
Audio Transformer LL1544A
LL1544A is a line input / general purpose audio transformer which can be used in many different applications
ranging from bridging input to microphone input applications. The transformer is built up from two three-
section coils with interleaved Faraday shields. The core is a two-component amorphous strip core. This core
type combines a high sensitivity for very low signal levels with excellent high-level capabilities. In addition, as
this type of core does not store energy (unlike conventional mu-metal cores), at low frequencies phase response
is excellent and resonance with a series capacitor is practically eliminated.
The LL1544A replaces previous types LL1544 and LL1554.
Turns ratio: 1 + 1 + 1 + 1 : 2 + 2
Dims: (Length x Width x Height above PCB (mm)) 30 x 22.5 x 14.5
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:
27 g
Rec. PCB hole diameter:
1.5 mm
Static resistance of each primary (average):
130 Ω
Static resistance of each secondary (average):
260 Ω
Self resonance point:
> 220 kHz
Recommended load for best square-wave response
(Termination alternative A below):
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 1kHz with termination as above):
0.2 dB
Isolation between windings / between windings and shields: 3 kV / 1.5 kV
Data at different termination alternatives, showed on the following page:
Termination Alternative
Turns
ratio
Copper
Resistance
Prim/sec
Idle impedance
@40 Hz, 0dBU
Suggested Use THD < 0.5%@50 Hz
primary level / real
source impedance
R4B / R4U : L4B / L4U
1:1
520Ω / 520Ω 80kΩ / 80kΩ 10 kΩ / 10 kΩ 20 dBU / 600Ω
R2B / R2U : L2B / L2U
1:1
130Ω / 130Ω 20kΩ / 20kΩ 600Ω / 600Ω 14 dBU / 150Ω
R2B / R2U : L4B / L4U
1:2
130Ω / 520Ω 20kΩ / 80kΩ 600Ω / 2.5 kΩ 14 dbU / 150Ω
R4B / R4U : L2B / L2U
2:1
520Ω / 130Ω 5kΩ / 20kΩ 10 kΩ / 2.5 kΩ
22 dBU / 37.5Ω
R4B / R4U : L1
4:1
520Ω / 65Ω 80kΩ / 5kΩ 10 kΩ / 600Ω 22 dBU / 37.5Ω
.
R030220
LUNDAHL
TRANSFORMERS
Tibeliusgatan 7 International Domestic
SE-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
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