Building a power amp from vintage components

[capt bullshot]

No, not another tube amp, it's a transistor amplifier.
It is build using some large transistor modules rated at 1000V / 150A, these went normally into variable frequency drives or power inverters. Not particular suitable for a linear power amplifier, but ... it works.

The project isn't finished yet, I've got a set of three working power amplifer "modules", each using one of these large BJT blocks, and some support circuitry.
Bandwidth isn't exactly audio (DC to 10kHz), output power is huge and sustained (not like your home audio amp that starts burning if you run it at nominal power for a prolonged time)

See the thing here:
http://wunderkis.de/pwramp3/

[Codebird]

What is this monster supposed to be used for? Competitive sub-woofer driver? Are you building a base cannon?

[capt bullshot]

Nah, no audio. Maybe hooking a 3 phase transformer to it to have a lab AC power source, spinning an AC induction motor the most inefficient way, generating lots of heat, ...

[cat87]

  Looks awesomely powerful.

Have you tried doing some measurements to see the actual bandwidth those monster transistors have ?

[capt bullshot]

No, I didn't measure their bandwidth alone. According to the datasheet, they should be pretty fast (switching on/off in the single digit µs range). With my amplifier, the BW limit is in the control circuit. From my experiments, I believe the transistors should be able to reach 100kHz in this particular configuration. At some point I stopped to optimize the driver / control loop for BW.

[MagicSmoker]

I have a pile of old BJT modules myself, so this is an especially interesting project to me!

Note that you can add emitter degeneration if you use "single" BJT modules, rather than the half-bridge configuration. I also would be wary of relying on inductance in the base drive circuit to quell oscillations in an emitter follower.