The Overture has these connections:
Power Link (two)
AUX
FM aerial, 75 ohm
AM aerial (Dedicated)
Master Link (ML)
Headphone/Mini jack
So:
1/ do you know if the AUX DIN is bi-directional ? can you output a line level signal through it ?
2/ does plugging in a headphone into the Overture mute the attached speakers
First B&O (1976) was a Beogram 1500 ... latest (2011) change has been to couple the BL11 with the BL6Ks *sounds superb*