Last night, my mom brought a pair of retro, over-the-ear headphones home for me (She got them for free, so if I can't get this problem fixed, it doesn't matter). I noticed that they had a 1/4 inch (6.5 mm) jack. I immediately went to test them on my stereo system, and they worked fine. So today, I go down to my local RadioShack and pick up an adapter so I can use the headphones with my MP3 player and my laptop. I tested them a few minutes ago, and it only plays through the left (Or right, because there's no marking as to which side is which) side with the adapter. The headphones themselves are fine, but I'm wondering if I got the wrong kind of adapter...I got the stereo to stereo, but I'm not sure if I should have gotten the stereo to mono. Can anyone help me with this?