I have this same problem as well, but under the VoodooHDA prefpane, I only have HDMI audio in the pull down menu. I'm using voodooHDA on my laptop.
Also, even if I move the mic slider all the way done (or even all the way up for that matter), the volume control is still the same. Basically, the slider is completely useless.
I'm trying to get this fixed as well. Were you successful?
P.S: I'm using v2.7.2 as well.