Pro Tools Clock vs. Interface Clocks

[sdelsolray]

Originally Posted by jd1234

Hahah. Yeah i think i was confusing sample rate with clock. Point made.. no clock on pro tools. I got it now.

Yes.

When there is more than one clock in a signal chain/system, the only thing that needs to be done is to choose one of those clocks for clocking the entire signal chain/system.

[spinsong]

With a dedicated clock you’re running a tighter system. Interfaces only can go but so far. So you get less jitter and superior crystals with dedicated units. You get what you paid for. Once transferred, the digital playback would be based on the operator’s word clock. It’s similar to translating from one system to the next.


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[BScout]

Originally Posted by spinsong

With a dedicated clock you’re running a tighter system.

Not necessarily

Originally Posted by spinsong

Interfaces only can go but so far.

Not necessarily

Originally Posted by spinsong

So you get less jitter and superior crystals with dedicated units.

Not necessarily

Originally Posted by spinsong

You get what you paid for.

Now you are just every marketing company's dream customer. Let's take for instance the original "vanity" clock: Apogee Big Ben. Same clock crystal was built into a bunch of their converters. Why would that be worse than a distant box that has a distribution amp? (it isn't.) OR Dave Hill and his Quantum clock -- which is the exact same clock found in his recent AD/DA designs. Or famously (for those of us who work in the high end) EMM Labs converters did not clock well to external clock. And those were the pinnacle. (It was a real pain to clock multiples of those units.) Or suggesting that about Prism (whether their Dream DA or AD or their latest) whose gear has always run on their own internal clock (even feeding external clock, they do not run off of that but buffer/reference it.)

The biggest point of external clocks is having a centralised clock for all your digital gear so they work seamlessly together. The rest, after that, is mostly marketing and very dependant on how each piece of gear deals with clock in the first place. But if you have 3 or less pieces of gear that need clock synchronization, spending money on an external clock is pretty worthless and funds are better spent elsewhere. (Why 3 -- because you can adequately send from one gear to 2 word clock inputs with minimal signal strength degradation or reflections using just BNC T connectors and 75ohm terminators. After 3, you need to consider cable length and distribution amplifiers.)

[Darryl Ramm]

Originally Posted by spinsong

So you get less jitter and superior crystals with dedicated units. You get what you paid

Nope. Much of this is vendor marketing ********. Clock technology is just fine in most interfaces, you would not hear any difference. And many interfaces can have lower jitter from internal clocks than claimed superior external clocks especially folks who still think their old Big Ben’s or similar are somehow magical. This is based too much on snake-oil and lack of hard measurements. If ya can’t hear it in a double blind test and you can’t see it in a phase noise plot it ain’t real (and even if you could see it in a phase noise plot it might not make any audible difference... but the reasons some of these vendors don't product phase noise plots is their devices are not great.)

(I spent time in a research group that developed exotic low phase noise precision oscillators, the marketing ******** in audio and especially idiot audiophile land just gets up my nose).

It is nice to see when folks do pull out a Miller analyzer or similar and actually measure phase noise… there are still products that get released with phase noise problems, including where a better external clock might not help. Some “audiophile” external DACs for example show phase noise in ways that makes me suspect they just don’t have competent engineering teams and just never bothered looking at this during development. It’s hard to have a well funded engineering team who can do all this, it’s easy to slap something that works into a fancy looking expensive box and make up some hyped claims for it.

[mups]

Hello,
This is a different topic but it fits the thread's titlle, so I guess the knowledge involved here should also be able to answer my question !
I'm a fairly advanced PT user and problem solver but this is something new...
My old PT 10, which is still perfect for recording and mixing music, doesn't open properly OMF or AAF files from modern softwares like Premiere and Resolve. As I have a more modern Mac Pro 5.1 for editing and color grading, I solved the problem by buying a PT 12-2018 license for that "modern world" computer, so I can mix to film.
At first, I had a small Ego-Sys U2A (old but still worth more than an Mbox, apparently) going into my monitor controller's analog inputs. Then I needed the converter for something else and decided to run a light-pipe from the optical output of the computer to the digital input of the controller. I did wonder about an eventual clocking issue but, as the software ran smooth and sounded okay (for films), I didn't question it very long.
Soon I have to record a voice over so, instead of switching to the old system (they share the same screens), I thought about connecting the ADAT output of an Amek DMCL to the optical intput of the computer and record directly into my movie mixing session.
Now I'm really wondering what's going to happen, clockwise...
Fundamentally, my question is : is it okay to have PT clocked by the computer or should I really use an interface ?

[audiolex1]

Originally Posted by jd1234

Can anyone here explain the drawbacks of using the clock of an external device? For example, i just started using a Apollo Twin X Interface (Thunderbolt) and i have it set to use the internal clock. So i believe (not a 100% sure) when i am using the Apollo with Pro Tools I am using Apollo's internal clock when recording.

I am thinking this may end up being a problem if I am going to eventually have someone else mix my project. Won't he need the Apollo interface if he wants to sync to the clock that i recorded the tracks on? Same thing with sending my pro tools session to other musicians to lay down parts.... won't they need the Apollo if i am using the clock in it. By contrast, if i use Pro Tools clock than it will be very easy for anyone with pro tools to open the session and lay down their part, mix the album on their gear, etc.

Is my understanding of this correct?

Clock - It is used to sync multiple external digital gear to the same time sample. Kind of like in analog tape machines, the 50/60 hz generator allowed the motors of both 24 track machines to run at the same speed.

So think of it as the sample rate running at the same speed when using multiple digital devices, like additional A/D/A converters. Within the studio.

If you are just using a single interface, then you should run it off the internal. There have been tests that have shown the noise/jitter is worse even using a "high end Master Clock".

If you plan to run the Apollo with a Ferrofish for example, you could even run the WC out to it and still be fine.
However, when you get into daisy chaining, I think that is when a master clock is going to be something to consider if you are running multiple external digital gear.

Not ever device is going to be superior in its output, at least they weren't 20 years ago. I would say you could daisy chain a few devices, but I would prefer a T splitter off the first device to DC.

Single interface, not necessary. Multiple devices after say 3, it would benefit you.

[Darryl Ramm]

In future please start a separate thread for your question. Spamming onto the end of other's threads is considered fairly impolite.

Originally Posted by mups

...a light-pipe from the optical output of the computer to the digital input of the controller

You mean S/PDIF over Toslink? Lightpipe == ADAT and the Amek DMCL output card is definitely S/PDIF not ADAT.

Originally Posted by mups

Fundamentally, my question is : is it okay to have PT clocked by the computer or should I really use an interface ?

But if you connect the S/PDIF TOSLINK output on the Amek DMCL to the computer's S/PDIF input you just set the computer S/PDIF In to clock from that S/PDIF input. And while clocking does not make as much difference as companies want to hype, it's still a good idea to clock computer internal interfaces off remote clock sources like the Amek DMCL. It's just typically a lot nicer electrical and thermal environment to run a clock in than a computer. But then going further and running an external Word Clock into the Amek DMCL is likely to 1. make no audible difference. 2. actually increase clock phase noise (even if you can't hear it). 3. confirm you as a marketing victim of clock box selling vendors.

[mups]

Originally Posted by Darryl Ramm

In future please start a separate thread for your question. Spamming onto the end of other's threads is considered fairly impolite.

Sorry, I didn't know about that rule. It just seemd more efficient to add my question to an similar existing thread rather than creating a new one...

Originally Posted by Darryl Ramm

You mean S/PDIF over Toslink? Lightpipe == ADAT and the Amek DMCL output card is definitely S/PDIF not ADAT.

Yes of course, S-PDIF, not ADAT.

Originally Posted by Darryl Ramm

But if you connect the S/PDIF TOSLINK output on the Amek DMCL to the computer's S/PDIF input you just set the computer S/PDIF In to clock from that S/PDIF input. And while clocking does not make as much difference as companies want to hype, it's still a good idea to clock computer internal interfaces off remote clock sources like the Amek DMCL. It's just typically a lot nicer electrical and thermal environment to run a clock in than a computer. But then going further and running an external Word Clock into the Amek DMCL is likely to 1. make no audible difference. 2. actually increase clock phase noise (even if you can't hear it). 3. confirm you as a marketing victim of clock box selling vendors.

Thank you, this confirms my thinking. I guess I'll set up an external converter again.
For what it's worth, a side note about WC : a long time ago back when we were using stock 192's, I bough an Antelope OCX and hooked it up while my partner was on tour. When he came back, unaware of the gear change he opened a recent session and rapidly asked me what magic I had done to the mix, as it seemed clearer, with more depth, etc... But I hadn't touched it !

[JFreak]

Clock is not irrelevant, but as said modern interfaces are equipped with so damn good clocking to begin with, external clock is useless if you only need to clock few devices together.

Rewind two decades and things were different. For example DigiDesign 002R @96k sounds almost as good as DigiDesign 96 @48k and DigiDesign 192 clocked with a superior external clock unveils the sound and makes you think you are monitoring via much more expensive unit.

Also already mentioned, but this Apogee Symphony II of mine has so good clock there is absolutely no need for a better one. THE only reason for external clock these days is easier clock distribution, but even then it does not necessarily mean clocking is better. And with Loop Sync even clock distribution became a moot point as the clocking loop keeps the interfaces together and each box has wordclock output for some 3rd party box which needs clocking.