Lundahl LL1538 and LL1538XL, Microphone Input Transformers

The LL1538 and the LL1538XL are high performance microphone input transformers, each with a high permeability mu-metal core and two three-section coils. In the LL1538XL the core is about 45% larger than in the LL1538, resulting in a larger level capability. In both types, primary and secondary windings are separated by electrostatic shields. The three-section winding structure of the transformers results in a very low leakage inductance and thus an excellent frequency response. The transformers are encapsulated in mu-metal cases for magnetic shielding.

• Turns ratio: 1 + 1 : 5
• Dimensions(Max. Length x Width x Height above PCB(mm)): 38 x 24 x 17
• Spacing between pins: 5.08mm (0.2“)
• Spacing between rows of pins: 27.94mm (1.1”)
• Weight: 46g
• Rec. PCB hole diameter: 1.5mm
• Static resistance of each primary: 44W
• Static resistance of each secondary: 880W
• Distortion(primaries connected in parallel, source impedance 200W): 0.2%@0dBU(0.775Vrms) primary level(50Hz), 1%@ +10dBU(2.5Vrms) primary level(50Hz)
• Self resonance point: >120 kHz
• Optimum termination for best square-wave response(Connection 1:5, source imp. 200W): No termination necessary
• Frequency response(source 200W, no termination) 10Hz - 100kHz +/- 0.3dB
• Isolation between windings/between windings and shield 4kV/2kV

• Turns ratio: 1 + 1 : 5
• Dimensions(Max. Length x Width x Height above PCB(mm)): 38 x 24 x 20.5
• Spacing between pins:5.08mm(0.2“)
• Spacing between rows of pins: 27.94mm(1.1”)
• Weight: 65g
• Rec. PCB hole diameter: 1.5mm
• Static resistance of each primary: 61W
• Static resistance of each secondary: 975W
• Distortion(primaries connected in parallel, source impedance 200W) 0.2%@+3dBU(1.1Vrms) primary level(50Hz), 1%@+13 dBU(3.5Vrms) primary level(50Hz)
• Self resonance point: >120kHz
• Optimum termination for best square-wave response(Connection 1:5, source imp. 200W): No termination necessary
• Frequency response(source 200W, no termination): 10Hz - 80kHz +/- 0.3dB
• Isolation between windings/between windings and shield 4kV/2kV