Use the record output from the SP-8 connected to the phono input on the LS-17, or any other input they are all the same.
Using the main outputs on the SP-8 will include the line section of the preamp as well. Since you just need the phono section this will be needless additional circuitry in the signal path and will degrade the overall performance of the system.
Using the main outputs on the SP-8 will include the line section of the preamp as well. Since you just need the phono section this will be needless additional circuitry in the signal path and will degrade the overall performance of the system.