First make sure you're selecting the correct source and the speakers on the preamp and then add some volume to see what happens. If that doesn't work, then you'd need to dig deeper.
Help with hookup
Inherited some audio equipment. Hooking up a McIntosh mc2300 preamp to a McIntosh mc352 amp to a pair of Acoustic Zen Adagio speakers, but I don't get sound out of the speakers. I can hear when I plug in the headphones, so there is that. Any ideas?