Does not work with USB audio device

[GoogleCodeExporter]

Volti fails with this error when used with my USB audio device. I've tested on 
another machine with a similar environment except that it uses on-board Intel 
audio:

$ volti
[alsactrl.py:__init__:41] can't open Master control for card Device, trying to 
select first available mixer channel

[alsactrl.py:__init__:49] can't open first available control for card Device
error: list index out of range
Traceback (most recent call last):
  File "/usr/bin/volti", line 53, in <module>
    volti = main.VolumeTray()
  File "/usr/lib/volti/volti/main.py", line 124, in __init__
    self.watchid = gobject.io_add_watch(fd, eventmask, self.update)
TypeError: an integer is required

--------------------
Other information:
--------------------

 # This is the intended sound device
$  aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Device [Schiit USB Audio Device], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

# I'm not using the nvidia audio device
$ lspci |grep -i audio
01:00.1 Audio device: NVIDIA Corporation GK104 HDMI Audio Controller (rev a1)

# aplay works as expected
$ aplay /usr/share/sounds/alsa/Noise.wav
Playing WAVE '/usr/share/sounds/alsa/Noise.wav' : Signed 16 bit Little Endian, 
Rate 48000 Hz, Mono

# alsamixer shows:
Card: Schiit USB Audio Device
Chip: USB Mixer
Item: PCM

Original issue reported on code.google.com by Andorn...@gmail.com on 11 Sep 2013 at 4:01

[GoogleCodeExporter]

I've added some python output:

>>> import alsaaudio as alsa
>>> alsa.cards()
[u'Device']
>>> alsa.mixers()
[u'PCM']

Note that alsamixer does not actually have a volume control for this audio 
device, it only has a mute/unmute control. That said, other volume applets, 
such as `gnome-sound-applet`, do work.

Original comment by Andorn...@gmail.com on 11 Sep 2013 at 5:15