Lundahl LL1674 Amorphous Core Mic transformer

The LL1674 is a large, high signal level audio transformer built with the well know Lundahl amorphous core. The LL1674 consists of two coils, each with a two-sectioned primary winding and a high level secondary winding separated by electrostatic shields. The core is a two-component amorphous strip core. The very high mu of the core results in a phase shift of less than 0.5 degree at 10Hz. The transformer is magnetically shielded by a mu metal housing.


Spacing between pins: 5.08 mm (0.2")
Spacing between rows of pins: 30.48mm (1.2")
Weight: 80 g
Rec. PCB hole diameter: 1.5 mm

Static resistance of each primary (average): 33W
Static resistance of each secondary (average): 605W
Distortion (primaries connected in parallel, source impedance 150W ): 22V rms (+29 dBU) secondary level, 30 Hz: 1% 22V rms (+29 dBU) secondary level, 50 Hz: 0.2%
Self resonance point : 70 kHz
Optimum termination for best frequency response (source imp. 150W ) : No termination required
Frequency response (source 150W , load 10k): 10Hz ? 45kHz +/- 0.5dB -3dB @ 80kHz
Isolation between primary and secondary windings/ between windings and shield (rms): 3 kV / 1.5 kV