User Manual

Microphone Input Transformers
LL1538 and LL1538XL
The LL1538 and the LL1538XL are high performance microphone input transformers, each with a high permeability
mu-metal core and two three-section coils.
In the LL1538XL the core is about 45% larger than in the LL1538, resulting in a larger level capability. In both types,
primary and secondary windings are separated by electrostatic shields. The three-section winding structure of the
transformers results in a very low leakage inductance and thus an excellent frequency response.
The transformers are encapsulated in mu-metal cases for magnetic shielding.
Turns ratio: 1 + 1 : 5
Pin layout (viewed from component side) and winding schematics:
LL1538 LL1538XL
Dimensions (Max. Length x Width x Height above
PCB (mm))
38 x 24 x 17 38 x 24 x 20.5
Spacing between pins
5.08 mm (0.2") 5.08 mm (0.2")
Spacing between rows of pins
27.94 mm (1.1") 27.94 mm (1.1")
Weight
46 g 65 g
Rec. PCB hole diameter
1.5 mm 1.5 mm
Static resistance of each primary
44Ω 61Ω
Static resistance of each secondary
880 Ω 975 Ω
Distortion (primaries connected in parallel,
source impedance 200Ω )
0.2 % @ 0 dBU (0.775V
rms) primary level, 50 Hz
0.2 % @ + 3 dBU (1.1V
rms) primary level, 50 Hz
1 % @ + 10 dBU (2.5 V
rms) primary level, 50 Hz
1 % @ + 13 dBU (3.5V rms)
primary level, 50 Hz
Self resonance point
> 120 kHz > 120 kHz
Optimum termination for best square-wave
response (Connection 1:5, source imp. 200Ω )
No termination necessary No termination necessary
Frequency response (source 200 Ω, no termination)
10 Hz - 100 kHz +/- 0.3 dB 10 Hz - 80 kHz +/- 0.3 dB
Isolation between windings/ between windings and
shield
4 kV / 2 kV 4 kV / 2 kV
3
2
1
8
6
4
5
3
2
1
8
6
4
5
3
2
1
8
6
4
5
1 : 51 : 2.5
R980616
Connection alternatives


Tibeliusgatan 7 International Domestic
S-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
8
2
1
3
4
5
6
LL 1538
(top view)