Grundig made some receivers in the 60's and 70's that had short wave radio as well. These receivers only had the speaker wire terminals as an output. The do have input for a phono or tapes. I want to use this receiver as another input to my Marantz 2252 receiver so I can use it to listen to the short wave. So similar to a separate cassette tape player, or record player, I want to connect the Grundig to the Marantz 2252, select the input, and listen to it though my primary system. How do I do that?