Hi Denys, I cobbled up a very quick and rough version of your filter as we talked about, I too did not have exact values, but looking at the res Search ults I am sure that you are on the right track. As mentioned I changed the switching diode feeds to 4.7k The images show the filter, a sweep with no switching voltage, 14 volts on the psu, and the sweep with markers at 3mHZ and 4.5mHZ , The vertical scale is on 10 db divisions, I am sure that your neatly built filter block will work as planned . When Ray sweeps it that will prove it