Volume Changes in Tracks

I just got the uTrack-24 set up and running yesterday with my Mackie Onyx 1640i mixer which has D-sub direct outs. I hooked the direct sub outs to the u
Track and did a little test recording with just one microphone. I was able to play it back, clear and clean listening to it on the uTrack, but the volume seemed to low. I had to turn up the phones all the way and it still was fairly low. On my block diagram on the Onyx, the direct sub outs come pre-fader but post gain, so I had to turn the gain knob up almost all the way, and it still didn’t seem loud enough. P.s. I recorded our band with it last night and most everything seemed ok, except when I came home and transferred it to Cubase Elements 7, the bass was too low. I may have just not had it up enough on my gain nob on my board, but the drums seemed a little low too. Any info on this problem would be greatly appreciated. Marc Trainor.