
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
Pin Layout (viewed from pins side) and Windings Schematics:
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 Ω
Static resistance of each
secondary (average): 75 Ω
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): >2kΩ @ 50 Hz, @+14 dBU primary level
Balance of output (according to IRT, source < 10 Ω , Load 600 Ω) > 60 dB
Frequency response (source 10 Ω, load 600 Ω): 10 Hz -- 40 kHz +/- 0.3 dB
Isolation between primary and secondary windings/
between windings and core: 4 kV / 2 kV
Suggested usage
1
9
2
3
4
5
6
7
8
10
11
13
14
15
16
Tibeliusgatan 7 International Domestic
S-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
4
3
2
1
5
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8
15
16
10
9
Can + Core 13
1
9
2
3
4
5
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7
8
10
11
13
14
15
16
+
-
+
1
9
2
3
4
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6
7
8
10
11
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14
15
16
+
-
+
1 : 1
Max. output level +27 dBU @ 50 Hz
Primary resistance 120 Ω
Secondary resistance 150 Ω
2 : 1
Max. output level +21 dBU @ 50 Hz
Primary resistance 120 Ω
Secondary resistance 37 Ω
R970729
LL1555
(pin’s side
view)
LL1555
(pin’s side
view)