LUNDAHL
TRANSFORMERS

Tibeliusgatan 7S-761 50 NORRTÄLJE
SWEDEN

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Domestic0176-13930
0176-13935

Audio Transformer
LL1545A
LL1545A is a general-purpose audio transformer with a variety of connection alternatives. The transformer isbuilt 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 inseries), 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+2Dims: (Length x Width x Height above PCB (mm))
37 x 22.5 x 14.5
Pin Layout (viewed from component side) and windings schematics:
87
65
4
3
2
1LL1545A(top view)

1615
1413
1110
9

129

348
7101114166515
Can + Core 13Spacing between pins:
Spacing between rows of pins:
Weight:Rec. PCB hole diameter
Static resistance of windings:

2-3 or 6-7
1-4 or 5-8
9-10 or 15-16

Self resonance point:
Recommended load for best square-wave response(Termination alternative R4B:L4B over):Frequency response (source 600Ω ,load (6.7 kΩ + 470 pF) in parallel with 56 kΩ ):Loss across transformer (at 1 kHz with termination as above):Core:
Isolation between windings / between windings and shields:

2.54 mm (0.1")
22.86 mm (0.9")46 g
1.5 mm122 Ω
182 Ω305 Ω> 220 kHz
6.7 kΩ + 470 pF
10 Hz - 70 kHz +/- 0.5 dB @ 0 dBU
0.3 dB
Mu-metal
3 kV / 1.5 kV

Data at different termination alternatives, showed on page 2 of this data sheet.
Termination Alternatives Turns Copper Resistance Idle impedance Suggested Use THD < 0.2%@40 Hz
ratio Prim/sec@40 Hz, 0dBU
primary level /real source impedance
1:1
R4B / R4U : L4B / L4U
610 Ω / 610 Ω80 kΩ / 80 kΩ
10 kΩ / 10 kΩ 22 dBU / 600 Ω
R2B / R2U : L2B / L2U 1:1 150 Ω / 150 Ω20 kΩ / 20 kΩ
600 Ω / 600 Ω 16 dBU / 150 ΩR2B / R2U : L4B / L4U 1:2 150 Ω / 610 Ω20 kΩ / 80 kΩ
600 Ω / 2.5 kΩ 16 dbU / 150 Ω
R4B / R4U : L2B / L2U 2:1 610 Ω / 150 Ω80 kΩ / 20 kΩ 10 kΩ / 2.5 kΩ 22 dBU / 37.5 Ω
4:1 610 Ω / 75 ΩR4B / R4U : L180 kΩ / 5 kΩ
10 kΩ / 600 Ω 22 dBU / 37.5 ΩR030220

LL1545A , page 1

91011131415
16Connection alternatives for LL1545AComponent side view

12345678

Component side view

Connection: R4B
Balanced source

Connection: R4U
Unbalanced source

Connection: R2B
Balanced source

910119101191011131415161314151613141516

Connection L4B
Balanced load

Connection L4U
Unbalanced load

Grounded atsourceConnection R2U
Unbalanced source
91011

12
34567813141516

Grounded atsource12345678Centertap

Connection L2U
Unbalanced load

Connection L2B
Balanced load

1234567812345678Connection L112345678

CentertapTurns
ratio

Application

Transformer
Input (primary)

1:1
1:2
2:1
1:1
1:1
1:2
2:1
1:1

Line input to unbalanced circuits
Line input to unbalanced circuits
Line input to unbalanced circuits
Low impedance line input to unbalanced circuits
Line input to balanced circuits
Line input to balanced circuits
Line input to balanced circuits
Low impedance line input to balanced circuits

R4B / R4U
R2B / R2U
R4B / R4U
R2B / R2U
R4B / R4U
R2B / R2U
R4B / R4U
R2B / R2U

Transformer
Output(secondary)
L4U
L4U
L2U
L2U
L4B
L4B
L2B
L2B

R030206

LL1545A , page 2