[Guy]

There’s no volume control on the pre-amp output, so you’ll need to find another solution. (EDIT:  Actually there is volume control of pre-amp – I was thinking of line- out!  Hence this should be useable for Beolabs))

Have a read of the second part of Steve’s response here: https://beoworld.org/forums/topic/beomaster-3000-naar-powerlink/#post-5835

You could use the speaker 2 sockets (via attenuator) for the Beolabs.  Be aware that the BeoCenter’s ‘Mute’ control would only work for the speaker 1 pair in such a setup, and does not mute the ‘pre-amp’ output.

I am sure that Steve will be along in a minute to confirm the correct cables!