First off. Completely ignore all of the boneheads saying that “break in time” is only you getting used to the way something sounds.

This is completely and totally wrong.

All of the components that audio equipment is manufactured from have their “break in time” listed in the engineering specs for that component. Prior to the formation time of things like resistors and capacitors the value can drift wildly. And since the values of these components are what determines what the equipment sounds like, all audio equipment sounds different after use than when new. This is also why all components have a % deviation and formation time listed in the engineering specs. Because it effects more than sound. It can cause circuit failure.

Better or worse depends on what the values are supposed to be and how close they end up after formation. But the value of every component changes over the first 50 hours of use.

And if this were not the case, component manufacturers would not do the testing required to post the formation specs for their product. It is lengthy and expensive testing. That they only do because the electrical engineers who design things with those parts demand it. So they can predict the performance of whatever circuit they are designing.

So ignore the “nothing matters, nobody can hear the difference” crowd. They have no idea what they are talking about. The values of components absolutely change over the first 50-100 hours and that absolutely changes the way audio equipment, particularly amplifier stages, sound.

The only way to “burn in” a piece of equipment is to run it. It must have both signal in and load out to move current. Current is what forms the components.

The fastest way being to run sine and/or square waves through it.

But I’d suggest just plugging it in and listening to it as part of your system.