I'm not crazy about break-in, and I try to design it out of my designs, if I can. Still, it exists, but go easy on yourself. It is best to have SOME AC signal passing through the amp. Just turning it on, helps, but is not complete break-in. You could find more about this from Blackgate caps, who INSIST on AC break-in for each cap. Don't ask me why, we haven't measured the difference yet to anyone's satisfaction.