Thank you Jan for your answer.
The screenshot that I show is the Avidemux Menu : Preferences.
Edit menu contains only Edit possibility : Undo, Undo all edit, Cut, Copy, Paste, Clear, Mark A, Mark B
I think an item is missing in Avidemux for Mac to choose Audio Output for Mac
I have found in the help Menu : Plugins with the screenshot attached.
I hope someone have the solution.