The type number of my BV7 is: 9361. A Mark2 if I understand correctly?
The ATV3 was connected via a hdmi --> DVI-I input and the audio came from the optical port, via a converter to the two jack connectors associated with the AV4 port.
In the connections menu the modus for AV4 is set to DVI-I.
Thanks - that all makes sense. In that case if you are happy that the ATV4k and all associated leads are working, it may well be worth trying the audio extractor that I linked to above, and connect its analogue L&R outputs straight into the two AV4 jack connectors.
Location: Warwickshire, UK
My B&O Icons: