Let's see what "amixer -c0 scontents" gives.
[root@seveneves mythtv]# amixer -c0 scontents
Simple mixer control 'PCM',0
Capabilities: pvolume cvolume pswitch pswitch-joined cswitch cswitch-joined
Playback channels: Front Left - Front Right - Rear Left - Rear Right - Front Center - Woofer
Capture channels: Front Left - Front Right
Limits: Playback 0 - 87 Capture 0 - 63
Front Left: Playback 85 [98%] [-1.50dB] [on] Capture 23 [37%] [0.00dB] [on]
Front Right: Playback 85 [98%] [-1.50dB] [on] Capture 23 [37%] [0.00dB] [on]
Rear Left: Playback 84 [97%] [-2.25dB] [on]
Rear Right: Playback 84 [97%] [-2.25dB] [on]
Front Center: Playback 83 [95%] [-3.00dB] [on]
Woofer: Playback 83 [95%] [-3.00dB] [on]
Simple mixer control 'PCM Capture Source',0
Capabilities: enum
Items: 'Mic' 'Line' 'Mixer'
Item0: 'Mic'
Simple mixer control 'PCM',1
Capabilities: pvolume pswitch pswitch-joined
Playback channels: Front Left - Front Right
Limits: Playback 0 - 87
Mono:
Front Left: Playback 86 [99%] [-0.75dB] [on]
Front Right: Playback 86 [99%] [-0.75dB] [on]
Simple mixer control 'PCM',2
Capabilities: pswitch pswitch-joined
Playback channels: Mono
Mono: Playback [on]
Simple mixer control 'Line',0
Capabilities: cvolume cswitch cswitch-joined
Capture channels: Front Left - Front Right
Limits: Capture 0 - 23
Front Left: Capture 0 [0%] [-17.25dB] [off]
Front Right: Capture 0 [0%] [-17.25dB] [off]
Simple mixer control 'Mic',0
Capabilities: cvolume cswitch cswitch-joined
Capture channels: Front Left - Front Right
Limits: Capture 0 - 63
Front Left: Capture 23 [37%] [0.00dB] [on]
Front Right: Capture 23 [37%] [0.00dB] [on]
Simple mixer control 'Mic',1
Capabilities: cvolume cswitch cswitch-joined
Capture channels: Front Left - Front Right
Limits: Capture 0 - 63
Front Left: Capture 23 [37%] [0.00dB] [on]
Front Right: Capture 23 [37%] [0.00dB] [on]
Simple mixer control 'Auto Gain Control',0
Capabilities: pswitch pswitch-joined
Playback channels: Mono
Mono: Playback [on]
Simple mixer control 'Auto Gain Control',1
Capabilities: pswitch pswitch-joined
Playback channels: Mono
Mono: Playback [on]
Simple mixer control 'Input Gain Pad Control',0
Capabilities: volume volume-joined
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 2
Mono: 1 [50%]
Simple mixer control 'Input Gain Pad Control',1
Capabilities: volume
Playback channels: Front Left - Front Right
Capture channels: Front Left - Front Right
Limits: 0 - 1
Front Left: 1 [100%]
Front Right: 1 [100%]
[root@seveneves mythtv]#