It seems these AC cables are being praised in just about every HI-Fi magazine I pick up. Aparently they provide better timing (no, I don't know what that meant either), better dynamics and deeper bass. At $2500 a piece they better had.

I'll get to the point now. I don't understand why the cable to the power supply in the component (amp, CD player etc) would have any effect on the sound. The electricity runs though all different kinds of crap cables to get to your house and somehow placing 2 meters of very expensive cable at the end of that chain make a different? I don't think so. Sure, good quality cable to hook everything up is vital - after all it's your actual audio that's runiing though them. But an audiophile mains lead?

Can some one please tell me a logical/scientific explanation of how this works? Is there one? Anyone actually heard the difference a good power cord caqn make to their system? It seems like a load of shit to me but there is just too many reviews and publicity for it to be completely false.

Tony

Can you spell B-U-L-L-S-H-I-T? FWIW, many amps have bell wire inside for power and audio. So who cares what is outside??

What difference would 'hearing' the power wire make unless it was done under strict controlled circumstances(DBT or ABX) and the test results scrutinized for errors? Psychological ias will effect perception.

As far as 'just too many reviews and publicity for it to be completely false'.

Uhm, popularity and mass propogation of bullsh_i_t just equals very popular and propogated bullsh_i_t. :-)

John Edwards or Sylvia Browne anyone? :-)

-Chris

I think it's impossible to answer part of your question without violating TOS #8. But I'll try to answer the part I can answer by quoting the available reasonable arguments, none of which I have verified. IMO, in audio there's very little you can rule out on the basis of simplistic technical arguments. A/C power cords are a case in point. Still, $2500 power cords are absurd and completely unjustifiable.

Do they make a difference in the sound? Sorry, can't anwer that (TOS#8). Is it possible that they do? Absolutely. Expensive power cords can, in principle, act as filters for high frequency nasties on the power lines. These nasties are often generated by digital equipment, sometimes in your stereo system. CRT computer monitors are also very bad. The worst source in my house is a cheap range with a digital control panel. A cord with a ferrite-impregnated jacket can act as a filter for high frequencies. I'm not claiming that the cord you mentioned actually does this, but it's possible. Also, heavy shielding can reduce the nasties that could get into the supply via radiation, via the cord acting as an antenna. It's well documented (see, for example, the classic book by H. Ott) that such nasties can adversely affect the operation of various types of electronic equipment.

Another factor is that by modeling an typical amplifier circuit you can see that the peak current in the power cord far exceeds the RMS value. That's because the power supply only "recharges" at the top of the A/C cycle. You can get some rather intense current peaks, exceeding the RMS value by a factor of 10 or 15. The result can be a very significant reduction in voltage as a result of resistive losses in a typical 18 gauge power cord and its associated imperfections (poor crimps, etc.). These very fast current pulses can also create high-frequency nasties, which can feed back into the A/C in the absence of shielding and filtering.

Those are (some of) the arguments, and I find them reasonable, though they certainly don't justify paying $2500 for a power cord. I don't know electronics that well, but I have a physics Ph.D.

Jim Austin

This all comes down to basic electrical/rf laws, though. The hi-end proponents specifically make their claims on supposodely 'mysterious' or 'unknown' variables. But any properly designed audio applanec should have an effective filter in the power supply. Personally I would question the value and engineering of audio equipment that required a special pwer cord that had special filtering properties in order to function properly.

-Chris

True, it all comes down to electrical/rf laws, but I don't know about "basic". Finding the answers to some of these questions would require careful experimentation and possibly modeling. As for questioning the value and engineering of audio equipment that requires a special power cord to function properly, I agree with you up to a point. There's some very expensive, very poorly engineered equipment out there. But I'm less inclined towards the polarized view this implies: good engineering wouldn't benefit at all, lousy engineering might. There's a lot of middle ground here between great and lousy, and many widely available products may fall in the middle...and consequently may benefit the extra filtration/reduced losses an aftermarket power cord might provide. There are some easy tests you can do, though visual ones are often easier than audible ones. Try using a good A/C filter on your television while watching a DVD. If your power is clean you may not notice a difference. But if the power isn't clean ... If A/C nasties can interfere with a DVD player's electronics, why not with a CD player or an amplifer?

Jim

WIth issues such as this, I tend to follow a logical methodology for consideration: IN this case, like many others: a claim is made, no substantiation is has been produced to confirm the claim/suspicion. I just can't take it seriously, especially with claims that have been around a while with no substantiation. If tht substatiation appears; I'll glady review it and accept if valid. I can not possibly assume or test/analyse for every possibility, since this would open up one huge can of worms you can't possibly count.



1st, I'm not comfortable discussing video implications. I have not researched, nor am I interested in video. However, since video and digital video devices operate at much higher frequencies then most audio equipment(SACD obviously being an exception), then it would seem to be rational that they would be more sensitive to high frequency interference from RF, etc as opposed to audio equipment that usually operates a much lower frequencies. Again, I have no knowledge of specific implicatinos on video.

-Chris

Every circuit inside an amp runs on DC. If the power supply is doing it's job (producing pure DC) and the amp layout is good (that is...PS is as far way as possible from the circuitry...to eliminate any 50/60 Hz hum). It's what inside the amp that counts.

xen-uno

I recall that this is not only WmAx' point of view. This is the very foundation of this discussion board. Claims about sound quality are not taken into account unless proven (see the Terms of Service, article 8, for explanations).

Not sure if this is directed at me, but for the record, I've made no such claims.

Jim

Once again, here's this polarized viewpoint. Perhaps this is a hazard of the (otherwise very sound) ABX mindset. Something is either one way, or the other. I think it's safe to say (and I'm making no claims here that violate TOS8) that the perfect circuit hasn't been designed yet. Why the assumption that something is either okay or not okay? What about the middle ground.

Hey, I know what it is. It's digital! All those ones and zeros! You know, in real life (not counting quantum mechanics) there's no such thing as digital! Every signal has a rise time, and usually an overshoot! I'm being metaphorical here, not literal...there's always a middle ground, and I believe that's where most available consumer electronics lie--in the middle, with adequate but imperfect power supplies, and adequate but not impervious circuit layout. Why should we assume that they're either perfect or defective? Where's your evidence?

Cheers,
Jim

Well...either you'll get an audible 50-60 Hz humm...or you won't. Pretty much black & white...no middle ground. If someone routinely runs power cords directly underneath, close to the sides, or on top of equipment, then these $$$ cords are for them (by virtue of the shielding...if present). The standard rule as we all know, is to separate power cords from signal carriers, and to keep those power cords away from the equipment as much as possible. Power supplies don't have to be perfect (as as you pointed out, seldom are)...just good enough to produce reasonably flat DC. A minor AC component (of the DC) probably does exist in consumer grade PS's, but is inaudible (if not, then it's a bad PS).

xen-uno

If it is defective, it must be proven. If it is perfect, it can't be proven. That's why we look for proofs of defective devices.
So far we don't have any proof, with listening tests, nor distortion measurments, that power cables can change the sound of a device. And, following the theory, it is unlikely that they can. We have such proof for speaker cables under special conditions, but nothing yet for modulation cables, power supply orientation, digital cables and a lot of other doubtful audiophile tricks.
That's why we apply the skeptical approach : first find a fact, then explain it. Trying to explain a fact before proving its existence is, in average, a loss of time, because sometimes the fact is true, and sometimes it is false.



No, I just found that WmAx could have formulated it in a more definitive way, instead of presenting it just like his own casual point of view.

My frustration with audio cables is that we rarely have the LRC data to talk about technical performance (L = inductance, R = resistance and C = capacitance). LRC data is provided in many other cable applications (cable TV, RF/antenna cables, data cable specifications, etc.)

The cable can be modeled quite nicely using an equivalent circuit to understand the first order performance effects. I might be able to justify some additional $$ for styling or some placebo-BS if I at least understood what the cable was doing at the LRC level. Heck, given that there are not any specifications for RCA jacks, there is some value just in good connectors that don't fall off.

To me, any discussion of audio cable should begin with the LRC data and the input / output impedance of the source and destination audio components. Then we can model the first order effects and get on with the rest. For example, an audiophile cable could make bold sonic claims and actually have a high capacitance which when used with certian audio components may roll off the high frequency response. This could explain it sounding different ("better" or "worse") than another cable in that circuit.

Is it too much to ask audio/video companies to publish these basic specifications? Do they not do it because it will expose the "BS" (cynical reason), because they don't know the specifications (more cynical?), because they don't think it matters (probably true for gullible customers), because nobody requires them to...? Would you spend $2,500 on any other audio component without ANY technical specifications other than length and connector type?

Until the industry begins including basic LRC data they will have a credibility problem to me - but maybe they like it that way.

I disagree. I would argue that, following theory, properly applied, it's likely that they can. Not certain, but likely.

Jim

With respect--and I mean that--both for you and for the rigorous standards applied on this board, I'm really not sure this makes sense. "Defective" is an intellectual construction. By extension, so is "perfection." If it is the absence of perfection, then (not meaning to get religious here) everything is defective, by definition. No proof is necessary: Everything is defective, to a greater or lesser extent. The key question is, can you reliably distinguish a difference, whether of character or of absolute quality? But I digress. Your definition of "defective" is inherently subjective: it depends on your hearing and jugement. Doesn't it make more sense, then, merely to speak of differences in quality, or even in character, rather than to embrace this perfect/defective binary?

A second question, of great significance to this board, but of far less fundamental significance, is: can you prove that you can hear it? Because to know something, and to be able to prove it, are quite different, as I think we all know from our everyday, nonscientific, nonaudio existence. Perhaps we COULD prove them, but we know them no less well in the abence of proof.

Jim

Do you have evidence to support this assertion? Do you have data that demonstrates that there couldn't possibly be any other audible effects besides 60 Hz hum?

I'm not asserting that there ARE other effects; I'm merely suggesting that there is a wide range of so far untested possibilities.

Jim

Yes. For some people, Musepack -q5 is transparent. For other people (well, to make it short, for Guruboolez and Xerophase), it is not.




This is the next step. For example, discussing a problem sample with MP3, first, the ABX test is run. If it is successful, it shows that the difference is audible. Then, we can discuss what difference : noise, drop out, ringing, annoying or not, where in the file...




We try to help people to prove it. It is sometimes difficult, but it is very interesting.




I disagree. Many things that I knew without proof turned out to be false. Just a product of my imagination. I thought that I knew them, but I was wrong. Some other things that I knew were true.
It is always possible to prove something that we know and that is true, if we spend enough time and effort in the process. Sometimes the proof is not worth the effort. I think that it is what you call "something we know but can't prove".

I think we're getting down to some fairly subtle--yet very meaningful--philosophical questions here. I can't disagree with anything you've written; absolutely there are deeply held commitments--held without proof--that change profoundly over time. Yet I can't help thinking we cripple ourselves by disbelieving things we KNOW are true, just because we haven't done a statistically significant ABX test and because we know some portion (minority?) of them will later turn out to be false. Yet as a scientist, in my (former) professional life (I no longer earn my living by doing scientific research) it's necessary to require proof. I wonder if that's not the crux of the issue here: this is largely a board for professionals, which do, and ought to, require proof. The audio mags that promote (eg) $2500 cables are for hobbyists, people for whom audio is not a part of their professional lives. It's natural for professionals to embrace a higher standard of proof. Of course the people who do reviews are also professionals, so it's reasonable to ask whether they should embrace a more rigorous standard. The answer, I think (as I've partly indicated in a different thread) is that 1. rigor is prohibitively difficult, and 2. that sort of rigorous approach may not be consistent with a magazine's editorial goals, even if (even though) there may be NO corruption and only the best intentions.

I think we are very close to agreement here. In the audio realm, things are indeed very tricky, and people--even widely published audio reviewers--probably are not as cautious as they should be. (Though everyone should carefully consider Stereophile's measurements, which often contradict dramatically, and are always run alongside, their subjective reviews, before reaching final conclusions about THAT magazine).

But by the same standard, or a similar one--we ought not to let a healthy skepticism and a scientific approach calcify into a closed mind and narrow expectations. The idea that a power cord could improve the sound of a DC device is counterintuitive. It's natural to be skeptical. But it's also appropriate to be skeptical, not of theory, but of our ability to apply it directly and carefully in drawing such conclusions. I will never pay $2500 for a power cord, but I don't believe there's anyone on this board who knows enough to rule out the possibility that it might make a positive difference. (Speaking here to the board in general, or at least to those who are following this thread:) Remain skeptical, apply your rigorous testing wherever possible, but don't let a superficial knowledge of science--and despite way too many years spent in graduate school, my knowledge, too, of these issues is superficial--get in the way of an open mind.

Best,
Jim

Rubbish!

When it comes to audio equipment, there will be imperfections.

Does the sum of these imperfections allow you to detect the presence or absence of one single imperfection? Do the other imperfections make it easier or harder to detect the single imperfection under scrutiny?

At best, you can say that the hum may be inaudible a your preferred listening volume through your speakers in your room to your ears when listening to your music. How do you know it will be inaudible at my preferred listening volume through my speakers in my room to my ears when listening to my music?

You can say when it probably will be audible, and you can say when it probably will not be audible. However, in between there is a great wide world of possibilities! Much equipment will be in that range; probably not for hum, but for less easy to control issues e.g. interference.


You do have to be careful of bullshit, but you also have to be careful of adopting this simplistic "back and white" mindset, which just isn't how the real world works!

Other wise you become like the man who asks "Is it raining?" and will only accept a "yes" or "no" answer: Allowing "not much", "it's just stopping" and "it's about to chuck it down" would have been much better!

Cheers,
David.

Yeah...whatever. You'll either hear it...or you won't. I don't care what you turn yours up to...or what anyone else turns theirs up to...they'll either hear it...or they won't. Read the thread title again so that we're on the same page, because in my previous post I state the conditions where these cables may be useful. It would be highly unlikely that the dimunitive effect of a properly run standard power cord would push humm (and other forms of interference) into the audible range (even when compounded by xxx number of cords). Theoretical?..forget about it...I speak from practical real world experience.

xen-uno

Yes, on the discussion board itself. The board doesn't assert that these claims shouldn't be taken into account, only that such claims can't be made on the board itself. And unproven claims about technical things can be made; it's only unproven claims about sound quality that can't be made. So Mr. Austin is staying within the rules, very nicely if I may say so.

Well...if you do get hum, buy a $4 length of steel conduit and run the power or signal wires through it. Shielding problem solved and you save $2496. If you still get hum, get some cheap 16 gauge and run a ground to each of your audio components. There are easier ways to deal with these types of problems than Nordost would have you believe.

And yes, the effect of a 2m power cable is insignificant compared to the noise picked up in the 200km of cables between you and the power station, or noise added from every transformer between here and there. Scientific proof? The length of that cord in the above example represents .0005% of the total length of the circuit, which rounds neatly down to 0. No need to get any more technical than that.

Anyone who still wonders why people buy these things? It's easier to understand when you consider that it's the same reason you buy diamonds, good luck charms, ionic bracelets, magnetic bracelets, lawn gnomes...and a host of other junk. People can be easily fooled when it comes to the relative value of consumer goods if manipulated correctly.

The best part about luxury audio cables is where they come from...they would have you believe that unprecidented research and development led to the design of these cables, and they were built with the finest materials and processes that noone else has...but the reality of the matter is that they _all_ buy their cables pre-made from a number of asian manufacturing conglomerates from basically a catalog. They occassionally order a few custom cosmetic changes, the finished cables are then manufactured, shipped to the 'Nordost' office and then the brand name is silkscreened on. How much would a $2500 cable like these cost directly from the manufacturer? If I had the catalog and inquired about the price I could probally find the cost of this specific cable, but from experience I'd say you'd be looking at well under $1 per cable, more like $0.10/foot + $0.04 per end in quantity. I'm not exagerating either.

Some examples?
http://www.asia.globalsources.com/gsol/Gen...d=6008808468477
http://www.asia.globalsources.com/gsol/Gen...d=6008808468477

My friend is actually a registered distributer for asian sources and managed to get a quote for a specific nordost brand square cable for the sake of disproving a group of audio zealots...unfortunately the post has long since expired. You need the manufacturer catalogs to find a specific brand and model of remarked cable, but I assure you, they exist.

Anyway, the point was to show how impressive the profit margins are on these cables. This goes a long way to demonstrate how a company can make money by selling only a few products to a very small handfull of gullible people.

Nope. It varies from model to model, but transformers generally have a fairly narrow bandwidth. They filter out most radio frequency (and above) noise. Lucky for us. So the step-down transformer at your house is likely to filter much, but not all, noise from the outside world. Furthermore, if the cord filters noise... (of course there are other ways of doing that...and as I've said, I'd never recommend a $2500 power cord to anyone).


Power delivery systems (in the U.S.) are designed to deliver 120 V A/C TO THE RECEPTACLE at the full rated power. Typical house wiring is 12 or 14 gauge. The typical power cord is 18 gauge. Currents drawn by an amplifier during the re-charging of the power supply can reach values that are 10-15 times larger than the RMS value. That can mean significant voltage drops in those 18 gauge power cords, perhaps 5 Volts, OVER THE LENGTH OF THE POWER CORD. Yes, there will be voltage drops in the household wiring, too. But they will be smaller if the wiring is up to code.

And yes, you can solve this problem (or greatly mitigate it) by buying a shielded 14 guage power cord from Belden, that will cost somehwere around ten bucks. Like I said, I'm not advocating $2500 power cords. What I'm trying to do is to convince folks not to rely on old saws based on the clumsy application of science insufficiently understood. I'm all for testing, but keep an open mind. There's plenty of snake oil in hi-end audio, but it's a lot harder than you seem to think to tell the good guys from the bad guys.

I'll close by not making any claims about the positive effects I might (or might not) have heard when I switched out my Belden 14 gauge shielded for a budget hi-end power cord (which cost about 5% what the cord being discussed here costs). I won't make any claims because to do so would violate TOS8.

Cheers,
Jim

Most. Not all.

Jim

I agree...but I wasn't really referring to the voltage drop across the cord (or the household wiring, or the transmission line wiring), but interference inducted into the cord, which is the main advertising feature of these cables. Even whether they are even recieving the full rated 120V usually is not a consideration to those buying these cables...it's whether they are getting a perfect 60Hz signal that interests them (which as stated above is rather irrelevant once the power supply converts it to DC). Basically, more noise is going to be inducted into the unshielded household wiring on the way to the local transformer than there ever will be from the socket to the component was my point. A thicker gauge power cord is definetly warranted if you believe an amplifer comes with an insufficient gauge... but someone who buys a $2500 power cable I assume is probally running a $10,000+ amp which I sure hope would come with a measily power cord whose internal resistance is within design spec.



Yes, I was generalising a bit. But even then, wires which aren't made overseas are still made from the same extrusion processes, the materials are obtained from the same suppliers and the cost is comparable, usually a bit higher.

Now THAT'S asking a lot of a measly power cord. You can filter out all the RF muck you want to, but you aren't going to be able to restore the shape of a typical distorted, flat-topped 60 Hz signal. For about the same as that $2500, however, you can buy an A/C power regenerator--basically an amplifier optimized to produce a single frequency--that'll give you a more or less perfect signal. Then again, most of the folks who buy the $2500 power cords already have those.



That's what filtration is for (or regeneration). I think the combination of filtration and shielding makes for a sensible conservative design: filter out the noise that gets in in the wall, sheild it once it's passed the wall. Also: One thing that's been mostly left out of this discussion so far is the noise generated by the components themselves. Digital components can generate all sorts of nasties that, if unfiltered, can get back into the household wiring. Filtered A/C cords work both ways. I can't verify it (or prove it) but I wonder if a ferrite-impregnated power cord couldn't even, perhaps, reduce high-frequency radiation by slowing down high-frequency transients. Pure speculation (I can do that as long as it's not about what I hear, right?).

Cheers,
Jim

Incredible but true, the French company Hi-Fi câbles advertises the superiority of their Made In France Câbles shamelessly relying on obscure and pseudo-scientific theories claiming the racial superiority of french people hearing over asian people hearing !
The text is available in French only : http://www.hifi-cables.com/04_03.html



Well, since you tell that it would violate TOS 8, maybe this is because you think that you can hear a difference. If you have the occasion to setup a blind listening test between two power cables that sound different to you, we would be inhterested to know the result.
It would also be interesting to run an RMAA analysis, if you can, on a device fed by different power cables, if it can show a difference in the background noise, for example.

I have some ideas for doing something along those lines. For me, though, this is a hobby, and finding the time is always a struggle. But, given that no one (that I've ever heard of) has done such a thing, I'm sure it'd be worth it.

Cheers,
Jim

Hi-fi Magazine Rules, why they can find peoples pay 2500$ for a Cable.


If you working for a HI-Fi Magazine, you need to travel around many miles, most of Hi-Fi manufacturers invite the reporters to an luxuriosy Hotel or whatsoever Sweet, don't ask why.

If you read a Article about a better Power Wiring, you should keep minded that this cables only are worth the copper inside, and PVC.
But some idiots believe to this stupid Hi-Fi Magazines just because a single idiot gets invited by a Hi-Fi Manufacturer to an Luxuriosy Hotel or whatsoever Sweet,
now, you know why.

Forget all those deep s**t Amp Racks, Get a Beton Rack and a few Rubber sticks from 3M or China it does it always.

Forget this ultra expensive Speaker Wires, & terminals

And last but not least:
Forget those clowns from Hi-Fi magazines.
And don't forget this message.

Slowing down high frequency transients?!? I'm not trying to be rude...but was this supposed to make any sense?

Would the whole John Dunlavy debunking of expensive speaker cables apply to power cables too? I'm inclined to think they would be even less critical as most houses aren't wired with 1400-dollar interconnects, nor are the components the cable plugs into. Someone should convince Paul Allen or the sultan of brunei to run stereophile magzine-recommended cabling back to the power company.

I wasn't answering the original post - I have no desire to defend $2500 power cables.

I was specifically criticising your blanket statement things are either black or white, you can either hear it or you can't.

Human hearing is stochastic, not deterministic. Even the masking threshold data at the heart of psychoacoustic codecs are probability thresholds (e.g. 50% chance or 70.7% chance of hearing something), not absolute thresholds (now you hear it, now you don't).

If you were only referring to the power cables in question, that's fair enough - but to suggest that every audio component can be judged with a black or white "this makes a difference" vs "this doesn't" doesn't make any sense. If that's not what you meant, then ignore my comments. If it is what you meant, then I strongly disagree!

Cheers,
David.

There is a rule of thumb in Hi-End Audio that you should expect to spend 10-15% of your total system value on interconnects, speaker wire and power cords.

With this in mind power cords that retail for $2500 would not be out of line if you have a $50,000 system....and yes many people do spend that much. It is common to see amps (mono blocks) go for $15,000 or 20,000 with preamps costing about half that. Speakers.....how much do ya got? It can cost as much as your car...or more.

Bottom line, don't knock what you have not heard. If your perspective is a amp wired with "bell wire" or a sound card and PC speakers you need to understand there is a whole new and expensive world out there.

Would I spend $2500 on a power cable?? No, but I will and did do a DYI and spent $75 doing so. Sound to me, in my system, using my ears, with my music and my gear is better than the stock 18 ga cord that came with one of my components .

As mentioned in earlier posts, there in no B&W on this issue and the improvement is very subjective.

Just hope and pray that some day you can afford to and not think twice about spending $2500 on a line cord.

Peace,

sdz

One should first demonstrate that they have a different sound than regular power cable before this is advised in this board.

Pio2001,

As mentioned the issue at hand and the impact these power cords have is in my opinion subjective at best. In my experience upgrading power cords has made a improvement in the audio quality on MY system to MY ears. I need not prove anything to anyone.

This is exactly like proving there is a God. I and others believe in one yet there are some out there that don't and still others that want proof.

There are many in the audio world that feel power cords and interconnect upgrades are worth the cost. They need not prove anything to you, me or anyone else. It is their money, their systems and their ears.

Here is a link to a group that would beg to differ on the value issue and if you care to read you will find what you search for:

http://www.audioasylum.com/audio/cables/bbs.html

There is a simple solution, don't buy them if you feel they are of no value.

Peace,

sdz

Yes, it was. And as a useless physicist, I'll be proud to display my useless credentials beside those of any useless engineer.

What it means (and I admit it might not have been clearly expressed) is that the instantaneous (or nearly so) demand for current that results from digital switching could not be immediately met, because the rise time of the current in the filtered power cord is slower than the PS would otherwise require in recharging. Very rapid changes in current result in noise. By slowing down the rise time, you reduce the noise. Pretty straightforward.

Cheers,
Jim

It works because it's voodoo... and the reviewer is bribed.

I have a related question. What kind of power cables are used on expensive, highly sensitive laboratory equipment? I'm thinking of raster tunnel microscopes or similar stuff. Considering the amount of money spent on such equipment, spending an additional $2500 on a power cord would be peanuts.

I don't actually know the answer, but I would strongly assume it's just your everyday cord (shielded perhaps). I suppose, if super expensive, specially designed power cords were beneficial, laboratory equipment would reveal it (higher resolution/speed or whatever).

Also consider the Pentium 4 CPU which is extremely demanding of the power source because of very rapidly changing load and very low tolerances regarding power stability. And yet there aren't any special oxygen free, yadda yadda cables used in your PC. The legs of the capacitors, resistors and coils are just standard. Miraculously it still works.

The analogy to God is inappropriate - please do not go there.

The reason you have to prove that you can hear a difference in cables is because of the rules of this forum (TOS 8). Search for numerous threads documenting the placebo effect of audible claims - it is an extremely powerful and potentially expensive psychological effect. If you claim on this forum that something makes an audible difference then you need to show proof, otherwise don't post it and enjoy the audio placebos and fetishes in private.

Now that makes sense The other post was worded like you were trying to 'slow' frequency. Although I have to say I'm having a hard time imagining a common amplifier with enough peak output capacity for this to be an issue...discharging the power supply capacitors faster than they can be recharged means implies you are overdriving the amp well beyond it's RMS design power and the distortion you get from this is going to be several orders of a magnitude greater than that of the filtered power wire.



The design of power cables for most lab equipment is fairly generic, they tend to be a slightly thicker and have decent shielding, but not considerably different than you'll find on say a decent computer screen. Ocassionally they are twisted pair (where the signal and ground wires are closely spiraled such that interference in one wire cancels interference in the other). Generally the noise reduction of the power lines is the job of the power supply...but needless to say your going to find a far higher quality power cord than lamp cable. Keep in mind that higher quality probally means the cord cost $5 as opposed to $1.

Most of the time the main concerns are grounding and the interconnects used between sensors and the measuring device. Typrically care is taken such that the chassis of the powersupply, amplifier, measuring device (say an oscilloscope) ect... as well as the shieldind on the interconnects, are all attached to a common ground (using sufficient gauge wire to minimize resisance differences).

The interconnects themselves are usually (but not always) twisted par with a metal shield. (like decent audio interconnects, decent meaning $30 radio shack cable - not kimber cable). The resistive, capacitance, inductance values are important here because they create a bandpass filter in the wire. This is true for audio cables as well, but is a fairly non-existant problem with a decent cable which will handle signals fine well past 100,000 Hz. It's far more important for something like an oscilloscope which may be asked to measure into the gHz range. For more difficult signals differential cables are sometimes used (like pro-audio XLR balanced cables) which used a differential error signal to cancel out induced noise or a sensor with a high output level (say 10V instead of 10mV...as 0.01V of induced noise would be insignificant at 10V vs. very bad at 10mV) or current loop transmission (signal is encoded by varying the current at a more or less constant voltage). I should also point out that the quality of the interconnect required to reduce noise is directly proportional to wire length...so you want to keep runs as short as possible. If your going to try and run an RCA cable 100ft you're going to need a much higher quality cable... but from 3-6ft like you should be using (and digital coax or optical for larger runs) the luxary cable's possible improvement should round to zero (this applies strongly to signal cables, much much much less so to power or speaker cables).

$2500 would be peanuts for some equipment, but you have to keep in mind that the goal of the engineer designing this equipment is to meet a maximum signal quality level at a minimum price, and they are going to do this by analysing the signal path in a repeatable, measureable, scientific manner. They will not rely on marketting gibberish or unproven subjective opinion. So unless he/she can prove such exotic cable is absolutely necessary it will not be used. The fact that super-luxury audio interconnects are NOT used for applications which require considerably more accuracy than the human ear will ever be capable of resolving should say enough.

That's the job of the filter caps in the power supply. Generally a good PS for a domestic amp will have some large capacitors to remove 50Hz (or 60Hz) ripple from the rectifier (10mF per channel is what I would chose for a 60W amp). Because big electrolytics have a large Equivalent Series Resistance and series Inductance, they don't filter out high frequency (over 500Hz) low amplitude (say 30dB below the main 50Hz component) very well, if at all. To solve this problem, a set of smaller film or ceramic caps are put in parallel with the filter capacitors (generally a couple of nanofarads). While this sort of first order RC filter doesn't produce pure DC, the Power Supply Rejection Ratio of the amplifier means that noise from power supply ripple is around -100dB. You'll be able to hear it only if you really crank the volume with no signal.

Generally the current demands for digital switching will be taken up by either the decoupling caps on the board. A little noise is the least of your problems if you let your rail voltage drop heavily when a switch occurs.

I bet we could sell some of these $2500 cables to the Pentagon....

Weapons of mass delusion?

Sorry - I'll get my coat...

Cheers,
David.