The first stage that raises a weak signal enough to be worked with. Everything after it inherits what it did.
From pre- (Latin prae, before) and amplify (Latin amplificare, to make larger, from amplus, large, + facere, to make); the first stage that raises a weak signal before every stage that follows inherits what it did.
The first stage that raises a weak signal enough to be worked with. Everything that follows inherits whatever this stage did to it.