turntable hum

Hi I have a Rega P5 table ,with new Exact Cart, got it used , it has a hum and gets louder as the volume goes up.It doest have a ground wire, I thought might be my prima luna integrated amp or my pro-ject tube box DS, so i hooked up to another receiver (outlaw 2160 ) and still has the hum, is this normal ,i don't think so ! Any ideas as to what would cause this and how to get rid of this HUM , Thanks Lloyd