Making a passive 50Hz Notch filter for my next ELF & VLF recording. 23K= 22K+1K and capacitor of 132nF is done with two 220nF series and one 22nF = 132nF. Will be placed in entrance just before high impedance of JFET transistor (2SK170). In near future active notch filter will be implemented as configurable function in my new ELF/VLF amplifier.
Franck D
