DSO Quad bandwidth

i am not so skillfull about the circirt , but i think, maybe you stimulation lacks a inportant item, the cpc1017 , which is not a wire when shorted, it contains a C about 30pF between the 2 legs in circuit , and also C between the 2 legs with the ground. that is what the designer (bure) told me, these C make the whole story different…