Tracking down audio hum

[Rusted Eyes]

Hoping someone can help me track down an issue with speaker humming. I have the A5+ wired speakers hooked up to Audioengine's D1 DAC. The DAC is connected via USB to my Mac mini M2. All of this and my peripherals are connected to a APC ups, which is connected to a properly grounded outlet. There is only one other grounded outlet available and using it does not change the humming.

I've experimented with holding/moving the speaker power cord and doing that affects the hum (decreases it). I also set up my laptop in my living room with the DAC and speakers and there's no hum at all, so something in my office environment is causing it. I don't have fluorescent fixtures or track lighting (things I read that can cause hum), just an Epson printer (wireless) and two monitors.

I can provide pictures of the room and my configuration if that helps, but what can anyone suggest to stop this from happening?

Thank you for your insights!

 

[arw]

Have you tried grounding the Mac mini? There is no proper way though. Perhaps temporarily connect a spare wire to the APCs ground and press it onto the Mac mini enclosure?
Humming speakers are a pain...

Edit: Apparently connecting the Mac mini via HDMI to a grounded monitor should have the same effect...

How to Ground a Mac Mini (for music produ… - Apple Community

discussions.apple.com

 

[Rusted Eyes]

Have you tried grounding the Mac mini? There is no proper way though. Perhaps temporarily connect a spare wire to the APCs ground and press it onto the Mac mini enclosure?
Humming speakers are a pain...

Edit: Apparently connecting the Mac mini via HDMI to a grounded monitor should have the same effect...

How to Ground a Mac Mini (for music produ… - Apple Community

discussions.apple.com

Thanks for that suggestion. I already have two grounded monitors connected to the mini: one with HDMI and one with USB-C. Would that align with what the provided link proposed?

 

[arw]

I would say so... unfortunately.
- You could try disconnecting the monitors temporarily simply to rule them out.
- Do you experience the same if you replace the Mac mini with your laptop? Same room, same outlet to charge the laptop, same USB cable to connect the DAC.
Hopefully someone else has better ideas... or is an electrician.

 

[Rusted Eyes]

I didn't try the laptop in the same room connected to the outlet; I did try it in another room and it was just fine (helped rule out replacing the speaker amplifier that Audioengine suggested).

Will give your suggestion a shot...

 

[Rusted Eyes]

arw,

I took your suggestion, hooked up my laptop to the same power source in the same room, and gave it a whirl. There was no loud hum! But if I put my ear next to the speaker I could hear a very, very subtle hum that did not increase if I turned up the volume on either the DAC or the laptop. To my 64 y.o. ears, it's acceptable.

Oddly enough, after reconnecting the DAC to the mini, the same barely audible hum was still coming through the speakers. The other day I had been futzing around with the various cords related to my desktop setup and disconnected an unused 6-socket power strip without much thought. Now I'm wondering if it was contributing to the much louder hum I initially heard. I'm going to consider this issue done. Thanks again for your intelligent suggestion!