Lundahl Microphone Transformer, LL1636

Microphone Input Transformer LL1636

LL1636 is an audio input transformer for applications where a high turns ratio is desired. 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. All winding ends are available on the pins. Thus, the transformer can be configured for a number of different turns ratios. The LL1636 is made with amorphous core material. As this type of core does not store energy (unlike conventional mu-metal cores) the low frequency resonance with external series capacitors is practically eliminated.

Turns ratio: 1 + 1 + 1 + 1 : 10 + 10
Dims: (Length x Width x Height above PCB (mm)) 30 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: 27 g
Rec. PCB hole diameter: 1.5 mm
Static resistance of each primary (average): 10 ?
Static resistance of secondary (average): 415 ?
Self resonance point: > 250 kHz
Frequency response (@ -10 dBU, all in series. Source 50? , load 100 k?): 10 Hz -- 25 kHz +/- 1 dB; 10 Hz -- 90 kHz +/- 1.5 dB
Distortion (primaries connected in series, source impedance 50? ): < 0.5% @ -2 dBU, 50 Hz
Primary no load impedance @ 0 dBU, 50 Hz, all in series: 8 k? typically
Core / Can: Amorphous Strip Core / Mu-metal can
Isolation between windings / between windings and core: 3 kV / 1.5 kV

Turns ratio and possible use at different termination alternatives. Termination alternatives are shown on the following page.