Lundahl Microphone Transformer, LL1530

Microphone Transformer / D-I Box Transformer LL1530

LL1530 is a microphone input transformer used for matching a 200 or 800 W microphone to 10 kW or for matching a high impedance source to a microphone input. The transformer consists of two coils, each with one primary and one secondary winding separated by an electrostatic shield, and a high permeability mu-metal core. The transformer is encapsulated in a mu-metal case for magnetic shielding.

For best performance, the high impedance side of the transformer (3.5 + 3.5) should be connected in series.

Turns ratio: 1 + 1 : 3.5 + 3.5
Dims (Length x Width x Height above PCB (mm)): 38 x 23 x 16

Spacing between pins: 5.08 mm (0.2")
Spacing between rows of pins: 27.94 mm (1.1")
Offset of earth pin from adjacent row: 2.54 mm (0.1")
Weight: 46 g
Rec. PCB hole diameter: 1.5 mm
Static resistance of each primary: 42W
Static resistance of each secondary: 790W
Distortion (primaries connected in series, source impedance 800W): : + 6 dBU (primary level) 0.1% @ 50 Hz; +16 dBU (primary level) < 1% @ 50 Hz
Self resonance point : > 100 kHz

Recommended termination for best square-wave response:
connection 1:3.5: 10 kW in series with 220 pF
connection 3.5:1: 2 kW in series with 2.2 nF
connection 7:1: 1 kW

Frequency response (1:3.5, source 800W , load 10kW in series with 220 pF): 20 Hz -- 30 kHz +/- 0.3 dB
Isolation between windings/ between windings and shield: 4 kV / 2 kV