Originally Posted by preiffer
VS use single, regular, 3.5mm jack connectors.
The only exception is Upper Class, where there's a smaller (2.5mm) power feed for the so-called noise cancelling power feed to their own headphones. If you're using your own, however, all sound is through the 3.5mm stereo connector, so you just ignore this one.
The new Premium Economy seat also has the second smaller power feed, but like
preiffer says you can just ignore this and plug your headphones into the other one.