Here are two PDF files from the National Semiconductor Web Site that contain good tutorials on the fundamentals of Op Amp circuits and some of the basic analog building blocks that they can provide.

I am looking at building a ~80W class A amp for experiance and to save costs. I am looking at the AE Aegis One's (nice kit for about $500 here) to couple it with for now but eventually will go up to ...

If you asked [Hans_Daniel] what he learned by building a tube audio amplifier with a dozen tubes that he found, the answer might just be, “don’t wind your own transformers.” We were impressed, though, ...

The problem with tube based audio is that it has so often been hijacked by people for whom the bragging rights of having a ...

The purpose of the project is to construct a high end headphone amplifier designed for the highest quality music reproduction with the minimum of distortion. The amplifier is an essential part of any ...