Tube amp for my car

[N2IXK]

Ran a modified Dynaco Stereo 70 in a '71 Plymouth Duster many years ago.

Rewired the heater circuitry for direct operation from 12VDC. Pulled out the stock power transformer and the 5AR4, and obtained B+ from an old surplus dynamotor from a 50s era mobile 2-way radio setup. Negative bias supply came from a little DC-DC converter circuit I cobbled together.

Soon discovered that EL34s and 7199s don't like vibration very much. Tubes developed loose internals and microphonics very quickly, even with the entire amp shock mounted on rubber isolators. If I were to try something like this again, I would strongly consider the use of highly ruggedized mil-spec tubes. Bendix Red Bank 6384s would be great for the output tubes, but they are getting harder to find and go for $$$ if you can find them.