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

[Randy and Sherry Guttery]

On 1/30/2011 5:57 PM, wli wrote:
> 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.
Likely ground loop - but only a "hands-on" determination 
could confirm it - and that it's not some sort of "Current 
Carrier" effect...
> 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.
Sounds like something that is plugged (audio connection) 
into the amp (when humming) is plugged into a different AC 
outlet that is on the opposite "leg" (or majorly different 
loaded circuit) in your house. Not knowing what the 
configuration is - hard to say where to start - other than 
I'd un-plug each component (both connectors in the case of 
stereo connections) one at a time to see if you can isolate 
which component is causing the problem - and see if it's on 
an outlet on "the other leg, etc."...  Of course - not to be 
overlooked - the amp itself could be on an outlet that is 
different than the "rest of them"...  in which case an 
extension cord might be in order (to get it on the same side 
of the circuit).

If it is indeed just one component that's on a different 
circuit - one could either run an extension cord to that 
device - or get an isolation adapter to go between the audio 
connections of the device and the amp.

best regards...

-- 
randy guttery

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