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power cables - not in the signal path?

According to popular wisdom the AC power is not in the signal path and therefore a power cord, AC conditioner or similar should have zero audible effect.

In a don quixotesque attempt I'd like to turn this perception around: the AC is 100% in the signal path - more so that the actual low-level signal that gets amplified, and I think I found the simple words to clarify this.

The low-level signal is actually only modulating the high-voltage (high-intensity) signal produced by the transformer. Those electrons from the transformer are the actual electrons we "hear". The low-level signal is simply lost in translation. In a simple example, a 0.1V peak-to-peak sine signal gets amplified (say) 10x by a 10 V continuous (transformed) DC. The output is (say) a 1V sinusoid oscillating back and forth in time. If the 10V continuous is NOT actually exactly 10V (but is actually has noise) - then the noise will directly reappear "riding" on the 1V output.

Hence the need to keep the AC noise-free.

(Of course I purposefully neglected for simplicity the other effects (need for instantaneous delivery of power, etc..) for which I did not find a simple enough description (without reference to I/V curves and impedance / capacitance details, that is).

Does is make sense?

Thanks
C.
cbozdog
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almarg
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06-12-14: Cbozdog
Geoffkait and Almarg - agree with both, with the small exception that attenuation of radiation takes place in any medium that is not vacuum to various degrees depending on medium and frequency (with the most striking example being metals - which are very effective in absorbing said radiation for practically all frequencies relevant here). The reason is (again grossly simplifying) that metals have those free carriers ready to move when they get pushed around by EM, so the EM energy reaching them is converted to electron motion.
Cbozdog, agreed. As I indicated, I was "assuming propagation through a medium that is conductive to it, such as air or a vacuum," air being a bit less conductive than a vacuum, consistent with your comment.

It should perhaps also be stated that the earlier comments pertain to propagation of electromagnetic energy through free space, as opposed to through coaxial cables, waveguides, fiberoptic cables, etc., for which the factors affecting attenuation as a function of distance are of course completely different than the "spreading out" effect I referred to.

Regards,
-- Al
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geoffkait
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Well, not sure I agree with your detective work, unless by "spreads out" you mean absorption and scattering. Low level signals for cell phones work pretty well even though they are "spread out." RF is not necessarily line of sight. Cheers, Geoff
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almarg
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Geoff, no, I'm not referring to absorption and scattering. I'm referring simply to a matter of geometry. A radio antenna, a radar antenna, a flashlight, etc., will not radiate energy in a beam that remains at precisely/exactly/100.00000000% the same diameter is it travels out over an extended distance. The cross-sectional area of the beam will increase in size as the distance from the source increases. That will happen to the greatest degree, of course, if there is no beam to begin with, i.e., if the radiating antenna or other source is omnidirectional. The surface area of a sphere increases exponentially as its radius increases (or more precisely, in proportion to the square of the radius).

Therefore the fraction of the originally radiated energy which intersects a GIVEN cross-sectional area will decrease as the distance of that cross-sectional area from the source becomes greater.

That is the main reason why although a radio station's transmitter may send out many thousands of watts, the signal seen by the input circuit of a radio receiver may be only a few microvolts, corresponding as a rough order of magnitude to perhaps a trillionth of a watt.
Low level signals for cell phones work pretty well even though they are "spread out." RF is not necessarily line of sight.
True, but not relevant to my point.

Regards,
-- Al
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mapman
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"...not relevant..."

Hey a new advertising slogan for many MD products!!! %^)
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geoffkait
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Hey, Mapman, see you finally woke up out of your stupor, welcome back!

:-)
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