[LAU] ground loop hell

[Len Ovens]

Beware old building with additions  :P  It appears we have power coming 
from two power entrances with two different earth grounds to the panels. I 
had found two power cords with the ground pin pulled which I replaced... 
big ground loop noise. I tried (as read from a number of sources) making 
unballanced cables with a small resitor in the ground path but this made 
things worse not better. I will be running a power cord from the stage 
back to the mixer next. All of our signal in paths are already isolated. 
It is only the two monitor mixes to powered monitors that are unballanced 
and causing problems. The outputs from the mixer are ballanced, but the 
lines to the stage are not... I may make cables to allow me to use two of 
the input ballanced lines instead and two more isolation boxes as a longer 
term fix. There will be a new stage going in and I have already been 
asking that power and grounding be corrected for the whole signal flow.

--
Len Ovens
www.ovenwerks.net