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Strange Problem with 788T files

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I've had a very strange thing occur on a whole days worth of files where self-noise and tiny clicks frequently appear on all channels of my 788T recorder, across the the CF and internal drive (I've attached a photo of the waveform to show the clicks that appear).

This was on a 12 day shoot, only 1 day has this problem. On that day I was using all the same equipment in the same bag from previous days (4 channels zax + 1 sanken cs-3e). 

Does anyone know what this problem might be, or has anyone faced a similar problem before?

 

IMG_5224(1).jpg

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I was feeding my channels 3-6 with AES out of zaxcom QRX's. But channel 1 was analog.

Just to clarify the picture shows mix, boom (analog), zaxcom lav (aes). 

Is there any reason it would bleed over to other channels? 

 

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It could be a clocking issue, but only if you had inadvertently switched the 788T‘s own clock to external. It would then attempt to clock itself to the first AES stream, should that work, the 2nd QRX digital stream would be unclocked. But the output from a QRX100 is normally (or always?) at 32k. If you’re 788 is set to 48 that could cause these clicks, although the 788 should refuse to record at all. It’s also strange that the clock would switch back. 

Anyway, check your clock settings 

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Hi mate,

Its bizarre just cause I have never had this issue at 48k before, and it was only on this day. I never play with sample rates as well.

I was also under the impression that the 788t had sample rate conversion per track. 

 

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It seems more like a clocking issue to AES sync. Meaning, the recorder did not slave its rate to the incoming signal.

If that is the case, there is also a AD conversion done before the mix, that also slaves wrong, otherwise your analogue input should be clean.

(Makes sense not to do the AD conversion and re-clock it for mixing.)
But then you should also hear small artifacts besides the obvious (asymmetric) peaks.

 

Having said this, this is pure a hunch.
Now, my SD PIX recorder recently also had issues with recording, and those seem magically fixed by doing a firmware restore. (Not sure if that is in the menu of your recorder, but I think it can't do you any harm to update the firmware.)

 

Oh, you might want to learn how to make a screenshot with your OS instead of your phone :-)

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5 hours ago, sciproductions said:

I was also under the impression that the 788t had sample rate conversion per track. 

 

 

Yes it does, but it will only do sample-rate conversion when its clock („sync reference“) is set to internal. If it isn’t it will look for an external clock, either word-clock or it can derive its clock from one of the digital inputs, like from an AES signal. If that AES signal is unstable or at the wrong sampling rate, this could cause problems such as yours. 

I have, once in a blue moon, experienced a settings change on the recorder initiated by the recorder. Double check the menu rec: sync reference and make sure it’s set to internal. For an external sync you would need to lock both of your QRX which is not possible 

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Yep, looks like a classic sync error to me as well.  788T on "Internal" for sync reference and the with the Zax AES on "Internal" (or whatever the setting is called on a Zax) perhaps.  Clocking protocol in the digital realm is a "must".  Bummer.

 

D.

 

Oh, and SRC and clocking are not the same thing.

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20 minutes ago, tourtelot said:

 

Oh, and SRC and clocking are not the same thing.

 

No, of course. But the SRC makes it possible to use different unclocked devices together. When using more than one Zaxcom receiver using the SRC is absolutely the only way to record them digitally.

 

As a side note, and I don’t meant to bash Zax, but I find it a bit strange that a piece of digital equipment - that prides itself on being fully digital - does not offer any external sync options 

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27 minutes ago, Constantin said:

 

No, of course. But the SRC makes it possible to use different unclocked devices together. When using more than one Zaxcom receiver using the SRC is absolutely the only way to record them digitally.

 

As a side note, and I don’t meant to bash Zax, but I find it a bit strange that a piece of digital equipment - that prides itself on being fully digital - does not offer any external sync options 

Or whose receivers aes digital outputs will not work with Sony Cameras..

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12 hours ago, Constantin said:

I have, once in a blue moon, experienced a settings change on the recorder initiated by the recorder. Double check the menu rec: sync reference and make sure it’s set to internal. For an external sync you would need to lock both of your QRX which is not possible 

 

I always set sync to internal, but thats good to know that the recorder can just change randomly. I'll make sure to double check every time i turn it on now. 

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I don't know.  I have had my 788T since I can't remember and it has NEVER set itself to another setting by itself.  Not ever.

 

Just an observation made over the course of many, many years as an owner.

 

D.

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20 minutes ago, tourtelot said:

I don't know.  I have had my 788T since I can't remember and it has NEVER set itself to another setting by itself.  Not ever.

 

Just an observation made over the course of many, many years as an owner.

 

D.

 

I‘ve had my 788 almost since its first release. Something that happens regularly is that the 0dB position on the CL9 (as the value shown on the display) can suddenly (after switching it on) be at the -30 position, or somewhere else. Other settings changes sometimes happen after an „event“ like a crash. Never had it change sync reference, but I don’t find it totally unlikely. 

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9 hours ago, tourtelot said:

Sounds like you might have a broken 788T.

 

D.

 

It‘s been with SD at least three times since this occurred and apart from this fader thing it works absolutely fine. 

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13 hours ago, MartinTheMixer said:

Hello, were you feeding any devices via cable on the output of your 788T?

Thank you, Martin

Hi,

Yep I was feeding 1 QRX a mix for 2.4ghz ifb. 

(This was done everyday prior).

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3 minutes ago, sciproductions said:

Hi,

Yep I was feeding 1 QRX a mix for 2.4ghz ifb. 

(This was done everyday prior).

Hi, Well your car started the same every day until it didn't. So that I'm clear, you had a QRX that has the IFB option installed, and you had that QRX across the room, some distance, and that was being fed from 788T? Or are you saying this was all in your bag or cart? 

Thank you, Martin

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2 minutes ago, MartinTheMixer said:

Hi, Well your car started the same every day until it didn't. So that I'm clear, you had a QRX that has the IFB option installed, and you had that QRX across the room, some distance, and that was being fed from 788T? Or are you saying this was all in your bag or cart? 

Thank you, Martin

 

All in a bag. 1 QRX being fed a mix (for IFB), and 1 QRX stand alone.

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