Noise Only When Playing

[offrhodes]

Check that the wall socket's earth terminal is actually connected to earth. In some places it was (or maybe even still is) legal to not connect it in building installation under some conditions. Sounds crazy but I've seen it myself.

You might have some luck with a "power conditioner". I suspect that strong power line harmonics are present (n x 50 Hz, n >> 1) for whatever reason, e.g. a broken or misused dimmer somewhere in the neighborhood.

 

[Rex]

I am a Certified Master Electrician and Sound Engineer, and am well aware of proper grounding and more...

We can debate this issue all day long and I'll gladly debate the proper grounding methods for anything electrical and electronic in a separate thread. But the discussion IS about trying to help the OP with his noise issue. I made a suggestion.

If you're a certified master electrician, you know what the NEC has to say about two-pronging anything that's not double-insulated, as well as the dangers of relying on signal cables for power grounding.

I made a suggestion, too—to potentially save a life. I'll gladly participate in a different thread. PM me if you set one up. Meanwhile, I'll leave you with this story of a CSU professor whose electrocution would never have happened if he hadn't thought that using a cheater plug was a good idea:

http://www.the-scientist.com/?articles.view/articleNo/23809/title/Ohio-cites-university-in-death/