magicmouse

i have a preamp that puts out a signal via an XLR connector, and i want to be able to listen to this on a pair of stereo headphones. You would think I could use a simple mono to stereo passive adapter, but those type of connectors, which are like Y cables, don't give me balance control, which I need for this application. perhaps someone can point me to a box that will (hopefully passively) convert mono to stereo and give me balance control so I can control how much goes to the left/right side.