It was only with the use of the Rossini Clock that the sound quality surpassed the Wadia and then significantly so.

It was a big enough difference that when I would shut off the clock random people in the shop asked what I just did because the sound quality became significantly worse - soundstaging and the sense of space in the room just went away.

What I mean is that with the clock you could clearly delineate the space in which the singer was singing (and it was a real space as it was a early 1960s Sinatra recording.)

With the clock off the space became diffuse and Sinatra was just “over there” with no real sense of space.

Turn the clock back on and the room and sense of space reappear.

Well, it’s been a few weeks since the rossini clock arrived and it’s opening out a lot more :grinning:. At times the sound is truly outstanding. I still think that it has more to give so i am looking forward to that.

I have also been having a play with some ethernet and clock cables; shunyata sigma and anzus A2 for the ethernet and shunyata delta and audioquest diamond for the clock.
I think the anzus takes the ethernet comparison, with the sound presentation seeming to be much cleaner and open particularly with voices.

With the clock cables, there was nothing that really said - here listen to this improvement! The sound of both (all shunyata & anzus / audioquest) was one i could happily live with; providing i didn’t have to shell out £1000 - £1600 for the privilege. I feel that for the cost, the money would be better “invested” in support/isolation.

Anyway, i am back with the designacable / wyde eyed combination and it does sound very good.
Although if i sell some excess cables and stuff i might jump for the anzus ( will have to have another listen).

Thanks for the assertion. Anything to back it up?

What a pity. I have been using dCS equipment for over 20 years. It now appears it is all a dud. Oh , and everyting else I have that is digital. What should I do ?

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Pete, you’re killing me! :rofl::rofl::rofl::rofl::wink:

I have some sympathy with meltemi’s deleted post. Here is a quote:

“A remote converter which sounds different when reproducing, for example, the same Compact Disc via the digital outputs of a variety of CD players is simply not well engineered and should be rejected. Similarily if the effect of changing the type of digital cable feeding the converter can be heard, the unit is a dud.”

Surely this converter behaviour (ie., immunity to jitter in the source) is what we’ve been hoping for as customers - but not really getting - for about 30 years, despite all the manufacturers’ efforts and often over-optimistic claims. And we know that the external clocks are beneficial, but not really why (apart from the usual “hand-waving” audiophile explanations). I remember reading in a pro audio magazine a test of the use of external clocks on some converters: there was no measurable difference in jitter in that test. So it remains a bit of a mystery, to me at least.

As for clock cables, I can well believe that the key to high performance is the connectors and impedance. After all, aren’t some of us happily using basic Apogee/Belden/Canare clock cables that correspond more or less to the simple recipe posted? What I have read in Belden’s literature about pushing 75 Ohm coax cable to perform better is all about what happens in the GHz range and at long lengths - not really relevent to our application.

Thanks Simon_C.

The quote was from John Watkinson, The Art of Digital Audio, 2nd Edition 1994,
chapter 3.9, Sampling Clock Jitter.

I deleted the posts because of the direction the “discussion” took.
I’m only interested in serious discussions with friendly and polite people.

Simon, as you know, I agree. Especially with digital cables, getting to spec meets my goals. I have tried to hear differences between spec’ed digital cables, especially clock cables, and I simply do not. Likewise, I am amused by the differences others claim to hear between similarly-spec’ed Ethernet cables, though accepting of the claims of sonic differences between different types of Ethernet cables (shielded vs. unshielded, for example). “I accept that you are hearing a difference. But two Cat 5 or Cat 6 cables properly made should not sound different. If they do, ask yourself “why” and seek out the likely most rational answer and effective resolution. Same with shielding. Something about your system is producing that difference. But it’s not the digital information.”

Properly spec’ed digital cables should deliver digital signals between digital components that introduce no new error in the digital chain (including parasitic noise). And therefore, properly spec’ed cables from different manufacturers should sound identical. If they don’t, we have to ask why and seek an engineering/scientific explanation that makes sense based on what we know or reveals something we did not previously know.

As for different clocks and different DACs, that such things do make audible differences in musical reproduction makes perfect sense to me.

Admittedly I don’t know the context this was written in, but taking what I can from the quote, this would assume that the converter used oscillators for its own internal clocks which were perfect and operated in a vacuum where no external factors could influence them. In reality, some interface jitter will be able to reach the converter and impact it, but to how much this happens depends on a number of design factors in the converter (clock oscillator type, PLL bandwidth etc.).

Again, without knowing the context and assuming this is talking about the digital audio cables, it is simply not true. Intersymbol interference will cause differences between cables on even the best DACs when locking to sync pulses in an audio signal, and is mitigated through the use of a Master Clock. I’ll explain that below.

We do know why, but it can be lengthy to explain. I’ll try and keep it as short as possible…

Locking a DAC to a Master Clock which does not have to contend with all of the sources of phase noise the DAC does (CD mech vibrations if present, power supplies running different circuitry causing changes in the power rails fed to the clock, the EM leakage from said circuits and additional processing for other functions like D/A conversion, heat generated by the product changing the frequency of the oscillator) means the DAC then has a much more stable reference to adjust its own clock to.

Why is this preferable to simply locking to the sync pulses in, for example, the SPDIF or AES signal coming from a CD transport to the DAC? Well, aside from the fact that the CD transport’s clock(s) have to deal with very similar sources of phase noise to the DAC which would put jitter into the signal, an effect called intersymbol interference comes into play.

When a digital signal is passed through a cable, the cable will act as a filter to a degree. A poorly designed cable, which is unfit for use with the interface it is designed for – like AES3 – could potentially filter out high frequencies from the signal before it reaches the DAC from the source device. This causes an interaction between any two consecutive data bits within the signal, called intersymbol interference. Depending on the relationship between one bit and the following bit, the transition between the two can be temporally smeared – the clean vertical line of the digital square wave becomes a sloped line, meaning the exact moment a 0 changes to a 1 or vice versa can be blurred. In short, jitter can be introduced purely from the interactions within the data itself.

If the timing data from the audio signal is being used to lock the DAC’s clock to, this intersymbol interference will have a negative impact on sound quality, as it can introduce jitter to the DAC’s clock. However, if the audio system is making use of a Master Clock, and the timing information embedded in the aforementioned AES3 signal is no longer being used, the effects of intersymbol interference are negated.

While the same sort of filtering can of course occur on a clock cable, as the signal is perfectly regular the filtering causes no timing change from one bit to another – no jitter from intersymbol interference.

Now, all of this is subject to how the PLL in the DAC is designed (the PLL is the circuit which locks the DAC’s clock to the same rate as an incoming signal) – should this actually have an impact in a well-designed DAC? Well, as with any engineering there is no such thing as a free lunch. If you design your product to reject interface jitter which is coming from outside the DAC (let’s say a jittery signal from a CD transport), you better make sure your DAC’s clock oscillators are very good, because your system will be more susceptible to intrinsic jitter (such as phase noise) as a result. If you are using a low phase noise oscillator such as a VCXO, this is doable – this is the approach we take. If you are using a VCO or to a lesser extent an OCXO based clock, you may have to bias the system’s PLL somewhat more towards accepting interface jitter to reject some of the intrinsic jitter from the oscillator. This may be necessary to get the best from that product. It’s a trade-off, and how the product designers work out which route to take depends on a huge number of things, not least product price point and use case.

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The quote is from
John Watkinson, The Art of Digital Audio, 2nd Edition 1994, chapter 3.9, Sampling Clock Jitter.

Thank you James, it is really interesting to have these issues explained in simple, practical, terms that have a technical basis. I am now trying to hold my hands away from the keyboard to stop myself typing a blizzard of further questions. Well, perhaps just one: what does this imply for AES cable design and construction, and can alternatives to the standard studio cables (Belden, Canare, and the Van Damme ones that dCS supply) be shown to be measurably better with regard to intersymbol interference or other factors?

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Thank you @James. Superb info.