Welcome to the forum stantonsound, I hope to learn a lot from you and it's always good to have more voices helping.
I would follow the steps on testing what's easy first before jumping into a X causes Y type of un-tested theory just because it seems to be fact.
Given the number if items, dimmers,
fluorescent lights, other arc sources, motors, computers, shorts in the
system all having similarities in causing noise, but different causes of it, it's not an easy subject. Yes, the dimmers seem to cause the noise but it's hard to say the exact reason that they are causing the noise in correcting it other than just citing a phenonomon. Do the simple first as test cables to the speakers would start with.
If the case does not prove to be because of a run to speakers, than it would be by far easier and less expensive to isolate and possibly condition your sound
system equipment than to correct the other problems. This after an electrician tracks down the cause and it's necessary.
First a few things I find curious. You say you have three 20 amp individual breakers that feed a 60 amp master on what’s perceived to be some form of sub-panel for the sound equipment. I would hope that I misunderstand this description.
Still what you describe in the
ground passing by this sub-panel is typical for a Isolated
ground system in it very properly terminating at the main panel as required. Path of least resistance, as long as your
ground for the
system is properly installed and your
ground is isolated you should not get noise from the rest of the building.
This is given you truly have a isolated
ground feeding the sound
system, and a good
ground it terminates at. A electrician can verify this in details about doing so.
Just because you for instance have the isolated
ground wire going to the main, does not mean the
receptacle itself in not being isolated from the mechanical
ground of the electrical box it’s installed in qualify as a isolated
ground. Unless using a specific
iso ground receptacle for instance which is not connected to the also necessary separately grounded electrical box, running that separate
ground wire is not doing the isolation job. In other words ensuring it's a direct end run in passing by all other outlets
etc. and the
outlet itself is isolated, you might have one of many potential sources for the problem.
Given it’s not a problem in the cable coming out of the sound equipment and you really do have an isolated
ground, various
power conditioners, or isolation transformers can help after this along with as stantonsound mentioned ensuring the low resistance
ground path at the
ground rod. This than makes it less likely that noise from the building will
effect your sound
system. There is methods as said to check this resistance and improve upon it.
Point is that you still do have to have the
ground originate at the same place as the service
drop. While at times it is permissible to add another
ground in addition to it, and before the main
system ground for a specific purpose, this is something for the electrician or electrical engineer to determine when necessary. What santonsound is talking about is more and extra grounding rods that supplement the main one for the service
drop and such extra rods are very much a part of this
ground so as to
drop the resistance of the soil down to an acceptable
level. Believe 20 amps of resistance as I remember is the
threshold for what is acceptable. 20 amps can also mean there is a lot of low resistance interference factoring into electronic sound gear even with a "good
ground." Another part of what stantonsound might be talking about is in adding more rods or longer rods in lowering this resistance to a more reasonable
level for electronics as can be possible to do here also.
This resistance can be a factor. All main service panels will have the
neutral and various mechanical -
conduit and
ground wires terminating at it. Sub-panels off the main panel are directly attached to the main in isolating the
neutral from
ground up until that main panel. Isolated grounds also by-pass sub panel attachment to
ground in a similar way to this
neutral not being attached at a sub-panel or
outlet to the
ground.
My next question would be about an installation of Cam Loc type
plug fed dimmers. I believe what you are asking is similar to the question of it you went say
twist lock instead of
stage pin for the lights. One type of
power outlet over another will not correct problems with
system noise be it
phase harmonics or noise on the
neutral and
ground. In the case of the dimmers, perhaps it’s a lot to do with an electrical field, could be something with un-balanced load, but the more normal answer would be in having a separately derived service
drop for the
dimmer packs from that of the rest of the building
power. This would also include it’s own unique to it
ground at the service
drop and main panel. Very good option in general especially for more
power but also sometimes not possible and if possible very expensive. Just because the dimmers have a
portable means of
disconnect, does not mean they will be powered any differently than they are now unless from another service
drop. Installing them in another location on the other
hand might also
play a factor.
In the end, there can be many factors in what causes noise and as theorized, it’s often not simple but there are some simple things you can check.
As for
ground lifts on equipment, given a
ground lift by design is only designed to allow a grounded
plug to
plug into a non-grounded
outlet, and is also designed to attach by way of
wire or screw to the
outlet box that is grounded it than becomes grounded, a
ground lift to remove a piece of equipment from
ground is both mis-stated and un-safe if not used as designed. Such a
ground lift also is not designed to work unless the electrical box it's moving the
ground from pin to box in is actually grounded.
First at the
point that the little metal ring hanging off the
ground lift touches the center screw holding a
receptacle onto it’s
cover, you are again grounded. The intended use of the
ground lift would be to install the ring under that screw in fact. Were you to remove this ring, or cut off and otherwise not use the
ground wire that is available on other types, you would have something that does not
ground in a similar way to that of removing the grounding pin. It's using the gear as not intended and un-safe. Were your gear designed to be not grounded it will have been.
"But the sound
system didn’t get interference" is a nice thing to explain to someone’s mom after you were responsible for putting a son or daughter in the hospital at best following a short within the equipment. No, I don’t do sound for a living as one might be able to tell, but removing the
ground - really reomving the
ground I know is not electrically safe on the other
hand. It's a quick fix - the same as one could quick fix by just shoving bare wires into an
outlet.