2. tech-talk
  3. 1019474351

buzzzzz, where did i go wrong?

The setup:
spectral monoblock amps
spectral preamp
theta front end

The NEW DEDICATED CIRCIUTS
4 separate circuits each with fuses jumped off the main box and grounded to the main box
one circuit for each monoblock
one for the preamp
one for the digital front end (MIT power conditioning)

the amps and preamp each share a supplemental grounding rod. The digital end has its own supplemental ground rod
The outlets are all FIM880. These do not have an isolated ground (could that be the problem?)

I still have a buzz.low but audible; it goes away when I lift the ground from my amps. I assume I have a ground loop but I am not sure how or what I do about it. I assume I have made some awful basic error but not sure how.
I know for instance from the posts that Garfish uses three supplemental grounding rods. Maybe I should have tied all those together? any other ideas
jdwek
jdwek OP
84 posts
 
Ok I think I am getting it. Let me be more specific. The panel and the two rods are separated by about 35 feet. The two rods are about 6 feet from each other. I am going to take one copper wire from each rod to the grounding bar in the main box.
The outlets are still FIM880's which do not have an isolated ground. The conduit is their ground. Should I also use their copper grounding wire and land it to the grounding bar?
About the fuses, they indeed are a subpanel but i am not sure what is meant by the neutrals being bonded to it or not. By the way...I do own a multimeter and I not afraid to use it!....maybe someone could tell me how?
Thanks JD
sean
6,231 posts
 
JD, i'll drop you a line in the morning, kind of late and i'm beat now : )

To start off, try grounding ALL of your ground rods together. That should get rid of your hum. If it does, you either need to replace the FIM's with outlets that isolate the grounds, leave all of the ground rods tied together or move the ground rods to within a few feet of each other.

If tying all the rods does correct the problem, you can also try removing the connection from one rod at a time and see which rod has different potential from the others. It is possible that each rod is different and that you would need to leave them all tied together to solve the problem. Once again, the only way to get around this is to isolate the audio grounds from the house grounds via different "floating" outlets. Sean
>
jdwek OP
84 posts
 
good night,...I am on the night shift!
jd
nick778
147 posts
 
one other supplemental thought. the three dedicated circuits should ideally be on the same bus in the panel to minimize ground differentials. also, if possible, this bus should be the one with the fewest amount of large 'noise' contributors from i.r.,dimmers, fridge, etc. this could involve some rewiring in the panel but is usally worth the effort.
jdwek OP
84 posts
 
I think my fiance soon to be wife is starting to really wonder about me!
More to discover