Lundahl Line input/output transformer, LL1674

High Level Tube Amplifier Input Transformer LL1674

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.

Turns ratio: 1 + 1 : 4 + 4
Dims (Length x Width x Height above PCB (mm)): 43 x 28 x 21
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): 33?
Static resistance of each secondary (average): 605?
Distortion (primaries connected in parallel, source impedance 150? ):

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. 150? ): No termination required
Frequency response (source 150? , load 10k) 10Hz 45kHz +/- 0.5dB -3dB @ 80kHz
Isolation between primary and secondary windings/ between windings and shield (rms): 3 kV / 1.5 kV