I'm hearing a low hum coming from my turntable.
This is probably evidence of a grounding issue. Make sure you have the computer and turntable plugged into different outlets or power strips. If there's a grounding wire hanging off the back of the turntable, try attaching this to the grounding screw that is on the back of most amplifiers. This can also be wrapped around a metal chair or table leg. This should properly ground the turntable and eliminate the hum.