Lundahl LL1517, Audio Output Transformer
LL1517 is an audio output transformer for balanced or unbalanced drive. The transformer is built from two threesection 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
Spacing between pins: 5.08mm(0.2“)
Spacing between rows of pins: 35.56mm(1.4”)
-
Core: Audio C-core
Housing: Mu-metal
Rec. PCB hole diameter: 1.5mm
Static resistance of each primary: 9.2
Ω
Static resistance of each secondary: 9.5
Ω
Leakage inductance of secondaries(sec. in series): 0.3mH
-
-
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, 30
Hz
-
Loss across transformer (at midband with 600
Ω load): 0.3
dB
Isolation between primary and secondary windings/between windings and core: 4kV/2kV