Thoughts on Mac Mini audio problems

[zefrenchtoon]

Hi everyone !

As said in my "Members introduction ..." post, I am a long time user of Macs of every ages (from System 6 to High Sierra).

There is something that I don't understand on my Mac mini G4 and I think that it is related to the "Mac mini G4 audio problem":
When I plug-in headphones on the audio output, the chime still sound using internal speaker. 

This was my easiest trick to start any Mac silently. I does work on my PM 6100, my Yikes, my MB Pro 2010 but not on my mini.   

Does anyone know (or have any idea) why ?   

[IIO]

the mini OS puts the speaker volume to a fixed value.

[Philgood]

How do you do that on a 2010 MBP ? On my INTEL macīs it just doesnīt work anymore. That is on my pre-unibody 2008 15" MBP, the unibody 13" Macbook and the 2010 15" MBP.