how can a line cord affect frequency response ?

i have personally auditioned over 10 different manufacturer's line cords. i hear differences. i don;'t understand how a line cord can affect treble response or bass response.

can someone provide an explanation ?
Ultimately, no. But there are lots of theories which are probably individually insufficient to explain it. There's skin effect, where electrons move faster on the surface of the wire than inside it. There's consistency of material (e.g., long vs short metallic crystal structures) that minimize interference of the signal. There's inductance and capacitance effects of the material and the interaction with the insulator and the other wires in the cable. There are noise reduction designs based on how the wires are wrapped and how they can cancel out inherent noise. There's radio wave and other high frequency interference (all wire is an antenna) which can ameliorated through insulator design or the introduction of a dc current. It goes on and on. The truth is, we know a lot but we probably don't know more. Be happy your ears are sensitive enough to hear the differences -- that means you can also pick up the nuances of the music we all love ;-)
Hi Mrt.

Since AC power cords seem to have kind of become my latest fascination, I'll chime in here.

As important signal carrying cabling is, I've come to the conclusion that AC cords are a cabling system's foundation. Very good reason for this...think power supply. All the music you listen to is the power supply being modulated and controlled by all the other circuitry.

In a nutshell, the reason power cords can have such an impact on the music we hear has to do with their power delivery characteristics. Counter to what many think, big gauge/low DC resistance is way down on the list of design priorities...with our AC cords anyway. Almost all aftermarket cords suffer from power deliver characteristics that are not optimized and as such, most cords act as euphoric coloring devices. The electrical parameters of these different cords are all over the place. The result is as you've experienced...some cords sound big and warm and some sound detailed but lean.

I don't think that to strike a balance between big and warm / detailed and lean is really the issue or should be the target. What does the power supply need to be able to respond to all the complexities of the playback software should be the target in our view.

When the power supply's demands for meeting it's task are met, it's really quite amazing what you'll hear. Details from top to bottom that were previously buried suddenly become apparent and can really reveal the vitality present if good care was taken in the recording.

So, hope this gives some insight Mrt.

BTW, I'll shamelessly put a plug in here...more so 'cause I'm simply very excited 'bout what's going on here. The Poiema!!! AC cords have been a great choice for those wanting a cord that doesn't perform coloring duties. The Alethias AC Cord is just around the corner and, as our top shelf offering, it's freakin' killer!

Kind Regards,

Always glad to hear your thoughts on the subject. Based on our previous discussions, I also suspect a device like the Z-der block, in conjunction with a properly designed power cord, provides an even greater capability for a components power supply to operate optimally. I know mine has performed nicely on my preamp with a Virtual Dynamics Nite II, and now a Virtual Dynamics Master power cord plugged into it.

BTW - the Volume II sampler is wonderful. Thanks so much.
Mrtennis, I'm just glad you hear the difference and are enough of a thinking man to wonder why.

Some people say line cords don't matter and argue for pages, but never stop to listen.

Thanks for listening, regardless of which one you prefer.
Just to be clear, I don't think the op's q has been answered, and that that is that there is no explaination as to how a PC can change the frequencey response of a device.

Easy question, easy answer!

One point is most power supply designers will assume they can design in any properties that a power cord may add to the mix, essentially negating the PCs affects to the sound. But that would eliminate the revenue source of many vocal suppliers and buyers, so that point is not well taken.

I guess an alternate approach is to modify your existing equipment's power supplies, which manypeople prefer to take.

robert, please read my post on the purpose of a stereo system.

i think you're attempt to sell is most inappropriate.

your gratuitous comments about your products and your implications about euphoric colorations are not appreciated.

perhaps i want to use cables to flavor the sound of a stereo system. i would therefore be curious to hear of the products which you imply are euphorically colored. care to name names, or will you criticize from afar. your comments are unprofessional, and unfortunatively indicative of what's wrong with the high end industry.

Your threads do seem to attract attention.

I was emailing with a buddy that I met here at Audiogon and the subject turned towards my dad, who will probably only be with us for a few more weeks or days. My dad fixed electronics and operated a store in Brooklyn from right after the war (1945) until he got sick in 1977. Back then, when a tube blew or a power cord needed replacing ... you just replaced it. The tubes that you used, were the ones that the supply house had or better still, were running a special on, as it kept the repair cost down. My dad preferred "cheetah" power cords (the cloth jacket type whose threads were woven to look like a cheetah's fur) as they would diffuse the heat better, but they typically only found their way onto steam irons (for obvious reasons).

My dad and I would get into discussions about the new technology ... 8 track tapes; cassettes; quadrophonic; hi-powered amps ... because he couldn't understand why the need for all this new stuff. He was a mono and tube man and few things sounded better to him than a Grundig console that he had in his store.

In re-reading your threads, maybe the answer to what you are after is in restoring some prime vintage equipment and using interconnects and power cords that interfere with the vintage sound as little as possible.

I have read so many theories as to why power cords and ICs do what they do. I am not sure if I believe all of it ... so much of it is either theoretical only and not audible or only truly noticeable when someone calls attention to it. Ozfly did a good job in summing up a lot of what you'll read. I do recognize though that the final effect is different with different equipment. Since I prefer a warmish and moderately detailed sound I have made out well with Signal Cable ICs & PCs; Better Cables ICs; and Cardas ICs and PCs. I deliberately mix "copper only" IC's & cables with silver/copper hybrids as that gives me the warmth/moderate detailed sound that I like. My systems do a good job of putting me to sleep ... but, I always thought that was because I was tired, though.

Maybe rather than flavor the sound of your system, stick with vintage ...
which got the mids right, the bass warm, and left out the highs.

Regards, Rich
Mrt, I did read your post and I understood what you wrote. Please re-read my post and correctly understand what I wrote. You simply asked for an explanation and I gave ours. I didn't say that cabling that provides coloration duties was an evil thing. While I understand the value of coloring the sound and some folks preference for components that do such, it's simply not my approach...that's all. It's a good thing there is more than one road to Euphoria since everyone's preference for the big "E" is a little different.

"perhaps i want to use cables to flavor the sound of a stereo system." Okay, good for you!

"your comments are unprofessional, and unfortunatively indicative of what's wrong with the high end industry." Sorry you feel that way. Some wonder why more manufacterers don't post more often. I don't. I anticipate almost every time I post I'm gonna get slugged for something. I could also say that your apparent inability to understand what's written and the overly suspicious attitude that draws off base conclusions is part of what's wrong with our society. I bet having a beer with you would be fun...really, no slam.

Cheers Friend.

Hi Cleo.

Thanks and you're welcome, glad you like Vol.II. I'm still kind of struggling with some of the selections.

Hi Wellfed.

The Z-der came out of our research of power cords. It basically re-clocks and corrects the relationship between the voltage and current that comes out of the wall. You're welcome to contact us directly if you'd like a more thorough explanation or a URL.

Sell, sell, sell! (what an antagonist I am) LOL!



Some time when I have a few grand to get rid of I will try out some different power cords. Til then I will stick to my belief that a properly designed power supply will produce DC without artifacts of the input AC power. There are many instances where physical characteristics are completely lost in a transitional state.
A simple analogy might be a river going over a waterfall. The smoothly flowing water below the falls shows no evidence of ripples above the falls. The river has been reconstituted from millions of droplets falling through the air, and has "lost its memory" of what happened above the falls.
Mrtennis, I had the pleasure of meeting Robert and Steve of RSAD spending a afternoon talking and listening to their system a few weeks ago. It was probley the best learning experience I have had since getting into audio, Robert and Steve have a true passion for music. The system I listened to was the most natural and neutral I have ever heard. I hope to add their cables to my system in the future so I can truely hear what my components can do. I would suggest you call Robert i'm sure he would be more than happy to explain his opinions and help you understand what cables can do for your system.
let me clairify my statements robert, which are not personal.

i think that a forum should not be a venue for advertising or attempting to sell equipment.

there is another section for buying/selling equipment.
i believe that you advertise your products from time to time.

if you have heard products, in this case power cords, which to your ears affect the sound in a certain way why not mention them, especially if someone requests such information.

i'm not judging you, just observing the obvious conotations from your words
Hi Mrt.

if you have heard products, in this case power cords, which to your ears affect the sound in a certain way why not mention them, especially if someone requests such information.

You'll never see RSAD do that on the boards. I would suggest if you want opinions on how a particular product sounds, ask other users who enjoy those offerings or the manufacturer. Not ask one manufacturer to comment on a competitor's efforts on a public forum.

Kind Regards,
While this may not answer your question, if you are looking for some type of guide as to the sonic signature of various brands of PCs, this thread by Audiogon member Tvad may be of interest to you:
i have listened to robert's latest interconnect cable in my stereo system. i would say it is a decent silver cable.

i personally would not want to own it or recommend it to anyone else.
Hi Mrt.

Your listening preferences stated HERE.

I would say the "P"!!! I/Cs are a great I/C that didn't meet your listening biases. Assuming you have listened to the "P"!!! I/Cs I would say this: Had you contacted us for your purchase instead of buying on the used market, I probably could have saved you some time and expense. Seeing what you prefer with your music playback, I would have been very hesitant to recommend our products to you. I've told people time and again that have contacted us that if they need cabling to sound a certain way, then by and large our offerings are going to be a crap shoot as to whether they'll work for a given set of ears. If one is looking for cabling that offers a least amount of editorial, then what we offer is going to be the ticket...says I anyway.

I point this out because too many times when a enthusiast doesn't like what a particular component brings to a music system, cables or otherwise, they tend to make comments like yours that insinuate the component isn't very good. Many times that's not the case at simply didn't meet your biases.

Kind Regards,
I can see where Mrtennis is coming from in this particular case. Robert's statement:
Almost all aftermarket cords suffer from power deliver characteristics that are not optimized and as such, most cords act as euphoric coloring devices.
would be reasonable if it came from an unbiased reviewer.

For a manufacturer of aftermarket cords to claim this in a public forum, with the implication that those cords that do not fall into this class include the ones that RSAD makes, is unreasonable.

If Robert is willing to provide more information to support his claim, I'd be delighted to consider his proposition.

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my response to robert has nothing to with line cords.

however, robert has made an assumption which is incorrect.

i did not buy his interconnect cable and his persistence at defending his product oin a forum which is clearly not commercial is inappropriate.

he should not be discussing his products in this forum.

if robert had not involved himself in a commercial discussion which belongs in another milieu, i would not have staryed from the topic.

i apologize for changing the subject, but i think it is important for manufacturers to avoid making statements about their wares in a forum such as this.
robert raises an interesting point. perhaps i will start a thread on the subject of good versus bad components.

i din't say that an interconnect is a bad component. i said i would not own it and would not recommend it.

one cannot logically infer a statement of quality from a statement about ownership.

robert, you assume to me much and you have mis interpreted what i said.

its too bad we can't have a debate about this.

back to the main point . what is a good component ?

is it what i like and a bad component is what i don't like, or is there something more ?

if disliking a component is not the basis for evaluation of a component what is ?

is there a standard ?

let's relate this to a line cord.

if i place a line cord into my stereo system interfacing an amplifier and after break-in i don't like what is coming out of my speakers., at the least it is a bad line cord for my stereo system. it may have expensive parts, be constructed according to certain criteria, but it does not further my sonic preferences.

such a line cord would be producing negative sonic results.

i would consider it inferior for my purposes.
I hope our friendly audio manufacturers DON'T follow that advice.

Currently we have Bob Graham, Steve McCormack, Mike Elliott, Ralph Karsten and many other respected inventors, creators and manufacturers occasionally entering the Audiogon forums to answer our questions.

Who better knows these products than the people directly involved? I will grant you that Bob Graham probably favors his tonearm over others, same comment for amps regarding Ralph at Atma-Sphere. I would hope so, is all I can say.

Anyway, I have spoken to Robert at Ridge Street on several occasions and love his humor. I really know nothing about his cables but I am certainly not offended that he loves them, in fact I would expect nothing less unless he secretly believed he made a design error.

Most at Audiogon have their favorite brands, surely we can decide for ourselves what is valid data, especially when the writer comes forth and identifies himself as all those I mentioned have done.

I do not have any say about forum rules (fortunately), but if I did I would be encouraging more manufacturers to join in our discussions.

Just one mans opinion.
Post removed 
back to your original question, I have a hypothesis(not a theory) on why a power cord would affect frequency response.
1)Almost all well known audio component manufacturers pay special attention to their power supply with their flagship products. The topline normally differing only in the power supply and delivery to their second in line.
2)Almost everyone also recognises that transformers and filter caps play an important role in the final sound and these falls within the power supply section as well.
3)I believe that human hearing is more sensitive to phase differences than tonal differences.
4)Given that any conductor carrying a current is going to generate a lateral motion in a magnetic field, capactance and inductance is inevitable.
5)In any pc, it is relative straight and would vibrate, the vibrational and dampening aspects plays a huge part in its sound, the same with tranny or caps. Not to say that the type of the conductors or the shielding does not matter, but I believe that vibration tuning plays a significant part.
6)the same pc's sound different in different setups because they are placed differently(coiled, draped on lifts, on the carpet etc) and hence their vibrational aspects are affected.
7) I divide pc's into 2 main categories, modifying and neutral. eg, elrod vs cardas. modifying cords affect the sound whether they are at the breaker or just before the component. I use both types, which you prefer depends on your biases and your overall system sound.
8) Other aspects such as geometry, guage, shielding, material, dielectrics, conductor cross sectional shape, length, connector types, termination, treatment, conductor state(liquid vs solidvs amorphous), length etc is left out for another day in this post as they do matter as well.

Yes! - to manufacturers continuing to have a say in this forum. They are also audiophiles with highly refined points of view. That knowledge is very useful.
i think it's ok for audio professionals to have their say as long as they do not attempt to sell on a discussion forum .

does anyone think its ok for a manufacturer to market his/her products on a discussion forum of this type ?
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i agree in principle, but if it quacks like a duck, looks like a duck.... it's a duck.

if someoneone wants to spin what is obviously selling into some other activity, we'll have to agree to disagree. like everything else in life, perceptions differ. you may see day when i see night.
Post removed 

You don't have to buy. It's all just other members opinions.

I would not concern myself too much about it. If you were subject to being unduly influenced and swindled out of your cash, that would be completely different. You're obviously evolved far beyond that point, so now we're really concerning ourselves with the appearance of a sales pitch disguised as comments in a forum.

Truth is, we all have our favorites including yourself.

As long as were pointing fingers, I’m guilty too.

I frequently post favorably about Dali speakers, VTL amps, Purist cables and other gear that's worked for me, so in a sense I'm "selling" that gear to others regardless if I have any to offer or not.

Most of these designers, creators, manufacturers and retailers really believe in their stuff. Many have it in their own systems and think it's wonderful. So how different is that from the rest of us?
i agree in principle, but if it quacks like a duck, looks like a duck.... it's a duck.
You mean power cords are pure quackery? Or your circuitous threads smell of troll quack? I'm so confused!!!!!!!

Howard, the petulant duck
i think you misuderstood what i said.

if a manufacturer is obviously trying to sell something and some one treis to spin the sale into something other than a sale, you be the judge.

are line cords quackery ? if you hear a difference its not quckery. if you don't, you be the judge.

by the way boa2, what is a troll, do you mean churl ?
hi albertporter:
the difference is obvious. if a mnufacturer sells he gains monetarily, if you attempt to persuade, or sell, as you say, what do you gain ? certainly, there is no monetary advantage to you if someone buys a product you recommend.
Mrt, I didn't know ducks could quake. That must be one feakin' duck! Look out energizer bunny...

Free quaking duck with the purchase of any of our power cords till December or till all ducks have gone South.

Saw a couple posts about correctly designed power supplies. Certainly correctly designed PSUs are important and contribute significantly to good sound but unless I'm mistaken, most PSUs have nothing except maybe a snubber before the primary. This does nothing for the poor quality AC that comes out of the wall and it's relationship to the primary.

There are a myriad of line conditioners that effectively address some of the issues of poor AC quality and improve sound to one degree or another. But, as I see, there are other issues left un-attended.

I prefer AC product designs that address what I see as un-attended issues and, a specifically designed power cord can do that. In my experience, when these other issues are addressed, other AC gremlins become significantly less relevant and line conditioners become more of a preference than a necessity. We use no line conditioners here and I'll assert that our system here is probably on of the most musical and life like presentations you'll experience. It has it's limitations like any other system but.... And yes, we use all our AC, cabling and loudspeaker products to help accomplish what our system does. This all goes to the original topic and question of this thread. Forgive me if you don't like how I'm willing to answer.

To appease Mrt, other AC cords I have respect for come from Prana, PAD, VD, and Micro-Omega. Though there are some commonalities (as well as vast differences) between these products and what we're doing, I suspect the materials and applications are for different reasons and so the design goals are optimized differently.

So Mrt, are you ready to buy?

Quack, Quack!
if i place a line cord into my stereo system interfacing an amplifier and after break-in i don't like what is coming out of my speakers., at the least it is a bad line cord for my stereo system. it may have expensive parts, be constructed according to certain criteria, but it does not further my sonic preferences.

While I agree with this statement, the key words are 'for my stereo system'.
In my experiences cables and cords are extremely system dependent. Though my musical tastes do not change drastically, I have found that changing gear/speakers can drastically change my opinion of a cable/cord. The change could be for the better or the worse. I'm almost at the point, after 28 years in this hobby, that I believe there is no bad product, it's all synergestically related.

I've heard components/speakers/cables that I enjoy sound terrible in certain systems, and I've heard components/speakers/cables that I had written off as 'bad', sound good in some systems. This is not an absolute, there is some gear that I've never heard sound bad and some that I've never heard sound good. The point is that I've learned not to discriminate against a certain product just by the sound of a system. Synergy is the most important aspect, IMHO.

For example, I've tried silver cables from several different manufacturers over the last 15 years, and never cared for the sonic signature of silver cables in general. However, after a speaker change last year, my current reference copper cables suddenly sounded lifeless and slow. I tried silver cables again, from some of the same manufacturers that I tried from before, all of a sudden, their cables clicked and sounded fabulous in my system. The first speakers that I've ever heard that sound best with silver cables. My opinion on silver cables changed dramatically. It's all about system matching, IMHO.

FWIW, I also agree that manufacturers should be encouraged to join in the forums, as their knowledge can be a valuable contribution. I also agree that shilling in the forums is in poor tastes. Here is where the gray area enters in, what is considered shilling by one may not be considered shilling by another. I, for one, didn't particularly feel that Robert was pushing his product.

Mrtennis (if that is indeed your real name :-)), if you take offense to what Robert has posted here so vigorously, I wished you had been here a year or so ago for the D&K thread parties. Talk about blatant shilling........


Hi John.

Robert, how can one lay his/her hands on one of these Vol II discs?

It's in there. ;) Or do you mean how can anyone get Vol.I or II?

I'm almost at the point, after 28 years in this hobby, that I believe there is no bad product, it's all synergestically related.
Thank you for your post. I agree completely, John. Your comments are thoughtful, and they remind us of how often in these discussions the focus is on winning rather than enjoyment.
Very well written post by Jmcgrogan2.

As for Albert influencing the rest of us to buy his gear, of yes, every time he upgrades, a number of us tail waggers sit there drooling and waiting for the hand-me-down table scraps. 8-) And Albert, did you notice the Wotans for sale? Or are you holding out on a pair of JL-2s or quad of JL-3's?
Boa2, my PCs quack real loud all the time. Especially when I take a wild gander, and goose 'em real big 20 amp IEC male connector down those ornithologically inappropriate tini 15 Amp female receptacles. Perhaps Robert should offer a new line of PCs insulated with authentic Canadian Artic Goose Down. . . or should we leave it to Virtual Dynamics?
And Albert, did you notice the Wotans for sale? Or are you holding out on a pair of JL-2s or quad of JL-3's?

Please don't get me started on more amps, I just got mine tubed up right and sounding good.
The power cord doesn't affect frequency response, however it can affect dynamics and in some cases become an antenna for RF. When RF gets into your amplifier, then it can affect the sound in many ways:bright, lean, hard, glassy, etc. Normally, the power supply should eliminate these effects, but in some cases, it doesn't.

It never ceases to amaze me just how cheap some expensive amplifiers can be. Some factory power cords are really inexpensive. When you replace them with better quality ones, there can be a small difference in DC levels in the power supply, which you will hear. However, none of this will affect frequency response.

Whether or not you will get the same effect(s) with a Belden 14 gauge shielded power cord for 10 or 12 bucks is a whole different matter.
I have followed this thread closely and until now have not felt like saying anything. But the last post by Sp has sparked me to reply.

Over the past ten years or so I have listened to atleast 100 or more power cords in my system. Never satisfied with the results, I started building my own. At last count, probably 30 samples. Every type of wire, geometry , shielding method and terminations imagineable.

None of my final designs, with the execption of (1) are shielded. Shielding, IMO adds an audible coloration that I find quite annoying.

The question, "how can a line cord affect frequency response?"

Based on my experience, the #1 factor by far is the type of conductor material the cord is built of. Everything else is secondary. How?, the same way an interconnect does. Use conductors that restrict bandwidth and the frequency response will be adversely affected.
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what about resistance ? suppose you design a poer cord with very high levels of resistance. will that affect treble reponse ?

or, suppose you design a power cord with a very high level of inductance, what then ?

Not sure if I completely agree with the power cord acting as an RF antenna. Once energized, it has more rejection qualities, and is more susceptible to large electro-magnetic field influences. Even placing two energized cords along side each other, will have little or no effect on the other's audio component. The newer switching class-D amps can inject adequate hi-freq noise into close-proximity sensitive interconnect cabling and component gain stages (even through some cable shielding and metal chassis), but would be hard pressed to have an audible affect when placed several yards up stream, along side another amp's un-shielded PC (via an extention cord for testing purposes). Oh, and can't forget about all the non-shielded Romex behind the sheetrock walls. Mainly what people hear from two-way radio communication, is affecting radio/television receivers or inadequately shielded sensitive components and IC cabling. That's the only time I've ever heard anything during audio playback, and I live next to a private air park where communication takes place throughout the day. I'm open to explanation, though.


Regarding conductor materials... copper, silver, or gold are capable of frequencies into the extreme RF bandwidth. The audio bandwidth is child's-play in comparison. Copper is utilized everywhere in these applications. Capacitance, impedance, and shielding are the main issues affecting an interconnect's frequency/performance, as they do with RF cabling or wave-guides.

Not real sure how or why you're having issues with shielded cords creating coloration. Any further explanation to help us understand what might be contributing to your findings?

For RF to propogate it not only requires some type of conducting surface, but the physics of the medium (IE the physical environment that contains the RF) play an important role. Effective transmission lines do not power cords make. True certain frequencies of RF energy may attach to the surface of things other than metal, but in our case, audio amplifiers in metal cases, with power cords going in and cables I/O etc...which under normal conditions are shielded enough. I believe that very few home audio amplifers have ever fallen victim to any incident RF of enough energy as to be noticable.

This report of hard or glassy audible results from "RF" ...where does this come from? Have these types of claims been investigated? Have tests been run where an audio amp and cable have been exposed to swept RF sources while listening tests and/or controlled measurements of the device under test are performed? I highly doubt it.

Like the study of speaker cables, etc... it is a hard test to do and there is no shortage of opinions on the subject.

Remember, we are talking about engineered products. Yes we derive pleasure out of them but, there are cold hard facts based on decades of knowledge and years of experience put into the designs we love...
We need to stay true to the basic facts of engineering and device physics to truly have meaningful conversations about it.

Back to the question: How can a line cord affect frequency response?
In a typical audio amplifier power supply, on one side (we will call it the ac-line side) the transformer sees some resistance (from the dozens of feet of ac line going all the way back to the transformer on the pole), some inductance, and some capacitance.
-Aside: homes typically have 12/14 gauge un shielded solid copper wire that is the standard. Increasing the diameter of the power cord to say 10 or even 6 gauge does nothing to the instantaneous current available "out of the wall". SUre current densities may be different on fat and skinny conductors, but the end result will be the same. These lines are in series.

So the transformer, itself made of two massive inductors wound around some magnetic core decouples the amp-side windings from the line-side windings. This is good news. ANy dc offset on the line side, besides having ZERO effect from the power cord, can now NOT "get across" to the amp-side winding.

SO, on the the next stage: the recitifers. So now we have a sinusoidal 50/60 hz signal driving a bridge rectifer of some sort. You have AC going in and rectified AC going out of the rectifer. THis means that, if you looked at the signal out of the rectifer's positive terminal you would see the negative going waves are now inverted and you only have positive ac-bumps, spaced either 50/60 hz apart or 100/120 hz apart, depending on the overall design of the rectifier stage.
To "make" DC the rectifed pulses charge capacitors. With ZERO loading on the caps,(ie output transistors completely off) the charging currents from the rectifer gradually reduce as the caps reach full charge. The caps can only be charged at a rate directly related to the ac-line frequency.
In the typical class A or A/B output stage of the three pins of the output transistors (either FET or BIPOLAR) are connected to this supply "rail" thus allowing useful operation of the device (I left out the other pins to simplify the discussion).

So now, imagine that the output transistors have a job to do and are now driving a speaker load. The current source for the output transistors comes from:
1) The resevoir caps directly -- during moments the recharging pulses from the rectifier are absent
2) The rectifer/power transformer directly -- During moments that the signal to be amplified places its demands on the output device during charging times. Under this condition the power supply current is not evenly split among recharging the cap and output device. Here is where a good stiff power supply carries the day for audio amps.

In the context of number 2-- consider higher frequencies that require amplification... it is very possible that higher frequencies cause related current spikes through the rectifer stages and back to the transformer/power cord/wall etc...
...also consider 'dynamic' signals such as drums requiring current during this window...

If you have a power cord with extensive ferrite beads or other ferrous material, it is possible that under these conditions, the higher frequencies may be diminished, due to increased resistance to the current at these frequencies b/c of the inductive response from the ferrite. This is why, I think, that ferrites in power cables may diminish dynamics or dull the high end.

It is more from a reducing-the-available-current-under certain-conditions effect than an actual designed filter result, though one can mimic the other.

Of course, the transformer itself has a frequency response and this may over-ride anything else by orders of magnitude under the high frequency analysis.

I hope this helps.

Regarding RF: I didn't mean to imply the line cord acted like an RF antenna when it was powered. What I was trying to say, however vague, is that it can act like an antenna and pick up RF energy. Although this energy should be eliminated in the transformer or perhaps some RF network in the PS input, there are cases where it can actually get into the amplifier itself and cause sonic problems. In this case, switching line cords may or may not make a difference. However, that being said, you still have lots of ROMAX in the walls which can pick up RF, too.

Dpac996: I believe you have bandwidth of the amplifier and bandwidth of the transformer, line cord, diodes, surge capacities, line droop, line drop, and dynamic compression all mixed up. Amplifiers simply don't work the way you describe. The power bandwidth of the transformer is typically no where near the amplifier bandwidth and sometimes it is not more than 47 toi 63 Hz. The line cord has wider BW to be sure, but keep in mind the only frequency on the line cord is 60 Hz, at least in the US.

Metro04: I do agree that materials do affect performance, but not like interconnects. Line cords only carry one frequency, 60 Hz here in the US. Interconnects can carry bandwidths from DC to 100 MHz with ease, if you use the right one.

Reb1208: Actually, if a line cord were to really seriously limit the power amp enough that it began to get warm and soft, it is more likely that dynamics will be compressed, rather than bandwidth. You might find that the low frequency peaks, not the high frequency peaks, is what got clipped. However, bandwidth below clipping, will be unaffected.
After writing that last night, it occured to me I should also elaborate a bit. When I said bandwidth, I was speaking in terms of the amplifier bandwidth, and I still state that line cords do not affect it. But since we are discussing line cords, let me relate the term "bandwidth" to line cords.

First of all, there is a voltage bandwidth and a current bandwidth but they are not the same. With respect to a line cord, the voltage bandwidth needs to be only a few Hertz wide, say 58 to 62 Hertz or so. Although the voltage bandwidth is much more than this, it doesn't have to be as long as the line cord can pass 60 Hz without loss.

The current bandwidth of the line cord, however, has to be much wider. In this case, a bandwidth from DC or a just a bit higher than DC to at least 600 Hz or so will do the job. The current BW can be higher than this without any problems.

I think I will start a new thread regarding line cord bandwidth as there is much to explain and it is really off topic from this one; probably next week sometime.