I've had a turntable for a couple years now but just recently got serious about it. I used to have this battery powered Radio Shack pre-amp, but I just got a McLelland RIAA-80 pre-amp and when I turn it up real loud I still get hum/buzz like a bass buzz. My ground wire is connected to one of the screws on the bottom of

my turntable (it's a Sony direct drive ps-t1....i got it off of a friend and it looks like the ground lead was maybe ripped out) and of course the pre-amp has a ground lead. I'm running it through a sony str-de185 reciever and sony ss-mf650h floor speakers. Is there any way I can inprove my sound without spending a whole lot?