Power supply hum transmitted to 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)

@atmasphere 

Yes, I agree with you that my earlier comment - the faint buzz when your ears are within about 3 inches of the mid-range drivers or the tweeters is perfectly "normal" - is more accurately stated when buzz is replaced with hiss.

I consider any sound other than the music itself - no matter how labeled or categorized - to be part of the systems noise floor and undesirable, regardless of the distance ones ear is from the speaker. 

Most transformers hum - and most of it is because of dirty power.  A good way to eliminate this is using a balanced power isolation transformer, it is exceedingly efficient in eliminating hum. 

I use a power transformer similar to this one.

https://www.sweetwater.com/store/detail/P2400IT?adpos=1o1&creative=54989263441&device=c&...

Good Listening

Peter

Audiobrian 1-20-12017
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)

I can’t really shed any light on that, Audiobrian. And my Renaissance 70/70 is of course a very different design than your 300.1a.  FWIW, though, my amp makes some very slight mechanical noises during the first 25 seconds or so after turn-on, at which point B+ is applied to the tubes, but it is subsequently totally silent in terms of mechanical noise.

The amp is placed atop a 4 inch Mapleshade Isolation Platform, which in turn rests on a set of Mapleshade Isoblocks.

Good comment by Peter, as always. In my case, I have reason to believe that I have better than average AC power quality.

Regards,
-- Al

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.