Thanks so much for answering. I've made several comparisons between my system preferences and those of Spin Doctor--I can find no obvious problem EXCEPT for the fact that I seem to have no real choices in my Mac.
the output gives me the Built-in Audio; and the Input reads Audio line-in port. Next I may have to try the Apple site again, after I figure out what to call this dilemma. (I believe I am supposed to have options available, which just may be what you were referring to in your reply. In fact, except for a place to check "mute", there is little else. No, I haven't checked the mute. )
Needless to say, I still have no audio.