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Author Topic: Help refresh my word clock knowledge  (Read 1909 times)

kristianjohnsen

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Help refresh my word clock knowledge
« on: April 03, 2015, 05:37:40 pm »

Recently, I was at an event where a Blue Ray player was unexpectedly introcuced last minute. 

The player only had a HDMI output and a digital audio output labelled "coax" (RCA-style connector).

The mixer was a Yamaha DM 2000.

Fully expecting it not to work, I connected the "coax" output to a free SPDIF input of the desk.  It worked just fine and I received a stereo signal to the two input channels I had the SPDIF-connector patched to.

Can anyone explain to me why there is no need for the Blue Ray player to be "synced" by the desk?

Going off of my old knowledge I was thinking the Blue Ray must be clocking the desk, but there were no issues switching the Blue Ray on and off.

Also, the way this mixer is set up it automatically clocks off a Dante card in YGDAI slot 1, regardless of whether the mixer is used with a Dante network or not (wich it wasn't on this gig).  The desk stayed clocked like this both with or without the Blue Ray player connected.
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Mac Kerr

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Re: Help refresh my word clock knowledge
« Reply #1 on: April 03, 2015, 06:02:38 pm »

Fully expecting it not to work, I connected the "coax" output to a free SPDIF input of the desk.  It worked just fine and I received a stereo signal to the two input channels I had the SPDIF-connector patched to.

Can anyone explain to me why there is no need for the Blue Ray player to be "synced" by the desk?

It is possible that the sample rate converter was turned on for that digital input. SRC is available on all 3 built in digital inputs, but it is not always turned on.

Mac
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kristianjohnsen

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Re: Help refresh my word clock knowledge
« Reply #2 on: April 03, 2015, 06:18:05 pm »

It is possible that the sample rate converter was turned on for that digital input. SRC is available on all 3 built in digital inputs, but it is not always turned on.

Mac

That sounds very likely, thanks!
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Luke Geis

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Re: Help refresh my word clock knowledge
« Reply #3 on: April 03, 2015, 06:35:15 pm »

I think you just got lucky on two parts. One was that the SPDIF was on and two was that the SPDIF on the desk was set for 44.1khz. that the player was likely broadcasting in.

But that does not mean they were synced. The info will still send and the mixer will play it, but if not synced there is possibility for clicks and pops to occur. The only way to know if they are synced is to look in the menu of the desk and observe the SPDIF settings. It should tell you if they are synced or not and what the clock setting is.

Usually digital outs on external devises like the blue ray player are meant to be the clock source. That is to say that if you set the blue ray player as your clock source and set the desk to sync to it, then it will work as it's supposed to. Not all external devises with digital outs can be set to be a slave, or sync to another source. This is not always ideal as now all the clocking in your desk is based on the blue ray player. Which means instead of only the 2 channels from the blue ray player clicking and popping, the other 16+ channels will click and pop instead if sync is lost.

I don't know if that made sense so I will bullet point it.

1. There can only be one clock source.

2. Most devises like CD players, blue ray players and other digital media devises will only function as the clock source and will not slave.

3. As long as the frequency between the two devises are the same, information will pass, but if not synced, the slave devise information can have clicks and pops.

4. If you set your desk as the slave and it loses sync to the master, you will have clicks and pops on all channels in the desk.

5. The two data rates are 44.1khz. and 48khz. Most media devices ( like the ones mentioned above ) are set for 44.1khz, but some can be changed or are set to the higher rate.
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I don't understand how you can't hear yourself

Lee Buckalew

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Re: Help refresh my word clock knowledge
« Reply #4 on: April 04, 2015, 11:08:25 am »

I think you just got lucky on two parts. One was that the SPDIF was on and two was that the SPDIF on the desk was set for 44.1khz. that the player was likely broadcasting in.

5. The two data rates are 44.1khz. and 48khz. Most media devices ( like the ones mentioned above ) are set for 44.1khz, but some can be changed or are set to the higher rate.

Ummmm, no.
BLU-Ray has possible sample rates of 48kHz, 96kHz, 192kHz with bit depths of 16, 20, and 24 possible.
DVD is 48kHz, 24 bit.
CD is 44.1kHz, 16 bit.
These do not take into account the other formats like, SACD, DVD-AUDIO, etc.

Read Mac's comment, most likely the SRC was engaged for those digital inputs.

I can have as many clocks as I want if I Sample Rate Convert. 

SPDIF and AES-3 differ primarily in one bit in the channel status frame and this makes them able to be interconnected in many, but not all, situations as long as the voltage requirements are present and the other digital needs (clocking and such) are within the required limits.

Check out this write up at Rane.
http://www.rane.com/note149.html


Lee
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Lee Buckalew
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Re: Help refresh my word clock knowledge
« Reply #4 on: April 04, 2015, 11:08:25 am »


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