I've tested all available AppleALC layout-ids. I recommend either 13 or 21, depending on what output you value most:
Available layout-ids: 1, 3, 13, 14, 15, 21, 28, 77
1, 3, 14, 15 - Headphone jack (noisy), no internal
13 - Headphone jack (noisy), internal (slightly soft)
21 - Headphone jack...