Yamaha DTXpress/DTXplorer/DTXtreme

Hey,

I have my CD player hooked up to my DTX, except I only hear music in 
one earphone.. Any suggestions, or is this standard?

I tried using my other discman, and got the same problem, so I don't 
think it's that. Also, I don't think it has to do with the cord I use 
to connect the discman to the brain.