Tin ear got the first post. Golden ear gets the one that counts.
Don’t need experience with your particular amp. Which you will understand after you do this enough, because they all go through pretty much the same process. Right out of the box the whatever it is will sound pretty much like what its ultimately going to sound like. Similar enough a lot of tin ears never notice the slow gradual changes that happen during the first 50 hours or so of use.
Early cold right out of the box sound is going to be thin, grainy, and harsh or aggressive. Then over time the grainy edges become less. If the component is really good the edges become less but not because they are smoothed over but in a way that you hear even more detail, just in a more natural and effortless way.
If you listen closely you should be able to hear that these changes are greater and faster early on, and become more fine and fewer as the hours go by. Like Bob Ross painting a scene. The colors and shapes, the scene doesn’t change but the details keep filling in until at the end it looks pretty good.
Some people, especially some dealers, use this as an excuse. "My Binford Symphonic Bombast 2000 requires 2000 hours of break-in! Its that good!" Liar. If its any good at all then it will sound good right out of the box. Yes it will also continue to sound better with time. But if its not good from the beginning send it back, it never will be. You just might get used to it is all.
If you are unsure what if anything you are hearing there is a simple exercise to move your ears from tin to golden. The type of sound that comes with burn-in is almost exactly the same as happens every time a stone cold component is first turned on. So simply leave your component on 24/7 for a while. Long enough to get good and used to that thoroughly warmed up sound. Then turn it off and the next night turn it on and listen right away. No warm-up. That same thin grainy aggressive sound will be there. Maybe even enough for tin ear to hear.
