I've never seen that particular model.....but if I use my experience with avr-3802 there are two ways

1 if you use the amp in 5.1 there are two channel left that you can use as multi room (1 zone only)at fixed output; so you must use external volume controls

2 you can use denon on 7.1 and use multi room output as rca only to run an external amp with variable output(on rca only) but still 1 zone only

all of this you change in the menu option(speakers) 7.1 or multi room