Stereo 4 Amplifier

This is my present stereo amplifier, designed and built in 2000. This project is unique in that I built two - one for use in my stereo, and another for use with my Korg keyboard.

I have been steadily improving the design of this amplifier for 25 years. The circuit topology is fully complementary, differential, cascode, bipolar transistor. It is direct-coupled from input to output except for one capacitor and a DC servo. It contains two power supplies: one unregulated supply for the output stage and a second regulated supply for all other stages. I think this amplifier can hold its own when compared against commercial high-end audiophile amplifiers.

The design outputs 80 watts per channel into 8 ohms and 160 watts per channel into 4 ohms. The amplifier contains roughly 500 discrete components. The semiconductor complement includes 94 bipolar transistors, 168 diodes, 2 JFETs, and 2 integrated circuits.