It's possible, but there's a little bit of hassle associated with it. You have to switch to the analog input: Run the Play Aux command from the Main menu, which causes the B2 to reboot. When you're done, you must run the Use HDD command (Maintenance menu) so the B2 will switch back to using the HDD for the music source. That's very important.
Also very important is that you will need a phono preamp between your turntable and the B2. The B2 input does not provide the phono equalization that a turntable requires. Some new turntables have a built-in preamp. But you have to have one somehow.