Paraphase amplifier (T389E)

This 6C5 tube circuit was found in a modern tube design manual. The circuit applies to other equivalent triodes.

Answering Machine (CB18202E)
This 1985 circuit takes advantage of an old cassette recorder to answer and record phone calls,...
Locomotive Sound (CB12323E)
This circuit is from 1990 documentation. It can be implemented with BC548 transistors instead of...
Crystal Test (CB13945E)
We found this 50 kHz 25 MHz crystal tester in a 1978 QST magazine. The FET can be the BF245 and...