When I start playing a song, the sound suddenly mutes. I have to manually adjust it in the ubuntu desktop itself. I have my htpc connected to a receiver via spdif. I discovered using alsamixer that there is a S/PDIF D, which is the Default PCM and another S/PDIF which isn’t the default. I think Mopidy is playing over the non-default S/PDIF which has the default sound level at zero. How can I tell Mopidy to play the music over the Default S/PDIF or to play over the non-default S/PDIF with 100 volume ? 
My /etc/mopidy/mopidy.conf
[core]
cache_dir = /var/cache/mopidy
config_dir = /etc/mopidy
data_dir = /var/lib/mopidy
max_tracklist_length = 10000
restore_state = false
[logging]
color = true
config_file = /etc/mopidy/logging.conf
debug_file = /var/log/mopidy/mopidy-debug.log
[audio]
output = alsasink device=hw:0,1
mixer = software
buffer_time =
[local]
media_dir = /mnt/joeri/htpc/Music/
data_dir = $XDG_DATA_DIR/mopidy/local
[m3u]
enabled = true
playlists_dir = /var/lib/mopidy/playlists
[mpd]
hostname = ::
[http]
enabled = true
hostname = ::
port = 6680
static_dir =
zeroconf = Mopidy HTTP server on $hostname
allowed_origins =
csrf_protection = true
[stream]
enabled = true
protocols =
file
http
https
mms
rtmp
rtmps
rtsp
metadata_blacklist =
timeout = 5000
Does “S/PDIF D” appear as a different device on card 0? Can you select that device instead of device 1? What does aplay -l show?
**** List of PLAYBACK Hardware Devices ****
card 0: Generic [HD-Audio Generic], device 0: ALC887-VD Analog [ALC887-VD Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: Generic [HD-Audio Generic], device 1: ALC887-VD Digital [ALC887-VD Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 7: HDMI 1 [HDMI 1]
Subdevices: 1/1
Subdevice #0: subdevice #0
Ah oops ok so “S/PDIF D” is “S/PDIF Default PCM”. You have a single S/PDIF device according to aplay and that’s the one Mopidy is using.
Does using autoaudiosink instead of alsasink work?
Have you tried disabling alsamixer’s “Auto-Mute mode”? You can use amixer -c0 to inspect the settings.
Using amixer -c0 it doesn’t seem the device is auto-muted. Relevant results:
Simple mixer control ‘Master’,0
Capabilities: pvolume pvolume-joined pswitch pswitch-joined
Playback channels: Mono
Limits: Playback 0 - 64
Mono: Playback 64 [100%] [0.00dB] [on]
Simple mixer control ‘PCM’,0
Capabilities: pvolume
Playback channels: Front Left - Front Right
Limits: Playback 0 - 255
Mono:
Front Left: Playback 255 [100%] [0.00dB]
Front Right: Playback 255 [100%] [0.00dB]
Simple mixer control ‘IEC958’,0
Capabilities: pswitch pswitch-joined
Playback channels: Mono
Mono: Playback [on]
Simple mixer control ‘IEC958 Default PCM’,0
Capabilities: pswitch pswitch-joined
Playback channels: Mono
Mono: Playback [on]
Using autoaudiosink makes no difference. The sound is zero again and I have to manually increase it via ubuntu desktop in the top right
Do you have any thoughts?