I just bought an EMX-1 and have been having a lot of fun with it - very happy with my purchase

So, this is gonna sound really stupid - please forgive these basic newbie issues. Anyways, my headphones have a switch on them to flick between mono and stereo (and I know they work in stereo, coz that's what I use in my DJ setup). But when I plug my headphones into my electribe's headphone socket, I only get sound in both ears if I switch the headphones to mono. If I switch my headphones to stereo, I only get sound out of the left ear. Is that what's supposed to happen?
The other thing is kind of related I guess... I made a couple of tunes and want to get them onto my mp3 player. I have an external sound card that has a line-in accepting a 3.5mm plug (again, I know this works in stereo, as I use it for my DJ setup). The EMX-1 has two 1/4" L/R output sockets. (Actually, I don't seem to be able to find a cable that goes from two 1/4" plugs to one 3.5mm plug. Does such a thing exist?) Anyways, I tried going from the L output (which can by used for sending mono, I understand) into my soundcard with a 3.5mm to 3.5mm cable using a 1/4" adapter. But again, I only get sound out of the left speaker. I guess I expected to hear the mono signal in both speakers, but just not in stereo (eg, no panning effects, etc). Did I misunderstand something? If I want to hear stuff in both speakers, do I need to connect both the L and R outputs into my external soundcard? If so, can someone point me to the correct cable to use?
Any guidance would be much appreciated
