Paraphase amplifier (T389E)

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

Adafruit Breakout PDM Microphone
Adafruit Breakout PDM Microphone This Adafruit tested microphone card is available from Mouser...
Peak voltmeter (CB7370E)
With this circuit found in a 1965 Electronic Design, it is possible to read a peak voltage of up to...
Two-tone solar buzzer (CB20493E)
This circuit was found in a 1991 publication. The transistor can be a general-purpose type....