Lundahl Line input transformer, LL1545A

Audio Transformer LL1545A

LL1545A is a general-purpose audio transformer with a variety of connection alternatives. The transformer is built up from two coils, each with a secondary winding surrounded by shields and two primary windings. This structure results in an excellent frequency response. The transformer can be used in many different applications such as a high impedance line input transformer (accepting signal levels of 22 dBU @ 40 Hz with primaries in series), for splitting or as a microphone input transformer.

The LL1545A is made with a mu-metal core and is housed in a mu-metal can.
Refer to page 2 of this sheet for termination alternatives.

Turns ratio: 1 + 1 + 1 + 1 : 2 + 2
Dims: (Length x Width x Height above PCB (mm)) 37 x 22.5 x 14.5

Spacing between pins: 2.54 mm (0.1")
Spacing between rows of pins: 22.86 mm (0.9")
Weight: 46 g
Rec. PCB hole diameter 1.5 mm

Static resistance of windings:
2-3 or 6-7 122 W
1-4 or 5-8 182 W
9-10 or 15-16 305 W

Self resonance point: > 220 kHz
Recommended load for best square-wave response (Termination alternative R4B:L4B over): 6.7 kW + 470 pF
Frequency response (source 600W, load (6.7 kW + 470 pF) in parallel with 56 kW): 10 Hz - 70 kHz +/- 0.5 dB @ 0 dBU
Loss across transformer (at 1 kHz with termination as above): 0.3 dB
Core: Mu-metal
Isolation between windings / between windings and shields: 3 kV / 1.5 kV