Return of the Vacuum Tube

<memorylane> One of my lab partners in my EE Lab class played bass guitar. He wanted a tube pre-amp, but didn't want to spend $1,000 for it. So we built one as our lab project. We pulled a transformer out of an old Hammond organ, pulled tubes out of some old random stuff in a cabinet in the lab, threw in a pair of 12,000 uF caps, and four ceramic diodes for the rectifier. Then we had to code our own SPICE model for the tube so we could simulate it. That was one stout amp. Except the transformer put out a really unstable power waveformm, so one of our ceramic diodes exploded (tripping a breaker and taking out power in that wing), which was actually kind of cool. But we had to find a different transformer. Another time I accidentally grounded the 600-V node, which blew a big hole in our trace line and evaporated the solder off of one of our caps. The edges of the trace line survived, so we soldered the cap back in, powered it up, and it worked great. It was perfect except we were never able to get rid of the 60 Hz hum when it was plugged in. If you unplugged it, you could play for about a minute before the caps drained, and it sounded spectacular.</memorylane>

I miss those days. Now I just sit around writing patents and pleadings all day.

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