educatedfilm:

I myself have taken a few years of education in the electrical industry. These courses have included transistor technology. The math is quite simple ie. the gain in a transistor, but for myself, I have also looked at building an amp for say my car stereo...but decided not to due to the labour involved. Maybe I'm just lazy, but someone else has done the work and I think it is just easier to buy the darn thing.

However, if you are interested in a hobby and spending some time to do it, best of luck to ya. I don't remeber the site but there are some on the site. One showed the schematic of how to wire it and a list of the materials (very specific) as to the equipment required for the particular project.