"Burn in" in amps (and all other electrical parts)

Can't say I've really seen any that hold water.

k

I believe the idea is that the metals move around and line up at the molecular level, helping the path of the signal. Or something like that.

I don't believe there's been any scientific proof of this though.

Not really responsive (or helpful) is it? It sounds like he's interested in hearing possible explanations.

I'd like to think he's not interested in explanations that don't hold water.

k

The only scientific explanation is that it's brain burn in - ie you become accustomed to the sound and therefore like it more over time.

There's much to be said for that.

I'll never forget an experience that really drove that home for me.

Since I was a child, and up until I was about 15, I'd always listen, as most every other kid my age, with the bass and treble cranked all the way up.

Then I came to be friends with the first "audiophile" I'd ever encountered who told me I had it all wrong. That I had to zero out the tone controls and listen "flat."

Well, when I got home I zeroed out my tone controls and threw on some music.

It sounded like ass. Like I was listening through soggy mattresses.

But I let peer pressure get the better of me and decided to leave the tone controls zeroed out. I may not have liked the sound, but by God I was doing the right thing.

And then over time it started sounding less and less like ass. I started hearing things in the music that I'd never heard before. Like the "metallic" sound of cymbals rather than big bursts of noise.

I eventually came to really like the sound.

And a few weeks later, just for fun, I decided to crank the bass and treble up.

It was painful.

Bottom line, the brain REALLY digs patterns. And when presented with the same pattern over time, that pattern wears a rut in the brain and the brain eventually accepts that pattern as the norm. Change that pattern and everything gets thrown out of whack.

Like the mirror on my medicine cabinet.

Once in a great while I'll walk into the bathroom, look in the mirror and suddenly feel a little off balance.

Why?

Because the cabinet door is ajar just a little bit. Maybe only a quarter of an inch. But that quarter of an inch causes the reflections in the mirror to be tweaked enough that my brain sees a different pattern than it usually does and freaks out for a moment.

Strange and amazing thing, the brain.

Something that has been tried: Take 2 of the same device that has a reputation for changing noticeably with burn-in. Use one but not the other for a few hundred hours, then compare them. I've seen quite a few people who believed that burn-in was rubbish do this and get a severe shock at the difference. Not that all gear changes, but some that I've owned has, correlated with numerous other people, changed in tonality over the first few hundred hours of use. However, in my experiments with audio gear, I put this down to heat, and not electricity. There's no doubt that heat causes changes in materials.

If the amplifier contains components that change over time, then burn in just applies some of working time to those components. For example the various x and y series ceramic capacitors. X5R capacitors lose about 2.5% of their capacitance per log10 hour - so while it changes 5% during the first 10 hours, it will then change a further 2.5% the next 100 - so a 33nF capacitor will have become a 30nF capacitor, consequently changing corner frequencies. Of course, there will be further changes at 1000 & 10000 hours (etc). The same applies to other components that have an aging effect. Whetever these are or should be used in audiophile equipment is a different question. Also, not all dielectrics have this aging quality.

If there is any explanation for this (i.e. if it isn't all bollocks) then it'd be the caps, resistors, diodes, etc. changing over time.
However in my experience even cheap components you wouldn't use in audio applications take thousands of hours to change a little.

It was clear what you were asking for to anybody who doesn't approach every thread like this with a certain agenda. You have to put a warning in bold at the beginning of a thread like this -- along the lines of what you said above -- if you want to get real answers. Hopefully, now that the thread is on track, others will chime in. I have seen this issue discussed before, with particulars about what changes in amps, so perhaps some of those folks will also contribute.

Remember while you can speculate and assume there isn't any real evidence to support your claim. It's like asking a roomful of scientists what the evidence for young earth creationism is - there simply isn't any.