Can someone explain this whole word clock thing or point me to a good explanation?

[guitarplayer888]

I don't yet have my head around the issues related to syncing digital equipment. I understand basically that word clock is like some kind of digital click track that keeps multiple pieces of digital gear in sync. I believe its tied to the sample rate (44.1, 48, etc.). I also understand that one device needs to be the master (generator of the clock signal) and the others slaves (recievers of the clock signal). But I'm having lots of little clicking sounds that seem to get worse the longer I leave pro tools open and while rebooting my mac seems to fix the problem temporarly, it does come back. And its really bad with my eleven rack when I set my digital mixer to 48khz.

For the record I use a Tascam DM-4800 digital mixer with integrated firewire card connected to a Mac running the latest Mountain Lion OS and Pro Tools 10.3.2. I also have an 11 rack connected to the mixer via high quality AES/EBU cables. All other gear is connected analog so I'm not sure its relevent.

I know there are all these fancy apogee and other dedicated word clock devices but do I need one? Is my problem related to buffer settings or word clock issues or some other setting somewhere on the board or on the Mac? Any help or clarification on this topic would be great, even links to good explanations elsewhere. Thanks!

 

[Bobbsy]

You're just about there on your understanding of word clock. Basically your digital samples are represented in data words. Every digital device has to have a clock that tells it when to start a new sample/word. However, left to there own devices, these clocks can drift against each other and, when they get too far apart, a glitch happens as they try to put the signal back together again.

It's certainly not always necessary to have a specialist central clock. On most systems, it's possible to set one device as master and lock other devices to that. For example, in my home studio, I've set my digital mixer to be the master and feed the word clock from there to all other digital devices.

(At this point I'll mention that there are people who will say that a highly accurate master clock like a Big Ben can improve the sound of your whole system. I've been involved in an A/B/blind test and didn't hear a bit of difference--and neither did the vast majority of other participants. You'll have to make up your own mind.)

Now, your problem. It MIGHT be word clock related but a quick look at the web site for you 11 doesn't seem to mention it having a specific word clock input (usually on BNC). It does say that it can take its word clock reference from the digital inputs.

If the web site is incomplete and it DOES have a word clock BNC on the back, hook up a short piece of coax from the mixer to the 11, set whatever software is necessary to make the mixer the master and the 11 the slave and see how you get on. If the 11 doesn't have a BNC word clock input, have a read of the manual, install either of the two digital signals that it can extract word clock from (output from the mixer to the 11 and again set the mixer as the master clock.

Otherwise I fear you're back to buffers etc. and I'll leave suggestions there to others since I'm not presently a protools user.

 

[guitarplayer888]

You're just about there on your understanding of word clock. Basically your digital samples are represented in data words. Every digital device has to have a clock that tells it when to start a new sample/word. However, left to there own devices, these clocks can drift against each other and, when they get too far apart, a glitch happens as they try to put the signal back together again.

It's certainly not always necessary to have a specialist central clock. On most systems, it's possible to set one device as master and lock other devices to that. For example, in my home studio, I've set my digital mixer to be the master and feed the word clock from there to all other digital devices.

(At this point I'll mention that there are people who will say that a highly accurate master clock like a Big Ben can improve the sound of your whole system. I've been involved in an A/B/blind test and didn't hear a bit of difference--and neither did the vast majority of other participants. You'll have to make up your own mind.)

Now, your problem. It MIGHT be word clock related but a quick look at the web site for you 11 doesn't seem to mention it having a specific word clock input (usually on BNC). It does say that it can take its word clock reference from the digital inputs.

If the web site is incomplete and it DOES have a word clock BNC on the back, hook up a short piece of coax from the mixer to the 11, set whatever software is necessary to make the mixer the master and the 11 the slave and see how you get on. If the 11 doesn't have a BNC word clock input, have a read of the manual, install either of the two digital signals that it can extract word clock from (output from the mixer to the 11 and again set the mixer as the master clock.

Otherwise I fear you're back to buffers etc. and I'll leave suggestions there to others since I'm not presently a protools user.

Thanks that is very clear. The 11 rack gets its clock signal from the AESEBU connection to the board, and it seems that all the settings for it are in Pro Tools. I need to dig deeper into this but I'd so much rather be working on my recording and mixing skills than troubleshooting little digital clicks. Frustrating!