Help! My A7III R records noise from the USB C port even though I use an external Mic.

elgourmet · Jul 10, 2019

I've uploaded a video to better understand the problem. As soon as I connect the USB C cable (in order to remote control the camera with my laptop) to the camera, I get some serious audio noise that is also recorded to the video and very disturbing once the video gets played back.

The noise per se is created due to the some badly isolated circuit on the motherboard of the laptop I guess. But the main question is: WHY does the A7IIIR record audio via the USB C port anyway, even though I am using an external mic (which also gets recorded)?

voronspb · Jul 10, 2019

I have the same problem. 50 Hz noise from laptop power adapter is going through HDMI-USB converter, then via HDMI cable to camera and finally it's caught by external mic.

I found 3 working solutions for this problem:

Using the internal mic.
Ensure proper grounding of laptop, if possible.
Swap the laptop to a model with better designed power unit.

Reto B · Jul 10, 2019

elgourmet said:
I've uploaded a video to better understand the problem. As soon as I connect the USB C cable (in order to remote control the camera with my laptop) to the camera, I get some serious audio noise that is also recorded to the video and very disturbing once the video gets played back.

The noise per se is created due to the some badly isolated circuit on the motherboard of the laptop I guess. But the main question is: WHY does the A7IIIR record audio via the USB C port anyway, even though I am using an external mic (which also gets recorded)?

Try to do a recording with the laptop only powered by its battery. If this helps get an external batterypack for the laptop (if something like this exists). But if the noise is still there you may also try a different (better) USB C cable. If both don't help then the laptop produces the noise and sends it to the electronics of the camera. In other words: the signal from the laptop compromises the electronics of the camera in which case you need a better laptop.

Entropy512 · Jul 10, 2019

Reto B said:
elgourmet said:

I've uploaded a video to better understand the problem. As soon as I connect the USB C cable (in order to remote control the camera with my laptop) to the camera, I get some serious audio noise that is also recorded to the video and very disturbing once the video gets played back.

The noise per se is created due to the some badly isolated circuit on the motherboard of the laptop I guess. But the main question is: WHY does the A7IIIR record audio via the USB C port anyway, even though I am using an external mic (which also gets recorded)?

Click to expand...

Try to do a recording with the laptop only powered by its battery. If this helps get an external batterypack for the laptop (if something like this exists). But if the noise is still there you may also try a different (better) USB C cable. If both don't help then the laptop produces the noise and sends it to the electronics of the camera. In other words: the signal from the laptop compromises the electronics of the camera in which case you need a better laptop.

A ferrite clamped on the USB cable and/or wrapping it a few times through a ferrite toroid might help if it's noise traveling on the shield.

Sadly, USB cables are kind of notorious for noise issues if the connected device is noise-sensitive. Big problem for the people doing software defined radio work... A noisy host PC can cause serious degradation in sensitivity by raising the noise floor.

SQLGuy · Jul 10, 2019

elgourmet said:
the main question is: WHY does the A7IIIR record audio via the USB C port anyway, even though I am using an external mic (which also gets recorded)?

It don't think it does, but the noise from the laptop's electronics, and/or a possible ground loop, is probably putting a bunch of electronic noise onto the camera's buses, and that's getting picked up by the analog audio circuitry.

elgourmet · Jul 10, 2019

thank you all very much, that is some very interesting input!!! So I guess i'll try to look for a better USB cable then?

using the laptop with just its battery and/or changing the laptop are not really options for me :-(

Entropy512 · Jul 10, 2019

elgourmet said:
thank you all very much, that is some very interesting input!!! So I guess i'll try to look for a better USB cable then?

using the laptop with just its battery and/or changing the laptop are not really options for me :-(

You should still at least test with the laptop on battery only to see if it makes a difference.

Is the noise you're picking up at AC line frequency, or higher frequency stuff?

Changing USB cable may not do the trick, as VERY few have ferrites built in - but this is a component you can add after the fact. Strangely, the cables I HAVE seen with ferrites built in (Monoprice microUSB cables) are some of the least reliable cables I've ever used.

Is your external audio equipment AC-powered or battery? Does it happen to have any connectivity to the laptop too if it is not AC-powered?

--
Context is key. If I have quoted someone else's post when replying, please do not reply to something I say without reading text that I have quoted, and understanding the reason the quote function exists.

voronspb · Jul 10, 2019

Neither ferrite ring, nor better USB cable will affect AC frequency noise.

There're certain devices designed for breaking the physical current flow through USB, while maintaining the data connection (in theory, to some degree). But their performance is questionable.

BTW, there's a possible way with better microphone on camera. XLR microphones are balanced (unlike those connected via 3.5mm jack), and they shall be free from AC noise. There's Sony XLR-K2M microphone, compatible with proprietary Sony hot-shoe, but it's ain't cheap.

Entropy512 · Jul 10, 2019

voronspb said:
Neither ferrite ring, nor better USB cable will affect AC frequency noise.

There're certain devices designed for breaking the physical current flow through USB, while maintaining the data connection (in theory, to some degree). But their performance is questionable.

BTW, there's a possible way with better microphone on camera. XLR microphones are balanced (unlike those connected via 3.5mm jack), and they shall be free from AC noise. There's Sony XLR-K2M microphone, compatible with proprietary Sony hot-shoe, but it's ain't cheap.

See, we still don't know WHAT frequency he's experiencing noise at.

If it's high pitched noise and not AC ground loops ferrite might help. That said it's a solution more suitable to RF...

If it's AC, then it's probably a ground loop.

elgourmet · Jul 10, 2019

i will post a video with more details the day after tomorrow. you guys seem to know a lot about this stuff!

voronspb · Jul 10, 2019

I'm pretty much sure that the problem is in AC noise, which is heard as loud humming, gone immediately after disconnecting AC power supply. I'm afraid, it's not the ground loop, strictly speaking. Poor quality power adapter passes some AC current to laptop DC input, while ideally there shall be pure DC current.

RF noise from laptop may be also present, but it's not directly bound to USB connection, as the microphone simply catches this noise wirelessly.

Paul Barnard · Jul 10, 2019

voronspb said:
I'm pretty much sure that the problem is in AC noise, which is heard as loud humming, gone immediately after disconnecting AC power supply. I'm afraid, it's not the ground loop, strictly speaking. Poor quality power adapter passes some AC current to laptop DC input, while ideally there shall be pure DC current.

RF noise from laptop may be also present, but it's not directly bound to USB connection, as the microphone simply catches this noise wirelessly.

voronspb · Jul 10, 2019

There shall be the proper ground in AC socket. And also the power adapter shall support grounding. Then it may work, of course.

Reto B · Jul 11, 2019

elgourmet said:
i will post a video with more details the day after tomorrow. you guys seem to know a lot about this stuff!

If none of the above suggestions should help, your last resort would be to remove the noise in PP. Adobe Premiere offers some tools for it, but Adobe Audition and the even more powerful iZotope RX 7 Noise Reduction & Audio Repair Software offer more in this regard. Just record a few seconds of video with the noise alone, without any other sound input. Then it's easy to remove the noise in post without noticable degradation of the audio. I rescued many videos and audio files like this.

voronspb · Jul 11, 2019

Reto B said:
If none of the above suggestions should help, your last resort would be to remove the noise in PP.

It works for me to certain degree. I do live streaming with my cameras, and software noise suppression (either in Windows mic properties, or OBS studio) usually works quite well. Of course the sound quality suffers somewhat, but for technical tasks it's OK.

For the best possible sound quality the ultimate solution for OP would be external sound recorder without direct connection to laptop.

Reto B · Jul 12, 2019

voronspb said:
Reto B said:

If none of the above suggestions should help, your last resort would be to remove the noise in PP.

Click to expand...

It works for me to certain degree. I do live streaming with my cameras, and software noise suppression (either in Windows mic properties, or OBS studio) usually works quite well. Of course the sound quality suffers somewhat, but for technical tasks it's OK

iZotope RX 7 goes far beyond of what Windows mic properties and OBS studio can do, but it's not cheap. I use iZotope RX 5 Advanced which I bought a few years ago for about $ 1000. The latest iZotope RX 7 Advanced costs $ 1199. Professional tools have their price tag but they deliver outstanding results.

But for the OP I'd suggest either RX Elements ($ 129) or RX 7 Standard ($ 399) which are all you need for very good noise reduction. OR if the OP has Adobe CC he can use Audition which also has noise reduction tools which are better than what Windows mic properties and OBS studio can deliver.

voronspb said:
.

For the best possible sound quality the ultimate solution for OP would be external sound recorder without direct connection to laptop.

This would be a good solution but it also costs money and means more work.

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Help! My A7III R records noise from the USB C port even though I use an external Mic.

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