Lundahl Line output transformer, LL1555

Audio Output Transformer LL1555

LL1555 is an audio output transformer for balanced drive. The winding arrangement is such that, connected as shown below, each secondary winding is surrounded by cold primary winding ends. The transformer is ideally used with a mixed feedback drive circuit (refer to our separate sheet). The secondaries can be connected in parallel (for low output impedance) or in series. The LL1555 is made with an audio C-core of our own production and is housed in a mu-metal housing.

Turns ratio: 1 + 1 + 1 + 1 : 1 + 1
Dims: (Length x Width x Height above PCB (mm)) 33 x 26x 20

Spacing between pins: 2.54 mm (0.1")
Spacing between rows of pins: 22.86 mm (0.9")
Weight: 59 g
Rec. PCB hole diameter: 1.5 mm
Static resistance of each primary (average): 120 W
Static resistance of each secondary (average): 75 W
Max. primary level (primaries connected as below): +27 dBU @ 50 Hz
Leakage inductance of secondaries (sec. in series): 1.0 mH
No-load impedance(primaries connected as below): >2kW @ 50 Hz, @+14 dBU primary level
Balance of output (according to IRT, source < 10 W, Load 600 W) > 60 dB
Frequency response (source 10 W, load 600 W): 10 Hz -- 40 kHz +/- 0.3 dB
Isolation between primary and secondary windings/ between windings and core: 4 kV / 2 kV