I have a PC with an AMD APU chip, and I'm trying to send sound to my Audiolab 8200AP processor over HDMI. The system is 'Ubuntu Studio 15.10'. I believe the hardware works - I can boot into Windows 10 and send audio from jriver. With Linux, however: - aplay -L does list the hdmi:Generic device, and pulse is using it - Pulse Audio volume control does detect whether the HDMI cable is plugged in at both ends - speaker_test -c 8 -D pulse loops continuously and thinks its playing - Pulse Audio volume control shows the ALSA plug-in [speaker-test] stream However, the Audiolab is stubbornly said the channel is 'silent' on its display. And then I used 'Settings/Display' to select the 'IAG 6"' and select 'use this display' and to mirror the displays - the computer is actually displaying on an attached VGA monitor. And that made things start to work. Ideally I would only access the system over xrdp - but you can't enable the extra monitor without being on the console. Quite possibly I would not have had the issue if either the display was running through HDMI or the VGA monitor was not plugged in - but it is worth bearing in mind if you are having issues. I guess it would be handy if the display on the volume control could indicate 'plugged in but output is inactive' - or (better still) if the HDMI output were active if either the display or sound system wants to use it, and the display is just an unchanged or black background.