Lefty.. there is a small issue there... what happens if some genius plugs a real AC adapter into the connector... some times it is best to start with the right hardware to begin. That was why I kept hammering the switched 'low level' audio. someone suggested putting some current through the jack so it could be "sensed", the major issue with that is in "Sensing" when the speaker was plugged in... the sense current would need to be an appreciable part of the main audio signal. I am of the opinion that it is usually bad work to try to save a few pennies or Worse... Time by these types of "Methods". In the time we have spent trying to solve the issue he could have the right installed and on to the next job.
Doc