1. Any tech should be able to clean up and replace the battery contacts cheaply if that is the only problem with the JC-1. It is pretty dated, though.
2. Any stereo pair of RCA inputs will take the output of your phono preamp.
3. Why have more than one phono preamp? If you want to connect two TTs at the same time, get a switch or buy a phono preamp with two inputs.
4. I cannot help you with this research.
5. Consider moving the phono preamp to the TTs as its output can support a long cable better than can the direct cartridge output.
2. Any stereo pair of RCA inputs will take the output of your phono preamp.
3. Why have more than one phono preamp? If you want to connect two TTs at the same time, get a switch or buy a phono preamp with two inputs.
4. I cannot help you with this research.
5. Consider moving the phono preamp to the TTs as its output can support a long cable better than can the direct cartridge output.