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House Wiring Defect?

Recently I introduced a new power amp connected to my preamp with XLR cables. The pre and power amps were plugged into different outlets in the same room which produced a pretty loud hum from both speakers with the preamp on or off and the power amp on. After the inital freak out and a check of all connections I realized one fix was to power the pre and power amps from the same outlet. This restored quiet operation using either outlet. The question is, does this indicate a house wiring defect or nothing to worry about?
rockvirgo

Showing 2 responses by rockvirgo

rockvirgo OP
587 posts
 
Thanks all for your responses. Those three light socket checkers are great but haven't been able to snag one yet. Visually, both outlets are wired identically and the breaker box looked ok, except for some red wires inside. My last guess is one of the two outlets is set up near the window aircon so maybe it has a separate ground.
rockvirgo OP
587 posts
 
Thanks Barry, yep I took apart my Kimber PBJ's overcomplicated Switchcraft XLRs to check their wiring before I figured out everything needed to be on the same outlet.

For the record, although the outlets are wired with three core wire, the electrician here at this circa 1930's rental says it's two core down to the box. One of the two outlets in this thread is a new one for the window A/C unit. The electrician says he used half the 240. From what I've read here all the 120 circuits are developed that way. My guess is these two outlets have different ground schemes.
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