
Audio Output Transformer
LL1517
LL1517 is an audio output transformer for balanced or unbalanced drive. The transformer is built from two three-
section coils, with primaries and secondaries separated by electrostatic shields, and a audio C-core of our own
production. The transformer is housed in a mu-metal housing.
The LL1517 has sufficient low copper resistance to meet broadcast specifications in a conventional drive
configuration, but is (as all output transformers) ideally used with mixed feedback drive circuits. (See separate
paper for mixed feedback design principles).
Turns ratio: 1 + 1 : 1 + 1
Dims (Length x Width x Height above PCB (mm)): 47 x 34 x 18
Pin layout (viewed from component side) and winding schematics:
Spacing between pins: 5.08 mm (0.2")
Spacing between rows of pins: 35.56 mm (1.4")
Weight: 105 g
Core: Audio C-core
Housing: Mu-metal
Rec. PCB hole diameter: 1.5 mm
Static resistance of each primary: 9.2 Ω
Static resistance of each secondary: 9.5 Ω
Leakage inductance of secondaries (sec. in series): 0.3 mH
No-load impedance: >1kΩ @ 50 Hz, +20 dBU
Optimum source impedance: Minus 18 Ω (See above)
Balance of output (according to IRT, source < 10 Ω , Load 600 Ω): > 60 dB
Maximum output level before saturation (sec. in series, load 600 Ω) + 24 dBU @ 30 Hz
Distortion (achieved with mixed feedback drive circuit, load 600 Ω) < 0.03 % @ 20 dBU, 30Hz
Frequency response (source 10 Ω, load 600 Ω): 10 Hz -- 80 kHz +/- 0.3 dB
Loss across transformer (at midband with 600 Ω load): 0.3 dB
Isolation between primary and secondary windings / between
windings and core: 4 kV / 2 kV
Suggested use
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Tibeliusgatan 7 International Domestic
S-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
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LL1517
LL1517
R980616
(top view)