How do you break in a preamp

Like Doak said, just use it, it will happen soon enough. The transformation process should be one that is appreciated, like a scenic drive through the country. I just love it when a component gradually transforms from a frog to a prince.

Take the top plate off, most likley just some phillips head screws need to be removed.

What are you going to do once you are in there? :)

Fire it up and let play!! That's the only sure fire way to break-in any component. After 100-150 hrs. it should be sufficiently broke-in.

Yep, follow unit instructions: Power on, play. I personally don't like sitting through the break-in process because it's harder to perceive the differences over time. I prefer to listen at the beginning and take note of initial reactions, let it play for a decent period of time, then listen again for changes.

You can accomplish the burn-in process either way. I'm too impatient, and don't like to sit through the transformations that take place, to listen for 200 hrs while components burn. I just sample for a while every day. Whatever your signal source, your power amp needn't be turned on to burn-in a pre. To save the hours on my CDP(and it's tubes) I use a tuner, either between stations(white noise kinda), or on a "rap"(yuch!) station for the heavy bass content.