This two-transistor circuit is from a December 1964 Radio Electronics. Modern transistors can be tested. The headphone must be high impedance or crystal with a 2k2 resistor in parallel.
This preamplifier is intended for the use with magnetic pick-ups. Power supply must have voltages...
This circuit converts inductances on two scales into voltages. The circuit was obtained from a...
The circuit shown was found in a 1994 Linear Applications Handbook by National Semiconductor. The...