Lundahl High level line input transformer, LL1690

Amorphous Core High Level Line Input Transformer LL1690

LL1690 is a high-level line input transformer with an uncut cobalt-based amorphous strip core. The transformer is designed for high end audio applications such as tube amplifier line input with or without phase splitting. The windings are arranged to give a high degree of symmetry if the transformer is used for phase splitting. The dual-coil structure also greatly improves immunity to external magnetic fields from e.g. power supplies and motors. Primary and secondary windings are separated by electrostatic shields. The transformer is housed in a mu-metal can.

Turns ratio: 1 + 1 : 1 + 1

Dimensions (L x W x H above PCB, in mm) 42 x 28 x 22
Spacing between pins 5.08 mm (0.2")
Spacing between rows of pins 30.5 mm (1.2")
Rec. PCB hole diameter: 1.5 mm Weight: 81 g
Static resistance of each primary: 150 W
Static resistance of each secondary: 150 W
Distortion (primaries connected in series, source impedance 600W ): + 23 dBU 0.1% @ 30 Hz + 26 dBU < 1 % @ 30 Hz
Self resonance point: > 150 kHz
Suggested load for best square wave response, serial-serial connection. 40k // 7k + 400pF
Frequency response (serial connection, source 1kW, load 40 kW in parallel with 7k + 400pF): 10 Hz -- 100 kHz +/- 1.0 dB
Phase splitting balance (connection 2:1+1. Source 1kW, load (20kW +20kW) in parallel with 7k + 400pF): >55dB, 10Hz 50kHz
Phase response (deviation from linear phase) (source 600 ohm, load 10k (Audio Precision)) 20 Hz 20kHz, < 2
Isolation between windings/ between windings and shield: 3 kV / 1.5 kV