There is quite alot to learn in this area.
I have no degree in electrical engineering, but I started out with guitar amps. Its easy to start out with those, because something that sounds good for a guitar is likely going to be bad for hi-fi, but you can get used to experimenting with swapping component values and see what part of the circuit does when modified, etc.
Adding negative feedback, etc will show you the basics of a tube amp. But thats where it ends, Hi-fi is all about getting the signal through with the least amount of distortion or other alteration of the signal from the source.
I would like to learn more on this, but ive really only got to the point of looking at curves on the datasheets for tubes, there is so much else you need to know about impedances, time constants for cathode bypass capacitors, etc, etc
I guess the basics are really about calculating correct load resistors, coupling caps, etc and then work from there.