This circuit simulates the effect of an inductance. Equivalent operational amplifiers can be used, and the power supply must be symmetrical. The circuit is from a 90's Poptronics.
This circuit can generate signals up to 100 kHz. Found in documentation from the 1980s, it makes...
Some old record players use variable reluctance phono pickups, requiring a special amplifier...
This circuit is from a Radio Electronics from July 1965. The circuit uses components from the time...