Digital Audio distortion

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Digital Audio distortion

Post by ghaffar3 » Wed Sep 09, 2015 9:33 pm

I have the following application:

We need to switch to a backup source in the case our main Audio feed has the following issues:

1)Loss of clock
2)Silence (below threshold levels)
3)Noise/Distortion in the AES signal.

Is there any solution to detect all of the above, and switch to backup source.

Kindly advise.

Ghaffar Ahmed.

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Re: Digital Audio distortion

Post by TPT » Thu Sep 10, 2015 5:46 am

Silence sensors are easily found--look at the Broadcast Tools line--just feed decoded analog audio to them & use the alert contacts to switch sources.

Maybe somebody makes a device that will catch the loss of your clock signal; I doubt that a "distortion alert" exists except as a carbon-based life form.

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Dale H. Cook
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Re: Digital Audio distortion

Post by Dale H. Cook » Thu Sep 10, 2015 6:53 am

TPT wrote: I doubt that a "distortion alert" exists except as a carbon-based life form.
Non-carbon-based real-time distortion detectors exist only in science fiction. :-)

Although systems such as Tieline can provide an alarm for AES clock loss I cannot recall seeing a standalone clock loss detector.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA

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Re: Digital Audio distortion

Post by dbuckley » Thu Sep 10, 2015 7:04 pm

I'd venture if you lose clock on digital audio signal, then you've got silence on your hands.

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Re: Digital Audio distortion

Post by kcbooboo » Fri Sep 11, 2015 6:59 am

A quick web search for:
aes clock loss detection
will show several units that can switch from a digital to an analog audio source when something goes wrong with the AES signal. Some can detect silence. Most have alarm outputs.

Distortion is something else though. This usually manifests itself when the analog input level is too high and causes the digital-to-analog converter to max out because it just can't push the peak any higher than, say "FFFF" in a 16-bit system. Once that happens and you lose analog data, you can't get it back. The damage is done. It's almost like trying to exceed 100% negative modulation on an AM system. Once the carrier is cut off, that's it; it's gone and can't get any lower.

Bob M.

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Re: Digital Audio distortion

Post by RodeoJack » Fri Sep 11, 2015 8:31 pm

Bob makes a good point. I would add... "Distortion, compared to what"?... or, "Distortion, from what part of the audio chain forward?" I don't know how anything could detect distortion without some reference to a point, prior to where the distortion did not exist.

Without something like that, most rock CDs would light a detector up pretty much all the time.

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