Power supply hum transmitted to loudspeakers

I believe most amplifiers/systems have some very minimal noise audible through the loudspeakers at idle. Some have background AC, ceiling fans, pool pumps etc which make this noise floor less or perceptibly inaudible.  I own some Clayton monoblocks which I love, have had their power supply upgraded, but still has a small amount of buzz at the loudspeakers, not audible while playing music beautifully.(with and without shorting plugs). I've learned to ignore it and realize the amplifier was meant to play music, not to necessarily be dead silent at idle.
Good luck!

I guess a good question is how much noise emanating from your loudspeaker, once your system is energized, is normal? I avoid saying acceptable as we all have different tolerances.  When we place our ears 12 inches from the tweeter or midrange driver and hear a low level, buzz, hum or hiss, with nothing audible at the listening chair, is this normal/expected? When I run tube gear I often hear a low level hiss, with solid state a low level buzz, but no more than 1-2 ft from the loudspeakers. 

This has evolved into a most informative discussion.  Ralph seems to indicate that buzz of any kind, even at 2-3 inches from tweeter/midrange should not be heard.  Can I take that to mean that an amplifier's noise floor should only express itself as hiss, if audible at all?  Any electrical buzz or hum at 3 inches should require investigation?  

Al, I do have a question for you.  I have both a VAC 300.1a and a Ren Sig 2A Preamplifier.  I have noticed no pertinent electrical buzz from either but both do have power transformer hum, not particularly disturbing, but noticeable in a very quiet room.  Kevin has suggested different stands that might not resonate but I am still unsure why potted transformers are quite so audible. (truly not disturbing while playing music through Kevin's most musical components)

As relates to the transformer hum from my VAC amplifier and preamplifier power supply, I have them both plugged into a Torus 20A RM-20 isolation transformer based power conditioner. I believe isolation transformers are just as effective in eliminating hum inducing DC as humbusters. No change plugged directly into dedicated 20A outlets.  I'll try some sorbothane under the components to see if it help....they sure sound great playing music when I don't notice the mechanical transformer hum.