That would be impossible. 0db is the max possible. Without the decibel volume option turned on, the range is 0-1 volume. We're just using math to give you the decibels scale. Yes, we are using Audio Source and Audio Clip just as native Unity, and you can also use the Unity Audi Mixer. However that doesn't display in decibels unless they have added that option. It displays in the 0-1 range.
It seems to me like I can increase volume beyond 0db through the audio mixer unity provides by slotting it into the Mixer Group input of a Playlist controller and that increases the volume of my clips up to 20db.
However, it does not work on audio groups, when I add the mixer to the audio source in an audio group variation, it has no effect.
The unity audio mixer group attenuation allows volume to be increased to 20db which is significantly louder than 0db, how can I achieve this for master audio audio group variations?
But the mixer can be put into the output of an audio source and that will increase the volume of the clip that audio source plays, it works with the playlist set up of Master Audio.
I found out why it doesn't work on AudioGroups.
If I put a unity mixer into the audio source output, when a new variation is created of that audio group, it does not have the mixer.
The output of new variations should match the audio group's first audio source... that way we can increase the volume of our audioclips..
I really dislike not being able to increase the volume of audio group variations a by 20db... as some clips just over power others and it's not an option to decrease the overpowering one when the real problem is one clip is too soft, yes, I can go and increase the volume of that clip in a different program, but Unity provides this for us in house, Master audio is basically removing this valuable functionality.
Audio Mixers are assignable to Sound Groups through their Buses. You need to use a Bus for your Sound Group and in the Bus section you can assign a Mixer Channel to it. At runtime all the Audio Sources in all Variations in the Sound Groups in the Bus will be assigned to the Mixer channel. It's been this way since Unity 5 came out many years ago.