Lundahl Microphone Transformer, LL1935

DI Transformer LL1935

LL1935 is a transformer designed for DI (Direct Input) applications, matching high impedance guitar pickups to low impedance microphone preamp inputs, but is also ideal for 1:10 microphone input applications. 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 high impedance windings are wound using a special low capacitance winding technique. The transformer is encapsulated in a mu-metal case for magnetic shielding.

For best performance, the high impedance side of the transformer (5 + 5) should be connected in series.

Turns ratio: 1 + 1 : 5 + 5
Dims (Length x Width x Height above PCB (mm)): 38 x 23 x 16

Spacing between pins positions: 2.54 mm (0.1")
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 (pins 5-6 and 7-8): 650 ?
Static resistance of each secondary (pins 1-2 and 3-4): 17 ?

Frequency response (reference 1.0 kHz)
10:1, source 100 k? , secondary open: 20 Hz 20 kHz +0 / -3 dB
10:1, source 100 k?, load 1 k? 10 Hz 45 kHz +0 / -2 dB
1:10, source 200 ?, secondary open 10 Hz 80 kHz +/- 1dB

Distortion -5 dBU input level, +14 dBU output level
For practical reasons measured in 1:10 configuration. < 0.1% THD @ 50 Hz

Source 150?, load 10k (Audio Precision portable) +7 dBU input level, +26 dBU output level
< 1% THD @ 50 Hz

Self resonance point: None detected in above configurations

Isolation between windings/ between windings and shield: 4 kV / 2 kV