I had a weird similar problem (buzzing noise inside amp, everything else in house aok) that was fixed by tightening all connections in my breaker box. The manufacturer suggested that it was more than likely a neutral connection that was causing the problem.
Would be interesting to play with wrapping the receiver in aluminum foil to see if this had any effect on noise just to eliminate emi as a possible source.
Another thing is to carefully eliminate the ground connection (assuming there is one) to the receiver using a cheater plug.
Yet another thing is to plug in a high wattage light to the same outlet your receiver is plugged into & see if this changes the noise.
I liked the previous posters ideas also.
Would be interesting to play with wrapping the receiver in aluminum foil to see if this had any effect on noise just to eliminate emi as a possible source.
Another thing is to carefully eliminate the ground connection (assuming there is one) to the receiver using a cheater plug.
Yet another thing is to plug in a high wattage light to the same outlet your receiver is plugged into & see if this changes the noise.
I liked the previous posters ideas also.