Re Googling "spark coil," I think that also Googling the term "inductive kickback" would further reinforce your recommendation about shielding.
To make sure it's clear to the others, inductance (which is present to a considerable degree in a transformer) resists abrupt changes in the current flowing through it. If the current flowing through it is forced to change abruptly, such as by the rectifier commutation Ralph describes, the result can be extremely large voltage spikes, resulting in high frequency noise that can radiate through the air as well as couple through circuit paths.
Magfan and Al, you want to keep in mind that the power surges are the ones where the power supply rectifiers commutate (that is to say they turn off and on) at the peaks of the AC waveform. As soon as the AC waveform drops below the value where the caps are charged in the power supply, the rectifiers turn off- please refer to my earlier comment regarding this.
The bottom line is that there are indeed HF power surges occurring in the power cord (yes, 60 times/second), unless you have another way of describing a current spike a few milliseconds wide :)
The rectifier commutation is often responsible for a great degree of radiated HF noise. They have to be properly bypassed to reduce it. However, the power transformer core has its own reaction to the ON/OFF load! If you don't believe me Google 'spark coil' and look at the principle of operation.
A fair amount of this noise manifests on the primary side of the transformer. That is why I think its a good idea to have a shielded cord :)
Magfan -- Despite the claims that some cable manufacturers may make in their marketing literature, I don't think that a power cord can have a significant power factor, because its inductive reactance and capacitive reactance at 60Hz will be completely negligible. Although I agree that the power factor of the load can certainly be significant, which would presumably be inductive due to the power transformer.
Using this inductance calculator, the inductance of say a 72 inch power cord of any reasonable gauge is in the range of 2 to 3 microHenries. That is roughly a milliohm (0.001 ohms) of inductive reactance at 60Hz, which is negligible both in absolute terms and in relation to the load (and undoubtedly also in relation to the house wiring inside the walls, as well!).
Capacitance will vary widely with the power cord design, but as a very worst case guess let's assume 1000 pf/ft. At 60 Hz, for a 6 foot cord, that would be a capacitive reactance (in parallel; therefore the higher the better) of about 500,000 ohms, again totally negligible both in absolute terms and in relation to the load impedance.
First, there are NO high frequency 'surges' in a power cord. If a power cord measures as highly reactive, you will have voltage and current not in perfect phase. Just for a trivial example for which I have measures. A 40 watt fluorescent light draws about .32 amp after warmup. The power factor (PF) is about .8, so the lamp really draws 40VA. If the PC is such a load, along with the powersupply of the equipment in question, that can be the source of some bad effects. The electric company really hates low PF loads, and at least in industrial applications, charges a premium.
As an aside, the same thing can be said of the amp/speaker relationship. A speaker with huge phase angles can suck the life out of an amp while having only a fraction of the power delivered to the load. Add low impedance and the problem compounds.
A voltage drop on the power cord is caused by two things: the gauge of the wire and the quality of the connections.
If your power cord is heating up at the connectors, here is an example of why things like the Porterport or medical-grade connectors can make a difference!
The wire itself will heat up if it is inadequate gauge.
If it is built improperly, it can resist the high current/high frequency surges required at the peak of the waveform.
I think its a good idea to have a shield too.
IMO, building a cable carefully with good connections at either end and a heavy gauge will hit about 95% of what is important. We built a few power cords just for fun and they turned out quite well. Some of our gear does draw some power and they seemed will up to the task. After you build a few and add up the costs, you start to see why some power cords cost what they do. Not all though :)
Stewie: "(Mr. T): this hobby is so subjective that when you have 2 audiophiles in a room, you will get three opinions."
That's nonsense. You will get four opinions.
True! After the first one changes his mind, the other one will follow suit.
Shadorne: And indeed that is what I have found to be the mystery around those extremely thick stock power cords that came with the higher powered power amps (at least those that I have been familiar with). Thick cable was not just all rubber/plastic but they came with thicker wires too!!!
Nice to see that at least some of our members can bring a sense of humor to this subject :)
True. But along the lines of Mitch2's comment, all of the effects mentioned in Ralph's post can be avoided simply by having adequately low resistance in the path between outlet and power amp.
An indeed that is what I have found to be the mystery around those extremely thick stock power cords that came with the higher powered power amps (at least those that I have been familiar with). Thick cable was not just all rubber/plastic but they came with thicker wires too!!!
Power cords are important when it comes to high power output devices.
True. But along the lines of Mitch2's comment, all of the effects mentioned in Ralph's post can be avoided simply by having adequately low resistance in the path between outlet and power amp. Which often may not be provided by stock power cords, but can certainly be accomplished via a modest upgrade that does not utilize exotic materials and construction techniques and cost megabucks.
We have measured nearly 3 volts in some cases. In a 100-watt amplifier that can account for a nearly 50% DROP in power!!!
Ralph -- Can you elaborate on how such a large drop can occur, and if that would hold true just for tube amps with unregulated filament supplies, or for tube amps with regulated filament supplies and/or solid state amps as well?
Every 200+ Watt per channel amp that I have owned came with extremely thick stock power cords. I think Ralph is on to something there. Power cords are important when it comes to high power output devices.
Thanks for that, Ralph! That's the most concise and clear explanation I've read on the subject.
A couple of questions:
What accounts for a 3-volt drop across an AC cord? How does that happen? Is this an argument for shorter power cords? Is it all in material and design?
Why/how can one power cord dump more current at the peaks faster than another? Isn't this limited or affected to some degree by the power source (the AC), and how that source is delivering power? I think (perhaps erroneously) about the analogy of a hose delivering water - no matter whether the hose is fat or thin or obstructed or not, it will always be limited to some degree by the delivery of the water from the spigot. If the water is being delivered in spurts and fits, the hose will not change that.
Hi Ralph, Not to "stir the pot" here, but to simply try and learn something; isn't your discussion largely related to resistance, and isn't that largely related to the gauge of the PC conductors and the length of the PC? Can a power cord achieve the "ability to dump large amounts of current during these peaks" simply by having adequate gauge conductors (say 10awg) and tight fitting connectors? Assuming noise is not an issue, are there characteristics other than the ability to transmit current that you believe to be important?
Ralph;are there any cords that work better with your amps that you like as a preference;you already gave me great advice on the Mogami balanced cables so I thought I would ask on the cords.
For those who wonder how a power cord can make a difference, consider this: an amplifier has a power transformer, rectifiers and filter capacitors in its power supply. Normally, the filter caps are charged by the rectifiers as the transformer makes voltage.
When the filter caps are nearly charged, the only time that the rectifiers will conduct is at the peaks of the 60Hz input waveform. So all the energy going into the amp is concentrated at the peaks. This is the point that the diodes turn on, as the voltage on them is higher than the voltage on the filter caps.
As soon as the wave is past peak, the rectifiers will turn off, when the filter cap voltage is higher than the voltage from the rectifiers.
So the energy going into the amp is often doing **only at the peaks**. The difference between a cheap power cord and an expensive one, in terms of its ability to dump large amounts of current during these peaks is only about 3%. It is that 3% that audiophiles hear.
A second phenomena is AC voltage drop across the cord. We have measured nearly 3 volts in some cases. In a 100-watt amplifier that can account for a nearly 50% DROP in power!!!
If you think these two phenomena are not audible you're missing a bet. The bigger the amp (IOW the more power drawn), the more audible power cords become.
We figured some of this stuff out nearly 20 years ago, which is why one of our bigger amps (the MA-2) actually runs two power cords per chassis (since there are 2 AC circuits in the amp for 2 power transformers) to limit the audible effects of the power cords. Back then there were not nearly so many exotic cords as there are now! -so we had to make do and adding a power cord worked out very nicely.
You won't be hurting anyone but yourself, in having ripped yourself off for the musical rewards. Even the better recording studios have discovered the audible benefits of upgrading power cords/cables in the recording/mastering chain. I suppose that's just their imagination too?
I'll change my stock powercords when audio engineers such as LFD's Dr.Bews and design engineers at Benchmark Media supply/sell ones they stand behind as providing sonic improvements with their products. Another words, very likely they'll be no powercord changes in my future (o:
Because they simply tend to 'UNBURN-IN'and that is logical..Next time find out for yourself when you buy a pair of new amps!! Run a varied signal through one of them for 48 hours-no more needed. Then listen to it in mono-carefully. Do not rush. Then listen to the unplayed one for comparison-in mono. Now unhook the first one and place it in another room for 2 weeks. It will not sound as good as it did before and not as good as the second one you had been playing for 2 weeks. It is changed= UN-Burned-in!
Rleff- I used to own a pair of Acoustat Model IIIs, and was just recently wondering if I would have heard any difference with some of the PCs I've got now. The voltage that electrostatics use is charging the speaker's diaphragm/membrane, and not providing gain to any kind of signal. That's one of the very few applications in which I believe would be hard to discern an improvement(No experience/just a guess). Then again- I've heard that Martin-Logan CLS's can be improved via upgraded PCs. You could plug those Kimbers into the SoundLABs,(before using them on the monoblocks) as an experiment(I would).
Rodman99999- I did purchase a set of kimber power cords don't remember the model but it does not have a network on the cable and will be installing them on pair of audio valve challenger 180 monos I just picked up on Audiogon and am looking forward to hear their performance vs the signal cable cords I had before. Do you think it is worth putting a high quality ac cord on my soundlab m2's backplate?; Let me hear your point of view.
Rleff- Once you've purchased a hi-end power cord(ie- Synergistic research AC Master Coupler, PS Audio XStream, Zu Mother- or better than those mentioned), and burned it in; you will understand the changes through which it will progress(the electrically biased ones excepted). That depends on the resolution of your system and your ability to discern the differences(system variances and aural acuity/training differences existing in so great a divergence).
I would think most manufacturers have some type of a QA process where the product is burned in for x number of hours to weed out infant failures that occur. Some may even have enviromental chambers that control temp,humidity,and vibration that affect the product. Power cords buring in may have some type of merit but I don't know what the audible improvement would be.
The simplest answer is that it's a business, you want all of that done for you, then you are going to pay for it! You aren't getting it for free. Component makers are not cable experts and are not about to squander revenues to research for the best cable for their component. Whether you like it or not, that's your job!
The tangential discussions are a reflection of the impacts and unease the buyers are subdued to when purchasing new gear. IMHO, we're still on track here.
With all due respect to the tangential discussions above, tje raises an interesting point: Why after paying a phenomenal amount of $ is it incumbent upon the purchaser to perform the break-in? I would think it makes more sense to have this done at the factory level as opposed to a dealer due to warranty ramifcations and the aforementioned stigma associated with buying a "demo'd" unit (versus new) from the dealer. Couldn't the burn-in serve a dual purpose in terms of flushing out potential defects as well?
Insist on buying the demo unit from the dealer, if it is in adequate cosmetic condition to you ! With full warranty starting the day you pick it up ( which is usually the case ). Let him break-in the next one !
i am not aware of any manufucturerer who will assert that cables which interface a component have no affect upon the sound of that component. most manufacturers willtell you to burn in the component before criticial listening.
regarding double blind tests to assess burn in, i would like to read the protocols of such experiments so i can judge for myself.
this hobby is so subjective that when you have 2 audiophiles in a room, you will get three opinions.
We do 90% of the burn-in here in our shop. The last 10% takes the longest time- up to 6-8 weeks depending on the number of hours a day. Especially when you have amps or preamps built up with custom options, doing an extended burn-in is just plain impractical!
As to power cords, we acknowledge that power cords are going to make a difference. That is why we install IEC connectors on our products. The problem is, what we think is the best power cord may not be what you think is the best power cord. In fact we have seen a power cord work great in one installation and make no difference in another. You have to take into account that variables of house wiring, cleanliness of the AC power, neighborhood line voltage and other system anomalies that will affect what the end user thinks is the 'best'.
Guess what? No-one can do predict all that- so that is why we supply our gear with IEC connectors. Our stuff is known for being really transparent- and we invite you to experiment. That is the only way I know of to sort out what is going to work in the area of power cords. It would be frustrating as an end user to realize that a $200 power cord had been included with the unit, only to find out that in your system its not the right combination!
I listened to my system for a year with the stock power cord. I decided to try a new cord and it did make a difference. A window in my room began vibrating/rattling. Never did before. Some frequency was boosted and made that glass vibrate.
why did manufacturers used to make power cords that were hardwired, and millions of music nuts didn't give a ratsass about burn-in? jeez were we simple?..or simply happy with the equipment? UL approved red cords always sound better than UL approved black ones, and blues ones always trump the red. throw in the words 'hospital' or 'military' and your electricity will really pay attention.
This I believe: components don't burn in; listeners burn in. "Burn in" is a metaphorical cousin of "break-in": baseball gloves require breaking in; conert grands--specifically, the action-- require breaking in. The wood in string instruments changes. We love to think of things breaking-in, balancing, aging into maturity and ripeness. We like to think of metal components, non-organic and w/ no moving parts (excluding drivers), doing the same. Isn't it odd, though, that "burning-in" is supposed to result in better sound? Isnt' that very congenial on the metal's part? Why should that be? We imagine things "limbering up," "getting settled." Just as I like to imagine that my tube amps give me a warmer, more open sound. I suspect that I'm transforming the literal warmth--the visible glow--of the tubes, and the delightful, illuminated open space inside the glass globes themselves, into my perception of the sound. Solid state. I mean who wants to hear music from something called Solid State. Definitely not open, and not warm and glowy.
IF burn in were required, just think of the facility required. 1 station with good power for each amp along with dummy loads appropriate to the power. One good power glitch and there goes a couple months of inventory....poof! The heat alone would put a dent in ANY electric bill. Unless of course you did all your burn-in during the winter! Bryston does so simply for infant mortality reasons and in order to provide for the #1 industry warranty. Also, I have read some posts where people periodically re-burn cables!! No mention is made of the other half of the equation....that your ear/brain gets accustomed to the sound it hears.
Power cords? Burn in? Seating the Pistons? LOL, I love this stuff.
I can't tell you how many times I have seen a performance engine built and tested up to it's estimated RPM limits as soon as it's ready with fluids and exhaust. Never, and I repeat NEVER does anyone talk about a break in period. That's a myth propegated by the manufacturers to help people justify thier expensive purchase. If you buy an M5 BMW you can floor it right off of the dock in Newark, Houston, or Long Beach, it will be just fine, your friends in Bavaria built it that way. Same goes for your Nissan, Caddilac, Corvette, or Porche.
BTW, we have built 550 - 900 HP engines, tested and tuned them at extreamly high RPM's, then dropped them right into the cars to race (strip and road) without any problems at all. No break in required. Most were the same blocks and components that come with your car from the manufacturer just modified with some performance parts, so these are not crazy one of a kind engines.
Watch Horsepower on SpikeTV on the weekends to get an idea of the myth of engine breakin. They start at 5000 rpm runs, and go up after about 30 seconds, that's the breakin.
Well not all companies are alike, I recently purchased a pair of Bryston 28B SST SQ mono blocks and went for a tour of the manufactures facility.
They have a long wall basically dividing their work area in the back of the building and on both sides of this wall this is their area specified for exactly this. They just don't burn them in they do a non stop torture testing on every piece. I was shocked to see all these pces and was told they put their product through a rigorous list of test with source plugged in 24/7 through cycles including turning on and off etc.
The power cables they provided where your basic cheapos, better than your norm but they still stayed in the box and my Stealth Dreams got hooked-up.
Even with them doing this the amps still needed many hours of burn in as I noticed changes along the way, I just don't think it would be feasible for long periods of time. Bryston for example is not a mass market type of company, they build each pce as ordered and but at least they do this which is nice where as other companies do much less if any.
20 Year WARRANTY to boot.
You are going to hear more and more about these 28sq mono's, absolutely amazing amps.
I have no affiliation what so ever, these replaced my CAT JL3 Signature MK11 mono amps listing at over $40K which drive my MBL 101E's so that should tell you something.
Cars, well any car needs to be driven when new at resonable speeds to break everything-in properly, just the way it is.
Burn in, for either audio gear or cars, is not performed at the factory (other than rare exceptions) for the simple reasons of cost and practicality. Would you want your "new" car to arrive with 2,000 miles on it just so you could run it flat out on day one? Both audio gear and cars were originally (and still are) set up to be displayed, demo'ed and sold by a dealer. The dealer's gear is assumed to be already run in so the buyer can get a feel for the end product during the demo. I believe that 50 to 100 hours is plenty of burn in for audio gear to achieve its characteristic sonic signature. It may continue to improve over time, but after 100 hours you should be hearing much of what you purchased.
Manufacturers do not include upgraded power cords for the same reasons they do not include stillpoints for support or other tweaks - first, including expensive extras will not allow them to achieve attractive price points, and second, the buyers who want something different will never agree on what "improved" power cords, footers, etc. are best.
Of course, if you buy your gear on Audiogon, it will come already burned in, and you will have saved enough money to purchase an upgraded power cord.
Thomas, Of all the high end equipment I've owned, I don't recall any manufacturer ever saying the component "will sound better with the RIGHT cord". Some do tell you to use a high quality cables.
Power cords, interconnects and speakers cables are subjective, so there is no right or wrong cable. The "right" cable for one person may the wrong cable for the other, therefore high end manufacturers leave such choices up to the customer.
On the issue of burn-in, many manufacturers do burn in their amps on the test bench for an extended period, but usually for quality control/reliability purposes. Its up to the customer to do any additional burn burn-in, if they feel that will make a difference.
Well, as always, there are 2 sides to any reasoning. The purely qualitative side of "burn in" is quite subjective in logic. New components will settle and ultimately interact synergistically so that the entire piece performs in unison. This is understood to occur via both a mathematical (calculated) and psychological (subjective) manner. Practically, the manufacturers know that owning a brand new piece is for many the first step in enjoying the hobby. Secondly, why would they interject an opinion that would divide their prospective clients? "Requires burn-in" impregnates (lol) ideas in many peoples heads that could confuse the way they want their product to radiate in prospective clients heads. They leave this to the voodoo of the hobby. You have to be very carefull how you market you product/ideas. After all, a fart in the wrong direction is only defined by which way the "wind" is blowing. Audiophiles are quite ruthless...especially with which fads are most prominent at the time.
For those that are using price as an excuse... give me a break!! A manufacturer could easily burn in an amp with tubes, then replace those stock tubes for $10 or $20 each. Assuming the amp was over $1000 to begin with, that's an insignificant amount.
Same thing goes with power cords. It might cost hundreds of dollars for an audiophile to buy a power cord as a consumer, but the actual manufacture cost should be insignificant. Any maker of components should have the connection within the industry to source quality cords -- it doesn't matter if it's hospital grade, or audiophile grade, or if it uses a different type of wire or twist. Those are easy! Some companies might charge you $20/ft of silver wire, for instance, but do the calculations: a ft of .1" diameter (roughly 10 gage) pure silver, weight around half ounce; right now, silver is $14.5/ounce, which yields about $7 for the wire. Just to make the point that component manufacturers who could mass produce this stuff could conjure up a fancy pure silver cable with techflex pvc covers dressed up for under $50 (or maybe $20), depending on the connector.
Most factors/dynamics(with the exception of speaker system drivers) that are involved in "burn-in" will also diminish with idle time, and require another burn-in period. If a manufacturer turned out 2000 amplifiers, and ran them the 200hrs, to their peak performance(burned-in) level, he'd then have to charge you a percentage of the electric bill. AND: By the time the unit was sold; (in most instances)It would require another burn-in. A waste of time and money(though SOME do burn-in their products). There are many differences in peoples' tastes regarding their music presentation, and various presentations that can be had via different power cords. How would a manufacturer know if what he provided would suit your tastes? Most of us would be rolling our PCs, still looking for that last drop of resolution, sound stage, impact, silence(or whatever) anyway. Why should they bother? Then there are many that can't hear a difference(regardless of how audible and obvious, to those that can), or are so convinced it won't make any difference; they refuse to hear any. I can easily understand why most manufacturers don't bother with burn-in or providing upgraded PCs.
If they include a power cord, they would not be able to stay at a competitive price for there gear. Also, many audiophiles already have a favorite power cord that they would use in place of the stock cord. I believe that a good power cord can make detectable difference, as always this is just my opinion and we audiophiles have been debating about power cords, speakers cables, and other tweaks for years, its just a matter of opinion.
Most performance vehicles do require driving at limited RPM's for the first few thousand miles of seating the pistons. Porsche's is about 2000 miles. I would guess that manufactures don't break in audio gear because it takes 300-400 hours of constant running sometimes within the context of being within a system with a signal running through (speakers and amplifiers). Ultimately it probably just doesn't make economic sense. OTOH, I see no reason, given the modest cost of materials involved, for any high-end manufacturer to provide "better" power cords. Again, I'm sure the reason is economic in that the more they can keep manufacturing cost down the more appealing to the consumer, the better it may look in the face of competition, and the more potential profit. It's the kind of thing where if one manufacturer starts a trend, other's may follow.
Cost, pure and simple. If tubes are involved, the catch would be that 'used' would need to be put into the spec's.
With exception of speakers, the 'burn in' is a myth to get you into the rituals of the hobby. Double blind test, the only true way of telling, has proved time and time again it is not necessary.
Personally, I don't believe that a power cord will make a detectable difference. I've never been able to detect one anyway. I've also never been to a hifi shop that has told me a different power cord will make a difference. Never had a dealer demonstrate different power cords. BTW, I'd love to be proved wrong!
The only cable I believe that makes a difference is speaker cable and that is barely detectable to my ears.
I had to keep my lastest new car under 3K RPM's for the first 1K mile, and I like many others, I didn't like the OEM tires. Some manufacturers aren't convinced that power cords make much difference. For that matter, manufacturer's don't offer "...good (or the "right") interconnects or speaker cables.
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