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Buddha
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Objective measurements of power cords...is this a sign of the Hi Fi apocalypse?

Hola,

I saw this posted at another Hi Fi site and felt compelled to steal the link and share it here.

This was not found by me.

It should add some fuel to the discussion about power cords.

Critiques?

Link to University of Toronto paper on power cord differences.

CECE
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Re: Objective measurements of power cords...is this a sign of th

Cool, at least they meausred, but the differences look like a big nothing, auddible, not. What kind of electronic amp has a slew rate so
BAAAAAAAD. My AVA stuff is up around 800v/uS freq resp like 0-500K...and I didn't get a second mortage. And it uses $3 line cords, when you plug in this fancy line cord, look inside teh componet it powers up, it is usually some proper guage hook up wire, there goes all the fancy stuff. How come teh test equipment like scopes, DVM's distortion meters, etc have some generic looking AC line cords, and these products are measuring these fancy AC cords, that somehow make a CD or pre amp do somethin better? huh? What happens if you use a magic AC line cord on a Ossiliscope, does it go into like a loop it can't get out of, in getting better and better, yet measuring on this improvement, pretty soon teh scope goes into a new dimension, a dimension of sound, a dimension we know as....THE TWILIGHT ZONE!!! Even Rod Serling couldn't dream up the sound of wires, he had all kinds of other cool stories. The wire Zone, another dimension,

SAS Audio
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Re: Objective measurements of power cords...is this a sign of th

"Cool, at least they meausred, but the differences look like a big nothing, auddible, not. What kind of electronic amp has a slew rate so
BAAAAAAAD."

Slew rate is not my favorite thing to use as it is related to voltage/power. It is possible to have two amps, "A" with much higher frequency response than "B", yet have a lower slew rate figure than "B", all because "B" has much much greater output power.

For instance, amp "A" may extend to 30khz, while "B" only extends to 20khz but with much higher output power. Yet "B" may have a higher slew rate than "A".

Take care.

Benonymous
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Re: Objective measurements of power cords...is this a sign of th

Forget your slew rates and bat-only frequencies. We're talking about a piece of mains cable here that conducts 110 to 240 volts at 50/60Hz. That's all it has to do. The next port of call is the power supply. Here's how it works, from the top:
An AC supply voltage, a step-down transformer of adequate capacity, a bridge rectifier
, large capacitors for smoothing and to provide a "reservoir" of energy to cope
with any large transient loads. Lastly a DC regulator to control the output
voltage to a specified limit which matches the needs of the amplifier circuits.
That's all there is to it, no black magic. All the equipment used to create the
vinyl discs so lovingly placed upon 100,000 dollar turntables used this design.
Either that or switch-mode supplies but I doubt any High End Hi Fi would use
such awful contraptions. Especially when a decent AC transformer adds so much
"perceived value" in physical weight
Now the thing all you tweakers have to get your heads around is that the cord
that gets the AC voltage from the wall socket to the power supply input is just
a couple of bits of wire. After the AC finishes its journey it comes out clean
(hopefully) DC. A complete and utter transformation has taken place. The
output energy no longer resembles the input energy in any way shape or form.
The capacitors in the power supply are there to provide a reservoir of energy
for the circuits to draw on for transient loads, not the power cord, it's not
in the equation as far as the amplifier is concerned. Now, based on this model,
how on earth could the power cord from the AC wall socket have ANY bearing
whatsoever on the signal being produced by the amplifier? Now don't hit me up
with any "damping" or "impedance" nonsense. It's a metre or two of mains rated
cable. If it was gong to "open up the sound stage" or "increase the depth" of
the musical signal being produced by the amplifier wouldn't there be merit in
running that same spec cable all the way from your house to the nearest street
transformer, or better still, back to the power station with ruthenium plated
connectors all the way?
If you don't believe me, ask someone who has designed a power supply for a high
end amp. They'll tell you exactly what I have and (unless they're a crook) and
tell you the folly of paying any more than five quid for a power cord.

SAS Audio
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Re: Objective measurements of power cords...is this a sign of th

Unfortunately, your scenario presents some misunderstanding since you are talking theoritcal vs reality. I would like to correct the misunderstandings since no component part is perfect.

"Forget your slew rates and bat-only frequencies. We're talking about a piece of mains cable here that conducts 110 to 240 volts at 50/60Hz. That's all it has to do."

>There is more to it. Caps in the power supply are not perfect and electrolytics, depending on the value, become inductive in the 5-20 kilocycle range. So filter capacitors do not totally eliminate the highs from the power supply; so the power supply becomes part of the plate/collector resistor. The higher the frequency, the more inductive the filter capacitors. The bass is also affected, probably more so, but depends on the power supply design.

"The next port of call is the power supply. Here's how it works, from the top:
An AC supply voltage, a step-down transformer of adequate capacity, a bridge rectifier, large capacitors for smoothing and to provide a "reservoir" of energy to cope
with any large transient loads."

>Again the filter capacitors are not perfect (I wish it were) and become reactive at relatively low frequencies. In general, the larger the filter caps, the greater the problems.

"Lastly a DC regulator to control the output
voltage to a specified limit which matches the needs of the amplifier circuits.
That's all there is to it, no black magic."

>I wish it were that simple. Unfortunately, there is more to it. The frequency response of the regulators become a factor as well and affects the sound.

"All the equipment used to create the
vinyl discs so lovingly placed upon 100,000 dollar turntables used this design."

>As one see above, the designs are much more complicated than one thinks.

"Now the thing all you tweakers have to get your heads around is that the cord that gets the AC voltage from the wall socket to the power supply input is just a couple of bits of wire. After the AC finishes its journey it comes out clean (hopefully) DC."

>That is the question everyone is asking. Does the power cord affect the musical properties of the music.

"The capacitors in the power supply are there to provide a reservoir of energy for the circuits to draw on for transient loads, not the power cord, it's not
in the equation as far as the amplifier is concerned."

>If every part were perfect, perfect capacitors etc, theoretically, yes.

"If you don't believe me, ask someone who has designed a power supply for a high end amp. They'll tell you exactly what I have and (unless they're a crook) and tell you the folly of paying any more than five quid for a power cord."

>If a manufacturer tells you as "Fresh" mentions, I would question his credentials as he does not even understand how simple component parts work in reality.

However, I agree, I also would not pay thousands for a power cord.

Hope this helps.

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