The sound from my system is often dry, reedy, really unpleasant -- even my girlfriend can hear it -- and the problem seems to be of an electrical nature. There's a sort of a buzzing noise through the upper midrange and low treble -- sort of the audio equivalent of those little trickles we used to see on the television when dad was running the electric carving knife in the next room.
The mains in my house are NOT grounded, so at this point I'm thinking that it's a buildup of fault energy in the amp or preamp, but why would that affect the sound intermittently, and why only in this very peculiar, difficult-to-pin-down sort of way?The mains should be grounded..... Even though you may not have 3 wire grounded receptacles your main electrical service is a earth grounded system. The neutral conductor is, (should be), bonded, (connected), to earth ground.
As for an intermittent buzzing sound heard through your speakers of your audio system a loose or corroded electrical connection could be your problem. The loose connection could be anywhere in your home's electrical system. All that is needed for the loose connection to act up is to have current flowing through it. Two things happen. EMI noise as well as generated RFI noise.
It may be time to call an electrical contractor and have things checked out. A loose connection, as a rule, will not cause a circuit breaker or fuse to open. If the load on a circuit is such and the arcing from the loose connection is enough, heat is generated. Enough heat, the connection may burn itself free, or may even cause a fire.
One thing you could try is to turn off every electrical item in your home except your audio system. Listen for a difference. If your system sounds better then it may be time to call the electrician.
I should note if your problem is due to a loose or corroded electrical connection the bad connection could be in the branch circuit your audio equipment is plugged into. It could very possibly be the receptacle. Poor contact pressure between the plug and receptacle can cause EMI/RFI noise. Does the plug feel snug when plugging it into the receptacle?
Also the branch circuit could be feeding many receptacles. If the branch circuit was daisy chained from receptacle to receptacle this could be the problem. A loose or corroded connection/s at a receptacle/s will cause EMI/RFI noise. Receptacle stab in terminations are the worst. Even side terminal screws can become loose or corroded over time.
A dedicated branch circuit could solve your problem.