I wrote PS Audio to find out exactly what they do to each piece of equipment before shipping to the new owners. I have had other manufacturers do the same thing. When I buy cables from the manufacturer, they ask me if I want them burned in which I normally do. Here is how PS Audio replied to my question on wether they burn in or test their equipment before shipping:
Thanks for reaching out with a great question.
Most of them only receive a “torture test” so to speak.
There isn’t really any way to “torture test” a DAC, so we test all of the inputs and outputs for about 15 minutes, and then send it on its way.
The amps get tested a little harder, and drive a dummy load for a few hours.
The powerplants get tested the hardest as they will sometimes have a heavy load put on them for around 48 hours.
All of this testing isn’t really enough to qualify as good burn in though.