Both ways shut it off. Pre-amp mode shuts all off and the other does it selectively. Look at the manual it is well explained in which menu to do it.I think I read somewhere that there are two ways to use only the pre-outs of the receiver: One way simply ignores the receiver's speaker out terminals and connects to the pre-outs; the other way actually shuts off the receiver's internal power amplifier channels, which I would like to do. Please enlighten me? Thanks.