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Ed Denton

Word clock in portable mixers

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I noticed that the Sound Devices 664 and 688 have word clock I/O on the bottom and it just got me thinking about it’s use in field recording and production sound mixing. I’ve actually never used word clock in any set up either in studio or field so I’m wondering what it’s use is? Obviously it is useful enough for Sound Devices to include it on their recorders but I’ve never come across it being discussed nor had any need to use it myself, but hoping to expand my knowledge in this area. TIA!

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Basically, a word clock prevents drift between two or more devices running together. Typically, a 'master' clock generates a stable signal which slave devices accurately sync to. TC alone does not prevent devices from drifting, especially a TC stamp, which is just a precise start time reference. A sync clock is usually not needed on a typical productions with normal duration takes.

Search "Tri-Level sync" and "Genlock".

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Rick has pretty much said it in brief. Word clock is a sync device - and is used EXTENSIVELY in post to sync several machines together. As Rick says, time code is not a provider of sync but, reliant on machines being synced, is a reference.

 

A digital feed (AES3, AES42, SPDIF etc) has an embedded sync which can be used to sync machines together. Word clock however is simpler (being only the sync) and thus more foolproof if you are dealing with multiple units (in post this will be a dedicated Master unit and several Slaves).

 

Hard to really elaborate beyond that ... look for a general write up on sync (post 1980?). Word clock on (eg) Sound Devices 7 series machines was put there for a good reason - to ensure a trouble free connection - even though clocking through AES would work well enough (albeit losing 2 channels).

 

Jez

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WC has allowed me to use multiple machines to record live music shoots where there was lots of leakage between mics/instruments, since it kept the recorders in strict sample lock.   This could be just 2 744Ts up to multiple JoeCo 24 track machines in lock with computer interfaces etc..

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I once really needed the w/c on the 664 when I had to send 8 AES channels to some video deck from Blackmagic.

The video guys gave me a 48k bnc signal out of their mysterical 19" video rack switcher unit. Without w/c audio-to-video just didn't work so I was very very happy about having this option.

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