Try pluging the stereo phono plugs into the NAD preamp, and the preamp stereo outputs into the “auxillary” imputs on your Marantz amp. Mind you, you must ground the phono leads, or you’ll get a loud buzz or humm. If you’ve got alternate impedence selections on the preamp, or marantz, try swithching them around too, all to obtain the best and cleanest signal available. Also, keep the volume down until you’ve discovered the best connections. I don’t believe you’ll have any disabling connection, as long as they’re “line level” signals. Just think of the phono leads as a microphone etc. It’s all related. Best impedence match is what you’re searching for. Cleanest dynamics will provide best results. You never mentioned whether your phono cartridge is a “ceramic” or “moving coil” or “magnetic” type. They are distinguished through the impedence ratings. High = Low. Just make darn sure the phono leads are grounded. Usually 3 leads. Left, Right, Ground. 2 RCA’s and the regular wire, which is the ground one. I’ve even attached the ground wire to the chassis of the preamp. The most common grounding used. { please don’t sue me if it blows up!!} just kidding!! good luck!! Hey, Most audiophiles agree, = Vinyl is far superior to CD’s. get a really great cartridge. it makes all the difference!!