hybrid tube/transistor stereo amplifier

Our final project for ee121 was to mangle together a pre-amp tube and an op-amp output stage, and produce a stereo audio amplifier. we did, and it sounded like my sony boombox, but the signal did honestly go through the tube and op-amp, as promised.



The whole shebang. The folded aluminum pieces to the left and right of the black chassis plate are "heatsinks". We weren't totally sure if they did anything, but the opamps got too hot to touch after a while, so we had to strap them to something.

The tubes were scrounged from some bin at Halted Electronics, and the opamps were generously 'donated' to us from TI or Motorola or somewhere that had a 'free samples' program. Naturally, we requested the most expensive item on the free samples list, and it turned out to be a giant 40W opamp that normally cost $50 a piece.

In our project presentation, we had to explain what was going on. Here, Andres shows how a tube works. See? Line with squiggles make sine wave.

Rested and cleaned up for the presentation? Nope! The last 72 hours in the lab with no sleep or shower.

See? Simple!