[BrianM]

The neat thing about noise on an AC line is that you can see it on an oscilloscope,it looks like fuzz on the back of the waveform,less fuzz equals less noise. I paid $135.00 for my 50mHz
Tectronix Scope on eBay. The point is you can see for yourself how much noise you have and whether your attempts to reduce it did any good.
Scotty

I would rather be able to measure AC noise at the speakers.  Reducing it before the analog chain doesn't tell you how much you've actually improved the sound.  I'd also like to know how much AC noise there has to be for it to be audible after it's converted.

[*Scotty*]

Brian,by the time the noise reaches your loudspeakers it has already intermodulated with the signal, this is what does the damage to high fidelity reproduction of your source.
You can't see it once it has gotten past the power supply and into your gain stages. It doesn't take much noise intermodulation to degrade the information to the point that you can hear the damage in a high resolution system. That being said a better performing circuit in a well designed component will out perform a poorer component when the noise level is the same.
That is why I would worry about the quality of my gear before I worry about how noisy my power line is. Anytime you spend more money on your powercords and filtering than you have in your audio gear you have gone past the point of diminishing returns and on to full blown obsession.
Scotty

[Russell Dawkins]

And that is what this twisted, sick hobby that we all love is all about:  The listeners opinion.  There is no wrong or right once we get past all the debates.  Does it make you smile?  Does it sound like music?  Does it make you happy?  Because that is what counts.  The rest is just a way to pass the time and exercise our debating skills .
Happy listening,
Walt

Amen to that.
I think the leading indicators as to how well a system is doing its job for you are:
1) how often do you turn it on, and
2) how long do play it before feeling you've had enough.

[BrianM]

Brian,by the time the noise reaches your loudspeakers it has already intermodulated with the signal, this is what does the damage to high fidelity reproduction of your source.
You can't see it once it has gotten past the power supply and into your gain stages.

I know.

It doesn't take much noise intermodulation to degrade the information to the point that you can hear the damage in a high resolution system.

That's what everyone says, which is why I expressed a wish that such a thing could be measured - not the AC noise itself but its effect, if my original wording was confusing.  How much "noise intermodulation" does it take, or is there?  And which components are "high resolution" enough to pick up on it.  Presumably all of them, since virtually everyone considers they need it.  But it's all left conveniently vague.

That being said a better performing circuit in a well designed component will out perform a poorer component when the noise level is the same.
That is why I would worry about the quality of my gear before I worry about how noisy my power line is. Anytime you spend more money on your powercords and filtering than you have in your audio gear you have gone past the point of diminishing returns and on to full blown obsession.

Well, agreed, and btw I don't believe, or see how, a power cord could do anything about AC noise, unless it had some filtering parts in it.  (Power conditioning, fine.)  But they're all built to obvious price points (power conditioners I mean) so the believer can just pick the price that represents a suitable percentage of his total money spent on gear, the assumption being that the more expensive your gear, the more expensive power conditioning you are justified in buying (i.e., an absurd bit of logic).  And as though an extra $1000, $2000 or $5000 on power conditioning is going to remove a commensurate amount of extra noise.  As for the cords, the only quasi-detailed, semi-plausible sounding explanation I've found for how they're supposed to reduce noise (or something) was written by Shunyata (a vendor) and was represented to me by someone who ought to know as basically pseudo-science.