Dover, thanks for your comment.
I don't mean to be picky, but I think it would be better to refer to "reflected noise," rather than "reflection noise." The reason I make a point of saying that is that Cjl's post seemed to say that reflections caused by impedance mismatches PRODUCE noise, which is simply untrue. Reflections of noise frequencies that may be present can ALTER the effects of that noise on the system, although with little or no predictability. But impedance mismatches do not produce noise, and reflections do not occur unless there is something to reflect.
In any event, the speaker will only respond to the instantaneous voltage DIFFERENCE that exists between the + and - output terminals of the amplifier. The noise levels that may be present in that difference, as a result of noise on the incoming AC, will be VASTLY lower than the noise on the incoming AC, assuming that the amplifier design is half-way decent. And the speaker, as well as our ears, will not be capable of responding to RF and digital noise frequencies anyway. The possible sonic consequences of high frequency noise on the AC line would result from intermodulation and other effects occurring in internal amplifier circuitry, that may end up affecting audible frequencies.
Again, thanks for your comment, and my intention in responding is not to be picayune, and (as my earlier posts make clear) is not to deny that power cords can make a difference.
Best regards,
-- Al
I don't mean to be picky, but I think it would be better to refer to "reflected noise," rather than "reflection noise." The reason I make a point of saying that is that Cjl's post seemed to say that reflections caused by impedance mismatches PRODUCE noise, which is simply untrue. Reflections of noise frequencies that may be present can ALTER the effects of that noise on the system, although with little or no predictability. But impedance mismatches do not produce noise, and reflections do not occur unless there is something to reflect.
Now unless you are running a floating balanced output stage in your power amp your speakers are connected directly to the main grid on the negative side. The negative speaker terminal in your power amp is on the wall side of the mains transformer.The negative speaker terminal will usually be connected to AC safety ground (and the amplifier chassis) through a low impedance, such as a low value resistor, or in some cases directly. The paths between AC safety ground and the primary side of the power transformer, in turn, will be via stray capacitance, especially within the transformer, and via the connection that exists between AC safety ground and AC neutral back at the electrical service panel.
In any event, the speaker will only respond to the instantaneous voltage DIFFERENCE that exists between the + and - output terminals of the amplifier. The noise levels that may be present in that difference, as a result of noise on the incoming AC, will be VASTLY lower than the noise on the incoming AC, assuming that the amplifier design is half-way decent. And the speaker, as well as our ears, will not be capable of responding to RF and digital noise frequencies anyway. The possible sonic consequences of high frequency noise on the AC line would result from intermodulation and other effects occurring in internal amplifier circuitry, that may end up affecting audible frequencies.
My understanding is that if a power cable is too short then the pc will behave as if it is part of the loop, whereas if it is say 2m or more it will behave as a spur. There is a difference.There is no hard and fast dividing line. It depends on the frequency of each particular frequency component of the particular noise that is present, and (to a lesser degree) on the propagation velocity of the particular wiring. For the very high 8 to 13 MHz noise frequencies that were among those Cjl referred to, 2 meters is a reasonable rough rule-of-thumb approximation. Noise frequencies that are much lower would require a much longer cable length to behave as a spur.
Again, thanks for your comment, and my intention in responding is not to be picayune, and (as my earlier posts make clear) is not to deny that power cords can make a difference.
Best regards,
-- Al