[Solved] Buzzing sound from touching charging laptop

I get a buzzing sound through my IEMs when I touch my laptop’s metal case when it’s charging. It only seems to happen when my body is in contact with the metal shells of the IEM (FiiO FD5)

I suspected a simple grounding issue at first, however toggling the “ground lift” setting on my amp (G111) doesn’t help. I can stop the buzz temporarily if I ground myself on something (amp, PC case).

The buzz is also fed back to the DAC via XLR: I hear the buzz through the DAC’s headphone output unless I unplug the XLR cables, since it doesn’t have its own ground. However, in this case, I hear the noise when I don’t touch the charging laptop.

I cannot reproduce the issue with headphones, even if I max out the amp. In fact, the volume of the buzz is entirely independent of the amp’s volume. I’m guessing then that the issue is more related to the metal shell of the IEM than their sensitivity.

Any ideas on how to troubleshoot this further and maybe resolve it? I can kind of minimise it by charging my laptop at different times, but I’d prefer not to have to think about it.

This likely has to do with the laptop charger having an output that is referenced to the mains (= power grid) instead of being fully isolated (= floating).

When you touch the IEMs shell, you create a loop from the laptop through the IEMs into the amp. The tiny current flowing through you gets amplified by the amp and so becomes audible.

A sketch showing your setup would help in figuring out options.

Also: What DAC are you using? Is that USB powered or running from its own PSU?

You could set the G111 to ground lift and then run a wire from its grounding screw to the DAC and the notebook.
To connect to the notebook, you could use the Sleeve of the headphone jack.

IIRC iFi has a ready made kit for providing ground, except that you do not want to go to earth-ground, but reference to the notebooks “ground”.

I don’t really have anything to sketch, but my setup should be easy to describe.

Single power outlet → multi-socket extension/surge protector. Everything relevant is plugged in to this.
Signal chain:

  • Desktop PC (i.e. not the laptop)
    • Coaxial cable
  • DAC (dac2541) with two-pin AC power. USB disconnected
    • XLR cables
  • Amp (G111) with three-pin AC power
  • IEM (FiiO FD5)

Laptop is a MacBook using the official 30W USB-C charger, which has a (very small) Class II isolation symbol (see below), which I guess might be relevant. Unfortunately, it doesn’t seem like the old chargers where it was possible to remove the plug and swap it for a grounded one

That sounds like an interesting solution, thanks, but a bit extreme. Easier for me to just re-schedule charging the laptop to when I’m using headphones :sweat_smile:
However, it gave me an idea. I connected the laptop to the DAC via USB and no buzz! It’s not an ideal solution because the laptop only has two USB ports and I never connect it to the DAC normally. But it’s an option if it gets on my nerves for now. Thanks for the tip!

If you think one of iFi’s kits would help, I’d definitely be willing to give that a try. Do you know which one(s) I should look at? I looked at the Groundhog, but it seems to solve the opposite problem: buzzing that stops on touch (which was the case without the amp connected). Or maybe I’m not reading it correctly?

Edit: the buzz is still there. But only just above the threshold of hearing, which is fine. No chance to notice it with music playing.

The ifi idefender 3.0 is supposed to fix that problem and I’ve known one person it worked for. Maybe try it from someone with a good return policy.

That’s a USB device though and I’m using a coaxial connection to the DAC. Or do you have some other idea of what I should do with it?

You said it was still coming through USB so maybe that could eliminate it completely. Doesn’t solve the problem of not being able to use the usb ports but a splitter is always an option or a powered splitter if need be.

Hmm, maybe I could have explained better. Connecting the DAC via USB to the charging laptop helps reduce the buzz to the point I don’t care about eliminating it, but I’d be using the desktop as a source via coaxial normally anyway and don’t have any need to connect the DAC to the laptop. I just tried it as a test, since MazeFrame suggested tying the grounds of the laptop, DAC and amp together and I was already aware that USB has a ground connection.

I’m rather looking for a solution that doesn’t need me to plug the laptop into the DAC, but it’s a decent workaround.

Someone described those Classes as “how difficult it is to get shocked”. They don’t tell you anything about voltage between output and input side.

What I suspect is happening is this here:

The charger and notebook being double insulated (= Class II) means it can be whatever voltage in reference to ground. You touching the IEMs (drawn in as headphones) creates a circuit.
The USBs ground essentially provides a lower resistance path to ground than you touching the headphones.

If you were to use that to ground the laptop, all components would be at the same potential again.

Piece of alufoil on the table as a contact to bridge the laptop to the G111’s ground screw maybe?
In that case, have the G111 Ground jumper set to connected.

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Thanks, I really appreciate the explanation and the possible solutions. I learned a lot, more than I was expecting.

I think I’ll leave things as they are, but connect the Macbook to the DAC via USB if it annoys me. I don’t have to charge it so often anyway. I also thought about putting some sort of tape on the IEM, since it seems to only be the shell that completes the circuit

Glad to see this was solved, but if you still would insight from an iFi point of view let me know!

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