Star Ground vs Buss Ground- Specific advantages?

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Ethan

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I think of a star ground as several resistors (several individual conductors with varying amounts of resistance) going to the same ground point. I have heard that this prevents current from "flowing back to the source". I don't quite understand that statement. Could someone elaborate on that for me?

What specific benefit does the 'several resistors going to the same ground point' have over Buss Grounding--several conductors tied together going to gound via one "resistor"?
 
Think of your signal ground path as the primary of a transformer with the secondary going to your headphones as music and noise]. Any noise you induce in the "primary" will end up in your ears, albeit, at a really low level. But minus 120 db noise is a really, really low level that you strive for. So keeping the noise out of that "primary" in the first place is the most desirable approach. Or as every good engineer will tell ya; "Supress the noise at it's source" which translates to:

Keep the noise off the signal ground.

That's really all you need to know.
 
> I have heard that this prevents current from "flowing back to the source". I don't quite understand that statement.

Nor do I.
 
I think the idea is that currents flowing in a buss ground can result in potential differences from one end of the ground buss to another. In a star ground since all lines are tied at one point, there is only one possible reference voltage...though it's still possible for current to flow in the ground lines.

I tend to do multiple stars... I bring my shields and chassis all to one point, and my low level grounds all to another point, my power supply grounds all to yet another single point, and finally (if there's a power output stage, like on a guitar amp) my power tube grounds and output transformer to yet another ground. Then, I play around with the interconnection of these grounds to make it as quiet as possible.

A few months ago I build an 18W Marshall amp with this technique, and it is very quiet...to the point where you can't tell its on until you start strumming.

Cheers,

Kris
 
People get really freaked out about grounding in audio circuits, but if you follow a couple of rules of thumb you'll stay out of trouble most of the time.

Ground follows signal.

Signal grounds and shield/chassis grounds are kept separate throughout the system except for being joined together at one point only. Shield/chassis should not be used as a return for signal currents.

Here's a 54 year-old explanation that's as valid today as it was when it was written (the laws of physics haven't changed). Warning: it's a big file, about 4.5Meg.

Right-click and "save as."

See also:
http://www.groupdiy.com/index.php?topic=91546
 

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