Comment 14 for bug 936539

Simple mixer control 'Master',0
  Capabilities: pvolume pswitch pswitch-joined
  Playback channels: Front Left - Front Right - Rear Left - Rear Right - Front Center - Woofer - Side Left - Side Right
  Limits: Playback 67 - 127
  Mono:
  Front Left: Playback 121 [90%] [-6.00dB] [on]
  Front Right: Playback 121 [90%] [-6.00dB] [on]
  Rear Left: Playback 121 [90%] [-6.00dB] [on]
  Rear Right: Playback 121 [90%] [-6.00dB] [on]
  Front Center: Playback 121 [90%] [-6.00dB] [on]
  Woofer: Playback 94 [45%] [-33.00dB] [on]
  Side Left: Playback 121 [90%] [-6.00dB] [on]
  Side Right: Playback 121 [90%] [-6.00dB] [on]

multi channel master playback volume was removed by this patch

http://cgit.freedesktop.org/pulseaudio/pulseaudio/commit/src/modules/alsa/alsa-mixer.c?id=527078523815587bfd021bc1d10782403e9b3e84

seem using 5.1 profile with 8 channels master playback volume

post the pulseaudio verbose log