Does EVERY component need break-in?

Every component that does not sound good to you right away needs breaking in.

I think that the concept of break-in time is a post-sale customer relations tool used in the retail trade. The non-believers say that after a while your ears should adjust to the character of the new component and it will sound better. (I am an agnostic in these matters.)

I've never noticed a difference with cd players, amps, preamps or interconnects. Speakers, obviously, speaker cables too, but not a long time.

I do it. My new ARCAM CD 92 sounded "OK" right out of the box but it wasn't as "full" and "warm" as I remembered it in the store. This weekend I put it on "repeat" for 36 straight hours and it sounded "fuller" and "warmer", the traits that attracted me to the unit. Ditto for my cables - interconnects and speakers. They sounded better after at least 48 hours of "burning". Good luck.

I feel that most everything changes with break in. Part of this could also be (in this case) from just having the unit powered up continuously for 3-4 days. I recently finished breaking in a Bel Canto DAC after it received the 1.1 upgrade and the sound fleshed and smoothed out considerably with 200+ hours of playing time (which exceeds it being powered up for 3-4 days), but I assume that both were contributing factors. As far as moving parts go, self lubricating bearings do operate more smoothly with use (which will cut down on vibration). I discovered this the first time as a kid when I made slot car frames and motors from scratch and raced them in competition. I just leave stuff on, use it and then hope for the best. I have never heard anything actually sound worse with break in with the exception of a Leviton Pro wall outlet that just got thinner and thinner in the midrange with use (I replaced it with an inexpensive P&S outlet which sounds much better overall plus has a much tighter grip on the plugs).

YES, Leave it on or in stand-by for at least a week before passing judgement.

Unplug your gear for a week, then plug it back in. Thin sounding? Absolutely. Give it several hours, and magically your system sounds just like it did a week ago. I've done this when I've travelled for extended periods of time, and also noticed the same effect when inserting a "new" piece of gear in my system (shipping time is generally over a week). Even used items need time to settle in and perform as expected. This may not be the technical diatribe some would hope for to prove that break-in is necessary but it certainly is easy enough to try for yourself. Unplug everything, wait a week or so, plug it back in. Proof is in the pudding. Jeff