What Exactly Does "Burn In" do for Electronics?

As I see it, it can be expected that by the time developmental testing is completed on the prototype of a new design, including final tweaking/voicing of the design, the prototype is likely to have accumulated a MUCH greater number of hours of operation than production units accumulate prior to leaving the factory. Both as a matter of necessity, due to the nature of the development process, and because the designer will want to assure that final tweaking/voicing takes into account any possible breakin phenomena.

Therefore if in fact breakin phenomena occur for a given design over a number of operating hours that is greater than the number of hours of operation of production units prior to shipment from the factory, those phenomena will continue to occur after the component is placed in service by the end user. And the component will not perform as its designer intended until after some period of use by the end user.

I would be very surprised if any of that were not the case, particularly when it comes to speakers, cartridges, AND major electronic components. So I am in essential agreement with ZD on this point.

Regards,
-- Al

06-22-14: Zd542
"Ok lets say things do change after "burn in", how does any designer compensate for this, in his calibrations, measurements, tests and design????"

They compensate for this by breaking the prototypes in before they listen and measure. For example, a designer may want to try several different capacitors when building an amp to see which one sounds the best. If they want to try 5 different options, they break the amp in 5 different times. They don't do any serious listening or measurements until they break the amp in first. This is the way they all do it. I don't think you could find one company that doesn't break their equipment like this. You don't have to take my word for it, either. Call some manufactures and ask them.

Ok if this is true, then this means all production units sent out that are not "burnt in" have been purposely miss-adjusted/calibrated for currents, bias, dc offset etc, NOT for the best ideal performance.
Hoping then that all these parameters of adjustments will all come together after the customer has "burnt it in" for a few weeks??? I think not.

Cheers George

On the contrary, the units are built to the spec that is finally agreed upon. It's just that anything new will not remain so and will alter over time until it's "broken" in.

Just because something is electric in nature and we can't see it doesn't mean that's there's no aging: wear and tear so to speak, over the short term. It's a big learning curve and we are just on the upward part of that curve.

I'm curious as to this: if we all experienced and agreed that the burn in was of a universally short nature, say a day or so, that there'd be general agreement. Using that as a priori, would it be so difficult to consider that some things take longer?

All the best,
Nonoise

It makes no sense that the expectation is for parts to fall out of spec in order to fall into a desired lower cumulative level of performance. Ridiculous. And how would this be accomplished within a reasonable time frame? By using inferior quality parts? Again, ridiculous.

06-22-14: Csontos
It makes no sense that the expectation is for parts to fall out of spec in order to fall into a desired lower cumulative level of performance. Ridiculous. And how would this be accomplished within a reasonable time frame? By using inferior quality parts? Again, ridiculous.

Exactly, when a unit is tested and adjusted up before it leaves the factory, it should stay this way for some time, for years we all hope.
To say that components change their characteristics after this because of "burn in" hours, means those adjustments will out out of spec, after the burn in.

Brand new capacitors do what's called "form" but this only takes minutes and they should already be "formed" by the time it takes to do the final spec adjustments in the factory before shipping.

The only thing in audio I know of that degrades relatively quickly from the first time it's switched on is tubes. And if they don't have auto bias circuits to keep them in spec, they need to be measured and adjusted every now and again. As they do loose the bias adjustment, depending on how many hours they are on.

Cheers George