Help!! Source button/headphone problem!

Hello folks,
Im very glad with my Cross DJ. But... I just bought this new headphones and i would like to listen to the music (for example) Dek B but what happends is that when I press the button on my U-Mix MIDI controller Pro the button (SourceA/B) then my Volume goes way up, even when my Faders are full down (so u wouldnt hear any music) It's still hearing thrue my Boxes. Or when My fader of the sound is way to the left(A) and I press Source(B) then u hear the music from deck B thrue my boxes WHAT I SHOULD hear thrue my headphones :S.
Very complicated...
I hope anyone could help me?
Thanks for reading.
Im very glad with my Cross DJ. But... I just bought this new headphones and i would like to listen to the music (for example) Dek B but what happends is that when I press the button on my U-Mix MIDI controller Pro the button (SourceA/B) then my Volume goes way up, even when my Faders are full down (so u wouldnt hear any music) It's still hearing thrue my Boxes. Or when My fader of the sound is way to the left(A) and I press Source(B) then u hear the music from deck B thrue my boxes WHAT I SHOULD hear thrue my headphones :S.
Very complicated...
I hope anyone could help me?
Thanks for reading.