Originally Posted by Sam Schulz
Anyway I bought a Panamax mr4300 from best buy today, no affect on the noise.
AC power is a sine wave, which may have some distortion (harmonics) imposed upon it by load, and some spikes where rectification diodes turn on prior to the peak, and to a lesser degree, turn off after the peak, and spikes where dimmers turn on and off - variable location on the wave depending on the dimmer settings. These tend to occur at 60 or 120Hz intervals, though the harmonic distortion of the wave could be other multiples of 60.
To get a hiss out of tweeters from the usual noises on the AC wave after rectification and filtering and regulation in the device would not be something I would expect. Maybe some forms of hum, but not hiss.
AVR's have many digital devices in them now, which may emit noises at various frequencies depending on their clocks and functions, so my guess would be the hiss is internal to the AVR.
I have an old pocket AM 8 Transistor radio. If I put it near the computer, the cable box, the Oppo, the plasma TV, the LCD monitors, it emits all manner of spurious tones whistles hiss and chirps. I don't have a digital AVR to try it on.
The flourescent displays are very noisy, and the plasma TV is amazingly noisy.
My audio is not, though. Having put an oscilloscope on the speaker leads in the past, I saw no difference between powered up and powered off, just the background RF hash in the air (which doesn't have the energy to cause a speaker to make a noise) while no musical signal is present.