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 obtained in a manual of the used old operational amplifier. However, the same...
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We...
The circuit is from an 80's publication, but the components are current, only special type diodes...