Lundahl Line output transformer, LL1585

High Level Audio Output Transformer LL1585

LL1585 is a high level audio line output transformer for balanced or unbalanced drive. The transformer is built from two three-section coils, with primaries and secondaries separated by electrostatic shields, and a audio Ccore of our own production. The transformer is housed in a mu-metal housing.

The LL1585 is (as all output transformers) ideally used with 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)): 47 x 34 x 21

Spacing between pins: 5.08 mm (0.2")
Spacing between rows of pins: 35.56 mm (1.4")
Weight: 130 g
Core: Audio C-core
Housing: Mu-metal Rec.
PCB hole diameter: 1.5 mm
Static resistance of each primary: 64 ?
Static resistance of each secondary: 64 ?
Leakage inductance of secondaries (sec. in series): 0.4 mH
No-load impedance, typically (primaries in series): 8 k? @ 50 Hz, 15V RMS.
Optimum source impedance: Minus 128 ? (Mixed feedback drv)
Balance of output (according to IRT, source < 10 ? , Load 600 ?): > 60 dB
Maximum output level before saturation (sec. in series, load 600 ?) + 28 dBU @ 20 Hz
Frequency response (source 10 ?, load 600 ?): 10 Hz -- 100 kHz +/- 0.3 dB
Loss across transformer (at midband with 600 ? load): 3 dB
Isolation between primary and secondary windings / between windings and core: 4 kV / 2 kV