Pro Tools Clock vs. Interface Clocks

[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?

[sdelsolray]

What "Pro Tools Clock" do you have?

[Darryl Ramm]

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. z

There is no clock in your computer that provides a clock to Pro Tools unless you are using a built-in audio interface.

Is my understanding of this correct?

It seems like you are trying to find stuff to worry about. If this was a problem like you seem to think, people would be unable to move digital audio around. Forget mixing, if I want to listen to a recording at home you are telling me I'm going to need the interface they used in the studio so I can clock my DAC off that?

You don't have a "Pro Tools clock", no such thing. In your case Pro Tools is clocking from your Apollo Twin interface, which is set to its internal clock. The other choices would be if you had an ADAT or S/PDIF optical source driving into your Apollo then you would need to clock from that source (since your Apollo Twin has no digital signal out or Word Clock out you have no choice for an outboard ADC to clock from the Twin) and all ADCs (and DACs) need to be sharing the same clock.

In the general or the specific meaning of "clock" a device to tell the passage of time... and that's all these clocks do. A quartz crystal vibrating away at some high accuracy, for most stuff that something around a few parts in a million frequency accuracy. So record with one clock driving an ADC, play back with a different clocked DAC, maybe they are off by a few parts per million. Who cares? Can you hear 0.0001% absolute frequency differences?

So clock DC offsets/absolute frequency accuracy in practice does don't matter... what does matter is the frequency jitter or phase noise in the clock at audible frequencies. And the reality there is any decent interface of DAC likely has clock phase noise so low that can't have any impact on what you hear. But it's still nice when vendors measure the noise floors to confirm that. But that is getting off into deep engineering areas where you don't need to go.

The era of belief that folks needed an external "better" clock to produce better sounding recording and playback is over. Modern interfaces just don't need it. ... but they still need distribution of a common clock across all interfaces/converters being used, and that's typically one of the boxes chosen for other practical purposes to be the master clock drivin the other boxes.

If you are interested in this stuff pick up a book on digital audio engineering.

[BScout]

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.

Yes.

Originally Posted by jd1234

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.

No to all of this. That's not how a sample clock works.

Originally Posted by jd1234

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.

No such thing as a "Pro Tools clock" in native Pro Tools. The "clock" is whatever your audio interface that is set as the audio hardware for Pro Tools.

Originally Posted by jd1234

Is my understanding of this correct?

Nope. Not in the least.
Basically, don't worry about it. If you have only the Twin, then internal is the correct setting and don't think any further about this.

[jd1234]

Originally Posted by Darryl Ramm

It seems like you are trying to find stuff to worry about. If this was a problem like you seem to think, people would be unable to move digital audio around. Forget mixing, if I want to listen to a recording at home you are telling me I'm going to need the interface they used in the studio so I can clock my DAC off that?

You don't have a "Pro Tools clock", no such thing. In your case Pro Tools is clocking from your Apollo Twin interface, which is set to its internal clock. The other choices would be if you had an ADAT or S/PDIF optical source driving into your Apollo then you would need to clock from that source (since your Apollo Twin has no digital signal out or Word Clock out you have no choice for an outboard ADC to clock from the Twin) and all ADCs (and DACs) need to be sharing the same clock.

In the general or the specific meaning of "clock" a device to tell the passage of time... and that's all these clocks do. A quartz crystal vibrating away at some high accuracy, for most stuff that something around a few parts in a million frequency accuracy. So record with one clock driving an ADC, play back with a different clocked DAC, maybe they are off by a few parts per million. Who cares? Can you hear 0.0001% absolute frequency differences?

So clock DC offsets/absolute frequency accuracy in practice does don't matter... what does matter is the frequency jitter or phase noise in the clock at audible frequencies. And the reality there is any decent interface of DAC likely has clock phase noise so low that can't have any impact on what you hear. But it's still nice when vendors measure the noise floors to confirm that. But that is getting off into deep engineering areas where you don't need to go.

The era of belief that folks needed an external "better" clock to produce better sounding recording and playback is over. Modern interfaces just don't need it. ... but they still need distribution of a common clock across all interfaces/converters being used, and that's typically one of the boxes chosen for other practical purposes to be the master clock drivin the other boxes.

If you are interested in this stuff pick up a book on digital audio engineering.

Okay now explain it to me like I'm 5 lol. So basically the gist of what you are saying is I don't need to worry about this, just use the Internal clock on Apollo. I do have 2 different chains (preamp & converter) that i often use with the SPDIF optical into the interface so i could switch from "internal" to "Spdif" clock on the Apollo, but if i am understanding correctly you are saying the difference will be extremely small, basically inaudible, so its not necessary? I also use the built in preamps on the Apollo though too though so another reason i am guessing i should use "internal' as the clock? And yeah i don't know where i drum all this **** up in my head, sometimes the over-analyzing has served me well and other times just drives me nuts. I think in this case i was confusing sample rate with clock stuff I dunno.

[jd1234]

Originally Posted by BScout

Yes.

No to all of this. That's not how a sample clock works.
No such thing as a "Pro Tools clock" in native Pro Tools. The "clock" is whatever your audio interface that is set as the audio hardware for Pro Tools.

Nope. Not in the least.
Basically, don't worry about it. If you have only the Twin, then internal is the correct setting and don't think any further about this.

Okay thanks for the response. Just to clarify one last thing... i do have a 2 different preamp-converter chains that i alternate using by running SPDIF optical into the Apollo so i could switch from internal clock to SPDIF on the Apollo right? But I'm gathering this is not necessary and won't even be an audible difference? Also use the built in preamps/converters on the Apollo sometimes too, so probs best to just use "internal" clock if i am switching around using internal and external preamps?

[jd1234]

Originally Posted by sdelsolray

What "Pro Tools Clock" do you have?

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

[BScout]

Originally Posted by jd1234

Okay thanks for the response. Just to clarify one last thing... i do have a 2 different preamp-converter chains that i alternate using by running SPDIF optical into the Apollo so i could switch from internal clock to SPDIF on the Apollo right? But I'm gathering this is not necessary and won't even be an audible difference? Also use the built in preamps/converters on the Apollo sometimes too, so probs best to just use "internal" clock if i am switching around using internal and external preamps?

How is that external converter getting clock? It needs to be clocked to the Twin. If it has no means of receiving clock (either digital input or wordclock connector) then you must set the Twin to use the spdif input as its clock.

[Darryl Ramm]

Originally Posted by jd1234

So basically the gist of what you are saying is I don't need to worry about this, just use the Internal clock on Apollo. I do have 2 different chains (preamp & converter) that i often use with the SPDIF optical into the interface so i could switch from "internal" to "Spdif" clock on the Apollo, but if i am understanding correctly you are saying the difference will be extremely small, basically inaudible, so its not necessary?

No what I said was.

The other choices would be if you had an ADAT or S/PDIF optical source driving into your Apollo then you would need to clock from that source (since your Apollo Twin has no digital signal out or Word Clock out you have no choice for an outboard ADC to clock from the Twin) and all ADCs (and DACs) need to be sharing the same clock.

"would need to" means you must do something, the opposite of not worry about it, even for a five year old. If your outboard ADAT or S/PDIF converter is running off its internal clock, and the Twin is running off its internal clock then the very slight differences in those clocks will often cause annoying pops and clicks. if you were using an S/PDIF or ADAT converter into the Twin you must clock from it, and that outboard converter must (in simple setups) be set to internal clock.(some studios might still run wordclock or some type of external clock to the outboard converters or all gear in the rack that has a clock input... so you need to sometimes work that out, but in your simple setup I doubt you have that, and you do not need it, the outboard converter will just clock from its internal clock.)

The pops and clicks that happen when external and internal I/O do not share the same clock is caused by that small ~few x 0.0001% frequency difference. basically the clock in the interface is being used to control timing of transfers of buffers full of audio samples to the computer...if an outboard converter is using a different clock those IO buffers might occasionally be sent before the outboard data is written to the buffer, and you hear that as a click or pop.

[IzzyTay88]

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?

A clock or master clock is just that. A clock. It keeps track of time, in this case the rate. The master clock sends signals to the slave clocks, which are in this case anything that receives a signal. So if you have any outboard gear or anything that needs to be converted to a digital signal the clock, makes sure that digital signal is in line as it needs to be. (To my knowledge I could be wrong).


In any case a good clock does matter because you can have peace of mind when it comes to any audio jitters or whatever conversion issues your gear may have, in theory.



Interfaces now a days have built in clocks, the "Pro Tools Clock" I'm pretty sure you are meaning your internal computer I/O?



In that case there is no pro tools clock. Just internal sound card which won't need to do much conversion for obvious reasons and your bound to the sample rate max of whatever the internal card is.



Long story short whoever gets the mix/files would not need to have your exact clock or the Apollo. As long as its converted good enough for you to hear it and do what you do, when they get the file it should be fine.



The sample rate saves to the project so, in any case as long as they have some type of interface it will work as an A/D converter/clock.