Why does it take so many hours to brea in arc preamps and amps?

Excellent advice- Ray (rspyder).
Happy Listening!

Nelson Pass IS an Authority.  But he is simply stating what numerous experiments by cognitive scientists have shown.

But ARC made their amp and can advise you best -- even if listener subjectivity is an effect, that does not rule out teflon caps needing some time.

Also, as ARC how long they listened to your unit - they listen to every unit they make not just a sampling.

randy-11
Nelson Pass IS an Authority

Exactly! That’s why it’s an illogical argument. An argument cannot be won by simply claiming to be an expert in the field. Besides, amplifier designers disagree on many things. I'm quite sure I can come up with another terrific amp designer who disagree with Pass.

Make two reasonable assumptions.
That there is some of legitimacy to the notion of "getting accustomed to the sound" burn in.
There is probably an element of the circuit undergoing real physical changes "during/over use" time as well.
Thus there is perceived 'burn in.'   QED....  EOD......