A:AnswerYes it should allow sound out of both ears as it is a stereo jack (has the 2 black lines on the male tip). I use mine with a pair of stereo headphones plugged into a stereo receiver.
The adapter looks similar to the one pictured on the Yamaha site.
https://usa.yamaha.com/support/faq/pianos/GJC14182.html
A:AnswerThis is a stereo jack adapter. Which means it plays in both ears. The way to tell if it is or not is to look at the tip and you'll see two black rings just below the tip. Those are the contact points that produce the stereo sound. A single ring is mono or just one side.
A:AnswerA 3.5mm female connector accommodates a variety of modern headphones, while the 1/4-inch male plug ensures compatibility with select amplifiers, keyboards and speakers.
