Lundahl Line input transformer for ZF input circuitsr, LL6404

Very Small Size Zero Field Input Transformer LL6404

In a Zero Field (ZF) transformer, the magnetic field caused by the input signal should be balanced by a feedback loop which includes the transformer's secondary winding (see schematic below). The feedback arrangement extends the low frequency range (to almost DC!) while maintaining the small size of the transformer. The very small size of the LL6404 requires that the feedback resistor value be very close to the secondary winding resistance.

Turns ratio: 1 : 1
Dims (Length x Width x Height above PCB (mm)): 15.5 x 11 x 10

Housing: Mu-metal
Core: Amorphous strip core
Impregnation: Solvent less epoxy resin
Spacing between pins: 2.54 mm (0.1")
Spacing between rows of pins: 10.16 mm (0.4")
Weight: 4 g
Rec. PCB hole diameter: 1.5 mm
Static resistance of primary (pins 4 - 6): 210W
Static resistance of secondary (pins 1 - 3): 160W
Isolation between windings/ between windings and core: 3kV / 1.5 kV