what is star grounding?

Basically, it is a process of pulling a separate wire for every ground back to a single common grounding point on the chassis. See if this helps explain it:
http://www.geofex.com/Article_Folders/stargnd/stargnd.htm

See, http:/www.aikensamps.StarGround.html. Usually means all grouds to a central point.

Gregadd the link did not work.

Sorry. I don't know aht happened. I can't access it either. I checked it just before posting it. I typed in star ground in my browser and it came up.

For audio frequency equipment a "single point" ground is best. This can be done by "daisy chaining" the grounds around to the single point, or by connecting multiple conductors directly from different parts of the circuitry to the single point. This is called "star" for obvious reasons.

For digital equipment multiple grounds are usually best.