Bob there are certainly passive preamps with switching or devices such as the Manley Labs Skipjack, which is a very high quality input switcher. The problem is that the phono signal is the smallest, and most frail, signal in your entire system. Do you really want to add a switch box followed by another set of interconnects and have that signal compromised even further? Not to mention the variable of capacitance in adding all of this stuff. It's not a desireable answer at all. Better to get a phono preamp design that accomodates multiple inputs, modify your existing phono stage or add other phono preamps and run then into your available line inputs.