Switchcraft 318 Mini AudioStix 1-channel Passive Laptop Direct Box
The Switchcraft #318 Mini AudioStix lets you connect the audio output of your laptop or MP3 player to a PA system. The 318 has an 1/8" stereo mini on one side and a mono XLR on the other, so you'll always have the right connections when it's time to give your presentation. You won't have to worry about hum and buzz caused by ground loops and RF interference, either, as the 318 has transformer isolation. You also get a handy volume control and a ground lift for killing the noise you sometimes encounter with consumer devices.