2 digital optical sources into 1 input without switcher?

Hi! I have 2 Sony 300 disc CD changers that I use with an Escient Tunebase 100 cd management system. Is there a way to use an splitter/combiner to feed the outputs of both changers into a single unit, say an out board DAC? Both CD changers are always on, but only one unit is playing (obviously) at any given time. I don't want to buy an expensive auto-switcher, since I will be upgrading to the Escient Tunebass 200 within a year and that unit has digital switching built in. I'm just looking for a solution that will sound better than the internal Sony DACs for the time being. Thank you so much!