I didn't quite catch the manner in which you have this stuff all hooked up, but are you sending a single source to two different preamps at the same time? This isn't necessarily a bad idea per se, but some (mainly older) preamps short out all the sources that aren't selected - this is to reduce crosstalk in their selector switches.
The logic is this: if it isn't selected, then you're not listening to it, right? So who cares if the signal is shorted? This of course doesn't anticipate another component trying to use the source at the same time.
The logic is this: if it isn't selected, then you're not listening to it, right? So who cares if the signal is shorted? This of course doesn't anticipate another component trying to use the source at the same time.