You have to select the 'direct' option on the front panel or the remote. This will pass the signal direct to the power amp side of the Cambridge.Thanks
I have now done this but I have no sound from the front speakers
Pre out on avr to input 2 on the 840a and set to fixed 840 volume set to 40.
I bought the av volume up but only got sound from the center speaker. I must have done something wrong.
One more try or I'll be up a night fiddling.