So I use a few gadgets known as the PS Audio Noise Harvester. These devices fit into a wall AC socket and "convert noise into light." There is a little LED light that sometimes blinks like crazy and sometimes once a minute. Sometimes it blinks not at all.
The idea is that it pulls noise from the AC line. My apartment is not wired for dimmer light switches, which in my last domicile was the biggest trigger for these little buggers going blinkedy blink.
I make no claim as to what these things do to the sound, but they certaintly are an indicator that something is going on with the AC line. And I figured out what causes them to go blink blink in my apartment--my computers.
When I fire up my desktop PC, the noise harvester on that line goes blinkedy blink and blinks with an almost mechanical regularity.
When I fire up my notebook PC, the other harvester on that socket goes blinkedy blink as the hard drive spins and retrieves data.
One thing is clear, certain types of PC activity is setting these things off. This leads to the question, if we are increasingly using computers as our sources, in our listening rooms, what if any steps need to be taken to ensure these audiophile unfriendly devices are not polluting our systems with noise. Can we build them better? Can we isolate them? Must we invest in more resistant power cables that filter the noise.
Is it the switching PSU? The mechanical hard drive? The video card fan? The processor itself, or perhaps it is the processor varying its clock speed, or using too much power, or not enough power?
Do we know? Do we dare ask?