low volume level on coreelec/s905x2

I’ve been running libreelec on a s905x system but recently bought a s905x2 system and installed coreelec on it. It works well except the sounds level are much lower than before so I have to turn the tv way up to hear it. I’m not sure if the lower volume is from the new hardware or from some setting in coreelec (I’ve been trying to boot coreelec on the old box to compare with the same hardware but so far haven’t been able to get it to boot). Is there a setting somewhere to adjust the sound level (something like alsamixer)?

Sound level is usually adjusted with remote control command, and there are additional sound controls when a file is being played. When playing a video file bring up player’s OSD (On Screen Display) and then choose cog wheel for settings; you’ll see there various sound settings.
See here section 5.4 and 5.5