What is "Word clock" on pro audio gear?

[kenratboy]

I have been baffled for many years on this one. Solve it!!!

[justin_tx_16]

Word Clock is a handshake signal, typically running at 44.1KHz or 48KHz, used to signal the timing of digital audio data words. Word Clock merely takes care of the transmission of digital audio via TDIF, AES/EBU, S/PDIF, or ADAT Lightpipe connections.

The flow of word clock

[kenratboy]

OHHHH, so just a way to sync devices perfectly?

[justin_tx_16]

Precisely my dear Watt(hehe)son. And let me tell you,they are NOT cheap. $50 for a 3 foot word clock cable!

[kenratboy]

Ouch, but all stuff like that is expensive.

Why can't the word clock signal hitch a ride at a high frequency on the normal cables?

[Super_BQ]

I'm glad you asked this question because in consumer audio, "word clock" does NOT exist. Even the most expensive high end digital gear does not incorporate it. Why? Well I myself do not know why.

In pro gear, running long lenghts of cable is not that simple. Some people think it's easy to run a 40 foot coax or Toslink cable from one end of the studio to the other end in another room. You can do it, but without any word clock interfacing, you are asking for a whole truck load of "jitter" problems. Take this the next step, how about in concert applications where the cable lengths can run 10 times that?

Often enough, this amazes me when looking at highend consumer audio. They do ALL sorts of funny things such has using external outboard DACs and separate CD transports in order to achieve better sound. I don't know why some of the circuits used in pro-audio are not incorporated in consumer audio? (ie. most DACs are fully balanced from the chip but end up being "single ended" rca at the end). They work so hard in trying to minimize jitter in the digital signal when all they have to do is incoporate "word clock". IMHO, they are on the wrong track. Or maybe they are selling a particular sound quality which suposely "sounds good"? rather than reproducing sounds as accurately as possible - the way the studio engineers had intended it to be.

Word clock cables are nothing special. They use standard BNC connectors (same as old PC network coax cables) and do not have to cost $50 for a 3 ft. cable. Remember, we are talking digital transmissions where cables isn't as picky as cables are on an analog setup.

BQ

[TheEAR]

Super_BQ,

You nailed the box,agree on all counts.

With all the super High-End transports and DAC's comnpanies release its almost too obvious.And often the best souning "CD" players are transport and DAC in the same box.Take for example the Linn Sondek CD player,as good as it gets all under one tiny roof.The my Pioneer DVAX10 also an high caliber CD playback system in one box,an what about the Sony SCD-1,and the newer Krell.All one box designs.

Wadia,Mark Levinson and a few other still ride the separate is better bandwagon.

I think the dual box design is geared towards the ubber high end elitists who think each component should be isolated in its own cabinet,what they dont know or forget is more important.

Genesis also released a jitter "corection" system a few years ago.Funny,another device to add to the transport/DAC combo.Just great more money to spend to recoup some lost quality.

The secret is they want you to spend more,the more you spend the more they make.

[marksdad]

damn justin, i know you are young, where did you pick up on so much info, you continue to amayze me

[Prana-Bindu]

Separates are used in high-end digital gear because there are many different-sounding DAC's out there from which to choose. As much as it contradicts the long-standing myths about digital sound being perfect because "it's just 1's and 0's", the variety of sonic characteristics that is presented by digital gear is probably greater than in any other gear category (except maybe speakers?). In my case, the transport and DAC functions were separated because I wanted to take advantage of the resolution enhancement offered by the Perpetual Technologies P-1A. If it wasn't for that unit, I would probably have gone with a one-box player to avoid the jitter problems presented by the S/PDIF encoding used by most separates.

There are many manufacturers out there that have addressed the jitter issue quite well with their separates, using units that sync both units' clocks to either the DAC or transport clock and avoiding S/PDIF encoding. This leaves the question open of why use separates to begin with if a one-box unit would not have to deal with the timing errors of separates. I suspect there are sonic benefits to minimizing the functions for which a power supply is responsible. The more a power supply is supposed to feed, the more fluctuations it experiences and manifests in signal errors. This, I believe, is why some transports and players have an option to disable the unit's display. There are multiple places in a digital system (8 maybe?) where jitter can occur. I suspect that most, if not all, such sources of timing error are directly affected by the stability of the power supply.

This is just conjecture based on limited understanding of the subject, so take it easy on me. My point is that high-end, non-pro gear has indeed addressed the jitter issue and the solutions presented by a word clock don't address all sources of jitter. If a word clock takes as input an S/PDIF encoded signal, it doesn't even address the biggest source of digital jitter.