I got a pHAT DAC for my birthday and just tried to set it up with my RPi2, running Raspbian upgraded to stretch, but it’s not outputting any sound. Everything appeared normal (ie output of aplay -l and aplay -L etc), except that speaker-test over ssh caused the connection to freeze. It seemed to work normally when logged in at a console, apart from being silent, so I don’t know if the ssh freeze is signifcant or just an irrelevant weird quirk.
mplayer tries to play my files, without showing any errors, but again the speakers are silent.
Then I tried plugging and unplugging the jack plug and discovered that when it’s halfway in it makes a kind of random noise (mostly white noise but with some sort of modulation) and this also seems to trigger kernel panics. So presumably I have faulty hardware? My soldering on the I2C connector isn’t the prettiest, but I’ve examined it closely several times, and can’t see any sign of a dry joint or short anywhere.
I reversed the changes the setup script made (to /boot/config.txt and /etc/asound.conf) and went back to the internal audio, which works fine with the same jack-to-phonos cable and amplifier, as it did before, so that rules out a problem between DAC and amp.