怎么只有一个音箱有声音啊?设置时左右声道都是有的啊

Master

# amixer set Master 80 unmute
Simple mixer control 'Master',0
  Capabilities: pvolume pswitch pswitch-joined
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 31
  Front Left: Playback 31 [100%] [on]
  Front Right: Playback 31 [100%] [on]
# amixer set PCM 80 unmute
Simple mixer control 'PCM',0
  Capabilities: pvolume pswitch pswitch-joined
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 31
  Front Left: Playback 31 [100%] [on]
  Front Right: Playback 31 [100%] [on]
一连播了好几首歌都是一个音箱有声音.
声卡芯片是VIA8233 AC97,驱动是编进内核的alsa,系统为gentoo 2005.1,播放器是mp3blaster

Master

是左右声道音量差地比较多,要将音量调高才能听到另一个声道
而且这个声道的声音音质比较差,这是不是驱动的原因呢?