You could run the Lexicon through the tape loop on the NAD. The tape loop is independent of volume control and should pass through a full signal.
How do I hook up 2 preamps to one amp
I have a NAD preamp that I use for music. I have a Lexicon preamp that I use for Video. The problem is I have 1 five chanel amp that I need to use for both preamps. When I try to use rca splitters/y adapters, my speakers play at a low volume. If I disconnect one preamp, the speakers play louder. What should I do to allow both preamps access to my 5 channel amp and not have humming or low volume.