
LL1545A , page 1
Audio Transformer
LL1545A
LL1545A is a general-purpose audio transformer with a variety of connection alternatives. The transformer is
built up from two coils, each with a secondary winding surrounded by shields and two primary windings. This
structure results in an excellent frequency response. The transformer can be used in many different applications
such as a high impedance line input transformer (accepting signal levels of 22 dBU @ 40 Hz with primaries in
series), for splitting or as a microphone input transformer.
The LL1545A is made with a mu-metal core and is housed in a mu-metal can.
Refer to page 2 of this sheet for termination alternatives.
Turns ratio: 1 + 1 + 1 + 1 : 2 + 2
Dims: (Length x Width x Height above PCB (mm)) 37 x 22.5 x 14.5
Pin Layout (viewed from component side) and windings schematics:
Spacing between pins:
2.54 mm (0.1")
Spacing between rows of pins:
22.86 mm (0.9")
Weight:
46 g
Rec. PCB hole diameter
1.5 mm
Static resistance of windings: 2-3 or 6-7
1-4 or 5-8
9-10 or 15-16
122 Ω
182 Ω
305 Ω
Self resonance point: > 220 kHz
Recommended load for best square-wave response
(Termination alternative R4B:L4B over):
6.7 kΩ + 470 pF
Frequency response (source 600Ω ,
load (6.7 kΩ + 470 pF) in parallel with 56 kΩ ):
10 Hz - 70 kHz +/- 0.5 dB @ 0 dBU
Loss across transformer (at 1 kHz with termination as above):
0.3 dB
Core:
Mu-metal
Isolation between windings / between windings and shields: 3 kV / 1.5 kV
Data at different termination alternatives, showed on page 2 of this data sheet.
Turns
ratio
Copper Resistance
Prim/sec
Idle impedance
@40 Hz, 0dBU
Suggested Use THD < 0.2%@40 Hz
primary level /
real source impedance
R4B / R4U : L4B / L4U
1:1
610 Ω / 610 Ω 80 kΩ / 80 kΩ 10 kΩ / 10 kΩ 22 dBU / 600 Ω
R2B / R2U : L2B / L2U
1:1
150 Ω / 150 Ω 20 kΩ / 20 kΩ 600 Ω / 600 Ω 16 dBU / 150 Ω
R2B / R2U : L4B / L4U
1:2
150 Ω / 610 Ω 20 kΩ / 80 kΩ 600 Ω / 2.5 kΩ
16 dbU / 150 Ω
R4B / R4U : L2B / L2U
2:1
610 Ω / 150 Ω 80 kΩ / 20 kΩ 10 kΩ / 2.5 kΩ
22 dBU / 37.5 Ω
R4B / R4U : L1
4:1
610 Ω / 75 Ω 80 kΩ / 5 kΩ 10 kΩ / 600 Ω 22 dBU / 37.5 Ω
8
7
6
5
4
3
2
1
15
14
13
11
10
9
Can + Core 13
1
2
3
4
11
14
16
9
8
7
6
5
TRANSFORMERS
Tibeliusgatan 7 International Domestic
S-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
16
LL1545A
(top view)
R030220