Web Presenter HD has terrible audio hiss / noise!

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BrandonWood

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Web Presenter HD has terrible audio hiss / noise!

PostWed Oct 13, 2021 8:54 pm

Hello,
I have been an original Web Presenter user for some time to livestream our church services through Vmix (using the Web Presenter as a webcam). After upgrading to the HD version for the same purpose, I have been extremely disappointed with the enormous amount of noise the SDI cable has introduced. I am running the SDI cable from a blackmagic ME/2 unit with sound running via aux output directly from our A&H board to the audio input on the ME/2 via XLR cable. The only way to kill the noise is to remove the SDI cable, which of course kills the video input. The XLR is supplying clean audio and not the source of the noise. I've also tried different SDI cables to no avail. I'm using the latest firmware as well. What could be the issue? Help!
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Asgeir Hustad

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Re: Web Presenter HD has terrible audio hiss / noise!

PostThu Oct 14, 2021 6:56 am

This sounds very weird, as the audio over the SDI cable is already digital, and should in no way be adding hiss or noise. Are you absolutely sure that the audio in the 2M/E-switcher is clean? As in, are you listening to it from the ATEMs outputs while observing the issues on the Web Presenter?

When removing the SDI cable from the WPHD you're removing the signal, so of course that will remove the noise. Does not tell you anything of value, though. Have you tried recording the signal from that SDI cable on another device to see if the audio problems are found there as well?
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floh79

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Re: Web Presenter HD has terrible audio hiss / noise!

PostThu Oct 14, 2021 7:02 am

Hello, I think Brandon is not using SDI for audio channels as he wrote:
BrandonWood wrote:I am running the SDI cable from a blackmagic ME/2 unit with sound running via aux output directly from our A&H board to the audio input on the ME/2 via XLR cable.
It sounds like if the XLR-cable is not properly shielded :idea:

@Brandon: Do the cables (SDI and XLR) run alongside? Try to separate the cable (if possible?) so SDI cannot inference the audio signal in XLR-Cable.

Best regards
Floh
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BrandonWood

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Re: Web Presenter HD has terrible audio hiss / noise!

PostThu Oct 14, 2021 8:15 pm

@Asgeir, I haven't thought to listen to the signal directly through the ATEM. That's a good point. @floh79 no, the cables do not run close together and I've also switched them both out to eliminate the possibility of a bad cable.
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Johannes Jonsson

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Re: Web Presenter HD has terrible audio hiss / noise!

PostFri Oct 15, 2021 3:46 pm

Test new cables.
Are you using a balanced audio cables?
Balanced audio cable has two copies of the same incoming audio signal, hot and cold plus the shield (ground), those two signals on the hot and cold wires are reversed in polarity canceling each other out to prevent noise, If the cable picks up noise the noise added is not reversed in polarity in the end so the noise on one wire cancels out noise on the other one so having bad connection on one of them is most likely the reason for the noise you are getting.
Johannes
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BrandonWood

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Re: Web Presenter HD has terrible audio hiss / noise!

PostMon Oct 18, 2021 6:24 pm

Update: I never found the cause for the hiss. I tried new (balanced) cables. Made sure audio was clean coming in to the ATEM. Cables aren't crossing, etc. The only explanation I can think of is the WP box itself. I've ended up using my old WP box for audio and the new WP HD box for video and setting the delay in Vmix to match. I don't believe I'm using the new WP HD as blackmagic fully intended by setting my IP address and streaming directly through it (instead I'm using it as a webcam like the old box), however, since I am using a private stream service (sermon.net), I don't believe there is a way for me to stream directly through the box and test the audio that way.

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