AW: To earth, or not to earth...

[Buck Buchanan]

Martin Czech wrote:

> This is very interesting, since I'm right now before this step of
> designing the first pcb and front panel. After that I can't change any
> more. I'd like to discuss this further. For this, we need some information.

Ha ha, I am in the exact same position and expect to be drilling panels
and printing boards within the next week or so.  So I certainly don't
wanna change after that process gets started (though I am making
allowances in the design for change if need be).  This thread has been
very educational!
 
> -Please declare if you belong to the "banana" or the unsymmetrical
> shielded party or whatever.
> 
> -And the ground scheme of your modules. Ground bar, or star like?

I'll throw out my basic plan here - Please, somebody throw a brick at me
if I'm screwing this up big time!  I suspect I'm either right on or WAY
off.

It seems that the grounding problem has always been related to the fact
that we can't make a perfect ground.  But it's been my understanding
that "less than perfect" grounds don't come up and bite you in a "star
grounded" system where only one ground path exists between everything.

So I'm ganna try this (I've accepted that this could backfire and have
made provisions in the design to completely change grounding scheme if
need be): 

1) Banana for all audio/cv within the system. Balanced XLR to talk to
outside (line level AC coupled) systems and I'll probably use
transformer coupling here.

2) Each module's individual "star" point will be at the front panel. 
Controls, etc. ground to the PCB's ground plane which in turn grounds to
star point with heavy wire.  

3) I'm using the Schroff Europack system which allows excellent chassis
grounding thus I'm hoping that all modules will have a very solid common
ground plane via their front panels.  So the system's star point will be
the front panel plane.  I've left room on front panels for grounding
wires between them all but this is a drag and I'm hoping to not need
this.

4) Power supply ground is of course floating (from mains) and connects
to the system star point.

5) Systems can be cascaded together with one (and only one) ground path
between them.  (I think there could be a problem here....)

I don't see any ground loops here IF I'm able to call the front panel a
solid ground plane.  If the individual modules can't be solidly
connected, this won't work.  While there don't appear to be any loops
per se', I do see a poor ground path (only one tho) when a module
connects to another in a different case.  I guess this wouldn't be a
perfect star grounded system even without any ground loops.

Am I not seeing the forest for the trees?  Will this fall flat on it's
face in real life.

It just seems like balancing everything is just too much work.  Yup, go
ahead and stamp "lazy" across my forehead.  ;-)

I'm not sure how much or how well this all adds to the discussion but
maybe it's some food for thought...

Take it easy all,

Buck