Wadia 170i and a Cary 306/200 CD player

The Wadia 170i has analog outputs i.e. L & R. you connect these analog outputs into your preamp line level input & you are set to go. Don't have to mess with the rear panel of the Cary CDP.
Now you can switch between the Cary & the Wadia 170i using the preamp selector switch.

IFFFF you are taking the digital output from the Wadia 170i then you need to feed that digital output into your DAC input. Maybe the Cary CDP can accept a digital input & act as a DAC? I don't know but you can look at the rear panel & determine that.

Not sure if this is what your asking, but You can use the coax output of the 170i to your Cary and use the Cary as DAC in your system. You will need a coax digital cable.