This circuit has a 100 dB dynamic We found it in a Popular Electronics from the 90s. Equivalent operational can be used.
The integrated circuit used in this configuration for noise reduction on FM radios is not common...
In the figure we have the circuit of a simple voltmeter with a 50 uA instrument and a 2k coil. The...
With this name, we found this electronic stethoscope with a coal microphone in a 1957 Raytheon...