I don't think it's that simple.
I have one Roku 3 (4200) where the volume is low. I also have one Roku 2 (4210) where the volume is normal. The 4210 is suppose to have the same internals as the 4200 - just different remotes.
The Roku audio settings are the same and both are connect to different models of Panasonic LCD's. Also, CBS News which is loud on the 4200 is normal on the 4210.