Hello there..
Yesterday I measured the original filter circuit in the Blofeld. The filter cut-off frequency is a little different than assumed. It is around 35KHz (-3dB).
Then I adjusted my filter circuit a little more.
Original filter plot:
My filter circuit with amplification of the output level
My new filter circuit
The question still arises as to whether an electrolytic capacitor is necessary at the exit or whether it can be saved
Greetings Rolf