This common circuit using operational amplifiers was found in the 1993 issue of Radio Electronics Special Projects. The circuit is sandwiched between the pickup and the amplifier input.
This circuit was found in an American magazine 73 for radio amateurs of the 80s. It is an...
Found in American documentation from the 1980s, this circuit can be designed with equivalent...
This circuit is from a 1977 documentation. It is powered by the power supply of the circuit under...