For HDMI, may help you, alsamixer
"...The MM label below a channel indicates that the channel is muted, and 00 indicates that it is open.
Scroll to the Master and PCM channels with the ← and → keys and unmute them by pressing the m key.
Use the ↑ key to increase the volume and obtain a value of 0 dB gain..." ( from arch wiki)
But i use sm1-sei610.dtb