
Microphone Input Transformer, Linebox Transformer
LL1578 and LL1578XL
The LL1578 and the LL1578XL are high performance microphone input transformers/linebox transformers with
high permeability mu-metal cores and two three-section (high bandwidth) coils.
In the LL1578XL the core is about 45% larger than in the LL1578, resulting in a higher signal 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 : 10
Pin layout (component side view) and winding schematics:
Dimensions (Max. Length x Width x Height above PCB (mm)) 38 x 24 x 17
Spacing between pins 5.08 mm (0.2")
Spacing between rows of pins 27.94 mm (1.1")
Weight 46 g
Rec. PCB hole diameter 1.5 mm
Static resistance of each primary
22Ω
Static resistance of secondary
880 Ω
Distortion (primaries connected in parallel,
source impedance 200Ω )
0.2 % @ -6 dBU primary
level, 50 Hz
1 % @ + 4 dBU primary
level, 50 Hz
Self resonance point
Optimum termination for best square-wave response
(Connection 1:5, source imp. 200Ω )
Frequency response (source 200 Ω, no termination)
Isolation between windings/ between windings and shield 4 kV / 2 kV
2
3
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5
6
1
8
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5
6
1
8
2
3
4
5
6
1
8
1 : 101 : 5
R970924
Connection alternatives
Pins’ side
view
Pins’ side
view
Tibeliusgatan 7 International Domestic
S-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
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LL1578