To Filter or Not To Filter . . .

I do hear noise in my speakers when the amp is on and no music is playing -would this be considered background noise from A/C, or just normal amp noise?

It could be a lot of things, and it's hard to say without more info on your system, and without doing some experiments. My guess, though, is that if what you are hearing is a low level hiss, that is always present at the same level, it is not related to noise on the ac line.

Good power amps are usually pretty quiet, but if you have highly efficient speakers (e.g., 95 db/w/m) that increases the likelihood that the power amp is the source of the noise. If they are inefficient (e.g. 85 db/w/m) the power amp is unlikely to be the source of the noise. Do you still hear the noise with the inputs to the power amp disconnected? Obviously, do not disconnect them while the system is turned on.

Is the noise independent of which source component you have selected, and is it independent of the volume setting on the preamp? Turn off (and preferably disconnect) as much as possible to try to localize it.

Another significant possibility is pickup in interconnect cables, contributed to by inadequate shielding in the cables or by close proximity to power cords or other noise sources.

Also, if any of your components have 2-prong unpolarized power plugs, try reversing the polarity with which they are plugged in.

HTH,
-- Al

Filter. The question should be which not if?

Dedicated mains if you can. If you are really going for it separate source and amps or digital and analogue.

Thank you for all of the advice thus far. While I'm installing a new panel, surge protection, and re-wiring my room, are there any filtration devices that can be installed in wall or at the panel, something to take the place of a conventional stand alone unit that plugs into the wall?

PS Audio has a new device similar to their Ultimate Outlet that installs flush in the wall. So it looks like a large wall outlet. But eliminates another box on the floor and an AC cord. There are large isolation transformers that can be installed near the panel. Low WAF but great for that Frankenstein look. And of course, several companies offer high quality in wall AC wire.