This 1969 Mullar circuit appears elsewhere on this site. The circuit uses germanium diodes and the indicator is microammeter with zero in the center of the scale.
This circuit produces pulses of great intensity and short duration at a frequency of approximately 1 kHz....
In the figure we show how to implement a voltage reference with the ON Semiconductor rail-to-rail...
This preamplifier for record players with crystal capsules was found in Radio Electronics magazine...