
Microphone Input Transformer Transformers
LL7903
The LL7903 is a large, high level, high performance audio transformer, made for extraordinary requirements.
The transformer combines high level capability (+28 dBU @ 50 Hz primary level) with low copper resistance
and is designed for the most demanding applications. The LL7903 consists of two coils, each with two primary
and two secondary windings separated by electrostatic shields. The core is a high permeability mu metal
lamination core.
The transformer is magnetically shielded by a mu metal case.
Turns ratio: 1 + 1 + 1 + 1 : 2 + 2 + 2 + 2
Dims (Length x Width x Height above PCB (mm)): 66 x 32 x 21
Pin layout (viewed from pins side) and winding schematics:
Spacing between pins:
5.08 mm (0.2")
Spacing between rows of pins:
5.08 / 45.72 mm (0.2 / 1.8")
Weight:
155 g
Rec. PCB hole diameter:
1.5 mm
Static resistance of each primary (average):
28Ω
Static resistance of each secondary (average):
125Ω
Distortion (primaries connected in series, source impedance 600Ω ):
+ 10 dBU primary level, 50 Hz:
0.1 %
+ 28 dBU primary level, 50 Hz:
1 %
Self resonance point :
80 kHz
Optimum termination for best square-wave response
(source imp. 600Ω ) :
30kΩ in series with 400pF
Frequency response
(source and load as above)
10 Hz - 70 kHz +/- 0.5 dB
Isolation between primary and secondary windings/ between windings and shield: 4 kV / 2 kV
R030216
7
1
8
2
12
6
11
5
19
13
20
14
21
15
22
16
23
17
24
18
7
8
15
14
13 + Core & Can
1
2
21
20
6
5
23
24
16
12
11
17
18
Coil 1
Coil 2
TRANSFORMERS
Tibeliusgatan 7 International Domestic
SE-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
Note! Isolation between shields is not guaranteed!