Lundahl Line output transformer, LL5402

Audio Output Transformer LL5402

LL5402 is an audio output transformer for unbalanced drive, ideally used with mixed feedback drive circuits (see application example below). If primary pins 1 and 5 are connected to ground, the windings are arranged such that cold ends of the primary windings surround each secondary winding. This reduces the effect of capacitance between the primary and the secondary windings.

Turns ratio: 2 + 2 : 1 + 1
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: 30.48 mm (1.2")
Weight: 92 g
Rec. PCB hole diameter: 1.5 mm
Static resistance of each primary: 30 ?
Static resistance of each secondary: 7 ?
Leakage inductance of secondaries (sec. in series): 0.2 mH
No-load impedance: >800 ? @ 50 Hz, +20 dBU
Optimum source impedance: Minus 15 ? (See application below)
Balance of output (according to IRT, source < 10 ? , Load 600 ?): > 60 dB

Note! Performance figures below are obtained using mixed feedback drive circuits. (See application example).Otherwise use lowest possible source impedance.

Distortion (connection as application example below, load 600 ?) + 22 dBU 0.1% @ 50 Hz
Frequency response (as below , load 600 ?): 20 Hz -- 40 kHz +/- 0.3 dB
Voltage loss across transformer (at midband with 600 ? load): 0 dB
Isolation between primary and secondary windings / between windings and core: 4 kV / 2 kV

Balance of output (according to IRT, source < 10 ?, Load 600 ?)

Output windings in parallel 60 dB
Output windings in series >50 dB

Frequency response (source 10 ?, load 600 ?, 0 dBU): 10 Hz -- 100 KHz +/- 0.3 dB
Isolation between primary and secondary windings/between windings and shield: 4 kV / 2 kV

Application example with mixed feedback: (NOTE! This application was covered by a German patent DE 29 01 567
with application day 13.1.79. Qs far as we know the patent is expired).