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

kingsleuy Details Discussions Posts This discussion Message User 173 posts 04-27-2023 at 04:35am Copy Comment URL Report Comment Edit Delete Interesting. When I worked on sensitive equipment, I had to use an AntiStatic Wristband to ground me to the workstation. It looked like the Twist 'o Flex watchband. Connected that wire to your dac. Some antistatic band did have a like a 100M ohm resistor in it, which we had to check every so often. Idea is to Bleed off the charge. Not current thru you. Or maybe put a ground lead from your headphone out to the padding of your headphone. I'll choose my wrist thank you. Why? I don't know. Guessing on it. The USB power ground might be floating and not part of aircraft ground. Like that 100M ohm resistor, your butt is it. You could take a jumper lead from your dac straight to a metal surface of the airplane. I you get a smoke from your laptop or dac or a big arch and the airplane stop working... hey! sacrifices must be made in the name of Science.