Lundahl Line input transformer, LL1922

High Level Stepup Line Input Transformer LL1922

LL1922 is a high-level input transformer similar to the UTC LS-10. Thus it is designed for step-up input from 600 ohm sources. To reach the LS-10 freq. response in 1:8 applications with nondifferential amplifier input, the internal Faraday shield must be tied to one of the source lines (the UTC LS-10 does not have any Faraday shield).

The two coils structure results in a high immunity to external magnetic fields from e.g. power supplies and motors. Primary and secondary windings are separated by electrostatic shields. The core is a high permeability mu metal core. The transformer is housed in a mu-metal can.

Turns ratio: 1 + 1 : 4 + 4

Dimensions (L x W x H above PCB, in mm): 47 x 28 x 24
Spacing between pins: 5.08 mm (0.2")
Spacing between rows of pins: 35.56 mm (1.4")
Rec. PCB hole diameter: 1.5 mm
Weight: 115 g
Static resistance of each primary: 60 ?
Static resistance of each secondary: 730 ?

Distortion (primaries connected in series, + 21 dBU 0.1% @ 50 Hz
source impedance 600?, load 47k. Primary signal level): + 26 dBU < 1 % @ 50 Hz

Distortion (primaries connected in parallel source + 11 dBU 0.1% @ 50 Hz
impedance 600?, load 47k. Primary signal level): + 19 dBU < 1 % @ 50 Hz

Frequency response, source 600W, load 47 k?
Connected 1:4 (fig 3), primary level +10dBU 10 Hz -50 kHz +/- 1.0 dB
Connected 1:8 (fig 4), primary level +10dBU 10 Hz -30 kHz +/- 1.0 dB
Connected 1:8 (fig 5), primary level +10dBU 10 Hz -30 kHz +/- 1.0 dB

Isolation between windings/ between windings and shield: 4 kV / 2 kV