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Interconnects, speaker wire, power cords. Ask the Cable Guys.

Re: How is it that power cords can make a sonic difference???

How AC cords can affect the sound:
http://www.AudioAsylum.com/audio/cables/messages/13538.html
(This is essentially the same as what I have at the web site, at:
http://www.geocities.com/jonrisch/ac-cords.htm)
http://www.AudioAsylum.com/audio/general/messages/188129.html
Tests of a power cord on a digital recording system:
http://www.thuneau.com/MPC/
AC Power artifacts getting past a DVD power supply:
http://www.hometheaterhifi.com/volume_7_3/dvd-benchmark-part-2-audio-9-2000.html

Now aside from all that I have posted/written already, I will address the other part of the issues with power cords, the "miles and miles" fallacy. Some folks contend that due to the miles and miles of power lines from the electrical utility generators to your home, tha the last few feet can not possibly amke any difference.

The very reason for the use of AC power, instead of DC power, lies in what is known as the "Eye-Squared-Are" (I2R) losses.

Using a very simplified analysis, for any given run of power cable, the power losses in the line due to the resistance of the power line, will be proportional to the current squared. Voltage drop will equal the resistance times the current.

With DC, these losses just continue to go up the longer the power line run is, there is no way to string power to a whole line of houses, the guy at the end of a long parallel power line run would not get the full voltage, not by a long shot.

With AC, the voltage can be stepped up with transformers, and then stepped back down locally. For long distance transmission, the voltage is stepped up to thousands of volts, and then at sub-stations, stepped down to hundreds of volts, and then just outside your house, it is stepped down to a 240 V center tap, and you use one or the other of the sides of the 240 V center tap for your 120V wall power.

The (electric) water heater or furnace and/or dryer use the full 240 V, hence the special plugs and dedicated runs from the panel.

Stepping the voltage up reduces the current, and this is what keeps the power losses down, and is why electrical power is transmitted using a high voltage AC system.

So what matters from a local perspective, that is, what is relevant AT YOUR HOUSE, is that there is a step-down transformer outside your house that is the local low impedance source for the AC power, and it is this low impedance step-down transformer source that is actually the 'beginning' of the AC power chain AS FAR AS YOU IN YOUR HOUSE ARE CONCERNED.

The wires run from the house panel to the transformer on the pole are typically much larger than the house wiring, and are of a reasonably low inductance geometry considering that they have not been optimized for this.

So the limiting factor for power delivery to your audio system tends to begin right at the breaker panel and is primarily concerned with the length of romex that exists, and with how many wall outlet push-in connectors it has passed through on the way to your audio system wall outlet, with some slight extension of the limitations out to the local step-down transformer.

This of course, should illustrate why the myth of "miles and miles" of power lines is just that, a myth born out of ignorance of the actual situation, and the oft repeated mistatements of some who have a hard time actually thinking about AC power issues, and what is going on.

This latter info rounds out some of the many reasons that AC power cords can make an audible difference.


Jon Risch


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