How can I isolate my 2 channel electronics from my home theater receiver?

I am currently running my turntable and Oppo CD/Blu Ray player through my Yamaha receiver. I'm using the receiver's preamp outputs for my main power amp, surround power amp, center channel amp and an MJ Acoustics powered subwoofer. I have a nice analog stereo preamp gathering dust in my basement. I'd like to use that preamp for 2.1 channel audio for vinyl and CDs and the receiver for home theater. Of course, I like to easily switch back and forth between the preamp and the receiver.

I have no idea how to get  this done. Any suggestions would be most welcome.