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Ground Loop Problem - Stumped

I've got a nasty ground loop problem that I can't seem to figure out. I've done extensive research and tried just about everything but to no avail. Here is how I have everything connected. I am using the ExactPower EP15A and SP15A. All of my sources both digital and analog are plugged into the SP15A which in turn is plugged into the EP15A. My amplifier is plugged into the EP15A. The EP15A is plugged into my wall outlet.

1. I removed all the interconnects between all the components but kept the speakers connected - NO HUM.

2. Connected my preamp (Meridian G68) to my amp (EAD PowerMaster 8300) via RCA interconnects - HUM.

3. The hum is not affected by volume level.

Any ideas?

Thanks
nvlashi
czbbcl's avatar
czbbcl
1,699 posts
 
Is this a recent occurance? Did you change something or add acomponent or has it been there for awhile? I would start by lifting the grounds on the components to determine which component or components is causing the ground loop.

Chuck
etbaby
137 posts
 
The EP15 is floating the ground from your electrical outlet. This is causing the hum. Call exact power and see if they have a mod for this problem or if they give you some procedure for grounding the unit.
hifi57audio
15 posts
 
I Haven't the time right now to read all the responses, so forgive me if this has already been addressed. The hum you describe is likely 120hz(full wave rectified 60hz line freq) picked up from the power supply. The difference in voltage drops between your two grounds,the innterconnects, and the power cords,cause this noise. If only one power ground,generally at the preamp, is used ground loops can be avoided. HOWEVER, if the interconnects come off you gots an ungrounded piece of equipment. Not good.
dacostab
84 posts
 
Are you sure your interconnects are good? You may want to get a meter and check continuity.
mds's avatar
mds
119 posts
 
Try grounding your amplifier to your preamp. You would need to losen a screw that attaches to the frame of your amp and preamp and attach a ground wire. I have the same problem and talked with John Bayloff @ Theta the other day and that is what he recommends to do. He suggest maybe doing it at the feet of the unit. I have a Meridian 568.2 and Theta Dreadnaught. It only occurs on the rca interconnects for the surrounds as I use balance cables for the L/C/R channels. I imagine that your EAD amp is balanced and the RCA cable is unbalanced only which creates the 60 hz ground loop. Good Luck
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