Using an Air as an iPod dock for extra headphone volume I have an iPod Classic 160GB synced with iTunes in Windows on a desktop computer.

Volume from the iPod through headphones is too soft. When I'm away from the desktop, is it possible to connect the iPod to my MacBook Air to listen to content through the Air as if it were a docking station? I could use headphones on the Air.
Try using a line-in cable and plug it into the headphone/microphone jack. This Apple support article could have your answer: https://support.apple.com/kb/HT201929