phono ground lug

I need to know how to implement a phono ground lug for the phono preamp I am building. It never occured to me to ask what the purpose for this was, I just always hooked it as needed. But there is another ground connection through the RCA cables (unless it's lifted at the turntable end). So here are my questions:

1) Why is there a separate ground wire for a turntable?
2) On the preamp, where do I connect the dedicated phono ground? Should I just bring it into the star ground on the chasis?

-Chris

> unless it's lifted at the turntable end

It usually is.

The RCA shells are pickup coil return. The ground wire is turntable chassis.

Exact grounding may be trial and error. It usually works to bond the green wire to the preamp case, and bond the case to the output RCA connector grounds.