Audio and Chrome and in Kodi works if I plug my amp into the computer, rather then plugging it into my TV (an LG 42LD520).
This means Chrome is using the PC audio out, not HDMI audio out.
Shell session
# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC662 rev1 Analog [ALC662 rev1 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 1: ALC662 rev1 Digital [ALC662 rev1 Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [LG TV]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 8: HDMI 2 [HDMI 2]
Subdevices: 1/1
Subdevice #0: subdevice #0
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Going off another forum post, I set the custom audio device to hw:0,3 Which I'm guessing corresponds to card: 0, device: 3 HDMI 0 [LG TV] above.