[LAU] ground loop hell

[David Christensen]

On 02/08/2015 08:42 PM, Len Ovens wrote:
> I want yes :)  Right now I don't have. The snake is old and the monitor
> returns are signal and ground  :P

Do you have unused balanced sends on the snake?  If so, you could swap 
the gender of both ends and make them into returns.  If not, you could 
swap the unbalanced return connectors to balanced, use the two 
conductors for hot/+ and cold/-, and leave the ground pins/sockets 
unconnected (with a warning label at both ends).  If it's wired right 
and there's only the two monitor returns, you'll probably never notice 
the cross-talk.


Another option is to pull more twisted shielded pairs.


> I am not afraid to spend money, but I would like to put it to the best
> use as it is limited. Fixed grounding comes before new equipment in my
> book.  ... There have been two very large breaker
> pannels installed already and there are many inspections to go through
> ahead. I am going to set up a plan for power, signal and data for audio.

It would be wise to complete the engineering before going further with 
construction.


Even if you are an electrical engineer, electronics technician, and/or 
electrician, you might want to get a second set of eyes checking your 
designs.


> I will do a second for stage lighting as well, if for no other reason
> than keeping the audio power from being used for lights  :)

It is wise to put lighting on it's own feeder and panelboard.


If your non-linear loads are significant, beware of harmonics. 
Solutions include oversized neutrals, specially designed transformers, 
shielding, etc..


> If I need
> more than one breaker for audio power, I will make sure it is on the
> same phase.

You should balance your loads evenly across all phases at every level of 
the power system -- from the service down to the branch circuit 
panelboards.  Load imbalance creates a whole new set of problems.


David