Vortex Sound Research

When the mk 2 filter is used, and I patch something (white noise for example) into the "external signal in" (not the esp), there is a decent amount of signal bleed. What I mean is, I can hear some of the unfiltered ext input signal. When using the mk 1 filter, this signal bleed is not present. Does yours do this as well? Does anybody know if that's how the original MS-20 mk 2 was?