Do cables really need "breaking in"?


The post about whether speaker cables matter has inspired me to ask another question...do cables really need a break in period to sound their best? Some people say cables need to be broken in or played for a while before they achieve optimal sound.

This sounds to me like it was invented by believers in astrology. Isn't that break-in period just allowing time for the human listener to get used to them? Has anyone ever done an A/B test with new cables vs. used cables of the same type and noticed a difference?

All I know is that new Porsche or new bed (or new girlfriend for that matter) feels totally different after you've had it for a month versus the first day. Ever moved into a house/apartment/hotel and noticed all kinds of distracting ambient noise that seemed to disappear after you'd been there for a while. It's human nature. Even if cables needed a break-in period, how could humans tell, with all these other much more noticeable factors distracting them?
matt8268
Bomarc, i agree that there is the potential for differences in perception when the speakers are sitting side by side as close as possible. However, listening directly on axis and in the nearfield ( i forgot to mention that part before ), the differences should be minimal at best. However, nothing is perfect, including ABX.

Since we are not concerned with imaging or soundstage ( we are in mono after all ), the basic things to listen for would be changes in tonal balance, transient response, inter-transient silence and harmonic structure. These are not just attributes of the cables under test, but how the equipment in the system loads into and responds to the specific impedances being presented to them. You are therefore not just testing for differences in cables, but which ones are most cohesive in your specific system. Sean
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A couple of cautions about Sean's "protocol" for comparisons. The side-by-side mono test does not cut it: If the two speakers are not in exactly the same place (a physical impossibility, of course), you get room effects, which can be very audible. Second, it's amazing how little information you have to give a test subject to bias them. Merely telling them they are listening to two different cables sets up the expectation that they will sound different. That's why researchers don't use AB comparisons, but ABX tests, which require subjects to positively identify the X.

However, we aren't researchers. We're hobbyists.And objective though I may be, I wouldn't expect anyone to go to the trouble of setting up a proper ABX test. I only mean to suggest that we should be a little careful in how we interpret the more relaxed comparisons we actually do.
Craig ... the concept of speakers (mechanical, with moving parts) breaking in is absolutely believable.
The post was referring to cables, not speakers.

1953 .. I don't think I scoffed, or at least I didn't mean to. I just pointed out that the ear can easily be fooled, as can the eyes. Please don't resort to capitals ... I can read lower case !
This is only half on pointbut I am a no count amateur speaker builder. But all of the guys I admire (Lynn Olson, George Short on and on) share at least two common traits.

1) They know all of the numbers and formulas and put great store in them. In this sense I get very tired of folks who talk about "cables" endlessly and NEVER about the design parameters used by cable makers and how it combines with a system. And why these designs cost so much $$$. If you have a speaker that has ridiculas load impedence (the old Quads and some others) that drop to under 2 ohms at high frequencies you have need certain needs in a cable. If you have a SET you have capacitance issues. If you have an ELS you have inductance issues...on and on. I feel a lot of stuff magically attributed to "cables" can be thought through and figured out without dropping ridiculas amounts of cash and chasing the latest gimmick that is thrown at us by the cable industry.

2)Knowing the numbers and respecting them, they know that the formulas just do not work. a) The cross over equations do not work, b)the frequency response curves are taken under artificial conditions, c) the Thiele/Small numbers given by most manufactureers are way off... on and on. That is, measurments, at least as we take them now,just do not tell the whole story. Another example of this phenom is why do SETS sound so good when they have such poor numbers(3 watts and THD .05). Again these examples can go on and on.

These guys spend endless hours tweaking by ear. Read Olson's account of how he developed the crossover for the Ariel.

Its the old joke about the two guys in the life boat arguing over which orr to keep in the water. You need both or you row in circles. You need to respect the numbers and such but in the end you have to listen too. The whole argument about numbers vs ears is, to me, idiotic and unproductive. You need both.

That being said I think There is so much fantastic hype and marketing around cables that it is a turn-off. The industry has not produced anything to justify the COST. (I am not saying all cables sound alike!!!) Well designed cooper suits me fine (I make my own).

By the way I do not feel thinking about how 18 inches of wire (the last .015%) overcomes a typical Audio chain that includes 100 opamps, dozens of connectors,and hundreds of yard of ordinary cable (I'm talking just the recording chain here-not the juice to your to your house) makes me a member of the flat earth society.

Sincerely, I remain
My friend has the Cable Cooker. He burned my i/c's for 48 hours and now I can hear a big difference. My cables (system) sound more like music than before. It works.
Paulwp, i WILL go so far as to say that the differences in the "sonic signature" of cables IS highly system dependent. Whether this is due to superior design (stability) of the components or the lack of resolution within the system are but two of the possible variables involved.

As to doing cable comparisons, it is VERY easy to do an unbiased test using an "outsider" i.e. "non audiophile". Hook up two speakers side by side and run the system in mono. The channels should be "plumbed" electrically identical except for the ONE cable under test. Have the listener sit directly on axis centered between the two speakers. Differences in frequency response due to room loading characteristics are not really a factor since the speakers would be firing into near identical environments. This takes for granted that the speakers being used are relatively well matched in terms of frequency response and amplitude output levels.

Since the listener does not know anything about brands, various designs or what to expect from any of the devices under test ( DUT ), you can simply play a selection of music for them and switch from speaker to speaker as instantaneously as is possible. This takes the "acoustic memory" debate out of the equation.

Of course, you can't tell them what to listen for as that surely would taint the results. Not letting them see the cables in use prior to testing also helps keep things on an even keel. Since different designs may appear "thicker, more solid" or "lighter, more airy", the listener may enter the test with preconcieved notions or effectively bias what they hear or percieve to hear based on visually preconcieved ideas. No talking should take place until the listener has formed their own opinion of what they are hearing and is willing to voice their appraisal of the situation.

If the unbiased listener tries to verbalize the difference in sonics that you were also hearing WITHOUT any assistance or guidance from you, chances are the differences in the cables under test are EASILY noticeable. If they are unsure of any specific changes, differences ranging from very subtle to no difference at all ( within the confines of that system ) would be a logical conclusion. The fact that there might be a disagreement pertaining to specific sonic differences between several parties listening to the same system under the same test conditions would leave us with nothing more than a "subjective" outcome. This could not be taken as a positive OR negative but would require further, possibly more controlled, testing.

I have found that by using this method, i am easily able to confirm what i thought the differences in various cables in a specific system were by comparing notes with the un-interested party. While this may not be as "accurate" as DBX under controlled conditions, there is also nothing extra hooked up into the system to further taint or confuse the results. The ability to repeat the test on a regular basis with consistent results supports my previous statements to the fact that differences in cables DO exist and that they are audible.

With threads that get out of hand / quickly become polarized such as this one has, is it any wonder that AA has taken the stance that they have ??? Sean
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I've only been through this topic about 300 times-- guess it's always popular or new to some.

A bit off subject, but relavent I think: In Oct. 2001, we bought a new, large, wide screen TV-- near $3K and from a major manufacturer. Right out of the box the picture was fine, but the sound was terrible. It sounded like a $19.95 transistor radio-- bright, edgy, an annoying echo, and fatiguing. News announcers sounded like they were talking from a culvert. This TV allows adjustment of bass and treble, and I did my best to correct the terrible sound quality. This helped a bit.

After the TV had been on for 6-8 hours, my wife came home and said "what's that smell?". Well of course it was the smell of the electronics of the TV "burning in", and then I realized that the TV speakers also needed to break in. The "burn in" smell lasted 2-3 days for me and 4-5 for my wife. I'd say it easily took nearly two months for the sound quality to smooth out and become non-fatiguing.

And now 3 months later, the TV sound quality is just fine-- well, for a TV, and I've been able to return the bass and treble settings to more normal positions. Am I supposed to believe that this improvement in sound quality/character is all in my mind? That no actual break-in/burn-in occurred except in my mind?

BTW, new and near new TVs of the same brand sound just as bad at the dealers, but when I auditioned it I thought it was just room acoustics. Cheers. Craig
Every time that one of these threads go up there's always a big controversy. If you don't want to believe it then don't, it's your loss. I used to be with the objective crowd too, being an EE with audiophile inclinations, but I ignorantly refused to believe anything about cabling, tweaks, etc. All I had to do was quit arguing & try listening; *wham* I'm now a subjectivist to the n'th degree. Don't worry about the spec's, the measurements, the proofs of performance. Just listen; that's what this is all about anyway - remember?
I too am an engineer who likes to "see the data" but in audio, there is more than one way to take data. I get real tired of people who scoff at the idea that the ear can be a meaningful measurement tool and insist that it be backed up with electrical data before pronouncing the effect real.

The ear/brain combination is a GREAT measuring tool for judging relative differences. For example, if I were to play a sinewave below 100HZ to somebody and then a 1KHZ signal, and while no audiophile may tell me exactly what frequencies I played, I'll bet every audiophile on this planet could hear a DIFFERENCE between the two signals.

What we were talking about here were the DIFFERENCES that burning in makes in the SOUND, not the measured electrical differences.

You don't need electrical measurements to hear an effect.

By the way, when I typed Sean in my previous post, I meant to respond to Seandtaylor.
My wife and I are both EE degreed engineers, myself at baseband, she at RF. I am open minded to many audio concepts, but not when the proponents use only their own stories of "how they heard it themselves" rather than a logical/technical explanation, perhaps backed up by repeatable measurement data.
Those who think that hearing trumps all are overlooking the fallibility of the brain and subjective measurements, couple with power of suggestion and "wishing it to be true".
I'm not saying you don't hear a difference, just that the difference may be in your own head or may be attributable to other sources (e.g. disconnecting and reconnecting oxidized connections).

But the bottom line is that we should not attack others ... if you believe something makes a difference go with it and be happy. If not then save your time and money and be happy. Remember guys it's all just opinions.
I meant to say "saying 'put up or shut' to someone" or "telling someone to 'put up or shut up'" was rude. Still is, even after the apology.

I was just thinking how nice it was to have two recent threads, do cables sound different and how do you a/b cables, wherein some people could say "DBX" and other people could say "Cable X floats my boat and Cable Y sounds like mud,' and nobody called anyone else an idiot or a fraud. At AA, you cant say "DBX." And at Audioreview or rao, you can't say you like one cable better than another without being subjected to ridicule.

For a trained ee to say "wire is wire and I'm going to use 12 gauge stranded or Romex, and you are all wasting your time" is a perfectly valid point of view. He isnt trying to sell you anything. He's trying to save you some money and maybe debunk what he considers to be a fraud on the consuming public. You don't have to take his word for it. Go play with cables. And he doesnt need to waste his time playing with cables to test his learning. If you want to do that, as I have, that's fine too.

Now, if that ee says you're an idiot or a fraud, that's different. That's not nice either.

The other issue is the words people use around here to describe what they hear from their components and cables, and from "burning-in" cables, are marketing words learned from the trade (and yes, I include the "reviewers" for the buff mags as part of the trade). The more I hear, the more I want to go down to the hardware store and buy some zipcord.
I guess that my post was pretty harsh. The point that i was trying to make is that many "educated" individuals try to pass off their limited electrical / electronic knowledge and experience as being "all-knowing" and "factual". The only problem with doing this is that they may have never specifically worked with / researched the area that they are talking about. They talk out of their hats based on "book knowledge" and by doing so, they present their PERSONALLY UNVERIFIED OPINION based on hear-say and what seems like "logical deductions" to them as "fact". They then try to wrap it up by using specific buzzwords and / or presenting credentials which would tend to lend credibility to their statements. Yet with all of their "techno-babble", they have never taken the time to actually test their own "theories" to see if they hold water.

It is to those people that i say "put up or shut up". It takes NO talent to repeat what someone else told you or to further promote myths and legends. FIND OUT FOR YOURSELF and THEN present your case. At least you'll have personal experience and a working knowledge of the subject before spouting off about what is / isn't "possible".

I have no problem with someone presenting a point of view as that: a point of view. I do however have problems with someone claiming that something is impossible and / or foolish, especially when they are personally lacking in first hand experience / knowledge in that area. If one is going to pass on information that was passed onto them, it should be noted as such. A link or reference to the source of such information can sometimes clarify or aid our understanding of what one is passing along. Otherwise, i assume that one is speaking from first hand experience and / or has direct knowledge of the subject at hand. NOT running off at the mouth and telling us that things that measure alike all sound alike. As you and i all know, that simply isn't the case. Nor is this the only thread that takes a similar stance.

This post and my prior one in this thread are NOT directed at any specific individuals. If you feel singled out, i'm sorry and appologize. I still stand by my statement of "put up or shut up" though. People are looking for "real world" comments from people that have tried / experienced these things for themselves. Those results could be "good" or "bad", either way. They want to hear it directly from the "Horse's mouth", not what was echoed out of the other end.

Having said that, would YOU want to base your decisions on information from someone that had no personal experience in that area ? You might find their comments helpful or offer some form of insight, but you would also want to know that they themselves were not speaking from experience. Sean
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You know, telling someone who is attempting to have a cordial conversation with someone else, and not trying to sell anything to him or anyone else is rather juvenile, i.e., childish and rude. The question was: do cables improve with breaking-in through use. I am one of those who say no, based on (1) the absence of any published evidence to the contrary, and (2) my own experience with cables. I'm getting on, and have a bit of experience.

I do not use $15 cables. I actually have some $10 interconnects from Radio Shack that are adequate for some applications, and I play with them sometimes to see if my opinion changes, but I don't use them in my hifi system. I do use rather inexpensive interconnects made by a pro audio gear company that I prefer to every other interconnect Ive listened to (well "broken-in" demos from my friendly hifi dealer). I use AQ Crystal speaker cables in my main system (that's my $ limit - 18 ft run can be very expensive) which I chose after rejecting several other name brands, e.g., AlphaCore, Kimber, Nordost, MIT.

So, you see, I do think cables sound different enough to make a meaningful choice. Must be my imagination.

But, based on my own experience, I don't think the sound of a cable changes through use, which was the question above. Of course, I'm probably just imagining that nothing is happening.

This in not "hearsay." I report my own first hand experience. "Hearsay" is if you say that my friend Joe says his system is much better now that he has the Valhalla. Now, can I say my preferred interconnects are just as good as the Valhalla? Of course not. I have never heard the Valhalla, and probably never will.

Other people say that they perceive a difference in the sound of their cables through use. Fine.

If one is concerned that he may unwittingly learn to live with an unacceptable cable that he thinks has burned in because he got used to it, the solution is simple: burn it in without listening to it. Ask the dealer how many hours, then feed a signal through it for that long before listening to it. Don't allow yourself to get used to it before it's adequately "broken in."

Apart from needlessly insulting other participants here, Sean says that breaking-in through use doesn't really get the job done, that you need to use a cable cooker of some sort. I have nothing to say about cable cookers because I have never used one. I don't know what they do to a cable. If they change the sound of the cable, I wouldnt have any idea how or why, or whether it would be an improvement. I dont talk about things that I dont know about.

Here's a quote: "i think that most folks would consider increased clarity, smoothness, transparency, detail, improved harmonic structure and a more natural presentation GOOD things."

Yes, no doubt, if that's what they perceive. Problem is without objective referents for those words, no one really knows what, if anything real, you are describing. The level of abstraction is too far removed from the actual event. If you're having fun, that's nice.
Sean :

My A/B test under what turns out to be controlled conditions IS data. Though not measured with a scope & voltmeter but rather with my ears, it's valid data non the less. The tools of measurement were just different from those typically used to measure electrical components. It would have been nice though to have a set of electrical measurements. To try for a correlation for such sonic effects to measured electrical effects I imagine would require a rather large test matrix.

I suggest you repeat my experiment and report your results.
Maybe some surface oxidation of the conductor occurs (which will make the sound slightly less bright. Perhaps some charging of the dielectric insulation occurs. I would not discount the possibility that the (measurable) characteristics of the cable change, but I'd like a proponent of the burn-in theory to show me their measured results.

However I think it is more likely a psychological effect : the brain rapidly adapts to new tonal balances, and comes to like them. I have a hifi in England at my parents' house and one in the US both of similar quality. I have noticed that on my vacations in England in the first few days my UK system sounds worse than my US system. Then when I return home the first few days after I get back my US system sounds worse. Over the long term I am very happy with the sound of both systems ... they're just tonally different.
SMW30: not all situations offer the resolution necessary to hear the "breaking in" of cables or electronics. The car is one good example, where the ambient noise is so great, you would never hear those changes. As for the TV: Most of it is on all the time, so its not "all day" thats critical but whether its brand new. It definitely looks better after a few weeks of watching compared to brand new. This was very evident with my projection tv. My DVD/CD transport got much cleaner and smoother after about 3 weeks of use.
Sean: First of all, I don't like participating in discussions in which someone tells me to "shut up." As for your "flat earth" reference, I don't think anyone here wants a discussion on scientific method, so I will only state that all of your experiences with a particular product do nothing to challenge the suspicions of some of us that perceived changes in cable sound over time may well be a psychological rather than a physical phenomenon.
I really don't know the answer to this, but if cables can sound better after time, why doesn't your TV look better after you've been watching it all day or why doesn't the radio in your car sound better after listening to it for hours? I, personally, have never noticed any changes in any of these. There may be very subtle changes, but don't think there would be any major change.
I've done direct fresh VS "cooked" speaker cable A/B's twice. First time with 4, identical 5 foot lengths of Kimber 4TC cut from the same spool and terminated in the same way (spades with Wonder solder). I was going to Bi-amp my Acoustat 1100 and needed the 4 identical lengths. First I listened to them fresh as pairs in a single wire configuration to make sure they were working ok. The two pairs sounded identical. I left the last pair hooked up to the 1100's and hooked the first pair up to my Duo-Tech enhancer in the basement. And I promptly forgot about the first pair. I then went on vacation for over a week. Upon returning, I fired up the system and 1100's and everything sounded as before. I then remembered the other pair of 4TC cooking (about 10 days by now) in the basement, brought it back up and swapped it out for the "fresh" 4TC pair. I sat down and pressed play.....GOOD GRIEF. The difference was immediate and not subtle. More open, more relaxed, more liquid, more quick..the usual suspects. I went back and forth several times between the cooked and fresh pairs of 4TC and it repeated each time. Things with the cooked 4TC got even better after about a day of "rest". I repeated the same basic experiment (this time with Apogee Slant 8's) when I upgraded to Audioquest Sterling II. Results were very similar but not to the degree as with the Kimber (the single 25 foot run of Sterling already had some time on it).

I'm not sure why there was a difference, but a difference there definately was and it was quite beneficial. I have a similar story with interconnect wire.
Yes,especially if you are using MIT cables. The digital reference took all of 2 weeks to settle down. The other MIT interconnects took about a weeks worth of time. Maybe it is just getting used to them,but I do believe they need time to become one with your system. Cables are not passive as we would think and your electronics before and after them make minute changes to thier circuts to adjust.After all they do have the properties of inductance,resistance and capcitance. Please excuse any spelling errors as it is very late here,4:00am.
Do cables really need "breaking in" ? The answer is a resounding YES. Will they ever FULLY break in under normal operating conditions within a hi-fi system ? I sincerely doubt it.

To those that have never experienced the difference between a cable that has been burned on a Mobie (or similar device) and an identical cable that hasn't, you have NO grounds to base your statements on. You are peddling hearsay based on YOUR preconcieved ideas and what you consider to be "common sense" and "logic". All i can say is that your "logic" is about as flawed as thinking that the Earth is both flat AND the center of the Universe. Just as the "heretics" known as Galileo and Christopher Columbus proved otherwise many years ago, we will someday have the technology to prove that MEASURABLE and AUDIBLE differences do exist in "burned" and "raw" cables.

While i can't speak for everyone, my experience is that interconnect cables used for hundreds of hours will typically demonstrate noticeably superior performance after "roasting" on a Mobie for a reasonable period of time. The use of another "cable burner" such as the Duo-Tech did nothing in my opinion / experience. I have no idea as to how effective Alan's "Cable Cooker" works either.

As to the "results" of "burning in cables" being positive, i think that most folks would consider increased clarity, smoothness, transparency, detail, improved harmonic structure and a more natural presentation GOOD things. As to the naysayers, put your money where your mouth is and find out first-hand. Music Direct ( or anybody else that may sell these things ) offers a 30 day return policy on a Mobie. Buy one, burn some of those $15 "competently designed" cables for two weeks non-stop and then give them a try. You can even "daisy chain" a few pairs if you make a trip to Rat Shack and invest in some double female RCA "barrel" connectors. If you don't notice a beneficial difference, then return the Mobie and get your money back. You won't be out anything other than the small cost of shipping. If you like the results, you will have made what could amount to a phenomenal purchase for the money invested. Either way, you can post the results right here for all to see, good or bad. You will be speaking with first hand experience then and nobody will be able to argue with that.

Until then, i consider any "negative" ramblings about cable burning or break in to be a moot point. Put up or shut up, your option. Sean
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Herman brings up a point that I have thought about quite a bit as well, while trying to understand what I was/am hearing. Herman says "I have never once heard anyone say that a cable sounded worse. They ALWAYS sound better." After playing with quite a few cables, I have answered this question to myself in this manner:

A good high end audio designer should use the END product throughout testing and voicing of a model, and I think a lot of them do just that. A simple example would be speakers. If I were building a pair of speakers, and wanted to see what 10 different midranges sounded like, here's what I would do: buy a couple of each of the midranges, and cook them on some signal/amp combination for say 200 hours. THEN, and only then, would I put each midrange into the cabinet, and see how it sings with the woofer/tweeter/crossover. Bear in mind, I would have cooked the woofer and tweeter for sure, and heck, maybe even the crossover parts (including some extra capacitors/coils to try). After this process, the combination of parts and some tweaking would produce the prototype. Now, to actually build to sell them, I would be ordering the parts in quantity, and assembling the speakers. Maybe I have time/space/money to give them 10 hours of burn in, or maybe more, and expect the owner to do the rest.

The end result is a product that out of the box does NOT sound the way I (the designer) heard it. But, since I accounted for this breakin, the speakers will sound BETTER with break in - every pair of every model that is designed as above.

Now, I have no idea how much of this is feasible for cables (that's why I used speakers for my example), but I know some cable makers do go through this process.

All in all, I agree that some of it is the listener breaking-in to the new sound, but I am very sure that cables do change their sound not only with burn in, but also from being moved. Some of the more noticeable examples I have run across include Purist Audio, Cardas, and some Straightwire models. Take a pair of these interconnects off, put them back in their box for a couple of days, put them back into the system, and there is a readily identifiable and PREDICTABLE course that the sound will take while the cables settle back in.
I agree with paulwp for this reason. After reading hundreds of testimonials in the usual magazines and online for several years now about the benefits of burning in cables, I have never once heard anyone say that a cable sounded worse. They ALWAYS sound better. How can that be? If they do indeed change, how can it always be for the better? If good sound consists of a synergy of all components, at least some of the time the raw sound of the cable would be more synergistic than the broken in cable. But no, they are always described as sounding better. There is no doubt that different cables sound different. But I think the effect of burn in is one of becoming accustomed to the sound of the cable.
Hi Matt,

I had three sets of Stealth PGS Gold interconnects. Two xlr's and one rca. I lent all my powercords, speaker wires and interconnects to a man I sold an amp to while I was away on vacation. He wrote me a note telling me which was the newest, the next newest and the most broken in interconnects. He was correct. I had a Resolution Audio Cd55 which I installed a xlr and rca pair to the pre-amp. I would switch back and forth and the result of the switch was that the newer interconnect would always sound brighter and more brittle. After a few months they became identical.

My experience.

Bill E.
Having an old EE degree, I thought this made no sense. However, I have noticed that cables do sound better after they have sat in one place for many hours. One article suggested that the crystaline structure is under stress when bent and that after playing for many hours, the cables "relax". Try it, you'll like it.
Matt, cables do need to break in, for about 10 seconds. Consider, if cables need to burn in, what changes? And if you say they sound fine after, say 50 hours, do they stop changing by some miracle or do they keep burning out?

For those who believe in DBX tests, there have been none, zero, to prove that wires benefit from any sort of burn in. For those who prefer anecdotes, many of us have never noticed a change in a cable from brand new to broken in. Many say they have. This is one cable dispute to which I think there is an answer. You simply have to decide which group is delusional, the group that thinks nothing's changed or the group that thinks something happened.

This burn in argument offered by retailers of cables is the best argument I know of for the proposition that cables sound different from one another. If they all sounded alike, none of them would have anything objectionable about their sound to get used to during the "break-in" period.
interconnects are the most sensitive to breakin & can take several hundred hours, speaker cable not quite as long. You won't believe any of this until you hear it yourself though. I once tried to return some expensive ic's but the dealer talked me into waiting a month & I'm so glad that he did. AC cords don't seem to change much that I've noticed, but others report differently & who am I to argue?
It is possible to argue that the properties of the dielectric change with increased use. I don't know whether this is audible. Given that audiophiles can hear the difference between different cables, it isn't inconceivable that break in could be audible. Audibility can manifest in a variety of ways.

People hear things in different ways. I always used to listen for frequency response effects when switching components -- cleaner highs, tighter bass, smoother mids, etc. My first experience hearing a cable change was a little startling. I had a high quality recording of a jazz trio that I knew well. With the music playing in my family room, I could imagine the trio in the family room when I was in the adjacent kitchen. But when I walked into the family room, I could tell they weren't there live. After I upgraded my speaker cables, I couldn't hear any frequency response differences, but this recording now provided a "same room live" illusion -- if I closed my eyes, I could imagine them in the room with me! I've been a believer in quality cables ever since.

Some discussion of cable break in from an engineering point of view is provided in Audioquest's cable theory treatise at www.audioquest.com. Check out Cable Theory page 5. Happy listening!
More likely it was invented by cable purveyors, who wanted to discourage returns. "Don't like it? Let it break in some more." I've never heard of a properly controlled comparison of old and new cables, though you can expect lots of personal testimonials to follow.

Given that there is no permanent physical or chemical change to cables resulting from their use, the most likely explanation for any perceived change in sound over time is, as you say, psychological. And your final point is a good one, too: There are too many confounding variables to draw any conclusions about how a cable's sound changes over time, even if it does. But that never stopped anybody.
Theoretically Yes.
It can happen that you won't have to break them in but that's rare.
It can happen that you won't hear the difference between cables that had been running for 200...800 hours and brand new.
A conductor's break-in process is to direct electrons to the "right path" with minimal energy loss.

In bunch of cases breaking-in cables with your home equipment will bring you no success throughout long time of listening since breaking-in process might require much higher current to "straighten out" dielectric or semi-conductor nature inner impurities randomly residing inside the conductor.
first i couldn't believe cables sounded different--it didn't make sense.

but they do.

then i doubted that they could break in.

but they do...some more than others (i.e. silver cables change substantially compared to copper)

rhyno