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 basic configuration can be found in a lot of articles on this site. In this case, the relay...
This circuit was found in a 1997 publication, but it uses few common components and is very...
This circuit prevents the passage of frequencies in a range starting at 1 kHz and can be adjusted...