OK. I think I see what the problem is, but don’t know how to fix it.
pcm0: <Realtek ALC225 (Analog)> at nid 33 and 18 on hdaa0
On hdaa0, my headphone output is on nid 33. The internal mic is on nid 18. My internal speakers are on nid 20. How do I associate hdaa0 nid 20 with pcm0?