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
Please be aware that most "microphone" cables (i.e. from a "music store") are incorrectly wired -- they often have pin 1 tied to pin 0, which is the shell. As clever as this is for electrocuting musicians, we still have musicians so the premise isn't working well...

Seriously, you'll have to open both ends and determine if the wiring is 1==1, 2==2 and 3==3, with nothing else.

You also might try disconnecting EVERYTHING, then start from the sub and speakers BACKWARD, listening to each step.

And of course IF you have TV cable connected to anything then that's very probably your culprit.

Regards,
Barry
Please be aware that most "microphone" cables (i.e. from a "music store" are incorrectly wired -- they often have pin 1 tied to pin 0, which is the shell. as good as this is for electrocuting musicians, we still have musicians so the premise isn't working well... Seriously, you'll have to open both ends and determine if the wirinfg is 1==1, 2==2 and 3==3 , with nothing else.

You also might try disconnecting EVERYTHING, then start fro thje sub and speakers BACKWARD, listening to each step.
And of course IF you have TV cable connected to anything then that's very probably your culprit.

Regards,
Barry
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.