I am kind of new to amp building and have a decent understanding of amplifying with op apms and single transistors, however I am having trouble really grasping how the differential pair commonly seen in the power section works... I've tried reading up here and there on the net about it, but I cant say I really know how to make use of this circuit.. I kinda get it, however I dont really understand how to properly set the feedback or how to design for a specific gain etc, set dc at input, single supply vs +/- supply ect.. IN any case, was wondering if anybody knew of any good easy to follow tutorials with examples anywhere?? Something you might see in a text book with various examples??