Lundahl Line output transformer, LL1524

Audio Output Transformer LL1524

LL1524 is an audio output transformer for balanced drive. The LL1524 is a 5-section output transformer. This results in a very low leakage inductance and thus excellent HF characteristics.

The LL1524 is (like all C-core audio output transformers) ideally used with negative source impedance achieved using mixed feedback drive circuits. See separate paper for mixed feedback design principles.

Turns ratio: 1 + 1 : 1 + 1
Dims (Length x Width x Height above PCB (mm)): 48 x 34 x 22

Spacing between pins: 5.08 mm (0.2")
Spacing between rows of pins: 35.56 mm (1.4")
Weight: 125 g
Core: Audio C-core
Housing: Mu-metal
Rec. PCB hole diameter: 1.5 mm
Static resistance of each primary: 7.3 ?
Static resistance of each secondary: 7.5 ?
Leakage inductance of secondaries (sec. in series): 0.1 mH
No-load impedance: >1k? @ 50 Hz, +20 dBU
Optimum source impedance: Minus 14 ? (mixed feedback)
Balance of output (according to IRT, source < 10 ? , Load 600 ?): > 45 dB
Maximum output level before saturation (sec. in series, load 600 ?) + 24 dBU @ 30 Hz
Distortion (achieved with mixed feedback drive circuit, load 600 ?) < 0.04 % @ 20 dBU, 30Hz
Frequency response (source 0 ?, load 600 ?): 5 Hz -- 100 kHz +/- 0.5 dB
Loss across transformer (at midband with 600 ? load): 0.5 dB
Isolation between primary and secondary windings / between windings and core: 4 kV / 2 kV