Lundahl LL7903 High level mic transformer

The LL7903 is a large, high level, high performance audio transformer, made for extraordinary requirements.

The transformer combines high level capability (+28 dBU @ 50 Hz primary level) with low copper resistance and is designed for the most demanding applications. The LL7903 consists of two coils, each with two primary and two secondary windings separated by electrostatic shields. The core is a high permeability mu metal lamination core. The transformer is magnetically shielded by a mu metal case.

Turns ratio: 1 + 1 + 1 + 1 : 2 + 2 + 2 + 2

The transformer is magnetically shielded by a mu metal case.

Technical Details:

• Dims (Length x Width x Height above PCB (mm)): 66 x 32 x 21

• Spacing between pins: 5.08 mm (0.2")

• Spacing between rows of pins: 5.08 / 45.72 mm (0.2 / 1.8")

• Weight: 155 g

• Rec. PCB hole diameter: 1.5 mm

• Static resistance of each primary (average): 28 ohms

• Static resistance of each secondary (average): 125 ohms

• Distortion (primaries connected in series, source impedance 600? ): + 10 dBU primary level, 50 Hz: 0.1 %

• Distortion (primaries connected in series, source impedance 600? ):+ 28 dBU primary level, 50 Hz: 1 %

• Self resonance point : 80 kHz

• Optimum termination for best square-wave response Source imp. 600ohms. Connection L4 : R4  : 30k ohms in series with 400pF

• Frequency response Source and load as above. Connection L4 : R4 10 Hz - 70 kHz +/- 0.5 dB

• Isolation between primary and secondary windings/ between windings and shield: 4 kV / 2 kV