@Deep333
There are about 40 videos on utube of Nelson Pass discussing amplifier designs. He's very generous with information and one of the kindest humans. If you're interested, a good place to start would be interviews by Steve Guttenberg and Pass. If you dig a little deeper you'll find some videos of Pass doing design seminars with the DIY community. I thought these seminars were very interesting and I learned some things about various transistors, use of feedback, input stages, output stages, and lots of nerdy subjects.