(You can do it if you are careful with levels but.....)
Why?
1 preamp out to a 2nd preamp in any harm?
I have two preamps and would like to run the feed from one preamp to the input section of the second preamp and from there to a monoblock amp to drive a subwoofer. I do not know if there is potential damage to any of the equipment by doing this. Or is it better to get two y out from the cd player with a feed to each preamp?