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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

Showing 2 responses by ghostrider45

ghostrider45
449 posts
 
I agree with Sean. Having two separate ground systems in your rig is an open invitation to hum problems. Tie the rods together.

BTW, just for fun, before you tie them together, hook a voltmeter across your two grounds (with nothing else attached). Set it for AC and try a low voltage range. I'll bet you see a potential difference!

Also, are you running balanced or single ended interconnects?
ghostrider45
449 posts
 
Good stuff so far, especially Sean and Rap. One thing is certain - having two separate ground systems (power system and ground rods) will cause trouble, especially with a 15v difference. It's not a component problem.

So pick your ground system. Either float everything and tie everything to the ground rod, or give up on the ground rods and use the power system ground. If you use three prong cords and tie to the ground rods then that 15v difference results in current flow through the ground paths (chassis, cabinent, etc) through the ground prong to the power system ground.

I don't know how old your house is, but I wonder if the power system ground is good. Sometimes you get corrosion in old electrical systems.

With your audio gear referenced to ground rods, you might get a slight tingle if you come into contact with a component chassis and some other appliance referenced to power system ground (like a metal lamp with a 3 prong cord) at the same time.
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