Pro Tools LE 7 Recording Vocals Problems.. Help!!

[dmt2828]

Im trying to record some vocals into Pro Tools LE 7 using the Mbox 2 and my Focusrite Trakmaster Pro. I am using the Focusrite Trakmaster Pro for the pre amp. The way I have it connected is: the Line Out -10dbV output of the Focusrite Trakmaster Pro is plugged into the Line Input 1 of the Mbox 2. (Is this the correct way to connect it? The other output is +4dBu. Should it be connected to that one?) I cut on the 48V on the Mbox 2 and the 48V on the Focusrite Trakmaster Pro. My mic is plugged into the XLR on the Trakmaster Pro. My Pre Amp Level is about 3 on the Focusrite Trakmaster Pro. Now heres the problem. When I go to record vocals they record very low. I tryed using the Input 1 volume knob. When i do that i hear the room noise (air sounding) while I record. If I cut it down to where I cant here the noise then it records low. I was also told by someone not to use the volume knob on the Mbox because then it bypasses the Trakmaster Pro Pre Amp. Is this true?

What should I do or am doing wrong?