Tony, Radio Shack does have the RCA extenders you seek. Many turntables have hardwired RCA and ground cables. I have been told that this is because one should have the shortest cable run possible with a turntable. I can see how this would be true, but I do find it annoying. In my current set-up...
Tony, I hope the Sony table works better for you. For the time being, I am using a Sony PS-LX350H manual turntable (current model; $200 at Crutchfield) that is surprisingly good for the money. I will probably upgrade it one of these days, but for now, it is serving me well.
Tony, sorry to hear that you are still having problems with the turntable. Saurav and Wayne definitely are on to something. I thought going through regular analog inputs (CD, tape, etc.) with the built-in amplifier turned on would have done the trick. Perhaps you should try a different turntable...
Tony, if the '3300 has dedicated phono inputs with a ground screw, then it is able to accommodate a turntable. This means it has an internal phono pre-amp. I am not the vinyl expert, but I would make sure the ground cable is secure on both ends. Then I guess I would check the cartridge to make...