Airplane Seat Power Ground Loop?

I’ve experienced the following on several flights, 787’s mainly:

I plug my laptop into the seat power outlet.

I plug in my Audioengine D1 dac.

I plug headphones into the dac.

If I am HOLDING (touching) the dac in my hand, it sounds great.

If I do not hold/touch the dac, there is a hum/noise.

The hum disappears if I touch the dac.

The hum disappears if I unplug from seat power.

What is going on and how can I stop this?

My computer battery cannot hold up enough for long-haul flights and it's impractical to hold it all the time.

Thanks.

Thanks!

tomask604-26-2023 5:37am

noromance Details Discussions Posts This discussion Message User 9,763 posts 04-26-2023 at 11:21am Copy Comment URL Report Comment Edit Delete Run a ground wire and ask different passengers to hold it. Have you tried it without the DAC?
clearthink Details Discussions Posts This discussion Message User 1,421 posts 04-26-2023 at 03:32pm Copy Comment URL Report Comment Edit Delete It is probably not a ground loop because there can not be more than one path to ground so it is a defective component that is the source and cause of your problems.
tomask6 OP Details Discussions Posts This discussion Message User 43 posts 04-26-2023 at 10:45pm Copy Comment URL Report Comment Edit Delete clearthink the problem does not occur outside the airplane ie when it’s plugged into a land-based power source. Also, I used another dac (a THX one) and got the same problem except the problem doesn't go away when I touch it.