how can a line cord affect frequency response ?

Better watch out guys and carps, Mr. Tennis's mechanical froggie is loose again in the audio pond with all its juicy and elegant sophistries. Before you know it he'll have you all wrapped around his magical pingponging fingers!

My Friends,
If any of my posts came across as arrogant or whatever, I am sorry. I am a music lover and audiophile, but alas, I have a degree in EE. That being said, having an EE degree does not automatically make someone an authority on power supplies and audio amplifiers. There are many paths one can take in this field but designing high performance audio amps, for instance, is a rare path indeed. My job involves digital designs with FPGAs for software radios, but my real passion is the analog stuff.

Although I am in the more objective camp, I have never stated that power cords can not make a difference. Rather, if you follow my previous posts, you can see I made a feeble attempt to describe how such a thing might be so.

One thing that I will never give up is my fundamental belief that if a real change is heard, however subtle, and repeatable, say between one power cord vice another, then there must be an underlying electrical change to manifest such sonic deltas.

If I did not believe this, then it really does boil down to faith in something else.

I do believe that there are material-electrical differences among pcs, and if in the right high resolution system with great acoustics, then these deltas may manifest. I think this can and does get out of hand and folks have to be somewhat realistic about expectations.

The longer I think about this, the more i'm inclined to believe that it's not simply reducible to the large amount of romex, nor the junction box, nor the long lengths from the step down xfrmr on the pole a bazillion feet away, nor the miles of 100 kV lines back to the distribution station. No. It must be the interface to this network. Why/ how I do not know yet but i have some ideas.

I listen to music alot, but I also love to measure things. I love to understand the physics behind something. In my view one reinforces the other.

A basic experiment to test currents on the ac-line:
A high power series resistor with the hot lead. The resistance will have to be low and this is not ideal, but it could work. A safe box of some sort will have to house the plugs and power resistor.
A basic ocsilloscope with a differential probe across the resistor (do not use the ground clip as you will be connecting the hot directly to ground via the scope cable--not good).
A test signal, like some continuous tones ala stereophile cd-2. Of course you need a trigger for the scope. Simply use the 60 hz ac line setting. This way you capture the events you want to see based on the power cycles of the ac.

You plug your amp pc into the thing you fabricated that houses the power resistor. Fire up the amp.

At this point, with the volume low, you might see some activity on the scope that relates to the charging of the filter caps, aka 120 hz (full wave rectifed).
If you can trigger the scope just right,and play with the time base, and vertical gain, sample rate, etc i bet if you crank up the input signal you will see, at the peaks, fluctuations that are directly correlated to the amplified signal.
Here is where i think power cords can make a difference.
The current is pulled sharply from the power amp at these peaks. We know that abrupt changes indicate high frequency. This is direct from theory and confirmation over hundreds of years.
(This IS not equal to whatever high frequency content in the signal to be amplified)

This is one fairly simple test that can be run. I currently do not have a working personal scope and probe of reasonable quality. I would love to do this however.

Of course this may be all wrong, but I like to offer possibilites to understanding our beloved hobby.

Later!

mr g, i will repeat what i said to others. stop taking yourself, the music, the sound so seriously. you resort to argumentum ad hominem instead of critiquing what i say.

your supercilious attitude is one reason why people think an audiophile needs a therapist.

if you lighten up your blood pressure may go down.

i must admit, i enjoy your british humor, it is so biting and civilized, but as a lawyer, i'd bury you in court.

Mrtennis essentially states that without proof, there is no knowledge, only opinion. But in the big picture, much of what we all personally consider knowledge is not proven until we too witness and experience if for ourselves.

I "know" that Canberra is the capital of Australia. But how do I really know that Australia even exists? I have not been there. Many people claim it is a continent in the southern hemisphere which I must take as faith. And since I have not witnessed its existence, is my "knowledge" of this indeed not knowledge? In my opinion, Australia exists but I do not know for sure. And even when my plane lands there, how do I still know I am in Australia? My weeklong trek across the Australian desert in a jeep may have in fact been through the California and Nevada deserts. Life is one huge box of faith.

What defines the line between opinion and knowledge and thus fact? Clearly we have a group here that continues to profess that we can not base our knowledge on what we hear. So what do we use to substantiate out claims? Our eyesight? If I alternate between power cables A and B, and repeatedly take measurements through various tests, compare the charts/plots etc., and can visually verify that cable A always has a higher peak than cable B and frequency X, and so on, then can I deduce from these efforts that I now have knowledge that there is truly a difference? But why do I only trust what my eyes tell me and not what my ears told me before? And if it is not a sight vs. sound issue, then it comes down to needing the test equipment to provide the basis for knowledge rather than my own senses.

As I tried to infer before, even when our senses tell us that differences exist, we may be a long ways off from identifying why they do exist. And as an engineer, I too want to know the how and why of everything around me. But this is simply not realistic.

Unfortunately this has turned into a freshmen 101 philosophy discussion.

Can we please stay on topic? please, can we let the pure technical treatment of this question carry forth?

I am one engineer who does not try to reduce the world around me to equations and mechanistic operations.
But, in this case
I do think there is a technically legitimate answer... This topic is a matter of electrical interaction, nothing else, pure and simple.

This thread is another example of how we audiophiles talk about hearing subtle differences/shadings, sure they are important, but then we rant and rave about this and that being so and the "well if your system, ear, room, etc are not up to resolution " blah blah blah...with no real technical discussion based on facts. It happens and will continue to just be so.

Why such an unwillingness exists to tackle the problem they way it should be dealt with is just lazy.

It's really ok to talk objectively. Objective science and engineering are what brings forth the awesome equipment we love and your music will still sound great to your ears if you choose to bury yourself in the technical details.
It's a matter of choice.