alsa.lua invokes 'amixer' with the argument '-c0', presumably to try and select the default sound device. Apart from the fact this should probably be configurable, it doesn't interact well with the way Pulseaudio muscles in to the ALSA framework.
On my system, the Pulseaudio server is the default device, but has no card number. Card number 0 gets mapped to my system's actual hardware.
Here's the output from various alsa commands on my system. Note how Pulseaudio doesn't show up as a card, but does show up as a device:
$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: CMI8788 [C-Media CMI8788], device 0: Multichannel [Multichannel]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: CMI8788 [C-Media CMI8788], device 1: Digital [Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0
$ aplay -L
default
Playback/recording through the PulseAudio sound server
sysdefault:CARD=CMI8788
C-Media CMI8788, Multichannel
Default Audio Device
front:CARD=CMI8788,DEV=0
C-Media CMI8788, Multichannel
Front speakers
surround40:CARD=CMI8788,DEV=0
C-Media CMI8788, Multichannel
4.0 Surround output to Front and Rear speakers
surround41:CARD=CMI8788,DEV=0
C-Media CMI8788, Multichannel
4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=CMI8788,DEV=0
C-Media CMI8788, Multichannel
5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=CMI8788,DEV=0
C-Media CMI8788, Multichannel
5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=CMI8788,DEV=0
C-Media CMI8788, Multichannel
7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=CMI8788,DEV=0
C-Media CMI8788, Multichannel
IEC958 (S/PDIF) Digital Audio Output
You might want to make the affected device configurable, either via -c (to select actual hardware), or via -D (to select devices, including the Pulseaudio virtual device).
alsa.lua invokes 'amixer' with the argument '-c0', presumably to try and select the default sound device. Apart from the fact this should probably be configurable, it doesn't interact well with the way Pulseaudio muscles in to the ALSA framework.
On my system, the Pulseaudio server is the default device, but has no card number. Card number 0 gets mapped to my system's actual hardware.
Here's the output from various alsa commands on my system. Note how Pulseaudio doesn't show up as a card, but does show up as a device:
You might want to make the affected device configurable, either via -c (to select actual hardware), or via -D (to select devices, including the Pulseaudio virtual device).