Burn-in period: what happens, how long?

[Netlist]

Many years ago I bought a new car and the dealer told me to come back after a 1000km to check everything, renew the oil…
Since then I always drive second hand cars. (They have their oil renewed.)

When buying electronics, no dealer ever told someone to come back to check everything after the burn-in period. Well, maybe some do, but certainly not to change oil.

Can anyone tell what happens to electronic gear in the so-called ‘burn-in phase’?
What happens to caps, resistors, transistors, coils…
Is it the whole circuit that becomes more stable?
When can one say: “My amp is burned-in now!” What are the standards?
Some people will say it is bull****, others will come with very strong arguments.
I remember a post from Nelson who said: “the normal burn-in time for … is …hours.”
If Nelson doesn’t consider burn-in as something stupid, there must be plenty of ‘food for thoughts’.

Although I think I cannot hear it, many people on this forum will claim they can.
The final result should be an improvement in sound.!?

/Hugo – hoping for a good technical explanations.

[Fusor]

Burn-in period = the amount of time your new project needs to run to give some hope it won't explode and start your house on fire.

[jean-paul]

Hi Hugo, the burn in period of electrolytic caps is a normal thing. They just need some time to settle. The phenomenon is the most strong with these components. Newly built amps sound better after a few days. I learnt this has to do with the oxidation on the cathode in the caps. When a voltage is applied the oxidation will disappear. I also learnt that the electrolyte in the cap needs some time to develop its full potential. Fact is that they measure better after some days of use.

Whatever explanation there is: I can clearly hear them improving. This counts for the devices as a whole too. New audiostuff always improves after some time ( and deteriorates after a lot of time too ) I replace old caps and my customers always hear the difference even when I use the same type and brand again.

I don't hear the "burn-in difference" when I replace resistors that much. I do hear it with opamps, they need some time to develop their sonical qualities. But electrolytics are the most changing components. With amps the thermal stability stabilizes after some time, maybe another small effect that contributes to the effect as a whole !?!?

Off-topic: the electrolyte itself is the secret of cap manufacturers. You probably heard about the faulty caps in computers because of a stolen and wrongly copied recipe for P50 electrolyte too ?
Millions of caps are produced with a low ESR electrolyte that turns into a waterish substance after sometimes only 250 hours of use. You repair pc's too so you must have seen some broken down pc's last time that had these components. Brands to look out for are Jackcon, JCcon and Tayeh to name a few ( replace them even when they're still OK !!!! ) The big brands like Compaq and IBM have the problem too with some of their systems.

http://www.careyholzman.com/caps/thumbnails.html

Japanese sources reported to the magazine that an unusually high failure rate of low-ESR aluminium electrolytic capacitors produced by Taiwan-based Lelon Electronics, Luxon Electronics, and other makers had been traced to a problem with an aqueous electrolyte that had been used throughout the Taiwanese electrolytic capacitor industry.

A scientist working for Rubycon Corporation in Japan left the company and began working for Luminous Town Electric in China, where he developed a copy of a Rubycon electrolyte used in the manufacture of low-ESR aluminium electrolytic capacitors. Unfortunately, some of his staff defected, taking the formula with them, and began to sell a cut-price electrolyte to many of the major aluminium electrolytic makers in Taiwan - the magazine claims as many as 11 companies were affected.

But the inept defectors only copied part of the formula, making the resultant electrolyte unstable, resulting in catastrophic failure of the finished capacitors. Tests showed the affected capacitors failed after 2000 hours of operation. Intel claims the aluminium capacitors with the poor electrolyte could fail after just 250 hours. Companies are now snapping up non-Taiwanese capacitors in a bid to avoid the faulty parts, causing shortages and price hikes.

Taiwan produces around 22.5 billion aluminium electrolytic capacitors a year - 30% of total global unit shipments - which are used in motherboards and modems; power supplies, monitors, and game consoles.

[bigparsnip]

I was a bit sceptical about this whole burning in thing till a few weeks ago when I bought a new CD player and conncted it up using some home made interconects. At first it sounded very bright, harsh almost. To check to see if it was the CD player, we brought my friends up (similar model, same manufacturer), allong wiht his interconects to compare the two. His unit did sound a lot more neutral them my new one, and I was a bit woried that this might persist. However, I then decided to try my player with his interconects, and there was a huge difference, the harshness was gone and the bass improoved quite a lot too.

So after I had found it was the cables that were causing the poor sound, I decided I would try and 'run in' my home made job before going out and spending even more money on a new pre-made cable. I was suppries that after only 24 hours wiht the CD player left on repeat, the cable had mellowed a lot. We compared it to my friends interconnect again, and the two ere far more alike. The home made one still had more of an air around the high frequecy, but it was far more listenable now, adn the bass on my cable had improved to the point of being more full than the bought cable.

So, now I am happy that I have a nice cable at a fraction of the cost of my friends, and I have been suppriesed by the effect of a few hours of running in could have on just under a metre of cable. From now on I won't be so sceptical when peopl etalk about running equipment in, or the difference a cable can make.

Andrew.

[Circlotron]

Except for electrolytic caps and brand new vacuum tubes, *my opinion* is that "running in" of electronic stuff is nonsense, particularly wires and cables. (quickly dodges incoming flak ) That said, I do believe the perceived sound changes after a while, but for some more obscure reason.

For example, a few months ago I got a lend of a fairly ordinary and =well used= pair of speakers, and initially they sounded very forward in the midrange and generally pretty ughh. Anyway, after a day or two they sounded much better and after a while I got to like them. Nothing had changed except the auto-calibration mechanism that exists between my ear and brain. *I think* that's what accounts for a lot of this burning-in stuff.

[DIY_Peter]

Originally posted by Circlotron
That said, I do believe the perceived sound changes after a while, but for some more obscure reason.

Yes, and for some strange reason, people always think the sound gets better after "burn-in".

[Circlotron]

Originally posted by DIY_Peter



Yes, and for some strange reason, people always think the sound gets better after "burn-in".

That's because if it gets worse it is called burn-out.

Anyway, waaaaaaaay back in 1972 when I built my first 4 watt self-designed valve amp (6V6, 5Y3G, 6G8G, *separate* bass & treble controls even ) I though it sounded just wonderful. If I still had it now and it was in exactly the same condition as it was all those summers ago, I expect I would consider it sounded only so-so. But.... the amp would sound the same as it always did, so what has changed?? My hearing has actually gotten worse since then, so somebody better tell me what's going on?

[Music Machine]

Perceived. No doubt. Easy experiment. Ever listen to a little walkman type player with the bass boost on for a couple minutes. When you turn the boost off it sounds like bass cut, even though it was fine before trying the boost. Acclimation is a big part of the "change in sound", but doesn't account for all the change. I had some interconnects (harmonic technologies) that rollercoastered for several hours and then started to settle out. With others I couldn't be sure there any change at all. Of course speakers can undergo huge change as new drivers break in. I think most people will agree on that.

Regards

[jean-paul]

Originally posted by DIY_Peter



Yes, and for some strange reason, people always think the sound gets better after "burn-in".

Hugo, people don't think this but they experience a change. Why not do a test with an amp ? Recap it and listen. Leave it on for a day and listen again the next day. Simple ! Tell us your results.

Except for electrolytic caps and brand new vacuum tubes, *my opinion* is that "running in" of electronic stuff is nonsense, particularly wires and cables.

I think a lot of the burn in can be described as perceived but even the most objective people that listen very carefully hear a difference. It is dangerous to listen to people that talk in terms of : magical, it was if there was a curtain hanging in front of it before etc etc. but apart from that there is a difference. In some cases quite small and in some cases easily hearable. BTW you say that running in is nonsense but you agree that the electrolytics ( which are soldered in large numbers in many audiodevices ) do need a run in time. Couldn 't it be the caps that are responsible in a large degree for the run in period ?? So you believe in it on one hand and you call it nonsense on the other hand. Quite contradictionary.


Calling it nonsense is premature when you didn't test it yourself. The most objective test is to have 2 new amps that are identical. You leave one powered on for a few days.
After that time you switch it off and leave it like that for a few hours. Now power them both and compare them. I did the test and if you don't hear a difference it's fine with me.

[Netlist]

Thanks Jean-paul
Also off-topic:
I actually wasn't aware of the problem. I only repaired older PC's over the last weeks, months. The newer ones who have the problem will still be in guarantee I suppose. How long is this been going on? This is really freaky. Mass burnout I would call it!

I can imagine that caps are the parts who are most influenced by burn-in. They are the most unstable parts in our systems.
I wonder if it's measurable. Maybe some test with square waves on caps and scope pictures over several hours could also reveal something.

/Hugo – anyone ever measured effects of burn-in with good equipment?