I cant hear anything through my headphones when i connect to the headphone jack on my studio 24c. When i plug it in the outputs i can hear everything. Does anyone know how to fix this? And yes i have tried the play back knob etc. I can see the sound coming through on the computer just not through my headphones. And im using a macbook pro. When i look at the io setup i have my two inputs and for the output it shows one line thats says main out L out R. Can someone help me with this?