So I dug up an old vinyl player from my basement, (akai semi automatic turntable ap a150) which doesn't have a dedicated power cable, and I have to plug it into the akai amp which came with it. When I plug the RCA from the vinyl player to the old Akai amp, it works perfectly. But when I plug it to my modern amp (pioneer VSX 423K) I get no sound.
The problem is the modern amp likely doesn't have a phono input. So you will need a phono preamp. I can't recommend a brand, as I don't have one. But run the rca to the preamp and then another set of rca's to the aux on your amp and you'll be good to go.