Are you wanting to control the audio OUT of the computer and INTO the DSR-11? You mean that kind of interface? I don’t think that is possible. Firewire out from the computer to the deck sends the audio from the timeline to the deck. You cannot adjust it from FCP before it gets to the deck. it is a digital connection. Just like you cannot adjust the audio when you go SDI out to a deck.
What you do is mix it in the timeline and adjust the levels so that when it is sent to the deck, all is good.
I have the Tascam FW-1082 and it has a firewire interface and uses the Mackie control surface to allow you to adjust levels on the timeline when you move the sliders. VERY cool. And under $600 I believe.
Shane
Alokut Productions
http://www.lfhd.net