I reconfigured my options and I actually can confirm that if you put a dummy plug into the earphone socket it will not switch to option 0 when the power goes out.
I have just a plug no cable, no soldering nothing.
This is also required for some funny reason to get sound on the AUX out.
I have BS9000 no speakers connected to my BC2 through the AUX. Works well, I can't remote the BS9000 but thats OK.
BS9000, BS2300, BC2, BL2500, BL3, Bl2, BS1, BV8, BC4, A8