Cwlondon - if you have been an enthusiastic audiophile for 20 years and never noticed the sound of a new component change over its first two weeks, then obviously the effect of burn-in is irrelevant to you. I find it hard to imagine that you have not heard it, because I have heard it happen so many times - and before anyone mentioned "burn-in" to me. For example, every time I have bought a new pre amp or power amp there have been a couple of weeks where the sound goes from "about right" out of the box, then increasingly thin and weedy, then suddenly fat and cloyingly warm, and then a slow sharpening up to becoming "about right" again. Then the sound just gets more and more natural for a further couple of weeks. These changes have never been subtle for me. Even if you just put a speaker cable that has lain in the cupboard for a few weeks into your system, the sound changes are very significant (for me) over about a week.
Burn In = Voodoo?
I have been an obsessive and enthusiastic audiophile for 20 years, I am not averse to tweaking and The Audio Critic infuriates me. However, I must admit I get a little uncomfortable reading so many posts about "burn in". While I understand that amps may need to warm up, speaker components may need to loosen up, the idea of burning in a cable or say, an SACD player just seems ludicrous to me. Unless of course, the party suggesting the burn in is a snake oil equipment peddlar and needs to make sure someone owns and uses your product for a couple of months before they decide it's really no good. At that point, of course, no one could actually remember what it sounded like in the first place and even if you wanted to return it, it would be too late. Am I being too cynical here?