@stargazer3 OP do you believe in the burn in process of an amp that over time the sound will settle and finally focus on a cohesive musical experience or is it to your opinion all in our brain that is adjusting to the sound of the component? When I mention burn in process its regard to periods of 300hrs and more (eg Naim or Simaudio Moon amps).
Speakers for sure. The are mechanical devices that have to loosen up. I hook up my woofers and drive them hard for a few days and can measure the resonant frequency drop a few Hz.
Amplifiers, only the tubes. When it comes to electronics and wire I believe the listener is becoming accustomed to the change.
For those who will likely disagree: If burn in exists in these devices why did we not know about it until recently. I find no references to burn in in the 50s 60s 70s.. when did it start?
I know the manufacturers love the idea because it gives them a reason for you to get used to the product. They are certainly going to promote the idea.
With digital devics I really have to wonder what is burning in. The digits?
We always burn in amplifiers to find infant mortality. We would rather have an amplifier break in our shop than in your home. This process is well documented and 24 hours usually does the trick. The failures are very rare and most often just a tube. We even cycle the amps on and off many times to temperature cycle the glass which is what usually fails but its just 1 out of 100 tubes.
With tubes I always set the idle current (bias) 10 % low because I know it will come up a little in the first 100 hours.