MBP: Buzzing from headphone jack when AV dongle plugged in

[Scam]

Argh this is driving me nuts. I use their stupid USB-C Digital AV Multiport Adapter to plug my MBP into a HDMI+USB switcher so I can use my desk monitor/mouse/keyboard that is shared with my personal PC.

I've got my MBP plugged into my speakers via the 3.5mm output but I get an awful buzzing/high pitched whining whenever the AV dongle is plugged in. It's not actually the power/charging cable causing it, I have that plugged into a different usb-c port on the MBP and it doesn't stop when I remove that.

Any ideas?

EDIT: The buzzing is coming from my speakers, not the Macbook

 

[b0rn2sk8]

Is the switcher powered and adding some noise into the mix?

Try removing the switcher from the link and plug the monitor, keyboard and mouse into the laptop directly and see if it solves the issue.

 

[Scam]

Is the switcher powered and adding some noise into the mix?

Try removing the switcher from the link and plug the monitor, keyboard and mouse into the laptop directly and see if it solves the issue.

Well actually the switcher isn't powered but it seems to draw power from the MBP - which I wonder has something to do with the noise. I know it's drawing power from the MBP because the switcher's light stays on when plugged in even when my power plug is off. I was messing around with it today and noticed that sometimes if I picked the switcher up off the desk the noise would stop (not always).

Unfortunately I can't remove the switcher from the equation because I need keyboard+mouse to go into the 1 usb port the AV adapter provides... Hmn...

 

[Scam]

Try removing the switcher from the link and plug the monitor, keyboard and mouse into the laptop directly and see if it solves the issue.

Unfortunately Apple being Apple there's no way to plug a HDMI or usb keyboard/mouse directly into the MBP (thanks Apple ).

I did some testing to try and isolate the problem;

1. Confirming it's not my 3.5mm jack (I tried another)
2. The buzzing half stops (just gets quieter) when I remove the hdmi from the AV adapter, same if I remove the usb from the AV adapter
3. So, if I take the switcher out of the equation and plug my monitor's hdmi directly into the AV adapter, I still get a quieter buzzing

This is driving me nuts, I wonder if I should just bite the bullet and buy one of these Anker adapters to try. (I'll need ethernet as I'm going to buy some powerline adapters.) I guess I can always send it back if it doesn't change anything Would that Anker one work on a 2016 MBP? It seems oddly omitted from the support years/devices

Any other ideas as to what I can try?

 

[Scam]

Update.. so I bought the Anker dongle. Still buzzing Which means it must be the hdmi/UBS switcher. That's so annoying because there aren't many out there sub £50. (Anyone?)

But I am buying a new monitor so may be able to use that as my KVM... Not sure yet..

 

[iraiguana]

You could try something like this:

AUKEY-Ground-Isolator-Systems-Included-Black

Not tried it myself, but could resolve you issue for minimal cost.

 

[Scam]

You could try something like this:

Thanks, I didn't know such a thing existed!

However I've just bought a new monitor which includes Audio Line-in and 3.5mm jack out.

So, I'm trying to get my head round it, but maybe if I do this --

MBP 3.5mm >> Monitor line-in* >> Monitor 3.5mm >> Speakers/amp

I'm assuming that'd sound better than taking the HDMI audio from my MBP and using the monitor's DAC?

*Could I use my 3.5mm splitter which is taking the audio out from my PC and MBP here, so that I can have both sources going into the monitor's line-in?

 

[iraiguana]

Depends entirely on what the route cause of the noise problem is. I imagine if you are combining two sources with separate power supplies, you might find the ground is varying slightly between them and therefore you are getting noise. So, in theory, pulling the audio from the monitor should avoid this. I am still a little confused how the USB-C port is affecting your 3.5 mm audio jack, but who knows!