Thank you Triryche for your comment works for me!!! it works.
solution for Mac:
- open AUDIO MIDI SETTINGS
- Ad a new device on the + sign
- Select the input of your mac "mic input" or "build in input"
- select the output of your mac "headphones"
- rename... in my case "entrada por salida"
that's it
In OBS select the this device as an auxiliar
see the images