[R-390] query re ground loop (OT)

[Chris Kepus]

It sounds to me that you isolated the problem:  "No noise if I use just a 3
to 2 adapter thus ungrounding the amp. Putting the amp on an AC receptacle
in another room: no hum."

I do not pretend to know how to suggest ways to "elegantly" eliminate the
ground loop, but since you accomplished the mission, what's not to like?
Simply use the three prong to two wire adapter.  Just for a safety check,
you might take a VOM or DMM and see if there are any AC voltage potential
differences between your amp chassis and the chassis of other components.

73 and enjoy the music,
Chris
W7JPG  

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of wli
Sent: Sunday, January 30, 2011 3:58 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] query re ground loop (OT)

I have a strange problem on my stereo. Loud interference-like mid-range
pitched (not 60cps) hum when plugged in using 3 wire plug. Turned off all
the dimmers in the house: hum persists.

No noise if I use just a 3 to 2 adapter thus ungrounding the amp. Putting
the amp on an AC receptacle in another room: no hum. 

The offending receptacle itself is grounded properly insofar as I can tell.

Do I have some sort of ground loop? What is wrong with my thinking?

Thanks for the bandwidth

W. Li



      
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