As I recall the T1-1 was spec'd at ~1 pF inter-winding capacitance so I'd expect whatever they are using inside the FTB-1-6 to be 6 dB worse for CM.
The T1-1 is in a bigger package and probably has more core material than the ADT1-1.
T1-1 (blue) ADT-1 (red) comparative S21 looked like
Hard to read but about 1.5 dB more IL at 50 kHz.
so the smaller ADT probably with less core and perhaps more turns still a couple of dB worse between 100 and 10 kHz, which is what the FTB-1-6 spec seems to indicate.
No doubt there are negative trade-offs for the smaller package but as John has indicated, there's really not room for the larger KK package.
Comments
As I recall the T1-1 was spec'd at ~1 pF inter-winding capacitance so I'd expect whatever they are using inside the FTB-1-6 to be 6 dB worse for CM.
The T1-1 is in a bigger package and probably has more core material than the ADT1-1.
T1-1 (blue) ADT-1 (red) comparative S21 looked like
Hard to read but about 1.5 dB more IL at 50 kHz.
so the smaller ADT probably with less core and perhaps more turns still a couple of dB worse between 100 and 10 kHz, which is what the FTB-1-6 spec seems to indicate.
No doubt there are negative trade-offs for the smaller package but as John has indicated, there's really not room for the larger KK package.