Comment 13 for bug 1192458

post the output of alsa-info.sh

https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/792528

Do you have the "PCM playback Volume" ?

Simple mixer control 'PCM',0
  Capabilities: pvolume pswitch pswitch-joined penum
  Playback channels: Front Left - Front Right - Rear Left - Rear Right
  Limits: Playback 0 - 200
  Mono:
  Front Left: Playback 200 [100%] [0.00dB] [on]
  Front Right: Playback 200 [100%] [0.00dB] [on]
  Rear Left: Playback 200 [100%] [0.00dB] [on]
  Rear Right: Playback 200 [100%] [0.00dB] [on]

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/tree/sound/usb/pcm.c

Do your command used for the setup of stereo stream and quad stream in set_format()

 if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
           hw_rule_channels, subs,
           SNDRV_PCM_HW_PARAM_FORMAT,
           SNDRV_PCM_HW_PARAM_RATE,
           param_period_time_if_needed,
           -1)) < 0)

are those channels_max is 4 and channels_min is 2 when add the rule for channels