Re: the burning-in phenomena

razak & william wrote:
|| Isn't the phenomena we call "burning-in" of new hi-fi equipment
|| really 5% actual physical change in equipment and 95% adjusting to
|| the new sound?

I know only of loudspeakers requiring this. For example the rubber-surround
and the spider need a couple of hours at some bigger excursion to reach a
stable state. This phenomenon can also be proofed by measurements. For
example the resonant frequency lowers quite a bit by this "burn-in".
The Thiele-Small-Parameters have up to 20% variation, because the rubber
gets more flexible, when the outer thin skin is broken up. Dust and small
particles and other residues of the production process in the air gap might
restrict the movement in the beginning.
This process is required only once or maybe after long storage.

Another thing is the "warm-up-time". the electrical parameters of
semiconducters change a lot with temperature, and the bias current required
to reduce crossover distortion of the power amplifier is particulary
sensitive to this.
Of course a good designer can layout the circuits that warm-up is not
required, but I have seen many designs which suffer from this.

Also the voice-coil in a loudspeaker will change its resistance with
temperature. This will affect the low frequency response. The same is true
for the coils in the crossover.
So generally around 20min. of warm-up is required to get a stable condition.
It doesn't need to be better sounding though.
It is something a lot of gear-owners are accustomed too and is widely
accepted.
-- 
ciao Ban
Bordighera, Italy
electronic hardware designer